Monday, December 23, 2013

Audio Games

Recently, I was trying to explain amateur radio contesting to a non-ham friend. "You know what video games are, right?" She gave me a cold look, as if to say, of course I know what video games are. "Video games," I continued, "are games you play with your eyes and fingers. Contesting is a game you play with your ears and fingers."

In a nutshell, that's pretty much it. Described that way, however, doesn't tell you a whole lot. Video games described this way doesn't tell you much, either. The reality is that every game worth playing has strategy.

To understand radio contesting, you have to understand the nature of radio. Most contests take place in what we call the "short-wave" or HF (High Frequency) bands. There are six bands in this spectrum, all identified by their (approximate) wavelength.

160, 80 and 40 meters are basically night-time bands. Ever notice that you can't hear far-away AM broadcast stations during the day, but you can at night? That's exactly how 160m is -- open during the darkness hours only. 80m and 40m are the same way, but are open a bit longer before dusk and after dawn.

10 and 15 meters open during the daylight hours, and possibly shortly after dusk -- just the opposite of 160, 80 and 40 meters. During sunspot minima, 10 meters may not open at all, and even 15 meters can be lackadaisical. 20 meters rounds out the bunch. It's mostly a daylight band, but during sunspot maxima can be open round the clock.

The basic idea of a contest is to make as many contacts (what hams call a QSO or "Q") in a defined period of time. Each contact involves the exchange of call signs ( unique identifiers assigned to each station by their governing agency ) and one or more other pieces of information. Typically, it's pretty simple - like a signal report and a state, province, country or zone identifier, maybe a name.

A game isn't fun if you don't keep score. Most contests use a two-factor scoring method. First, you get a certain number of points per contact, depending on the contest. You can't contact the same station more than once, or at least once per band. Those duplicate contacts don't count for any points.

Next, each contest defines a set of geographic areas that count as "multipliers." These could be states, provinces, ARRL sections, ARRL DXCC entities, or zones. In some contests, the multipliers count for each band.

The final score, then, is the number of contact points times the number of multipliers. As you can see, it's important to have a large number of both contacts and multipliers (or "mults") in order to make a high score.

There are two ways to make contacts in a contest. You can call CQ -- for the old morse-code pro-sign for soliciting for contacts -- and get people to call you. This is called "running." The alternative is to tune the band and look for others calling CQ. This is called Search and Pounce, or "S & P." Generally, you can make a lot more contact points running than you can doing S & P, provided you can attract people to call you. The disadvantage of running is that you may miss some rarer mults who are also running. The best contesters use a mixture of both techniques - periods of running punctuated with S & P.

Add to this mix the need to get multipliers on multiple bands, the varying propagation during the day, night, by season of year and the 11-year sunspot cycle, plus the unpredictable nature of the sun, and you have the recipe for a big challenge.

Plus, a contest can really help build your confirmation totals in pursuit of any number of awards -- like ARRL Worked All States, ARRL DX Century Club, CQ Worked All Zones, CQ WPX as well as others.

There's something satisfying to calling CQ and running a rate of 100 contacts per hour for even a few minutes, or to tune across a band at an oddball time and be the only one to catch a rare multiplier. You can run the same contest a dozen times and never experience the same situation. It never grows old.

Wednesday, November 13, 2013

160m / 80m / 40m Inverted-L

Can you see it? I can't either. The black wire in the middle
ascends into the tree, but the traps are virtually invisible

The 160m Inverted-L went up nearly a year ago. Six months ago, I added a trap for 80m, making it an 160m / 80m Inverted-L. At that time, it seemed like a good idea to add a 40m trap. It's taken me a few months to do this.

I used CocoaNEC 2.0 to model the trapped inverted-L. With multiple traps, there's lots of interaction in the antenna segment lengths. More than you'd think, since the trap resonant frequencies are well outside the operating frequencies of the antenna. This means that the trap impedance, while high, doesn't completely cut off the flow of current in the rest of the antenna. This means the 160m segment length affects 40 and 80m and vice versa.

My model showed the 40m segment would be about 32.5 feet, the segment between traps would be about 3.6 feet and the rest of the antenna would be about 69 feet. The problem with this model is that it uses NEC 2 -- which assumes a perfect ground, so the real antenna different. My approach was to insert the 40m trap at about 34 feet, and then slowly trim to a resonance in the band. Then I'd trim the segment between traps, and finally the 160m segment.

Comparison of 40m (left) and 80m (right) traps. Note the
turns on the 40m trap are a bit loose
40m trap was built for 6.7 MHz. This required about 7 turns of wire on my 3" schedule 20 PVC pipe form and a 100 pF capacitor.  Same technique was used to trim the trap -- the Heathkit gate-dip oscillator.

Trap went in at 34' and after three trims it was a 29' 7". A couple of trips and the 80m segment was 7' 4" long. Everything looked good.

Note that the between traps segment is considerably longer than the model. Could very well be the traps I built are not exactly the same as what I modeled, in addition to the lossy ground effects. I think the modeling work is useful, though, because it has gotten me in the ballpark.

Another view. 40m trap uses 100 pF, 80m trap uses 200 pF.
Last trip was 4 feet off the 160m segment, for a total of 63'. Hmm. 40m is now resonating just above the band. Drat.

I'm not sure if maybe the turns on the trap may have loosened when I raised it last, or if the 160m trim caused the shift. I ran out of daylight to test it. However, the antenna still works pretty well. I've been running this antenna on all bands through the KAT3 antenna tuner, and it is pretty effective on the designed bands, as well as on 30, 17, 12, 10 and 6m. It works ok on 20 and 15m, but I always feel I'm competing with tribanders and other beams there.

Hasn't been a whole lot of activity on 80m this fall -- I think part of it is because everyone is enjoying the conditions on 10 and 12m. Hope to see more activity as the nights lengthen, so I can work some more DXCC entities there. I also want to try this puppy in the ARRL 160m contest.

This antenna really worked well during SS CW. I used it on all bands through a tuner. Although, for domestic contests, the 80/40m dipole works much better.

Tuesday, September 17, 2013

Wayne Green, W2NSD/1, SK

I learned with some sadness today that Wayne Green passed away this weekend. He was 91. If you are new to amateur radio, you may not have heard of Wayne. He definitely made his mark.

Wayne was a pioneer. In the late 40s, he was an engineer at a television station, and he got into Radio Teletype (RTTY). Back in those days, this mean maintaining very noisy electromechanical monstrosities. Somewhere along the line, he started publishing a newsletter for other RTTY enthusiasts, eventually being hired by CQ Magazine. By the mid-50s, he was the editor of that publication, at least until he had a falling out with the publisher.

So, he started publishing his own amateur radio magazine: 73 Magazine. His initial goal was to get hams building equipment again. He focused on well-written, easy to construct articles. He must have done something right, because 73 continued publication until 2003.

Wayne was well known for his long, rambling editorials, his strong, sometimes bizarre opinions on just about any topic, and his irascible nature.

I've told my novice story, but I neglected to mention the part that Wayne had in it. My brother, NJ8J, started receiving 73 magazine in 1971 or 72. A couple of years later, I began reading these as well, whenever I could sneak them away from my brother. Back in those days, we would both read the print off the page -- absorbing every word. Christmas 1974, my brother gave me my own subscription to 73, starting with the January 1975 issue. (That way, he could read my copies, instead of me stealing his)

I learned virtually everything I knew about amateur radio back then from 73 or from the 1975 ARRL Handbook. I remember visiting the shack of a ham in Grafton, WV in the fall of 1974. Sadly, I don't remember his name or call. He let me make a few contacts on his Swan 500 -- one of the fellows asked me what I was interested in doing if I got licensed. I replied that I was interested in playing with Slow-Scan Television (SSTV). I knew a little bit about SSTV, because Wayne kept publishing articles about it. To date, though, I've never operated SSTV. (Although I did pick up a homebrew SSTV receiver -- replete with P7 phosphor tube -- for a song at a hamfest some 15 years ago. Perhaps another article)

Wayne Green was a visionary. After the Altair 8800 became available in the fall of 1974, Wayne set about creating a magazine for computer hobbyists. He founded Byte magazine. Unfortunately, his ex-wife and business partner made off with the magazine in the fall of 1975. Wayne responded by adding  the I/O section to 73 with the February 1976 issue. Then, he started a competing magazine, initially called Kilobyte, renamed to Kilobaud before the first issue in 1977.

Those articles in the I/O section convinced me to check out these newfangled microcomputers. In the fall of 1977, I used my paper route money to purchase a SWTPc 6800 computer system and CT-64 terminal. Those kits got me started with computers, which lead me to my current career. I have Wayne to thank for that.

73 was a thick publication in the late 70s and early 80s, with some issues closing on 400 pages. Five years later, it was much smaller, as Wayne was focused on the other computing-related publications in his small empire. Around 1984, he sold the entire lot to IDG, which was nearly a disaster for 73. A year later, he bought back the remnants of that magazine from IDG, and continued publishing until 2003. I'm still a mad at him for that -- I renewed my subscription that year for three years, only got seven issues and never got a refund.

I can't stay mad, though. I owe a lot of my interest in technology to the encouraging words Wayne wrote in his editorials so many years ago. Part of that spirit will always stay with me.

Rest in Peace, Wayne.

Saturday, August 31, 2013

The Pursuit of 5BDXCC

I really can't call myself a DXer. I know too many guys who have made the Honor Roll. Those guys are the real DXers.

When I was a Novice back in the mid-70s, I always thought I would get WAS, then move on to DXCC. I found collecting the cards for these awards to be something of a tiresome chore. Ten years later, I slowly got into contesting -- which meant I made a lot more contacts, but getting the QSLs was still a chore.

Then something happened -- the ARRL opened up the Logbook of the World (LotW). Suddenly, getting the confirmations as no longer a tedious chore -- simply upload your contacts and wait for the confirmations to roll in.

I first focused on earning 5BWAS, and I eventually did win that award. I also earned DXCC mixed, CW, Phone and 20 and 15m. Today, I'm sitting on enough credits for 40m, 10m and Digital DXCC. This means I have four of the five bands completed for 5BDXCC.

That leaves 80m. Today, I have 70/71 on that band, which means I need 30 more confirmations for DXCC. 80m is a tough band for working DX. Noise levels in the summertime generally limit DX work on 80m to the winter months. I've been thinking about this most of the summer. My plan is manifold.

I've already gotten the antenna ready. Based on my limited use this summer, it seems to play fairly well on 80m. I also have a K9AY loop I need to get set up. Currently, it has a very simple rotating knob, but I have an idea for a push-button controller. Need to get that going in the next month.

I've also contemplated moving the amplifier from the Gwinnett QTH to Floyd County. As it stands, I can't use the amplifier with the shunt-fed tower. Biggest issue is determining where to plug it in, as it is wired for 240 volt power.

But, the most important thing is to be on the air. My plan is to try and be on 80m in the evening several times a week. You have to be there when the DX is. There are often europeans on the air just after darkness comes locally, and there are several european countries I still need on 80m. Some of them ought to be easy to work.

The goal is to bag 30 countries on 80m this winter season, and maybe work a few on 160m as well. (I have 30/31 confirmed there). Wish me luck.

Friday, August 2, 2013

The Elecraft K3 is a Joy on RTTY

K3 - Right in the operating position
I built the K3 just after Christmas. Since then, it has been a joy to operate in many ways. Having just completed my third RTTY contest this year, I'm especially pleased with how it operates on RTTY.

Although I operated packet radio back in the 1980s, I never got a make a RTTY contact until 2005 - using my Elecraft K2. I built an audio interface using a couple of audio transformers and some resistors.

In many ways, the K2 is a great radio. Gary Breed K9AY told me that the K2 was, "a simple radio, superbly executed." While I do enjoy the K2, it is not at it's best running RTTY or any other digital mode. It suffers several limitations:
  • Duty Cycle - The K2 is designed for a 50% or less duty cycle - CW or SSB. Without supplemental cooling, you can't run the K2/100 much more than about 25-30 watts. I added a small fan on top of my K2, and could safely run 50-75 watts of RTTY without overheating. The K3, of course, is a 100% duty cycle rig - no problem running 100 watts for hours. The case doesn't even get warm.
  • Tuning Rate - Because of it's design, the K2 tunes in roughly 9 Hz steps. While the display shows the nearest 10 Hz at all times, the firmware selects the closest tuning point. As you turn the dial, it's not entirely smooth, sometimes jumping twice as far. With the finicky tuning of RTTY signals, you'll notice this.
  • Frequency Readout - I put this one in my K2 Wish List. The K2 frequency doesn't account for the mark frequency, and thus reads 1-2 kHz high, depending on what audio tones you are using. While some contest software can compensate for this, the K3 works correctly by showing the mark frequency on the display.
  • Variable Transmitter Gain per Band - this is the most annoying thing about using the K2 on RTTY. Because of the way the K2 transmitter gain control system works, you have to adjust your audio levels on each band -- very high levels on the higher frequencies, and extremely low levels on the lower bands. Every time you change bands, you must adjust the transmit audio level. Every time. The K3, on the other hand, calibrates itself so that it has the same gain on every band. 
But the best part isn't that the K3 can run flat out 100 watts, tune smoothly, display the right frequency, or make it so you don't have to mess with the transmit audio level in the middle of the contest. These other features of the K3 really enhance RTTY operation:
  • Variable-Bandwidth IF - My K2 is programmed with a variety of bandwidths for RTTY: 1000 Hz, 500 Hz, and 300 Hz. But this isn't nearly as convenient as being able to select any bandwidth from 100-4000 Hz. On a quiet band, a bandwidth from 600-800 Hz works well. When the QRM gets tough, pulling down to 300 Hz puts it in its place. The K3 allows you to pick exactly the right bandwidth for the situation.
  • Dual Passband - RTTY contests can get downright ugly. Sometimes strong stations are interlaced on top of one another, so the mark or space frequency of one station is right between the tones of another station. This situation does no good for anyone, as it makes it nearly impossible to copy either station. I'm convinced that this is largely due to the over-use of  dual passband filtering. This type of filter puts a huge notch between the mark and space tones. It's not useful for S & P work, because if you are slightly off frequency, you won't hear stations. And, it's not terribly useful for calling CQ, either, since someone can easily move in between your tones and you won't hear them. However, every once in a while, this filter makes the difference between completing a QSO and losing one to the QRM. Just don't use it all the time, OK?
  • Fine Tuning - While the K3 tunes in perfect 10 Hz steps, you can select fine tuning mode with 1 Hz steps. I used this all the time as default for CW and RTTY and move it. It makes tuning across the band take longer, but it's easy enough to switch to 10 Hz steps when you need to.
So, every time I changed bands, tweaked out QRM with the filter or passband tuning, marveling at how cool the rig is running pumping out 100 watts hour after hour or just simply tuned stations in -- I'm consumed with joy over this fine radio. Definitely worth it.

Tuesday, July 16, 2013

My On-Again, Off-Again Relationship with Cocoa

My personal logging program.
It's been a long time ago, but I did Mac development when it was new. I started in August 1984, which was pretty much on the ground floor. My employer switched me back and forth between Mac and DOS, and later Windows development. I really loved doing Mac development in those days. But, in 1994, they abruptly ended all Mac work and later that year filed Chapter 11. I left the company about six months later.

I found another job that was part-Mac, part-Windows. That lasted until they laid me off in 2002, just after WWDC. Those were pretty dark times to be a Mac developer. The Windows hegemony was nearly complete -- with over 90% of personal computers running Microsoft's operating system.

Apple tried very hard to get developers ramped up on Mac OS X. Although you could certainly port over a classic MacOS application using Carbon, the writing was on the wall. Cocoa was the future. At WWDC 2001, Apple seeded every developer with the book Learning Cocoa with Objective-C by Davidson. And in 2002, again with Building Cocoa Applications by Garfinkel and Mahoney. I'm sure these tomes jumpstarted many developers.

I tried. I worked nearly all the problems in both books. In those days, there was no Xcode, just Project Builder and Interface Builder. And they were pretty klunky compared to Metrowerks CodeWarrior. But I only had one machine that could run Mac OS X in those days. I was still fooling around with CodeWarrior and PowerPlant. At least, until I got laid off.

The best I could do at the time was a job that was solely Windows. I figured I'd take it as a bridge job, and here I am still at it ten years later. But, that's another story.

I still love the Mac. My whole family uses Macs. I use mine each day. 

Back in the fall of 2003, I started uploading all my logbooks to Logbook of the World (LotW). All my electronic contest logs were pretty easy, even one Field Day log that had a corrupt binary file was eventually rescued and uploaded. 

The hardest part was entering all the hand-written logs. Some time in 2005, I finished this job. While my contest contacts were in electronic form, I was still hand-writing my casual contacts. By spring of 2006, it was time to give the hand-written logbooks the heave-ho. 

I decided I wanted a Mac program. So, I set about to write one. Back to those Cocoa books again. I wrote a very simple program designed to replace the paper log and not much else. You can see a screen image of it above.

With that immediate problem solved, it seems like I forgot what I learned. A couple of years later, when the iPhone SDK came out, one of the best ways to learn Cocoa was the Aaron Hillegass book, Cocoa Programming for Mac OS X. I managed to get one the earliest copies of the third edition, and was again working my way through a Cocoa book.

But, life intervened, and I never did quite finish all the problems. I've since gotten a couple of other books on iOS programming (and I still need to work my way through those, too). What amazes me is how quickly these books go out of date. They try to hand-hold you through every step in using XCode -- except that XCode has likely changed since the book was printed.

All this came to a head recently a work when another team asked me to put together a presentation on how to get started with iOS programming. This team had an iOS application that was developed by an outside consultant, and they needed to take over development.

Well, despite the absence of recent experience, I manage to put together a pretty good introduction. It was heavy on the things I understood well, such as Objective-C, Interface Builder and many of the design patterns used in Cocoa. If anything was lacking, it was details on the classes in the Cocoa Touch framework. But I felt like I gave them the tools to figure it out.

I've used a number of different object-oriented frameworks over the years, MacApp 2 and 3, TCL, PowerPlant, and even a smattering of MFC before tackling Cocoa. Like any framework, understanding really comes from experience -- the more you use the framework, the better your understanding will be.

Now, where is that book...?

Wednesday, May 29, 2013

The Reason I Hate Windows

It was going to be a typical casual contest weekend. I had the new 160/80m Inverted L ready to go. I had hoped to work a few more countries on 80m for DXCC, as I inch ever closer to 5BDXCC. My employer even let us out a little early, so I should have plenty of time to get everything set up. Right?


It seemed simple enough. Just crank up the Acer and set the N1MM software for the WPX CW contest.   The Acer started ok, but for some reason, the N1MM software would not run. Strange, it ran just fine last time I tried it. Well, that's ok, the copy I have is a few months out of date anyway, I ought to update the software to the latest before the contest.

So, uninstall N1MM, go out to the site, grab the base (2011) installer, install it, then install the latest build. Try running. Oh, it says it has to reboot before you can run. Go to reboot - the Acer waits a long time at Logging Out....

And it was about time to go off to marital arts class, so I just left the computer Logging Out.... I figured it would be done by the time I got back, and maybe I would finish the setup then. But, after three hours of class, I was pretty beat and figured I would tackle that job in the morning.

So, around 1300z, I hop out to the shack and crank up the Acer -- and it is STILL Logging Out.... Well, it spent so long trying to log out that the computer went to sleep. I'm out of patience at this point. So, I pull the battery, and unplug the power, and poof, it is ready to reboot.

Turns out, the reason it was taking forever to log out was because it was installing updates. You see, somewhere in the infinite wisdom of the Windows designers, they decided that the best time to install updates was when you were trying to log out of the computer. It obviously never occurred to them that you might want to log out only to log back in on some other account, or perhaps just reboot the machine so some software you just installed would work. No. You say you are done using that account, and it's time for Windows to take over and install the almighty updates.

Oh, and if you happen to bypass that by yanking the power and rebooting the machine, Windows takes care of that by installing the updates when you boot up. But, at least during the boot-up phase, it gives you progress information as to what it is doing, rather than simply saying it is Logging Out....

Half an hour later, it finally finished the update process, and I could successfully run N1MM. Set it up for the WPX CW contest and....

It can't talk to the K3.

OK. It was working just fine back in March -- what changed? Well, nothing, really -- except I had just installed an upgraded copy of N1MM. The Elecraft K3 Utility has no trouble talking to the K3 at all through that same port. Hmm. Maybe I should go back to the old version that was working, except when it didn't work for some weird reason.

So, uninstall N1MM, go out to the site, grab the base (2011) installer, install it, then install the latest build. Go to reboot - the Acer waits a long time at Logging Out.... Hey, I just installed all those updates! Pop battery, pull plug, restart. OK, there's just a handful of updates, should only take a few minutes.

And, once Windows had finished updating AGAIN, run N1MM and.... It can't talk to the K3. Looking more closely, it is repeatedly reporting 8020 errors. A bit of searching the internet, and this appears to be a problem related to the serial port drivers. Seems some USB serial port drivers work fine with other applications (and the Elecraft K3 Utility had no trouble talking tot he K3)

So -- what changed? Looking at the Plugable site, the latest driver is v1.8, and that's exactly what's installed. However, from my work back in January, I remember a different version -- v1.7. Maybe that's what happened -- one of those many updates must have updated the serial port driver in a way that's no longer compatible with Visual Basic.

Easily fixed, right? Just install the old driver. Well, first you have to FIND the old driver. Unfortunately, I did not make a copy of it when I installed it in January. Fortunately, after about 15 minutes of searches, I did find a copy of v1.7. Uninstall, reinstall, and pray that plug-and-play doesn't just go update it all anyway.

Behold, start up N1MM and -- it can talk to the K3! It's now almost 1500z, I've wasted two hours of contesting time fighting with the stupid computer over what was, in reality, a dependency of the N1MM software on a serial communications driver that hasn't been supported by Microsoft for five years now. (All Visual Basic support ended in March 2008)

I need to wean myself off Windows software. If only there were decent contesting software for the Mac. Hmm.

Tuesday, May 28, 2013

160m / 80m Inverted L

Just left and below center you can see the trap hung up on
a branch at around 42 feet.
From the minute I put up the 160m Inverted L, I had planned to add a trap for 80m. First, however, came more radials. With the original four 125 foot radials, the antenna seemed rather quiet, and that should have been a sure sign it was too lossy.

Adding four more 125 foot radials made a big difference. Noise level went up, along with the performance. Eight more 62.5 foot radials followed, for a total of sixteen - eight long and eight short ones. For any antenna with ground-mounted radials, sixteen should be considered the minimal number of radials. At least, for any antenna not mounted near salt-water.

I used this antenna to work and confirm two new countries on 80m phone in the WPX Phone contest. 

OK, so radials are easy. Not cheap, since a 500 foot spool goes for $45 these days. The next step was to add an 80m trap. The easy way to do this is to simply create a resonant trap on the operating frequency and stick it into the antenna by trial and error.

80m trap wound and set up for
trimming, Note the temporary solder
connections with the capacitors.
However, that's not the most efficient. W8JI wrote an excellent article about making efficient trap antennas. Two important lessons from this article: traps work best when they are made from very high-Q components, traps should never be resonant at the operating frequency. 

With my previous 80/40m trap antenna, I had followed half of this advice -- but still used coaxial traps. W8JI found that these traps are much more lossy than those made with discrete components.

And since wire is so expensive, trial and error isn't the best way either. The tricky part about using traps that are not resonant at the operating frequency is that some antenna current flows in all parts of the antenna at all frequencies. This means adjusting one part of the antenna affects the resonance at all frequencies. And while a trap at resonance offers an effectively infinite impedance regardless of the actual values of capacitance or inductance -- off-resonance impedance is definitely affected by the choice of capacitance and inductance.

So, how does one figure out all these variables? Antenna modeling! I used CocoaNEC, developed by Kok Chen W7AY. While it is pretty easy to use the spreadsheet model for very simple wire antennas, I ran into some bugs trying to model trap antennas. After e-mailing Chen, I discovered that Chen recommends the NC interface (a C-like programming language) for modeling, rather than the spreadsheet.

Once I figured out the NC interface, I started to get better results. Then the virtual trial and error part began. Lots of programming, running and bug-fixing later, I had a pretty good idea what was needed to build this antenna.

I found some 100 pF 15 kV ceramic disc caps from Mouser, and used two of them for 200 pF. I used a piece of 3 inch schedule 20 PVC for the coil form. I computed that it would take about eleven and a half turns on this form of close-wound 14 gauge THHN wire. THHN is really designed for house wiring inside a conduit, but it is relatively cheap and easily obtained at your local home improvement store. The wire is secured to the form by drilling 1/8 inch holes through the PVC.

Proper technique for measuring trap
resonant frequency. Note wooden work
surface and nothing metallic nearby.
Unless you have a vector impedance analyzer (and who does?), the easiest way to see if you trap is even close to the right frequency is to use a Grid/Gate/Emitter dip oscillator. Mine is a Heathkit HD-1250. I found it at a hamfest years ago for about $30 including all the coils and carry case. It was modified to add a switch to test the battery condition on the meter, and whoever did the mod did a great job. Only two things wrong with this unit: the lettering around the meter has completely rubbed away, and the foam inside the case to hold the coils down completely disintegrated. (I have never seen a HD-1250 carry case where the foam has held up)

Once you have your trap built, careful technique is necessary to measure the frequency. The coil end of the dip oscillator couples to the trap. Couple too closely, and the trap will pull the oscillator, and it will be difficult to find the exactly frequency. Couple too loosely, and you won't find the dip at all.

I set my trap on a wooden workbench and cleared away everything metal for at least 12 inches around. First, couple the coils very closely to be sure you can find a dip in the meter indications somewhere close to what is expected. Then slowly move the meter away for less and less coupling. The best spot is where you get a good meter indication, but it doesn't pull the oscillator too much -- which you can see as you tune across the dip. From the photo, you can see that the best spot was found with the dip oscillator coil just outside the trap form.

Great -- so you've got a good dip on the meter with the right amount of coupling. What frequency are you on? Good question. Unless your dip oscillator has an output for a frequency counter (another useful mod), the easiest is just to spot the oscillator frequency in a nearby receiver. In reality, the exact frequency of the trap doesn't matter so much, so the dip oscillator dial is probably good enough.

Completed trap ready to install.
I modelled my traps at 3450 kHz, but the trap I built was resonant at around 3350 kHz, which I deemed close enough. I drilled a four more 1/8 inch holes for securing the antenna wire to the trap.

With the trap ready, it's time to install the trap into the antenna. My model told me that the trap should go around 47 and 1/3 feet above the feedpoint. I started at 48 feet and used an MFJ-259 antenna analyzer to spot lowest SWR. About three trims later, I have 44 feet to the trap bringing the low SWR just below 3800 kHz.

Completed trap temporary installed for trimming. No solder
used on the connections yet, just twisted together. Note
how the antenna wire (black) is looped up and back down
the trap. This will hold it securely in place.
The modeling work told me that the 80m frequency wasn't affected terribly by changes to length of the upper portion of the antenna. I did a couple of quick calculations on my phone and cut the upper portion to 67 feet. Low SWR came right in at 1830 kHz. Perfect. 

Using the analyzer, the actual antenna measurements don't exactly match the model. For one thing, the NEC 2 model software assumes perfect grounds, and the actual ground is a bit more lossy. The model shows very sharp resonances, but the antenna measures more broadly -- indicating expected ground losses. 

Using NEC 4 would allow more realistic ground models, but I didn't feel like it was worth the $300 to get a license to it. In any case, the modeling did exactly what I expected -- it guided me to produce a workable antenna design in the field.

How does it play? Works pretty well on 160m still, and I used it in the WPX CW to work another new country on 80m with 100 watts. Of course, it's not the right season for low band work right now, but I think this antenna has promise for next fall.

Of course, I could slip in another trap for 40m. Hmm. Let's fire up that antenna modeling software....

Sunday, April 21, 2013

Hamfest Special - $25 Oscilloscope

B & K Precision Model 1442 Oscilliscope
To paraphrase Forrest Gump, "life is like a hamfest, you never know what you are going to get." It's true. I've been to many hamfests, and even when I have a pocket full of money, I never know what I'm going to walk away with. Sometimes, I barely spend much more than the price of admission, and other times I miss out one some good deals because I just don't have the cash.

Perhaps that's what keeps me coming back over and over -- you never know when you are going to find that great deal.

The Dalton hamfest wasn't as big as last year -- no doubt the drizzly rain had kept many away. But it wasn't really cold -- just a little damp. Not enough to dampen the spirits of a true hamfest hunter.

I've gotten to the point where I take a list to each hamfest. It's too difficult to remember all the bits of equipment and parts I need to keep an eye out for. It fits on one page, so I can fold it up and stuff it into a pocket. I'll take it out a couple of times during a hamfest and go over it, just to keep the items fresh in my mind.

Despite the preparation, there's often something that catches my eye. Like this oscilloscope. While prowling the tables, I saw another unit (a model 1420 - 15 MHz) on a table that was partly disassembled. All the pieces appeared to be there, it looked like it just needed to be re-assembled. The owner was busy at the time, so I figured I'd swing back by later and ask about it. Well, someone else got to it first, because I didn't see it again the second or third time I went by that table.

Another seller also had a small 'scope -- a model 1422 - 20 MHz. It was intact, if a little dusty, and clearly the carry handle wasn't original. One of the knobs was missing. But, it looked promising, so I asked the seller how much? $25. Hmm. I've purchased a Heathkit solid-state 5 MHz scope for $10 before, but it was a full-size unit. But this was a small portable scope. Given the heft, I bet it even had battery power. I asked if it worked, and he said it did. (Not that that means a lot at a hamfest) So, the sale was made.

Now that I had another 'scope, I needed probes. Half-way decent probes can be expensive -- more expensive than this oscilloscope. After a pretty thorough search, I found a new-looking Avex 10:1 probe for $15. One is good enough for now, I should get more at the next hamfest. ('scope probes, after all, are on the list!) I also picked up a miniature knob.

Of course, the first rule of bringing any new equipment home is to take it apart. I did plug it in and verify that it appeared to be working -- two nice traces on the screen. Taking the panels off, it was apparent that this unit was battery-powered. A nice sealed lead-acid pack in the back of the unit was perhaps half of it's weight. But, of course, the battery was stone-cold dead. I wrote the numbers down in case I wanted to order a replacement.

An hour of gentle work with a soft cloth and a bit of Windex took care of the dirt. And the replacement knob fit perfectly, if looking a bit different from the others. No matter. The rubber stick-on feet had long since departed the unit, but I had a few in the junk box in Gwinnett county. A few adjustments, and this little puppy was working perfectly, as you can see from the picture.

A sweet little addition to the micro-shack -- a perfectly sized micro oscilloscope!

Sunday, February 24, 2013

Samlex SEC 1223

Unit #2 - before modifications.
I guess you can say I'm pleased with the Samlex  SEC 1223 power supply. After all, I own three of them.

Back in 1988, I bought a CB-grade 12 volt linear power supply capable of 25 Amps output. It needed a little work to function correctly, but it powered my venerable TS-430S and later the K2/100 for 19 years. It finally went west one day when the power transformer opened in the primary winding.

Soon after, I was hunting for a replacement at a hamfest. I found a Samlex SEC 1223 that fellow had replaced with an Astron SS-25M. Used, the price was right, at about $50. The unit is impressively small, and it had no trouble powering the TS-430S, K2/100 or K3/100 to full output on every band.

However, this unit had numerous spurs on 160m. I found the loudest one was around 1845 kHz, about S7 on the very scotch K2 S-meter. Note that the location and strength of the spurs varies with the supply load. Using snap-on ferrite cores as an experiment, I found that putting them on the power cord and the output power leads led to a reduction in the spurs.
Unit #1 - showing seven FT50-77 ferrite
toroids on power input leads.

My first modification was to de-solder the white and black power cord jumps inside the unit and slip on seven FT50-77 toroids. That reduced the spur to about S5.

Unit #1 - Output lead modifications.
I then made a modification designed by ZL2DF and published by N0SS. My unit was different from that of ZL2DF. It did not have the screw / compression power terminals. Instead, my unit had binding posts soldered directly to spade terminals on the PC board.

I pulled out the PC board and removed the spade terminals. I replace them with 16 gauge wire fed through eight type 43 ferrite beads. The wire is a bit small, but is the largest that will fit through the beads. The output terminals are bypassed across each other and to ground with .1 50v multi-layer ceramic caps.

With this change the 1845 kHz spur was just audible. Atmospheric noise covers it up at night.

Last year, I found another one of these gems at a hamfest for $20. Took it home and sure enough, a few spurs on 160m. Made similar modifications -- toroids on power leads, ferrite beads on output, caps across output terminals. Again, the spurs don't disappear, but are much less pronounced.

Unit #3 - perhaps only needs power input filtering?
This year -- you guess it -- I found another one for $5! This unit is a little different, as it has a large ferrite bead with both power leads run through it to the compression terminals. Perhaps it will only need a big of work on the power leads. We'll see when I can get it on the bench.

These are very capable little power supplies. They are easily able to power a 100 watt transceiver, and with a little work, they are quiet enough for MF and HF use.

Saturday, February 2, 2013

Six Meters

In January, I operated the ARRL VHF Sweepstakes contest. I guess they don't call it that any more, it's just the January VHF contest. I haven't operated this contest since 1992, and have done no VHF events since 1993.

Back then, I had two Microwave Modules transverters: MMT144/28 and MMT220/28. I modified the latter with a new crystal to be based at 222 MHz. I had an F9FT long-boom yagi for 2m, and nothing more than crossed dipoles for 222 MHz. With 10 watts out, it wasn't much, but I made several dozen contacts on 2m. I never did make a contact on 222 MHz.

I sold that gear when I moved from Stone Mountain, GA. Instead, I focused mainly on operating HF, which is plenty challenging.

Upon receiving the K3/100 from my XYL for Christmas, I naturally had to give 6m a try. I've never before had 6m equipment. Well, that's not true. For a while, in the early 90s, I had a JR remote-control radio system on 6m that I used to fly model airplanes. But, you couldn't talk on that radio, so it doesn't really count, does it?

I had already worked four contacts on 6m on December 31st. I figured the 100 watts would be plenty to work quite a few contacts. While I don't have a 6m antenna, I could load up what I had with the tuner and make do.

On Saturday, I was also working the NAQP Phone contest, but occasionally I would take a minute and jump up to 6m and tune around for some activity. Nothing.

Sunday afternoon, I spent about four hours in the shack, mostly listening to static. I worked a few local stations, who could just barely hear me. I was beginning to wonder if I would work anyone outside my own grid.

Then it happened -- an opening. Just before 2300z, I worked K1TR in FN42. Fifteen minutes later, the opening started in earnest. I worked seven other stations up in the northeast in the next 45 minutes, along with about three locals. By HF contesting standards, it doesn't sound like much. But the signals from the northeast were booming in, and they didn't have any trouble hearing me, unlike the locals. The conditions moved like a spotlight down the eastern seaboard, ending somewhere in Virginia.

How exciting! I'm going to have to improvise a real antenna before the next VHF contest. Something with a bit of gain. Maybe a Moxon, or perhaps a three element beam. Maybe I can hide in up on the hill behind the Micro-shack. Rotating it would be nice as well.

Sunday, January 20, 2013

Awards Made Easy - LotW

I passed a milestone this week. Somewhere in my NAQP Phone log upload, I passed 20,000 QSLs in the Logbook of the World(LotW). I have nearly 57,000 QSOs upload into LotW.

I can't imagine collecting 20,000 QSLs by conventional cards. It would take an enormous amount of work. Granted, most of the confirmations I have are for pretty routine contest QSOs that would likely not have bothered with the formality of a paper cards.

In any case, all those confirmations have gone a long way toward earning awards. I've already discussed getting 6-band Worked All States. I've also gotten DXCC, Mixed, CW, Phone, 20m and 15m. I have enough confirmations to get 40m and 10m as well -- I just tend to get one certificate each year.

I was intrigued when the WPX award came on-line in LotW. I found that I have enough confirmations for dozens of awards. I decided I'd hold out for the WPX Award of Excellence.

If you are interested in these operating awards, there's no better way to get the needed confirmations than Logbook of the World. Sure, it's a hassle to get on the system, but once you do, uploading submissions is relatively easy. And then the confirmations just keep on coming.

I wonder how long it will take to get to 30,000?

Saturday, January 12, 2013

USB to Serial

Re-arranged a few things in the Micro-Shack just before the RTTY Roundup.

For years, I have been using an ancient Toshiba 4000-series laptop. My wife bought this monstrosity back in the late 90's in order to work with custom embroidery software. I'd upgraded it to Windows 98 SE, and it managed to do OK running various Windows contest logging software. While I'd rather run stuff on the Mac anyway, writing some good contest software for the Mac has been one of my Great Unfinished Projects (GUP) for many years now. That's far too long a story to go into right now.

The old Toshiba 4000 wasn't much, 400 MHz Pentium, 800x600 screen. One serial, one parallel and one USB port. It didn't even have networking (much less wireless networking). Old.

When I purchased my MacBook, I set it up through BootCamp to boot in Windows 7. I had tried to run the Windows contest software using it, but I ran into a weird problem. Randomly, after a few minutes to an hour, the machine would flash the screen blue, then reboot. Certainly you could use this in a contest -- at least, not one you were serious about.

About the same time, I attended PDC 09 and came home with an Acer 1420P. Every attendee got one. Although Acer built it, Microsoft had specced this machine. The idea was pretty simple. Microsoft had been tired of evangelizing technologies such as Tablet PC, or 3G networking, Windows 7, etc. Only to have developers say "Well, I don't have a machine that does that." Instead, they seeded the 4000 or so attendees of the conference with these machines. Sweet.

I tried to use the Acer to run contest software, but ran into the same weird problem. Since I couldn't see what flashed up on the blue screen before the reboot, it was hard to tell what was going on. So, I went back to the old Toshiba, and the Acer found some utility at work. Until about a year ago, when the Acer took a tumble off a desk and cracked the screen. It still worked, but the two jagged cracks across the screen made it difficult to use.

My XYL wanted the Toshiba back to do some embroidery, so I went about fixing the Acer. I found a replacement screen for $70, which seemed a reasonable investment. The replacement didn't have the touch interface -- so no Tablet PC. Considering I have an iPad anyway, and Microsoft has moved beyond the Tablet PC with the Surface, it seemed to be a small loss.

As I was setting up for the RTTY Roundup, I ran into the same problem as before -- random BSOD and reboot. However, I'd learned more about Windows 7 in the intervening years. Turns out the automatic reboot is a "feature" you can turn off. Now I can read that blue screen.

After a couple of trials, the culprit appeared to be the driver for the Keyspan USA-19HS. You see, the one thing that the MacBook and Acer have in common (other than running Windows 7), is they have no serial ports. In order to talk with the K3/100, you need a serial port. So I used this Keyspan device that I bought several years ago. Updated drivers were no help. Same problem.

This surprise me somewhat. I really like the Keyspan. It works great on Mac OS X. I was a big fan of Keyspan products -- a decade or so ago, I even met a couple of their developers at Apple's WWDC. At least, I was a fan until Tripp-Lite bought them out. Now, I'm not so sure.

While I suffered through the RTTY Roundup with the occasional BSOD, this seemed like an easy problem to fix. Elecraft sells the KUSB device which would be sure to work, but it's a little expensive at $40. I found a Plugable 2303 USB to Serial converter on Amazon for $13. I was encouraged when I read the driver release notes for this device had the same BSOD problem on Windows 7, but it had been fixed in the latest release.

I got a chance to try it earlier this week. Getting the drivers and setting the thing up was an experience, but not atypical for Windows. Once configured, I cranked up N1MM, put the K3 in TEST mode, and set it up to repeat CQ in CW after 1 second and left it for a few hours. All the DTR access should give the serial port a work-out. Six hours and no BSOD. Seems like it works.

The Plugable 2303 appears to be a good solution. I also tried it on MacOS X. Works fine there. It appears I can retire the Keyspan USA-19HS to MacOS X-only use.

Wednesday, January 9, 2013

Straight Key NOT!

Since I was thinking about Straight Key Night before, you might anticipate I would have an extensive operating report of the Homebrew 40m Transmitter and Receiver. Well, not exactly....

I did go and review the rules. There are no prohibitions against using electronic keyers. Indeed, the guidelines state "This 24-hour event is not a contest; rather it is a day dedicated to celebrating our CW heritage." I certainly consider my nearly 34-year-old Mini-MOS keyer part of my CW heritage.

So, that was my plan -- to cheat on Straight Key Night and use my keyer. 

I was busy during New Year's Eve, so I went out on the morning of New Year's Day and hooked up the keyer to the 40m Transmitter. With the spotting function, it appeared to work. The keying was a little soft, but I was able to find my transmitting frequency with ease. I tried two or three crystals, and then I noticed the oscillator wasn't stopping. If I unplugged the keyer and plugged it back in, I could send one element, and then it would stick on. Then it stopped working altogether.

At this point, I was sort of in a panic. I pulled the cover off the keyer and looked inside. What I saw next set me back a moment -- there was no battery in the keyer! I had been using the keyer solely on the stored power in the electrolytic capacitor for about five minutes. Now that is a low-power station accessory!

I scrounged up a 9 volt battery and verified that I had not fried the 30+ year old CMOS chips. However, it appeared that the CMOS gates had enough leakage that it would not reliably cut off the 6CL6 oscillator. 

The original Mini-MOS design keyed through a PNP transistor in order to work with grid-block keyed rigs -- with a negative keying voltage. That worked great with my SB-401 and later with a DX-60B and the FT-101E that I borrowed. When I bought a Kenwood TS-430S in 1985, it had a positive keying voltage. I simply removed the PNP transistor and connected the keying line directly to the CMOS 74C02. Since it worked, I kept using it.

I think the original problem was there are no free gates in the seven chips that make up the keyer. In order to drive a NPN transistor or enhancement-mode FET to key the transmitter, the keying sense has to be reversed -- instead of bringing a positive voltage to ground, we need to go from ground to a positive voltage for the base / gate of the transistor. In retrospect, it would have been easier to have left the PNP transistor in place, use it to drive an NPN transistor or  FET.

A quick look in the junk box revealed some 2N7000s -- an excellent enhancement-mode FET to key the transmitter. (The K1EL keyers use this same device) I just need to dig up a PNP and some resistors. Ah, a project for another day.

Oh, and what about Straight Key Night? Well, since I had just gotten the K3 going, I decided to play with it instead of SKN. I ended up working DX spots on 12 and 17m, including working VP2MRV on RTTY using the K3's FSK D CW to RTTY mode. Cool.

SKN? Maybe next year....