Saturday, October 10, 2009

My Elecraft K2 Wish List

I've owned my K2, SN #2548, for several years now. It has been my primary radio since the fall of 2002, when I added the KPA100 module to it. I really enjoyed building it, and I'd like to build another. A couple of years ago, when the K3 first came out, Wayne Burdick at Elecraft collected wish lists of K2 features. Given the runaway success of the K3, I have my doubts if they will ever get back to enhancing the K2, but in the spirit of hopefulness, here's my list:

Firmware-only Suggestions:

  • RTTY Mark Display Frequency - Just as CW displays the carrier frequency of the received CW signal, the RTTY mode ought to display the frequency of the Mark signal. A menu option would be needed to set the frequency of the Mark signal. (This would essentially subtract or add the Mark frequency from the LSB / USB carrier frequency, respectively)
  • VOX Toggle - I'd rather toggle VOX on and off, and have the VOX delay time set in a menu. Having to cycle through all the VOX delay times to turn VOX on and off is a real pain.
  • Tuning Rates should follow mode - 10 Hz tuning is fine for CW and RTTY, but too slow for SSB. 50 Hz tuning is fine for SSB. The rate button could then be used to switch to 1 kHz step and back to 10 or 50 Hz. It would save a lot of button presses trying to get the right tuning rate. You could also display all the digits of the frequency regardless of tuning step (in which case SSB would alternate the bottom digit between 0 and 5)
  • RIT / XIT Display - momentarily display the RIT or XIT offset on the main display when it is changed (much like for power or keyer speed).
  • Unified Filter - Rather than having to separately select XFIL and AFIL settings, I'd rather have three of four filter presets that allow me to combine an XFIL and AFIL setting for each mode. One button (say XFIL) would then cycle through the presets. That way, you're always selecting an optimized filter solution, rather than selecting it manually, which is made more difficult because there is no filter display indicator.
  • IF Shift - This very handy feature could be implemented with a firmware change. Biggest problem is how to control it. I find the XIT to be useless, so I would vote to replace XIT with IF Shift. An alternate would be to use the Keyer Speed knob in SSB or RTTY modes.
  • CW Tuning Direction - an option to flip sidebands on 15m and above, so that the tuning direction stays the same. (This won't work on RTTY or SSB, of course)
  • CW Memory Command - have a computer command to write to the CW memories. That way you can program them from the computer and use them from the front panel.
  • INP mode for CW PTT - This mode would allow PTT on the dot line and CW keying on the dash line - great for contesting work. (this would disable auto-detect of hand keying)
  • Variable Rate Turning - normal tuning is one step at a time, but if you turn the knob faster, the tuning rate increases for as long as you tune quickly.
  • Auto-Tuner Out -- Allow one-touch selection of Tuner AUTO/CAL. This would allow one to easily switch the tuner on and off.
Hardware Improvements:
  • Improved KSB2 module -- starting with a filter with sharper skirts (better than 1.5 shape factor), 6-10 dB more mic gain available, more positive VOX (using separate VOX amplifier), anti-VOX circuitry.
  • Improved KNB2 module -- allow selection of longer blanking times, more thresholds, better blanking action.
  • PFx Module -- a tiny little module that has four (or so) buttons. Hooks into the aux line and offers access to eight functions of the K2 (four on tap, four on hold). Obviates the need for FPLY, opens the K2 up for easier access to things like switching filter presets, noise reduction modes, RIT clear. Lots of simpler and cheaper than the KRC2, because it is just the buttons. (This might also be useful for the K3)
  • Remote Tuning Knob -- borrow the idea from Ten-Tec. Perhaps part of the PFx module.
  • Opto-encoder for RIT/XIT knob -- Replace the potentiometer with a optical encoder. That way, we wouldn't have to manually re-center it.
I intend to keep using my K2 for several years. It's my hope that Elecraft will be able to deliver some of these enhancements.


Thursday, July 16, 2009

Cushcraft A3S/A743

As mentioned before, I've been using a Cushcraft A3S for several years now. I purchased it back in 1989, had it up for about six years, in the basement for five, loaned out for a couple of years to W1YM, and then back up since 2001 at my QTH.

There's many things to admire about the A3S. It's quite rugged, having survived several freak Georgia ice storms, but it only weighs 25 lbs even with the 40m option. While it's one of the last tribanders designed without computer modelling, it has reasonable performance on a small boom of 14 feet. It's been a popular product both in home installtions and even for Field Day. I have one ham buddy who used to use one on a pneumatic mast mounted to his conversion van.

Here are some of the things that I have learned about the A3S and A743:
  • Tape the driven element insulator
A layer of electrical tape protects the driven element insulator from the Sun. There's not much of it exposed, but the sunlight will slowly break it down over time. Covered with tape, it will last forever. Use a sharp knife to open the U-bolt holes.
  • Tape the trap end caps
The plastic trap end caps won't last forever. After about 5-8 years in the Sun, they will split. Cushcraft also thinks quite a lot of them -- replacing all 24 end caps cost me almost $50 in 2000. Try to preserve them by placing a single layer of tape around the circumference of the cap where it goes over the trap tube. The flat ends don't tend to split, since they aren't under any tension.
  • Keep the trap holes down
While it is in the instruction manual, it's pretty easy to have an element section rotate and have one or more holes pointing anywhere but down. Leave them that way, and the traps will fill up with water quickly. Get the screw clamps on tight enough so the element sections don't rotate.
  • Mount traps the correct way
The traps are designed so that the end connected to the cover tube is closest to the boom. Make sure all of them are this way. If you are not sure which way they are, you can carefully slide an end cap off to check. Mark the trap tube with an arrow using a Sharpie so you can remember. If you put the trap on backwards, it may be hard to diagnose.
  • Use a balun
Cushcraft recommends making a balun by taking six loops of coax and taping them together. WA2SRQ wrote a posting to TowerTalk back in 1996 that showed that such a balun is much more effective when the turns are in a single layer and do not overlap or bunch. Six turns of coax on a 4 inch PVC form should work nicely. Ferrite beads a foot and a half long works well, too. I found a set of 10 of ferrite beads large enough to fit over RG-8 and wired them underneath the boom.
  • Twist the element support rope
With the A743 option, the driven element droops far too much, so Cushcraft includes a non-conductive support rope and support mast. The instructions show the support rope should have a twist right at the top of the support mast. The twist prevents the rope from sliding back and forth through the plastic grommet as the driven element moves in the wind. It will eventually break. Don't ask me how I know -- just remember to include the twist.
  • Element spacings
The A3S offers three choices of spacings along the elements, CW, MID and Phone. I took a tip from K7LXC. With the Cushcraft 40-2CD,
Steve recommends going half-way between the CW and MID settings.

The last time I had my A3S up, I used the Phone settings, and the SWR was very high at the bottom of the bands. So, I used values that were midway between CW and MID.

This results in a good compromise in covering the entire band. Here's the SWR curves through about 130 feet of RG-213.

Based on these graphs, I could probably shorten up the spacing between the 20m and 15m traps, and the 10m traps and the boom.

Regardless of the values you use, double check the measurements before putting the antenna up. When I first put up the A3S, the 10m director spacing was about six inches too short. You couldn' t tell from the SWR curves, but the antenna likely did not work as it should.

There may be better tribanders you can buy, but the Cushcraft A3S is a great performer. The A743 option adds 40m. At my QTH, this is my best 40m antenna, partly because it is mounted higher than anything else. Being able to rotate the pattern is often helpful in crowded contest conditions.

Friday, June 26, 2009

Phonetics

There's been a few letters in QST lately about the proper use of phonetics. The latest QST (the one from the future -- July 2009) has an op-ed piece about phonetics.

The original letter that set this recent discussion off was a couple of months ago. The writer complained that he heard a station signing "London Radio" and thought he'd be talking to England, but was disappointed when the station was merely in the US.

That was probably me.

The writer insisted that everyone should just use the standard phonetics, and never anything else. While well intended, I'm afraid that the ICAO phonetics, while they work very well for aviation communications, don't always cut it.

"Romeo" -- this is just not a great word. It works OK most of the time, but not everyone in the world knows Shakespeare. "Radio" is a word that all hams know. It's the one phonetic that will get through when nothing else will.

"Lima" -- this is just a weak word. Watch your wattmeter when you say it -- it doesn't have that much punch. Using it, I get all kinds of guys who heard everything but the "Lima". They think it is "Charlie" or "Kilo" or "Echo" -- anything but "Lima". "London" works more often than not. About the only place that "Lima" is recognized well is in Central and South America.

"Alpha" -- try saying it twice. It comes out kinda funny. A lot of guys hear "Alpha Delta", but I also get "Delta Alpha" and "Papa Alpha" responses -- particularly from stations in europe who may be more familiar with those prefixes. At that point, the longer "America America" seems to work -- it communicates the letter as well as the country of origin.

In short, I've had this callsign for 25 years now. I've had all sorts of experience with what gets through and what doesn't. The standard ICAO phonetics don't cut it for my callsign. Pardon me if I use something a little unusual -- but it works. And isn't that what ham radio is about -- communicating?


Saturday, June 13, 2009

30th Year as an Extra

I was writing a note in reply to a ham who was upset that a certain DXpedition had posted operating frequencies that were all in the Extra and Advanced-class portions of the bands. He was worried that as a General-class licensee, he wouldn't have the opportunity to work the expedition.

Of course, he had nothing to worry about. These expeditions regularly listen for callers in the General-class portions of the bands. I did point out to him that between now and the time of the expedition, he had plenty of time to upgrade.

Then, it hit me. It has been 29 years since I took the Amateur Extra-Class exam.

Exams these days are pretty easy, compared to conditions years ago. Back in 1980, the FCC still administered the exams. For Extra class, code was 20 wpm, and you had to take a total of three written tests -- one for General, Advanced and then Extra. Plus, the exams were only given at FCC offices at major cities -- so, if you lived far away, you faced quite a road trip.

It was the end of my Freshman year at Georgia Tech. My family had come down to visit my grandparents, and take be back to West Virginia after finals. My brother, then KA8DTD, figured he might be able to schedule an upgrade exam before the week was out. Sure enough, amateur exams were available on Friday. Ben had a Conditional class license, and I was a General, having been tested at a hamfest just a year before. So, he scheduled both of us to take the Extra exam. Friday, June 13, 1980.

Neither of us was terribly worried about the code test, although I hadn't been down to the club station in weeks. I did borrow his Extra-Class Study Guide for that week, and managed to go over it in the midst of studying for and taking final exams.

Friday morning came, and our father dropped us off at the FCC examination building. We filled out paperwork and sat for the code test. I sweated it a little, but passed. Ben passed with no problems.

Then came the Advanced written examination. I figured it would be easy, since I studied for my Extra. Wrongo -- the old Advanced test was the largest of the bunch, with 50 questions, all of them tough. Only my private pilot's written exam was harder. 

We both passed the Advanced written, and so far it had been worth the trip -- we were both guaranteed an upgrade. After the Advanced, I was convinced I was going to flunk the Extra -- but the test turned out to be a lot easier -- only 40 questions, and most of them I studied for.

After sitting through three exams over several hours, I got the news. I had passed! I was an Amateur Extra class. Ben didn't fare so well -- he had missed the Extra by one question. And that was probably because I "borrowed" his study guide all week.

So, this begins my 30th year as an Amateur Extra-Class. Hard to believe it has been so long ago.

Friday, May 8, 2009

Carlisle Tires...BOOM!

Camping is fun. While tent camping has it's attractions, it's not nearly as convenient as taking an RV. With an RV, you can pack many of the conveniences of modern civilization. There are several choices with an RV. Years ago, a buddy and I invested in a camping trailer. The biggest advantage of the trailer is that once you get to the campsite, you don' t have to break camp to go somewhere, as you might do with a Class C or Motorhome.

While we sold that trailer a few years later, my family found we liked trailer camping. In 2002, we bought a new Travelstar 21SSO. It's easy to tow, light, and has plenty of room. It came with five ST175/80R13 tires made by Carlisle.

Trailer tires take a lot of abuse. They are small, and are asked to carry a lot of weight. These tires are designed to run at 50 psi cold, and the manufacturer recommends the trailer be towed with the tires inflated to that level. Even a slight under-inflation can cause tire failures.

Imagine my surprise a couple of years later when I lost two trailer tires on one trip. We were coming back from the forgotten coast of Florida, and one blew out in south Georgia. I didn't think anything of it -- I just put the spare on and continued driving home. This turned into a disaster near Byron, GA. I was watching my remaining tires in the rear-view mirror and saw one go flat. By the time I could turn off the highway 2 miles later -- the tire was completely shredded.

After losing two tires in one trip, I didn't want to repeat that experience -- so I did the most rational thing -- I called the company who sold me the trailer. I was trying to find out how I might prevent failures in the future. The dealership couldn't offer any information, other than the number of the tire manufacturer. When I called the manufacturer, before I could even ask my question, the person I was talking to told me they wouldn't give me any money. Huh?

A year later, we were headed for Florida again -- and just short of Tifton, GA, we had a tire blow out so forcefully that it broke my gray water drain valve. We immediately sought a tire store that had the right size tires. Not only did I replace the blowout, but also another tire that was showing an unusual bulge. At this point, none of the tires I was running on were Carlisle tires. I had the shop move the only remaining Carlisle tire to the spare.

Funny, I haven't lost a tire since. Last year was the final straw. I was prepping the trailer for a trip, and went to check the pressure in the spare. Now only did it not have any pressure, it would not pump up! Taking the tire cover off quickly showed why. This tire had a large crack across the tread -- which is why it didn' t hold air.

So, in six years, all five Carlisle tires failed. And the one tire, the spare, which had less than 150 total miles on it, had cracked across the tread. Today, I have three different brands of tires on my RV, and none of them have failed since they were put to use.

A couple of years ago, I asked a friend of mine who has been trailer camping for over 20 years with an A-liner how he dealt with blown trailer tires. He said in all the years he's been camping, he'd never had a tire go flat for any reason.

A co-worker of mine also bought a TravelStar 21SSO about two months after I did. He also had Carlisle tires. After three blowouts of his own, he has replaced all of them with Goodyear tires.

What conclusion can you draw from this? In my experience, Carlisle tires are defective. They clearly cannot meet the basic requirements for tires of this size. If you have any of these tires, I would strongly recommend you replace them with another brand. If you do this now, before they fail, you can shop for bargains -- rather than having to buy a tire where ever you can find one on the road.

I've had good luck with three Denman tires, even the Chinese-made SuperTrailer tires have outlasted the Carlisles.

Good tires are important on an RV. Nothing spoils a good camping trip like not being able to get there (or get home).

Wednesday, April 8, 2009

Shunt-Feeding a Short Tower on 80 and 160m

I've operated 80m since I was a Novice. With a little room in the yard, it's not hard to put up a basic 80m dipole. Getting an 80m dipole up high enough for it to be effective is not so easy.

160m is more of a challenge. A simple dipole doesn't fit in your typical yard. A quarter-wave vertical requires quite a support structure. What we need is a effective compromise antenna.

I think it was my involvement in the NAQP that got me determined to get on 160m. I had managed to make a few contacts loading whatever antennas I had and trying to call the loudest stations on the band. After I had my tower up, K9AY encouraged me to get on the ARRL 160m contest with my 80m dipole. He also suggested that I try to put up an inverted-L. I but one up for 160m with two 100 foot elevated radials. I found the 80m dipole was more effective. 

W8JI once wrote that his full-sized 160m dipoles at 300 feet were only more effective than his verticals a few percent of the time, and that was only during very unusual conditions at sunrise. The way I interpreted this was that vertical antennas can be very effective on 160m, perhaps also on 80m. What I needed was a way to put up an effective vertical antenna for 160m and 80m.

K9AY originally suggested I try to shunt feed my tower. His advice was to run a wire all the way to the top of the tower sections, then measure the impedance at the bottom, then design a matching network to match the resulting impedance. So, that's exactly what I did.

You can see the upper shunt wire mount in the photograph to the right. A piece of 1"x1" angle aluminum U-bolted to the tower provides the support for a piece of 3/4"x3/4" angle aluminum that separates two 12 gauge insulated wires. The wires are about 10 inches apart and join again another piece of 3/4"x3/4" angle aluminum fastened to a NEMA matching box at the bottom of the tower.

The shunt design has been through several iterations at my QTH. First was a single wire that was matched for 80m using an omega match. This worked ok, but I started with just seven 50-foot radials. When I added eight more, the shunt worked much more effectively.

At this point, I felt that all those radials might work on 160m, so I added an L-network that I could switch remotely with a relay. This worked until I added the A743 40m add-on kit to my Cushcraft A3S. The omega match no longer would load on 80m. 

The Mark III match used a common tapped inductor for 160 and 80m, and a relay that switched in variable capacitors for each band. I had a lot of trouble with arcing. The Mark IV is what you see below. It uses a separate L-network for each band, switched in or out with a DPDT relay. Everything is contained within a 6x6x6 NEMA box shown below, which is mounted on a 1"x1" angle aluminum U-bolted to the tower.

160m is on the left. The coil uses two stacked T200-2 cores with 42 turns of wire tapped every two turns. Capacitor is a dual-section which I measured at 15-325 pF per section. The small silver-mica capacitor has been replaced with a 4 kV 160 pF disc ceramic part. The result is about 180-800 pF of capacitance, of which I'm using about 750 pF. 

80m is on the right. Coil is 38 turns of wire tapped every two turns. Capacitor is a 13-250 pF unit that was the plate tuning capacitor on a Heathkit HW-40.

The photograph shows enameled wire, but I've since re-wound the 160m coil with insulated wire. Biggest problem is that the heating and cooling cycles of being outdoors cause the turns to rub against each other. This eventually results in arcing between the turns when RF is applied.

The matching networks aren't designed for a lot of power. The 80m network can manage about 200W, and the 160m network only 100w. Higher power networks would require beefier networks. Except for the NEMA box and angle aluminum, this was all stuff I had in the junkbox. 

Does it work? Well, I have WAS confirmed on 160m CW, with three states left to go on 80m. For DXCC, 21 confirmations on 160, and 34 confirmations on 80. Yes, this antenna works! The key to making this antenna work well are the radials. I have twenty-five 50-foot radials, plus four 100-foot radials. Or, at least, I did. Some recent septic-tank work cut several of the radials.

I plan to lay down more this summer. I put my radials straight on the ground, held close with small loops of copper wire pushed into the ground. This keeps the wire down until the grass can grow over it. Once the grass covers them, I have trouble finding the radials.

If you have a short tower, consider shunt-feeding it to get on the low bands. It's worked well for me.

Tuesday, March 31, 2009

Schematic for the Step-start

Dennis N2RIT wrote to ask me about the schematic for the Step-start circuit. Well, Dennis, it's pretty simple. I used the design posted by Rich Measures AG6K here. For the AL-80A, I used the +12 volt supply, which is about 15 volts unregulated. The coil of the relay I used is about 360 ohms, so to get the voltage about right, I used a 100 ohm dropping resistor.

I also added a 1n4148 diode across the relay coil to absorb the back EMF when the relay opens. Probably not needed, but it seemed like cheap protection. 

Friday, March 27, 2009

Step-start for the Ameritron AL-80A

For many years, I did not own an amplifier. I ran barefoot at 100 watts. You can work a lot of stations with just 100 watts. When I contest, I generally enjoy competing in the 100 watt category. But, a four years ago, I bought a used amplifier.

It had been owned by one of my fellow contest club members, K4GA. I didn't know Archie that well, aside from the e-mails we exchanged on the club reflector. After he passed away, his widow wanted his radio equipment to find a good home. I made an offer on the amplifier, and it was mine.

K4BAI later told me that this Amplifier had a bad trip to Barbados once -- it had been damaged in shipping, but had been repaired by insurance. When I got it, it needed a little TLC. The cover was on backwards, and several of the cover screws were missing. The meter switch had been replaced with one that had a shaft about an inch too long. 

I fixed the meter switch with a few minutes work with a hacksaw. I bought all new screws and put the cover on the right way. The meter reading for the high-voltage was a bit low -- this turned out to be a problem with one of the divider resistors. I had much higher-quality replacements in my junk box. That fixed, the meter for high voltage read exactly as it should. The open-frame antenna relay would sometimes leave the receiver antenna disconnected. This was easily taken care of with a little contact cleaner.

This amplifier has given good service in the last four years. I've used it pretty heavily in RTTY contests, running about 400-500 watts out. I've had only a couple of complaints.

One was the jarring THUMP that would sound when I switched the power on. It didn't happen every time, but often. All that inrush current couldn't be good for the power supply components. It didn't take long to figure out I needed a step-start circuit.

Step-start is simple. Low-value resistors are placed on the main power leads. They limit the inrush current when the unit is switched on. Once the capacitors charge to a certain point, the resistors are shorted out by a relay. For the AL-80A, this is easily accomplished with two 10-ohm 10-watt resistors. Selecting the relay was a little trickier. I found a nice 12 volt relay, an Omron G2RL-24. This is a DPDT relay with contacts that can carry 8A at 250 volts. This sealed relay was only about $3.00 from Mouser Electronics. 

I designed a simple circuit board for this project. It was also my first experience with TEC-200 film. The first
 version of the board didn't come out too well, as I tried to flood-fill to leave as much copper in place as possible. The result was pretty ugly, because all that toner didn't stick well to the board. I probably didn't have the heat setting right. I redesigned the board without the flood-fill, and I also beefed up the size of all the traces. Getting the TEC-200 film to transfer the toner with just an iron is going to take more practice, but I'm pleased with the results.

Note from the design -- I layed out this board in 2007, but I didn't get a chance to build it until recently. I will admit that I drilled some of the component holes a little large. I'll have to remember to use the smallest of my numbered drill bits next time I make a circuit board.

The one nice thing about designing your own board -- it's guaranteed to fit your parts. There's only five components on this board, and it goes together with a few minutes of soldering.

Getting the board in the AL-80A took more doing. For one thing, it is heavy. Moving it around is not easy, and must be done with great care to avoid damage to the amplifier and also to myself.

The next problem was getting in to wire the board up. The power connections are on a barrier strip that's close to the power transformer. Fortunately, one can remove the screws and unsolder a few connections and the back panel lays down flat. 

Figuring out how to connect the board was tricky. Like I said, this AL-80A had a bad trip to Barbados. The original transformer had been replaced with an AL-80BX transformer -- which also has buck/boost windings. 

I ended up hooking the board from the connections from the fuses to the barrier strip. 12 volt power from the auxiliary jack drives the relay. 

While I had the amplifier open on the workbench, I also added a glitch resistor to the B- lead from the rectifier stack. This is a 10-ohm 20-watt resistor. If the tube were to become gassy and short out, the glitch resistor will help dissipate the energy stored in the capacitor bank. I borrowed a couple of unused lands on the rectifier board in order to mount the glitch resistor.

Buttoning it all back up, then came the smoke test. Fortunately, I kept the smoke in. Step-start works great. No more loud thump.

Tuesday, March 17, 2009

The Tribander Experience

Most hams start off on HF with modest antennas. Perhaps a simple wire dipole, or maybe a trap vertical. These simple antennas can work, and often work well -- when installed at the proper height and with the appropriate number of radials, respectively.

But those starting off often don't have the experience to do things quite right. My first ham antenna was a simple 40m inverted V -- it followed the roofline of the house on 6" standoffs. The apex was all of 25 feet up -- and the ends were only a couple of dozen inches from the ground. It worked, but not well. With the 50 or so watts I coaxed out of my novice rig, it did OK. I also tried various dipoles strung between trees and buildings, random wires, even a vertical made out of a slinky.

Anyone who uses these simple antennas often dreams of something better. I thought that the guys with the tribander at 50 feet had the high-end installations.

When I bought my own house, I wanted to put up some good antennas. First was a 300 foot longwire at about 15 feet high. Fed with an L-network, it could load up on all bands -- even 160m. It did not work well. For a while, I used a "Loop Skywire" -- a 80m full wavelength loop positioned horizontally. This was about 15 feet up -- just barely higher than the longwire. It worked OK, certainly better than the longwire. But really, none of these were any better than my novice antennas.

Somewhere along the line -- I had an epiphany: for horizontal antennas, the most important single dimension was the height above ground in wavelengths. I built an 80m dipole and got it up in the trees about 45 feet high. This antenna worked great -- much better than the Loop Skywire -- and it only required two supports instead of four.

I eventually put up a beam. First was a Butternut HF4B. It was mounted on a roof tower at a height of about 35 feet (10m). Certainly not optimal for a tribander. I eventually replaced the HF4B with a Cushcraft A3S. I've written about this antenna before -- it is probably one of the best of the small trapped tribanders.

When I moved to my current QTH, I decided not to repeat the roof tower experience. It took nearly seven years before I could save up enough to put up the tower. In the meantime, I used a number of dipoles at successively higher heights, a trapped vertical (the Cushcraft R7000), and even a couple of two-element delta-loop wire beams in the attic for 15 and 10m.

During this time, I had the fortune of being able to guest op at W4AN's superstation near Dahlonegah, GA. NQ4I also invited me to come and operate at his Multi-Multi station. These stations have multiple mono-banders for each band, often at heights much greater than your typical tribander-at-50-feet, and many times stacked mono-banders to certain areas. Operating at a super-station is pretty amazing.

Moving from a simple dipole or vertical to a tribander is an eye-opening experience. With a tribander, the band opens earlier, stays open longer, you have directivity that can bring stations out of the noise or null out unwanted signals. Bands you thought were dead come alive with signals. Pileups that were too big and crowded with a dipole are easily busted with the tribander.

It's curious that going from the tribander to monobanders or even stacked monobanders isn't as dramatic as the shift from a dipole to a tribander. Using a monobander or stacks is much like the tribander, only better. It isn't a sea-change.

Not every ham can afford towers and stacks, but every ham interested in HF ought to consider putting up a modest tower with a tribander. It will make a huge difference.

Tuesday, March 3, 2009

Amateur Receivers circa 1950s

I recently read with some interest K2TQN's column about the HBR Receiver in the February issue of QST. I had never heard about this receiver until this column -- this design likely pre-dates my involvement in amateur radio by 10-15 years. 

When I got into ham radio in the early 1970s, the transceiver was beginning to come of age. In the 1960s, SSB had replaced AM as the primary mode for voice operation. Transmitters and receivers for SSB have many of the same circuits -- so it made sense to share these in a single box. Before then, most hams had separate transmitters and receivers.

Looking at the HBR receiver stage descriptions, the basic design seems foreign to our modern designs. Selectivity is provided by high-Q LC circuits in the low-frequency IF near 100 kHz. But such a low IF frequency wouldn't result in very good image rejection, so a first IF near 1700 kHz comes first. 

Now, in the 1950s and 1960s, the amateur bands were simpler. 160m was covered up with strong LORAN A signals and was virtually unusable. The 30, 17 and 12m bands hadn't been invented yet. So, most radios only needed to cover five bands. The HBR accomplishes this through plug-in coils. 

From a modern view, the lack of bandswitching and sharp IF filtering stand out. It's hard to imagine changing bands by opening up the top cover and swapping out coils -- particularly when a couple of them have potentially dangerous plate voltages on them. Perhaps a band switch was something of a luxury.

The IF filtering confuses me. My little 40m receiver has excellent IF selectivity from just four crystals. Hams in the 1950s could have built ladder filters in their receivers using crystals from 2-10 MHz. Although, I'm not sure the ladder filter design was invented until the 1970s. Perhaps the cost of the crystals was prohibitive -- crystals are often expensive, even today.

In the same issue of QST, there was a reference to an all-transistor receiver design by W2TGP. I looked up the article in the ARRL archive. It was very odd to see a rig using all PNP transistors, especially with a +12 volt supply. (The power goes to the emitters, and the collectors connect to ground -- somewhat opposite of today's convention)

Other than the use of transistors, the design is a curious mix of older and modern elements. The rig is small, so there's plenty of room for a bandswitch for five bands. Selectivity comes from a 455 kHz mechanical filter --  455 kHz is a bit low for good image rejection, so the first IF is around 2000 kHz. 

This transistor receiver likely outperformed the HBR in terms of selectivity, but the HBR likely had better dynamic range. The single-ended mixers of the 1950s can't hold a candle to even simple Gilbert-cell mixers today.


Wednesday, February 18, 2009

Campground Rule for Modifying Code

Dealing with other people's code challenges most software developers. If you program professionally, you can't avoid it. Any project of reasonable size requires multiple developers, meaning someone other than just you. Even if you only deal with your own code, it may look different to you later. At one job, I remember looking at something thinking, "who wrote this?" -- only to find in the comments that it was me, about 10 years earlier.

Code that has been in use for any length of time tends to rot. Design decisions that made a heck of a lot of sense five or ten years ago, when machines were less powerful and memory more expensive, seem silly -- perhaps wrong. As revision after revision is piled on, it tends to make a mess. Add to this the hands of a hundred programmers -- each one knowing the one true way to write code -- and a lot of code tends to become a hopeless jumble.

Worse, that hopeless jumble is tested and works. 

As Joel Spolsky explained, modifying existing code has two dangers. First, code is hard to read, and that hopeless jumble you're trying to enhance already does things that you won't understand without a lot of work. Second, the more you alter the code, the more you'll have to retest to ensure you haven't broken the existing functionality.

Now, if you are lucky enough to have a full suite of unit tests, then you can let yourself go wild and refactor with the assurance that the unit tests will catch any errors. But this is old, revised code. Even if you have unit tests, they probably are out of date or perhaps they no longer work.

One thing that I remember from Boy Scouts -- you have to have the right attitude toward camping. Ideally, you should leave a campsite without any evidence that you had been there. That's probably not possible. But our scoutmasters had  a simple for us to follow: always leave the campsite cleaner than when you arrived. 

This rule applies equally well to code. No matter how badly some bit of code has been abused in the past, you can always have it leave your hands in better shape than when it arrived. If the code needs comments, add them. As you figure out how something works or some obscure requirement that's buried in the code -- note it for future programers. 

If the code has a jumble of if-statements, and you can restructure it to be more clear, do so. If you find dead code, eliminate it. Just be ready to test it fully before you leave it for the next developer. No matter how much you temper your changes, you can always do something to improve the code for the next guy.

And if everyone did this, we'd have fewer hopeless jumbles.

Sunday, February 15, 2009

Your Novice Accent, Revisited

UPDATE 6/16/2017 - The original link for Your Novice Accident (and What to Do about It) below is now returning a 404 error. I found another reference to it here.

When I received my Novice license back in 1975, the ARRL sent me a little pamplet on the proper procedures for CW operating. It was a reprint of an article by Keith S. Williams, W6DTY from the November 1956 issue of QST: Your Novice Accent (and What to Do about It). I read it many times before I had a transmitter on the air. I'd heard some of the poor operating practices that W6DTY noted. Even in 1975, things had changed somewhat since W6DTY penned that article. Still, it was a great resource for proper operating procedures and helpful operating tips.

The Novice bands of the 1970s, 80s and early 90s were hotbeds of slow speed CW activity. Any time of the day, and most of the night, you could find QSOs in progress in the 80 and 40m Novice bands. By the 1990s, things had changed, and the code-less Technician class became the preferred entry into the hobby.

Today, the Novice bands are no longer -- and new CW operators are thrown into the mainstream, as they were in the 1940s. Although it's harder to find slow-speed QSOs on the bands to copy, and many of the operating procedures have changed. Perhaps it is time to revisit Your Novice Accent.

International Morse code is just as much a language today, although the dialect has changed. The old procedures came about from the operating practices in the 1930s, when most stations were crystal controlled. It's hard to imagine today, but a typical contact might take place between two stations who were many kHz (well, kc in those days) apart. With only a handful of crystals, hams would work across the entire band.

The Novice license originally required crystal-controlled transmitters, from the early 1950s until 1972. Most Novices in this era likely had only one or two crystals for each band. (if they were lucky)

Today's operating is almost entirely simplex -- the two stations transmit on almost exactly the same frequency. Certain types of DX and contest operation end up being split in frequency, but split is the exception.

Tune Around

W6DTY's first bit of advice -- tune around and listen. This is great advice today, but for different reasons. Of course, we no longer wait for the filaments to warm up -- solid state rigs are ready to go when switched on. We still tend not to listen much -- tuning around the band will give you an idea of what is happening. I once worked ZL4PW during a very short opening around midnight local on 30m, just from tuning around.

W6DTY advises to answer another CQ rather than adding your own. Tuning around should let you find anyone calling CQ. Given th elower activity levels on today's CW bands, often a CQ or two would be welcome -- many times the bands are open, but no one is transmitting.

If you do CQ, it's no longer expect for you to tune around many kHz for an answer. Crystal control is no longer the norm, so it is OK to expect an answer on or about your frequency. Tuning a kHz on either side of your frequency should be more than sufficient.

Calling & Answering a CQ

The form of a CQ has changed a little bit from the 1950s. While the basic three by three still applies, there's no reason to repeat this three times. Instead, the basic three by three can be interspersed with periods of listening:

CQ CQ CQ DE AA4LR AA4LR AA4LR K
... listening ...
CQ CQ CQ DE AA4LR AA4LR AA4LR K
... listening ...

Listening periods are short, just a few seconds. These short listening periods allow another station to respond without having to wait a long time.

During a contest, this process might be even more abbreviated:

CQ TEST AA4LR
... listening ...
CQ TEST AA4LR
... listening ...

Notice that we have entirely dispensed with prosigns -- the DE and K are implied.

Answering a CQ is also simplified. There's no need to repeat the CQing station's call three times. After all, he's not going to have to tune around to find you -- you should be calling close to his frequency. You still must decide how many times to send your own call. If conditions are good, once might be enough. In more marginal conditions, two or three times may be more appropriate:

AA4LR DE W1YM W1YM

(Note we've omitted the prosign AR) Quite often, operators dispense with the CQing station's call and the DE prosign altogether -- answering stations simply send their own callsign once or twice, and listen for a response.

The DE prosign is most properly used to  separate the called station's callsign from the caller's callsign. If you are just sending your own callsign, there's no reason to send DE.

Making QSOs

The structure of a beginning QSO hasn't changed in 50 years. We still send RST, QTH and Name, and pretty much in that order:

W1YM DE AA4LR R TNX FER CALL BT UR RST 579 579 IN LOGANVILLE GA LOGANVILLE GA BT NAME BILL BILL BT RIG HR ... etc

Prosigns &  Abbreviations

While many of the formal procedures have been dropped for brevity, we still use abbreviations for the same reason. The ES prosign is actually an old American Morse character for the and symbol (&).

W6DTY's advice about using the BT prosign as a separator of thoughts and ideas is still sound today, as well as avoiding the period and comma.

HW? is typically used today. I can't say that I've heard WATSA? recently.

Most operators today dispense with sending the AR before signing over. They simply sign over:

... BT HW? W1YM DE AA4LR K

The prosign KN seems to get more abuse than any other. It was all too commonly used on the Novice bands, and is much less common today. There's probably no need to use KN in ordinary QSOs. Just use K.

The prosign VA appears today as SK (it's the same prosign -- didididadidah, we just abbreviate it differently). Since the use of AR has diminished, SK more frequently appears as a substitute for K.

W6DTY's advice on the proper use of the R prosign is dead-on today. And, I have encountered a few operators who fall into the deadly silences. I hope I don't do that.

Sloppy sending is still around 50 years later. Although you do hear quite a bit of precise, computer-generated CW these days. It's a pleasure to listen to. Practicing sending before getting on the air is great advice today. Be sure you can handle the key or paddles with confidence. 

CW remains great fun, even 50 years later. There's a timeless quality about it -- it never gets old.

Saturday, January 31, 2009

My Novice Story

Seeing a link to the Novice Historical Society, I thought I would write my own Novice Story.

My start in radio was pretty conventional. If you have ever read So You Want To Be A Ham, the conventional entry in amateur radio comes after being a short-wave listener (SWL). You encounter other hams talking on the air, and eventually discover you can do more than just listen. Up until the widespread adoption of SSB, this was perhaps the most popular technique for discovering amateur radio.

I got started through my brother Ben (now NJ8J). Ben is five years older than I, and my mother always joked that I wanted to do everything he did. (And she was surprised when I often could) Christmas 1969 found us with our grandparents, and my Uncle Frank didn't know what to give us boys. He ended up getting Ben a Radio Shack Science Fair Globe Patrol receiver. This was a three transistor regenerative receiver, with AM broadcast and short wave bands. Frank, Ben and Dad built it, and my Grandfather had to step in and troubleshoot it (one reverse connected diode was enough to keep it from working).

Unfortunately for Frank, that was to be his last Christmas, he die tragically in April 1970, just short of age 25. But that little radio started something for both of us. Next Christmas, our parents bought us each Heathkit short-wave radios. Ben received a GR-64, and I a GR-81. We quickly became avid radio listeners.

The GR-81 wasn't that great on short-wave, so I initially concentrated a lot of AM broadcast DXing. (Best DX was WOAI in San Antonio, TX from Fairmont, WV) Ben took to listening to more short-wave broadcast, and he quickly found the ham bands as well. Ben had learned morse code in scouts, so he was "reading the mail" on the CW bands as well.

I had tried to learn morse, and about age 14, I had convinced myself that I was just one of those people who were incapable of mastering it. Then something amazing happened. Ben got his Novice license in February 1975. Of course, I always had to do everything he did, so naturally, I started to learn the code again. I bought and built a Heathkit HR-10B, and I began to practice by listening to W1AW and the Novice bands. By November 1975, I passed my Novice license, and was WN8WOY.

Getting licensed was one trick, actually getting on the air was another. By this time, I had realised that the HR-10B was not a great receiver for CW work -- the IF response was just too wide. Using money from my paper route, I bought a used Heathkit SB-301. The difference between the two receivers was amazing. You really could listen to just one signal -- especially after I bought the 400 Hz CW crystal filter.

The SB-301 kinda broke my budget for a few months, so it wasn't until June 1976 that I could afford a transmitter, in the form of a used Heathkit SB-401. Thus, I had the matching pair of Heathkit SB-series twins. Novices were no longer limited to crystal control, so the SB-401 wasn't a bad choice.

One problem being a Novice in those days -- you were limited to 75 watts power input to the final amplifier. The SB-401 could do about 180 watts, so I removed one tube and operated that way. During that summer, the FCC changed the rules to allow Novices up to 200 watts PEP output. Of course, I didn't find out about this until the fall. The FCC also decide to drop the distinctive Novice callsigns, so in the fall of 1976, I was now WB8WOY.

The summer of 1976, I did a fair amount of operating -- a handful of contacts every day. Mostly 40m, some 80m, and a few 15m. My antenna at first was a 40m inverted-V that was mounted on standoffs just underneath the eves of the house. The ends were within about a couple of feet of the ground, so this antenna really didn't work well. I also build a small L-network tuner for the long-wire I used for SWLing for use on 80m. It didn't work well, either. 

The Novice bands in the 1970s and even 80s were very different from today. Today, most evenings you could tune the CW bands and fail to hear more than a few CW QSOs, and none of them at slow speed. (Of course, if there's a contest or DXpedition active on a weekend, you'll hear lots of activity) Then, the Novice bands were a hotbed of activity, with slow speed QSOs going on all the time, every day.

In a year and a half on the air, before my Novice license expired, I made about 210 QSOs. That experience made a lasting impression on me. When I got my General class license in the summer of 1979, I often found myself operating in the Novice bands. 



Sunday, January 25, 2009

Three Safety Rules for Tower Work

For myself, I've adopted three rules in order to ensure the safe execution of all tower work. But, before I write about the rules, I first have to tell a sad story.

When I moved to my current QTH, there was a fellow ham nearby -- he lived less than a mile from me. Though he lived in the neighborhood near me, I never met him. I believe his name was Paul.

Paul had a modest tower and tribander, like me. At a hamfest in November, a fellow ham loaned him an MFJ antenna analyzer. Paul was quite eager to climb up and make some fine adjustments to his antennas. He asked his friend if he would come over, but it was a cool, slightly drizzly day, and his friend suggested he do it at another time. Paul couldn't wait.

So, he climbed the tower himself that day. When his wife and kids came home from shopping about three hours later, they found him at the base of the tower. Unfortunately, it was too late.

Near as anyone can figure, he tried to climb while holding the analyzer with one hand, so it wouldn't be damaged. Somewhere on the way up, he lost his grip with his other hand. Ironically, he had full safety harness, but with one hand occupied, it was too difficult to clip in to the tower.

Tower climbing is a dangerous business. I knew of Paul's accident when I built my tower, so, for myself, I made three rules:
  1. Never Climb Alone.
  2. Never Climb Except in Good Conditions.
  3. Always Take All Safety Precautions.
I borrowed the first rule from SCUBA diving. SCUBA divers know never to dive alone. Tower climbers should never climb unless they have at least a ground crew. If nothing else, a ground person can call 911 should anything bad happen. I've taught my kids from an early age how to properly act as ground crew. If nothing else, if I should fall and be hanging from the safety lanyard, I know someone will call 911 and get the emergency crews out there. I wouldn't want to be hanging there for hours until someone notices.

The second rule is pretty broad. Good conditions include the weather. I refuse to climb in rain, snow, windy, dark, or really hot or really cold conditions. Good conditions also apply to the climber. Tower work is demanding, physically exhausting. I refuse to climb when I'm tired, under the weather, or just not mentally "with it". 

The third rule should be common sense. I climb with a full safety harness. I have a fall arrest lanyard clipped into the D-ring on my back, and it is always clipped into the tower. When I'm moving the fall arrest, I have a short 3-ft rope lanyard from the D-ring to the tower. I also always use my positioning lanyard during the climb. It allows me to stop and rest at any level. 

All these precautions slow me down. I have some friends who like to free climb to the top, then they belt in. That's their prerogative -- but it's not for me. I'd rather be slow and safe than fast and sorry.

So, there you have it. Enjoy your tower, plan your climb, execute your plan, and stay safe.



Saturday, January 17, 2009

The Little Receiver That Could

A couple of years ago, when I build my "Novice" transmitter for Straight Key Night, I figured I had to have a receiver to go with it. I used my K2/100 as the receiver in 2007 and 2008, and nearly fried my K2/100 that second time when I accidentally hooked up the transmitter into the K2 instead of the antenna.  (The K2/100 front end is really tough! It survived about 12 watts of CW for about two or three minutes)

The transmitter was built using techniques typical of the early 1960's -- all tubes, except the power supply used silicon rectifiers. I figured that the companion receiver ought to be all solid-state. And not just all solid-state -- but using nothing but integrated circuits.

Well, I'm pleased to say that I almost achieved this goal. The receiver uses one transistor, but we'll get to that in a moment.

I took my design inspiration from the Norcal Sierra, as published in the 2000 ARRL Handbook. The receiver in the Sierra uses the common NE602 Mixer / Oscillator and the MC1350 IF amplifier. An LM386 provides audio amplification.

The NE602 is a very flexible and powerful part. I'm sure the receiver builders of the 50's would have loved to have a component such as this. The oscillator block is stable, and covers a wide frequency range. The mixer is fully balanced, offers some gain, although it's dynamic range leaves something to be desired by modern standards. 

The MC1350 is practically an entire IF strip in one chip. It has lots of gain, and easily applied gain control. 

Perhaps the best advice for building a receiver is to start with the power supply, then proceed to the audio stages, working your way backward to the front end. Which is exactly how I began. Power comes from a 12 volt supply, but the NE602 can only take 8 volts. An LM7808 would be perfect, except I didn't have any. I did have a bunch of LM7805s, so I used one of those, and boosted the voltage by stacking four 1N4001 rectifiers in the ground lead, giving about 7.5 volts.

Next was the LM386 audio stage-- while really popular, it can be somewhat cantankerous. Initially, it was fine, but as I added stages, it become unstable and would oscillate until I put a 10 ohm resistor and .1 uF cap to ground. 

An NE602 (I used the equivalent SA612A) is the BFO and product detector. At this point, the receiver was working great. Then comes the MC1350 IF stage. it was pretty painless as well, but for some reason, the radio was less sensitive than before. 

Turns out I had a solder blob shorting across the LM386 inputs. I wasted a lot of time figuring that out. 

At this point, I added LM324 for the AGC amplifier. I wanted to use a 8-pin chip, like the others, but all the op amps I had required dual voltages. 

By the time I finished before SKN 2008, the receiver looked as on the right. You can see a four crystal ladder filter, with matching toroids on each end. You can see the schematic evolving as I build. 

At this point, the receiver consists of a 4.915 mHz IF, product detector, amplifier, and audio-derived AGC. The tricky part is the oscillator and first mixer. Another NE602 stage brings the 40m band to the IF. At 7 MHz, the oscillator would be on 11.915 MHz. This had me a little worried. I remember as a Novice trying to build a 7 MHz VFO and having trouble keeping it stable. A few turns around a T50-2 toroid, and the receiver is on frequency and quite stable.

Tuning is accomplished with a 6 pF variable capacitor. This unit has a 8:1 reduction built in, and came out of a Heathkit SW-717. By selecting the right inductance, the oscillator tunes about 150 kHz, which means about 35 kHz per turn.

With the basic circuit going on the workbench, it was time to move everything to a nice-looking package. I had a nice painted aluminum cabinet that was perfect. It's always a bit gut-wrenching to drill into a new cabinet. The hardest part was getting the geometry of the tuning capacitor holes right, so that's where I started. 

The tuning dial is made from a brass bushing and a piece of acrylic. It fastens to the main shaft of the capacitor, the inner shaft connects to the knob. I actually had to make two of these, as the first one didn't have enough clearance to allow for the thickness of the panel.

One item I wanted for the receiver was an S-meter. I found three surplus edge-on meters in the junkbox that looked perfect. I believe they may have been decided for CBs, as the top scale has S-units, the bottom is labelled Tx Power. 

By this time, I had replaced the LM324 with the smaller LM358, but had one unused op amp -- which I used as a voltage follower on the AGC. This op amp drives the meter. 

One last detail was muting the receiver. At this point, I abandoned my restricting on using transistors. A 2N3906 PNP transistor channels 7.5 volts to the AGC input on the MC1350 when it's base is grounded through a 10 K resistor.

Here's a view of the inside. I had to make a few adjustments once I started using the rig. First problem was the AGC time constant was too long. Even with the rig muted, the receiver still responds to very strong signals -- and so acts as a sidetone for the transmitter. But the audio from this drives up the AGC and it would take a while to hear anything when going back to receive. I reduced the 10 M ohm resistor to a 3.3 M ohm, and this seemed to work well enough.

Second problem was the pitch of the audio was a bit high. Adding a bit of capacitance to the BFO oscillator moved the pitch down to around 700 Hz.

The ladder filter provides a modestly narrow response, even with three crystals. Single-signal reception is easy to achieve. Tuning is a little sensitive, but does not require too delicate a touch. Audio response is quite good and very listenable. It's not really microphonic, but if you tap the case roughly, you can hear a small change in frequency. This is likely caused by the long lead to the tuning capacitor.

Rig could still use a bit of refinement. First, it needs a speaker, and could use a stereo headphone jack. Second, I'm still hearing a bit of oscillation on really strong signals, so audio amplifier is probably being over-driven. Third, the frequency dial is currently the back of an old QSL card. This rig deserves something neater. Forth, I'd like to tweak the circuit, perhaps replacing the single-ended choke on the output of the MC1350 with a full toroid transformer stage. Last, the S-meter is a bit sensitive. It tends to go to S9 even on very modest signals. 

Funny how much fun it is to listen to the band with a receiver you've built yourself. I get a real kick out of it.






Friday, January 9, 2009

Putting Up a Tower - Antennas, Etc.


With the tower up in our previous installment, it's now time to add the antennas, feedlines and everything else that makes the tower system work.

A tall tower is a great target for lightning, so every tower system needs a protective ground. Mine has four 10 foot ground rods -- one next to the tower base, and three others fifteen feet away, all tied together with 6 gauge copper wire. 

Getting forty feet of ground rod into the ground might be a lot of work, except I built a special tool. It's a 12" steel pipe nipple with couplers on each end and a plug on one end. fifteen pounds of dumbell weights are added to the other end. Basically, it's a 15 lb sledgehammer that can't miss the end of the ground rod. I've been using this tool for years, and it works really great. 

So long as the soil has a reasonable amount of moisture, you can pound in a ground rod within a foot of the ground in less than five minutes. The last foot is taken care of with an ordinary eight pound sledgehammer. During the drought in the late 1980's, the Georgia red clay was particularly difficult to put ground rods in, but this tool could handle it.

With the ground portion in hand, let's look at preparing the antennas. I purchased a Cushcraft A3S years ago. It's one of the last tribanders designed without computer modeling. It's rugged yet lightweight, and offers reasonable performance. For a small (14 foot boom) tribander, it's probably one of the better designs available. 

It was up at my old QTH for about six years, then in my basement for five years, then up at Mike, W1YM's place while he was waiting for his Butternut Skyhawk for almost two years. At this point, it needed some help. 

I ordered replacement trap end caps from Cushcraft -- all 24 of them. With the end caps off, I blew all the debris out of the traps. I also tightened up all the sheet metal screws which secure the ends of the traps to the elements. I wrapped electrical tape around the driven-element insulator, in order to protect it from the Sun. 

As I re-assembled the elements, I chose to set the beam half-way between the CW and MID settings. I believe this is the best compromise to cover the entire band with a reasonable SWR. I got the idea from the recommendations that Steve, K7LXC made about the Cushcraft 40-2CD.

It's always a good idea to test an antenna on the ground before getting on the tower -- where it will be much harder to make adjustments. This can be done by pointing the antenna skyward with the reflector 3 or 4 feet of the ground. I used my back deck to support my antenna on a short piece of mast lashed to the deck rail.

At this time, I also added the feedline pigtail for the antenna, and the balun. Cushcraft recommends making a coil of coax feedline and taping it to the boom. While this will work, it may not be the best choice. WA2SRQ wrote a posting to the TowerTalk reflector several years ago that showed other balun designs would work much better. 

Originally, I planned to add a piece of 4 inch PVC mounted to the boom with eight turns of coax. However, I happen to stumble on some very large ferrite beads that would fit entirely over RG-213 coax. They appear to be of type 77 or similar material -- excellent for a choke balun. 

So the balun consists of ten of these beads, strung on the coax pigtail, held in position to the coax with wire ties. The coax is suspended below the boom with twisted 12 gauge solid copper wire. 

A quick test with the antenna analyzer showed the antenna SWR curves were right where the should be -- about 50-100 kHz low because of the near effects of the ground. Now it's time to put it on the tower.

Remember, this was my first tower work. While I had done all the climbing to stack the sections, I wasn' t really comfortable with the tippy top of the tower. Once you are 20 feet above the upper bracket, there' s a certain amount of sway thats rather unnerving. Fortunately, my friend Gary K9AY was close by. Gary has much more tower experience than I, and he was kind enough to install the antenna. I was on the haul line for the gin pole, but I did managed to snap this picture as the antenna goes in place. 

With the antenna on the mast, there's still much work to be done. Loosening the mast set screws the gin pole is used to move the bottom of the mast well above the rotator shelf. And then the rotator was installed. Be sure to position the antenna North to match where we left the rotator.

I routed my feedlines an rotator cable up the inside of the tower. This is much harder than just taping it to the outside of the tower, but it prevents complications if you later want to shunt-feed your tower. The cables are held to the tower alternately with electrical tape and twisted 12 gauge wire. The twisted wire is better than a wire tie, because it can be reused. It's also really cheap to salvage bits of wire out of household romex. 

Remember my rotator had a defective motor cap. One really odd thing about the Ham series of rotators is that the cap is in the control box, instead of in the rotator. I opted to place the cap near the rotator by installing it in a small NEMA box that is U-bolted to a tower leg. To allow the rotator to be removed, I used two 4-pin trailer connector sets. These are inexpensive, weatherproof and very rugged. To avoid cross connecting, I used the mostly male and mostly female ends  on each side. The trailer connectors join with the rotator cable inside the NEMA box.

So, in early September, 2001, my tower was fully operational.

Thursday, January 8, 2009

Putting Up a Tower - Erecting the Tower

In our last installment, a solid foundation for the tower had been successfully constructed. The next phase is the erection of the tower itself.

At this point, there's almost 20 feet of tower standing, but 4.5 feet of the bottom section is below the surface of the concrete, so the tower is a little more than 15 feet tall, bracketed at about 9 feet off the ground

In the picture, you can see the remaining tower sections lying on the ground, as well as the Gin pole loaned to me by Dan, W4EA.

Before erecting the tower, I had done some preliminary work. Since this was a used tower, I had fitted all the sections together on the ground to ensure they would mate properly. I also did some work on the top section.

I used the Rohn 25AG3 pointed top section. This section ends in a 2 1/4 inch inside diameter galvanized tube, which can be used to hold a mast. I wanted to make sure the rotator shelf and mast were properly aligned on the ground, so I came up with the following technique.

With the section horizontal, I fitted the mast through the top. I then mounted the rotator to the mast. The rotator is an ancient Ham-M that I found at a hamfest for $50. It needed a bit of cleanup and a new motor cap, but then it worked fine. I then mounted the AS25 rotator shelf first to the rotator, then to the tower and tightened everything down. This ensures all the parts are aligned with each other.

At this point, I used bungee cords to prop up the top section next to the standing sections and wired up the rotator for a test. The mast turned without any binding. I then removed the rotator and mast from the top section, leaving the shelf in place. Rotate to North before removing the rotator.

Before going any further, the next step is to drop the mast into the tower. This will make it much easier to later haul up inside the tower, rather than having to hoist it up and insert it down through the top section. My mast is 9 feet of 2 inch diameter, 1/4 inch aluminum tubing, donated to my project by Gary K9AY. 

Stacking sections is pretty straightforward. Hoist the gin pole near the top of the existing tower, then use the gin pole to hoist the next section in place. Bolt the sections together and repeat.

I planned for brackets at 17 feet and 25.5 feet. The top bracket is just underneath the eaves of the house. After putting the third section on, I mounted the 17 foot bracket. It is tied into the rim joist with lag bolts. This is not an optimal arrangement. The lag bolts could easily pull out of the wood -- but the 17 foot bracket is just there to help stabilize the rest of the tower from flexing, and to act as a backup should the top bracket fail.

These brackets are first mounted to the tower, then bolted to the house. This ensures proper alignment between the two. Just make sure the tower is plumb before drilling into the house.

After the 17 foot bracket was in place, I removed the bracket at the 9 foot level.  The next section is added, and it's time to mount the top bracket. 

The top bracket gets a lot better mounting treatment. I removed part of the siding so I could get directly to the top plate of the wall. I added a 2x4 to make up the missing depth. Fastening the bracket to the tower, I then used the bracket holes as a guide and drilled entirely through the top of the wall. 

Carriage bolts inserted from the inside of the wall through to the outside and secured with nuts. The ends of the bolts inside are hidden under a bit of crown moulding. 

The last section is the top section, with the rotator shelf in place. Once mounted, the gin pole is used to lift the mast to the top, and locked in place with the set-screws in the top section. Tbe tower is ready to receive antennas, so we'll get them ready next time.


Wednesday, January 7, 2009

Putting Up a Tower - Pouring the Foundation

At my last QTH, I had a tribander on a roof tower. The roof tower installation wasn't perfect -- it leaked when it rained hard. I promised myself when I moved to my current QTH 14 years ago, I would put up a real tower. I sold the roof tower and put a vertical out in the yard on an eight foot mast in the meantime.

I didn't realise but it would be seven years before I finally got that tower in the air. I really owe it to my friend Mike, W1YM. He encouraged me to put up the tower, he gave me some radio-related items before he moved to Oregon to sell to help finance the project, and he supplied lots of helpful information. 

During the construction process, I took several pictures using a Casio QV-11 digital camera. This was one of the earliest consumer digital cameras, so the image quality is pretty poor. I apologize in advance for the poor quality of the images.

The process starts with the foundation. Rohn calls for rebar in the foundation, so the first we build the rebar cage. I built mine in the basement using just a piece of stout pipe to do the bending. Here's a photo of the completed product.

To keep the cage from skewing, I added some pieces of steel wire across the face to hold it square. You can't see the in the photo but they were necessary to help the cage retain its shape.

The second step was tricky. I had to make sure that the tower was placed exactly the right distance from the house. Too close, and the tower would lean away from the house, too far, and the tower would lean toward the house. The HB25B brackets I used only have adjustment holes every couple of inches.

I thought the solution was pretty clever. First, I mounted a bracket to the house at about the 9 foot level. I held it in temporarily with lag screws into the rim joist.


I used a plumb bob to drop a line down to the ground level. I build a two foot square frame using a couple of 2x4s and then placed it on a reference line below the plumb bob. 

Voila! Perfect placement of the hole directly below the bracket.

I dug the hole out through the frame. An ordinary shovel worked at first, but after getting down about a foot, it was very hard to use. I ended up digging out most the hole using a post hole digger. Since the post hole digger only nibbled out a bit of dirt each time, it took a while, but it wasn't really difficult. A nursery shovel (the kind you use for planting saplings) turned out to be really handy in truing up the sizes of the hole.

With four and a half feet of my two foot square hole, the next step is to get everything in place. The bottom of the hole gets six inches of pea gravel -- which allows condensation to drain out of the tower legs. Then the rebar cage goes in after. I set mine on a set of small bricks, and made sure each side was at least three inches from the side of the hole. You don't want moisture to leach into the concrete and rust out the rebar.

Last bit to go into the hole was the tower itself. I dropped two sections in, and then fastened to the house bracket mounted earlier. I built a small wooden fixture to hold a plumb bob line in the center of the tower. On a calm day, it's pretty easy to get the tower in line with the plumb line. Rohn only specifies the tower be vertical to within 1 degree, which is readily accomplished.

Some additional wire holds the cage to the tower sections -- so that nothing will try to move around while pouring concrete.

If you look closely, you'll note one more ingredient -- a DX QSL card, which is used to ensure good performance of the antennas attached to the tower.

OK, it's time to pour!

I rented an electric mixer from Home Depot. This puppy could hold two 80 lb bags of concrete mix at once. It was tough to get it to pour into the hole, but a stout piece of plywood helped.

Each bag of mix requires a bit less than a gallon of water. I used a knife to cut the top off a gallon milk jug. When filled up, it was the perfect amount of water per bag. 





The process for the pour went like this:
  1. Pour one jug of water into the mixer. This prevent the first bag of dry mix from sticking to the sides of the mixer like, well, concrete. 
  2. Put each bag of mix into the mixer. 
  3. Start the mixer. 
  4. Add another jug of water.
  5. Mix for about two minutes.
  6. Pour mix into hole.
  7. Repeat
So, you may be wondering -- when did he have time to measure another jug of water between steps 1 and 4? Well I cheated. I had a bit of help -- my eldest daughter, who happened to be seven years old at the time.

The job of filling the jug fell to her, and she was quite adept at it. We mixed 28 bags of concrete in a bit under 2 hours.

With the pour complete, it took seven days to reach 90% strength, so we had to wait for the next part -- and so will you.

Monday, January 5, 2009

Alas, Macworld, we hardly knew ye....

Well, tomorrow brings the last keynote of what is most likely the last Macworld of any import. Of course, IDG may well try to host Macworld without Apple next year. We all know how well that worked in Boston.

In any case, I don't think that trade shows really matter much any more. Back in the early days of microcomputers (back when we still called them that), trade shows were a pretty effective way to generate some buzz about your new product. The first Macworld was incredibly well attended. I worked the booth for my employer -- I was scheduled for two hours on, and one hour off alternating through the day, but the reality was that I worked seven and a half hours for three days straight. My feet hurt just thinking about it. (And this was back when we wore suits and wingtips at trade shows, too)

Today, one can generate quite a bit of buzz about a new product or service just by making a press release and a couple of Twitter tweets. The internet has us so interconnected that it's just not hard to communicate.

Of course, the other thing about trade shows is that they had gotten so big that your message was getting diluted. Consider what might have happened if Apple had introduced the iPhone and CES instead of Macworld. 

Chuq Von Rospach noted that Macworld caused all kinds of problems for Apple -- from people working through the holidays to messing with the delivery schedule for products. The real truth is that Apple has outgrown Macworld. Apple can generate buzz any time, just by calling a press event -- or perhaps by not calling one. That always gets the rumour mills hopping.

Apple will still have their annual WWDC as a platform for regular announcements. It's curious to me that Microsoft hasn't copied this idea. Sure, they have PDC -- but they only call for a conference when they feel there's some release of note. If they were smart, they do it every year. 

Sunday, January 4, 2009

Saturn S-Series: I Love Mine

Back in 1994, I decided I needed to buy a car. With a new baby, I needed a four-door automobile. At the time, I was driving a 1985 Honda Accord Hatchback.It wasn't a bad car, but it got horrible gas mileage. Unusual for a Honda, you say. Well, there were reasons for this.

The original Honda CVCC engine had a carburetor. As the emission standards changed from year to year, they kept adding more devices in order to meet the standards. I once worked on a 1982 Honda Prelude. This engine had about 7 vacuum hoses. By comparison, my 1985 had 70 vacuum hoses. And when those devices were not working correctly -- the engine wouldn't quite run correctly. Honda fixed this problem in 1986, when all their cars switched to electronic fuel injection. Not so for my little hatchback.

One hot July day, the Honda finally gave up the ghost with a cracked block. At the time the Saturn S-series was pretty new, and I went to look at them. I test drove an SL1 automatic that I really liked. I also went and test drove a Honda Civic Wagon. It wasn't as nice as the Saturn, but the dealership quoted me over $4,000 more. Heck, for that price, I'd buy the Saturn. So, I did.

I drove that car like crazy for the next nine and a half years. In that time, I put 144,000 miles on it. It was a great car. Never left me stranded, got great gas mileage -- and all on very little maintenance. It was a tough little car. OK, so at 144,000 miles, it burned a bit of oil -- you generally had to put in a half quart at each fill-up. This worried my wife, so, on her advice, we traded it in on another car.

The Saturn S-series really was a different kind of car. It was a great experiment by GM -- new design, new technology, new sales team. Sadly, though, the experiment didn't pan out, and now Saturn is just another label GM sticks on platform cars designed by other divisions.

Recently, when gas prices were over $4.00 a gallon, I bought another Saturn -- an 1995 SC1 manual. Unlike my 1994 SL1, it actually has cup holders. I'm amazed at how much I enjoy driving it. This is not a sports car, or a hot rod. It's basic automobile. Plus, getting about 30+ mpg doesn't hurt, either, even with gas prices down to a more reasonable level.

Too bad GM no longer builds the Saturn S-series. With more cars likes this, perhaps GM wouldn't be needing a bailout.