Thursday, December 31, 2015

The PIC

K9AY controller that doesn't
work.
For a year and a half, I've been working on a push-button controller for my K9AY loops. The loop remote box is pretty much as K9AY originally designed it -- two 6 volt DPDT relays, fed with 6 volt pulsating DC or AC that is coupled into the coaxial feed line. While some people used separate control lines for the relays because of hum problems, I never encountered this issue.

For years, I used a rotary switch to select the direction. Then I decided I wanted a push-button controller so I can immediately select the desired direction.

The push-button controller design was based on a 74LS175 Quad D-type flip flop and SPDT buttons. Pressing a button drives the clock line low and also raises the corresponding D input on the flip flop. Releasing the button causes the leading edge to latch the state of the button. The not-Q outputs of each flip flop drive the LED on the button, while the Q outputs feed to an VN10KN MOSFET that drives a SPST relay that supplies voltage. Six volts for NW, minus six volts for SE, six volts AC for SW, and no voltage (no relay) for NE. Simple.

Except it doesn't work.

The buttons are the problem. Like all mechanical switches, they bounce. These bounces are probably a handful of times within 2-10 ms, but that's enough to throw off the logic which switches within a handful of nanoseconds. Sometimes you press a button and nothing happens. Sometimes you press it, and more than one relay activates.

It's frustrating. The whole purpose of the push-button controller is to command the loops to go immediately to one direction, except the circuit isn't reliable.

I wanted to keep this circuit simple -- one 14-pin chip. Now it looks like I'd have to add a lot more logic to get this design to work.

As a software developer, I kept thinking -- if I only had a micro-controller, I could avoid the switch bounces with software. And I could fix other problem with the design. For example, if you accidentally pressed two switches at the same time, two LEDs would light. With software, I could make it so only the last switch press is selected -- only one direction selected at a time.

This made me wonder -- if I were going to use a micro-controller -- what would I use? I got started on my software career when I built a 6800-based computer in 1977. I was familiar with the 6802, 6801 and 6805. But these were relatively huge chips, and required a lot of support logic. What I needed as a micro-controller that would fit into a 14-pin or 16-pin chip, and allow for four digital inputs, and seven digital outputs without any support. What was available, and how much would it cost?

So, I went to mouser.com and started searching. Hey, these Microchip PIC micro-controllers seem like they would work. After all the Elecraft K2 has a bunch of them. There were also ATmel AVR chips, whatever they are. Seems to me those are used in the Arduino.

Actually, there was an abundance of these devices that might work. It got more interesting when I sorted them by price. I ended up selecting the Microchip PIC16F1503.

This is a pretty amazing device! Two kilowords of instruction memory, 128 bytes of RAM. Capable of up to 5 MIPS. Low power consumption, very flexible operating voltages. With a whole host of interesting I/O features: 12 input and 11 digital output channels, 10-bit A/D converter with eight external and three internal channels, 5-bit D/A converter, two comparators, three timers, 10-bit Pulse-Width Modulator, two configurable logic cells, and a 20-bit numerically controlled oscillator.

Of course, you can't use all of that all at the same time, but this seemed like a marvelously flexible device for all kinds of projects. The best part was the price -- 90 cents a piece. Naturally, I ordered 10 of them.

This device has plenty of power for my K9AY controller. The first step was to figure out how to use it. Microchip offers the free MPLAB X IDE software, which can be easily downloaded for Windows, Mac or Linux. The IDE alone will let you write software and run the simulator. The next question is -- how to get the program into the chips. Microchip also makes a device called the PICkit 3 -- a USB device that easily connects to PIC processors and allows for programming as well as some limited hardware debugging. There was also an end of year special, so I could get it for $36 plus shipping.

The circuitry to connect the PICkit 3 to the chips is dead simple. I looked into building a little board with a ZIF socket. However, ZIF sockets are like $10 apiece. Before I could submit my order for one, I found a little board on amazon.com from DIYMall that is exactly what I was thinking of building for less than $8.

It took me a couple of nights to figure out how to use the IDE. The PIC itself is mind-numbingly complicated. First step is to set the configuration bits, which tells the PIC things like where it's clock signal is coming from. Then you actually get to the start-up code, where you have to program the chips innards to reflect the configuration you wish to use -- which pins for I/O, and what function blocks are connected to those pins. The PIC16F1503 is complex enough that it would actually take a lot of time and code space to configure each block. But, again, you can't use all that stuff at once, so just focus on the items you need.

The configuration is done by writing to specific memory addresses. This would be easy if the chip allowed direct access to all of the data memory. However, because of the programming architecture, it really only has direct access to the first 128 bytes of memory. So, of that space, all but the first 32 bytes and last 16 bytes of that space are banked into 32 banks of memory. Interspersed in those banks are the configuration registers.

Confused yet? Well, the PIC instruction set is nothing to write home about either. There's only one accumulator (W) and no other implicit registers, other than those in low memory. The PIC16F1503 is at least a mid-range CPU, so it has some additional instructions to make things easier to program.

If you are not an assembly language programmer, you really ought to ask yourself what the heck you are doing writing micro-controller software, but there is a C compiler that can be used.

I had little problem writing a program on the simulator. Getting it into the chips was something more of an ordeal that took me about three days to figure out. I wrote a little program that takes all 6 bits of PORTC and outputs a counter on them. It increments the W register from 0 to 0 (256 times) between counts, so the results should be visible. I used a 32 kHz clock speed, so things ought to happen slowly enough to observe.

At first, I couldn't get MPLAB X to talk to the PICkit. MPLAB X seemed to know the PICKit was there, but when going to program, it just sat there, doing nothing. After digging around on the web, I found that you could reset the PICKit by holding down it's button while you plugged it into USB.

At that point, MPLAB X was now talking to the PICkit, but it still wouldn't program. The PICkit has an option to supply power for programming, but the default is not to. Once I turned the power on,  I was getting a warning that the PICkit was trying to supply 5 volts, but it was reading only 4.75 volts. Now, there's nothing on the DIYMall board other than a ZIF socket and a couple of jumpers. Setting it to 4.75 volts made the warning go away, but it couldn't find the chip.

It was about this time I started studying the DIYMall board more closely. It came with no documentation, and I couldn't find anything on-line about it either. When I turned it over, I found there were jumper indications. I moved the first jumper to the B position, which was correct for 14-pin chips.

No difference. This shouldn't be so hard!

Looking at the board some more, it turns out that the 14-pin chips aren't supposed to go in pin 1 of the ZIF socket, but way down around pin 30. There was a heavy white line on the backside of the board indicating this. That's the first time I've encountered documentation printed solely on the board itself. I figured I'd try it. Low and behold, it programmed!

Putting it in a board, it worked the first time. I've included a little video of the chip in action.

video


Wednesday, November 25, 2015

Forty Years of Ham Radio

My novice key.
I don't remember a lot about forty years ago. I don't remember much about taking the Novice exam, or the name or call of the fellow kind enough to give it to me. But I do remember, in November of 1975, receiving my Novice license. I became WN8WOY. It took months for me to get on the air in June of 1976. I kept that call until the FCC  issued me WB8WOY the next fall. I've told many of the details in my Novice Story.

I do remember ham radio being a lot different forty years ago. I was using all tube type gear. Although all-solid-state gear was available, it was rather uncommon until the early to mid-80s. I remember learning about transistors and tubes at the same time. It was easier and cheaper to generate RF using tubes, something that's still true today at the higher power levels.

I remember that I didn't have a clue what I was doing with ham radio. I had read a lot of 73 Magazine articles, but that didn't prepare me for actually being on the air, or how to put up reasonably effective antennas. In retrospect, I did a lot of dumb things, and perhaps missed some opportunities. But, I was having fun, and learning as I went along.

In those days, I remember working toward the goal of getting Worked All States. I believe I collected cards for about thirty states, but came nowhere close to working them all. Today, I've earned WAS on six bands, and worked all fifty states just last weekend in a contest.

I do remember I was quite shy about transmitting, and I did a lot of listening. Perhaps my first decade was much more about listening than transmitting.

I also remember I enjoyed building things. I'm glad I still do. Here's to forty more years of building, learning and enjoying ham radio.



Friday, November 20, 2015

Mark V Shunt Feed Matching Network (80m)

Inside of the Mark V matching network. Notice the larger
capacitor in the back upper right, and the new inductor,
both for 80m.
I wrote earlier that I was having trouble with my 80m shunt-feed matching network. I managed to identify the problem using an enormous variable capacitor, but that was only temporary. As it was, the Bread-slicer obtained several spots of rust for the week I left it outside. I needed a permanent solution.

Having nothing in my junk box that was suitable, I found a 80 pF variable cap with reasonable (4 kV) plate spacing on eBay. It would fit into my NEMA box, but just barely.

In my earlier hunt for the 80m issue, I had already re-wound the 80m inductor on a T200-2 core with insulated wire.

While I was doing this, I realized I had no more T200-2 cores. I was giving idle thought to going to 2 T200-2 cores, as I had for the 160m inductor. Double cores would allow me to use fewer turns, so I could use a larger gauge wire, increasing the inductor Q.

T200A-2 core in center, cover in
fiberglass tape on left, and a
finished 80m coil on a T200-2 core
for comparison on right.
While I was shopping on-line, I came across a new product from Amidon. It is variously labelled T200A-2 or T200-2B, but it is essentially a T200-2 core that is 1 inch thick -- the same as stacking two cores together. Needless to say, I bought two.

New 80m inductor.
Using the larger core, I went from 38 turns on the T200-2 to only 28 turns on the T200A-2 core. The most difficult part of this exercise was finding suitable wire in the junk box. I ended up using a bright orange 16 gauge wire that had much thicker insulating than I needed -- but it is what I had. The resulting coil was a bit difficult to wind, and I used a couple of wire ties to keep the ends from unravelling.

New cap and inductor for 80m.
Shoehorning the capacitor and the larger inductor into the NEMA box took some doing. I had to move the relay just to get the capacitor in the box. And the wiring had to be re-done.

I used two 100 pF 6 kV disc ceramic caps in parallel with the 80 pF variable to get enough capacitance to match.

All assembled, it tunes up nicely around 3800 kHz with a 1.1:1 SWR. And the SWR doesn't change at all when going to 100 watts. Perhaps with the new cap and inductor, I could put a few hundred watts through it with no problems. I'll have to wait to fix the AL-80A before I can test that.

Next step will be to get the 160m network to tune better, it's a little off lately, I think I need more capacitance.

Wednesday, November 11, 2015

Enter the Bread-slicer

Dual 300 pF variable capacitor. Plate spacing is about 1/2".
That's a half-dollar coin on the workbench. This sucker
is BIG. Breakdown voltage is probably around 14 kV.
I've been having trouble with my 80m shunt-feed matching network. Since I moved from Floyd County, I found that the SWR shifts when I transmit more than about 20-25 watts. The Elecraft K3 will work just fine at it's tuning level of 5 watts and find a perfect match. But, when more than about 25 watts is applied, the SWR shifts.

This has made the shunt-fed tower unusable on 80m. This is especially bad, since the tower is my only 80m antenna at the moment in Gwinnett County. I've written about my pursuit of 5-band DXCC. I need an 80m antenna.

The question in this case -- what causes the shift? No doubt it is due to arcing. Initially, I thought the 80m network had the same problem as I had on 160m -- that the inductor was arcing between turns. I originally used enameled wire to wind both inductors. Over time, with the heating and cooling of the coils caused the windings to rub against another, which eventually caused the 160m inductor to arc between turns.

I re-wound the 160m inductor with insulated wire back in 2006, right at the start of the ARRL 160m contest. I haven't had any trouble with arcing. It was behaving much like the 80m network was.  Re-winding the 80m inductor was easy. Unfortunately, it didn't solve the problem.

There's not much else to the matching network. It's a simple L network with a series inductor and a shunt capacitor. It might be the capacitor, it might be some part of the switching network. How to find out?

What I needed was a capacitor with greater breakdown voltage. The variable capacitor I used on 80m is a 15-250 pF unit that was the plate-tuning cap in a DX-40. A survey of likely substitutes found nothing that suitable in my junk box. I'd need to buy a replacement. But first, I needed to know if the capacitor was the problem.

I did have one part in my junk box that I might use. The Bread-slicer. You see, when my friend Mike (now W1YM) moved away from Atlanta, he gave me a whole bunch of ham-related stuff, with instructions to sell off what I couldn't use and fund my tower project. And that's exactly what I did. Among the items he gave me were a couple of very large variable capacitors.

One of them was far to small to work -- only about 15 pF max. The other, however, was perfect. It's a dual 300 pF cap with a plate game around 1/4 inch. Breakdown voltage for this cap is over 10 kV. I call it the Bread-slicer, since it looks large enough to slice an entire loaf of bread at once. It would be perfect for a test.

The Bread-slicer in position at the base of
the tower. Note that I don't even have a
knob large enough to fit on the shaft.
The problem with this cap is that it is huge. It's literally bigger than a breadbox. No way it would fit in the 6" cube of the NEMA box that houses the 160m and 80m matching networks. But, it would prove to me if the variable cap I was using was the failing part.

So, one very damp evening this week, I put the matching network back on the tower without the 80m capacitor and jumped the Bread-slicer in the circuit. Lacking any knobs large enough to fit on the shaft of this enormous capacitor, I used a pair of vice-grips.

With some quick work with the MFJ-259 antenna analyzer, I found a 1:1 match right around 3800 kHz - just as expected. Hooking up the coax and stepping back inside, I tuned the K3 to the 80m shunt-feed, and gave it a quick full-power test.

No SWR shifts. Yes, it's definitely the variable capacitor that was arcing. Since I can't use the Bread-slicer on a permanent basis, I've already ordered another part. It's only 80 pF, but has a 4 kV breakdown voltage. And, it should fit in the NEMA box. Once I get it, we'll see how well it works.





Thursday, October 15, 2015

The Last One Hundred (Plus Nine)

Back in 2007, after uploading logs to Logbook of the World for three and a half years, I qualified for DXCC. I'd been licensed as a ham 32 years earlier, and had worked nearly 200 entities, but didn't get the confirmations until 2007.

I mentioned this on the SEDXC email-reflector, and got many positive replies. David Johnson K4SSU wrote me and said that he envied the enjoyment I would have working and confirming the next 200+ entities.

Now, eight years later, I have been at 231 current entities for a few months now. It dawned on me that I have only 100 more to go to reach the honor roll. I'm now working up that steeper slope that David Johnson mentioned, where the thrill of working a new one comes only after much waiting.

I haven't been idle. I'm inching closer to 5BDXCC, and trying to work the DXpeditions as they pop up -- especially those that aren't on the air but once a decade.

Still, there's a lot of DX, even easy DX that has eluded me. I still haven't gotten the hang of postal QSLs -- still depending far too much on LoTW. That's probably something I need to fix. There's probably a bunch of DX I've already worked that can't be confirmed any other way.


Friday, September 18, 2015

The Venerable TS-430S

The Venerable TS-430S with AT-250 antenna tuner.
I realized earlier this week that my backup rig, the Kenwood TS-430S, turns 30 years old this month. Yup, I bought that rig back in September of 1985. For the next 16+ years, it would be my only HF rig.   I held on to that rig so long, by 1995, I was already calling it "venerable."

How I got to that point is an interesting story. My original Novice setup was an SB-301/SB-401 combo. In my second or third year of college, I sold my SB-401 to my brother Ben (now NJ8J). I still had the SB-301, and eventually I set it up in one of my college apartments. But I lacked a transmitter.

One summer, I attempted to rebuild my Novice transmitter using a 6GK6 and 6146 design published in the ARRL handbook. I added a lot of extras, like a built-in VFO and a KOX (key-operated-switch), with automatic T/R switching. (the VFO and KOX board were salvaged from a home-brew 40m QRP rig project that I assembled, but never could get to work) I never could get any output from that 6146 rig, and it chirped pretty badly.

Shortly after I finished college and moved into an apartment, I borrowed a friends FT-101E. The rig worked great. Because of my crummy antenna situation, I had a lot of trouble making contacts. Eventually my friend asked for his FT-101E back.

Since he bought the SB-401, my brother wasn't using a Heathkit DX-60B he had, so I borrowed it. I pulled the VFO out of the Novice transmitter, mounted it in a box with the KOX circuit board, a power supply and connectors for the DX-60B. This actually worked! I made a handful of contacts, but again the antenna situation really limited me.

In the summer of 1985, I moved to a new apartment much closer to work. It was two stories tall, and there were a number of trees about 30 feet away from the back. I took a couple of 100 foot spools of #26 wire wrap wire and strung them into the trees from my second-floor shack window, fed from the back of a crappy MFJ tuner with a balun. This formed a crude doublet.

For an operating table, I bought a door, placed it on two short two-drawer filing cabinets, and finished it with stain and polyurethane. I did a good job, because this door is still my operating table to this day in Gwinnett county.

I still needed a rig. I decided I didn't want to fool with tube-type radios any more. (That urge would return later) I wanted something that was all solid-state, had a direct-reading frequency display, supported the new WARC bands, and didn't cost terribly much.

At that time, the top contenders were the Kenwood TS-430S and the Yaesu FT-757GX. Both had a reasonable feature set, and were similarly priced around $600. I don't know what tipped me toward the Kenwood. In retrospect, based on what I know today, the FT-757GX had more features -- it does full QSK and has a built-in keyer, as well as supporting computer control via the CAT system. Computer control would be something I would pine for a few years later when I got into contesting.

Back in 1985, I wanted to get the best deal on my TS-430S, and I must have called a dozen different dealers for a price quote. The deal I found was a TS-430S for about $630, including the optional FM board. I placed the order with my credit card -- and this was perhaps the first time I would go into debt for my hobby.

I didn't do a lot of operating from that apartment, but I did enjoy the TS-430S. The crude doublet actually worked pretty well. I spent a fair amount of time on 30m, which was a relatively new back then, but I also hung out around the Novice bands on 80, 40 and 15m.

I moved to a house in Stone Mountain, GA, and the TS-430S was my main rig. My antennas progressed from a 300 long wire to a loop skywire, to a 125 foot doublet, eventually complemented by a Butternut HF4B beam on a roof tower that eventually gave way to a Cushcraft A3S. I started contesting in 1986 with CW Sweepstakes. The TS-430S paved the way for a whole lot of radio experience for me.

As a rig, the TS-430S is not a bad performer. There are two key deficiencies that were fixed by it's successor, the TS-440S: a) computer control, b) 100% duty cycle. The TS-440S adds a host of other features (100 memories, internal antenna tuner, selectable filter bandwidths, FSK, selectable AGC) Ironically, the TS-440S would be introduced at Dayton in 1986, just a few months after I bought the TS-430S.

CW performance is reasonable, depending on your expectations. There is no QSK, but the VOX operation from the key is quick and reliable. You can at least listen between words. AGC action is fast. The 500 Hz CW filter is a must-have.

SSB works well. VOX is fully adjustable, and the speech processor produces reasonable results on air. Choosing LSB or USB, though selects the slow AGC, which is annoyingly sluggish.

FM is interesting. I played around with 10m FM in the late 80s. There used to be a few guys in the Atlanta area that would hang out there back then. I think it may have faded, along with a lot of 2m FM.

Receiver performance is pretty good considering the up-conversion design and the vintage. There's certainly some front-end IMD, which you hear as a "sparkle" sound, especially on 10m when it is open during a contest. Usually hitting the attenuator knocks that out. The notch filter is pretty good, provided you are only dealing with one carrier. Of course, you have to adjust it manually. Noise blanker is one of the better ones.

Some contesters would be displeased with the manually-centered RIT. Never bothered me. IF Shift can sometimes help fight QRM -- but not in really crowded conditions.

This rig has some features I have rarely used. General Coverage Receive is one of them. Program scan has got to be the most useless of all -- since you have to manually hold the scan if you hear a signal.

I have made a handful of mods to my TS-430S. I did the 10 Hz frequency readout right away. (Why they didn't ship it from the factory this way, I'll never understand) Back when I used transverters for 2m, I enabled all-frequency transmit. Oh, and I did a simple mod that allows the YK-88C 500 Hz CW filter to be used for SSB narrow. This is useless for Phone, but makes easy work for RTTY.

Running RTTY is a mixed blessing. With the 500 Hz filter and the IF Shift adjusted, it does respectably on receive. The slow AGC is a little bit of a problem. Transmitting, though, should be limited to about 50-75 watts. Be sure to turn off the speech processor.

This rig has been with me at five different QTHs, as well as a host of Field Day operations. Although I long ago bought an MB-430 mobile mount bracket, I have never mounted it in a mobile.

Considering all the rapid changes in electronic and radio equipment in the late 70s to mid-80s, what with the transition from tubes to transistors to integrated circuits, plus the addition of new amateur bands -- it is amazing this rig still holds its own. I certainly didn't expect to be using it 30 years later.

Wednesday, September 9, 2015

BAM! - AL-80A Broken Again

Well, crap. The AL-80A is broken again. Yup. I was on 17m chasing a bit of DX, when I decided I needed more than 100 watts. I hit the A->B button, then A/B, then tuned a bit away from the DX frequency (never tune up on DX - ever), dialed in 50 watts, switched the amp to operate and hit the Tune button.

Heard something go POP! as I turned the plate tuning knob, and immediately the grid current meter pegged. Not good.

A little diagnoses -- with no RF, keying the amplifier the grid current meter reads about 100 mA. Even with about 20 watts, the grid current meter pegs. Seeing the output meter peg, too.

At the worst, I may have fried my tube. I suspect I may have blown more of the metering circuitry.

This amplifier is very picky about 17m....

Monday, August 31, 2015

Pursuit of 5BDXCC III - 80m

I wrote of this dream first two years ago. Back then, I thought it would be an easy thing, perhaps to work (and confirm) nearly 30 countries on 80m in a single winter. Boy, was I naive. I only added six confirmations on 80m the entire year.
Can this shunt-fed tower put me over the top?
The next  year, I at least had the sense to understand the difficulty of the proposition. I enumerated things I might do that year. In the end, I only did a couple of them. I did not add more radials to the Inverted-L, I did not bring the amplifier up to Floyd county, I never did finish the new K9AY controller. 

However, I was there a lot. I spent a lot of time on 80m. As a result, I now stand at 89/88 confirmations - I added a dozen over the year. That's twice as productive as the previous year. 

If I can pull it off again this year with a dozen confirmations, I should be able to meet all the requirements of 5BDXCC.

It's going to be interesting. At the moment, the Inverted L, with over 30 lbs of radials, is sitting in a box. I'm still trying to figure out if I can put it somewhere where I can lay down those radials safely. My only 80m DX antenna is the shunt-fed tower in Gwinnett county. 

Wish me luck.


Wednesday, August 12, 2015

AL-80A Repairs

AL-80A back in the operating position
Hard to believe, but it has been 10 years since I purchased the AL-80A. Archie, K4GA owned it before me, and it has served me well since that time. I added a step-start circuit a few years ago, and it's been doing well until April 2014.

I wrote earlier this year that the AL-80A had a failure that I traced down to an open 1.5 ohm 3 watt resistor on the meter board.

I finally got a replacement part from a source in China. (Well, it was cheap, but not fast) Installing the resistor was the easy part. While I had the amplifier away from the operating position, I decided I needed to do a couple of other updates.

Back in 2009, I added a glitch resistor, but I installed it on the wrong side of the B- line. It was between the capacitor bank and the rectifier, where it wasn't doing any good. I moved it into the B- line between the capacitor bank and the meter board.

Glitch resistor on the rectifier board.
My AL-80A rectifier board had a number of unused lands (likely for full-wave rectifier bridges in other amplifier designs), two of which were perfect for the glitch resistor. If you look carefully at the photo, you'll see a darker brown wire going from the capacitor bank land near the middle back to up the board. This goes to the far end of the glitch resistor.

The near end is hooked up to the brown wire that disappears off the bottom of the capacitor board, heading to the meter board. 

This made for a neat installation, and now that is is on the right side, it will actually do some good.

The other issue I addressed was the meter lighting. Because of a bad trip to Barbados long ago, the two grain of wheat bulbs were not affixed to the grid meter. One of them had been destroyed, and one other bulb on the multi-meter had burned out.

Grain of wheat bulbs like this are nearly impossible to find these days, plus I didn't want to have to fool with changing them when they burn out. So, I took a tip from the internet and replaced them with white LEDs. The LEDs were ones I had bought some time ago from Mouser.com. (Mouser part # 593-VAOL-5LWY4 - 4000 mcd standard white / clear LED -- these are still in stock, although you can get way brighter ones (35,000 mcd!) for less money) At 5mm (T 1-3/4) they were the perfect replacements for the old bulbs. 

The Grid Current meter did not have the holes drilled for the lamps. I held my breath and did this, using a very slow drill speed and working slowly. I didn't want to mess up the meters. Since the lamps are run from the internal 12 volts supply (actually about 13.5 volts), a 1.5 kiloohm resistor was wired in series to set the current at about 9 mA.

LEDs being glued in place on the meters.
The LEDs are glued to the back of the meter faces. Superglue would have been perfect, but unfortunately, I was out. I ended up using 30 minute epoxy, but this particular stuff is so old it was more like 240 minute epoxy.

I re-used the blue leads from the defunct grain of wheat bulb to wire in the negative terminal of the LEDs, and picked out some red wire for the positive side. I mounted the LEDs so the negative and positive corresponded to the terminals on the meter. Less chance of screwing something up.

Toughest part of this exercise was wrestling the meter board back into place. After buttoning it all up, it was time for the moment of truth.
Lighted meter faces.

Et voila, it works! The LEDs are not quite as diffuse a light as the grain of wheat bulbs, but they do a respectable job of indicating that the amplifier is turned on. 

It might be nice to get some more even illumination, but I'm pretty satisfied. Perhaps I might add some reflection inside the meters next time I need to open the box -- which hopefully, won't be for a while. Maybe in another five or six years.



Saturday, July 25, 2015

Fixed the AL-80A (Sorta)

My AL-80A amplifier has been busted for a while now. I think it was back in April of 2014 that I was chasing some DX, trying to quickly tune up the amplifier and something went ZAP! inside the box.

After that, the grid meter was reading all funny, like registering about 60 milliamps even with no RF. That's not right.

I put it on the workbench, and at some point disassembled it. I had pulled the front faceplate off, then pulled the meters and meter switch board out through the meter holes. But I never got around to fixing it. It sat like that, taking up much space on the workbench for months. Until today.

I had determined that the 3-500Z tube was likely OK. No indication of shorts or other damage. I figured the problem must be on the meter switch board -- one of the components there must have gotten damaged. Sure enough, a little probing around found that the 1.5 ohm 3w 1% resistor in the grid current network was showing as completely open.

I also figured out that the 10 ohm 20w "glitch" resistor I put into my amp was wired in incorrectly. The resistor needs to go in the B- circuit on the same side as the capacitor bank. I had placed it before, were it wasn't doing any good.

It's quite possible a glitch took out the 1.5 ohm 3w 1% resistor. This is not a typical value that I have lying around in the junk box. However, I did have a 1.5 ohm 1w 10% resistor. That would do at least for a proof of concept fix.

Wired the resistor in, put the switch board, meters back in place and put the front panel and covers back on.

Moved it over to the operating position, and behold, it amplifies! Well mostly. I got it to work on 80-10m, but I wasn't getting much of any output on 160m. Not sure what's wrong there. That fix will have to wait a bit.

However, I don't have any antennas for 160m that can take more than 100 watts anyway. Seems like the AL-80A should be good to use for a while, at least until I can get the proper resistor and troubleshoot 160m.

Wednesday, June 24, 2015

Farewell to the Micro-Shack

Micro-Shack desk in all of its glory, just before I started packing
Impermanence is the only absolute in life. Once you get used to something, it's bound to change. And so it is with the Micro-Shack. It took a couple of months to prepare this space in 2011. Now the time has come to leave.

My wife has been assigned to a new church, so we leave Floyd County and go half-way across the state to the new church in Walton county. The good news is that the new church is just a few miles from my Gwinnett County QTH -- so I'll be able to spend more time there.

For now, though, I wanted to reminisce about this tiny little room where I spent many hours enjoying my hobby. It's hard to get a picture of the place -- camera angles are difficult in such a tiny room. The view above shows a clutter of equipment on the shelves, as well as other electronic debris at the periphery of the very tiny desk. To the right is the storage room door that swings outward (because there's no room to swing inward), to the left a window, and behind me, water heaters, electrical breaker boxes, and a miscellaneous pile of tools on a cheap plastic shelf unit.

In other words, it's a cluttered but well-loved and well-used space.

The operating desk is just 29 inches off the floor. I found this to be the perfect height. At the Gwinnett County shack, the operating desk is a 30-inch door sitting on top of a couple of filing cabinets. It's too high (about 31") and makes for uncomfortable operating. I'm seriously thinking about building support legs for the door and moving the filing cabinets elsewhere.

Micro-Shack just after construction, before
I brought in a bunch of stuff. Note the
nice stack of shelves. Plenty of room for
just about anything. The desk and shelves
will stay with the parsonage.
That desk has seen a variety of equipment. Originally, I had the Kenwood TS-430S there, as well as my "Novice" transmitter and receiver. As I spent more time there, I swapped the Kenwood for the Elecraft K2/100 in Gwinnett. And two and a half years ago, my wife surprised me with the Elecraft K3/100, which I assembled on that very desk.

I build several projects on that desk - several antenna traps, the K1EL K12 keyer, rebuilt the Mini-MOS keyer, as well as a couple of other projects I have not written up yet.

The antenna setup out here in Floyd County has been extremely modest: R7000, 80/40m Trap Dipole160/80/40m Trap Inverted-L, and a 6m Dipole.

To be honest, the R7000, despite the rebuild and the ground-mounted radial wires, has pretty much been a waste of time. This antenna never did perform well at the Gwinnett QTH, and while it is better than no antenna, it couldn't hold a candle to the wire antennas in the trees. I don't plan to put it back up, I'll probably sell it off.

The 80/40m Trap Dipole, despite being at a modest height of roughly 10m has done extremely well, especially on 40m. On 80m, I did have some trouble with a weird fundamental overload of the Acer laptop keyboard -- transmitting on 80m would cause the Acer not to accept keystrokes for a short time afterwards.

The 160/80/40m antenna has been the sweetest deal out here in Floyd County. With 1500 feet of radials, it's reasonably efficient, and has worked well even as a random vertical on the other bands. I made my first 6m contacts on this antenna.

I haven't written about the 6m dipole antenna, because there's not much to talk about. It's just a simple  dipole made with junk wire hanging in the trees at about 3m high. When 6m is open, it works!

In this tiny room, I've done a ton of operating. Contests - CQWW CW (3), ARRL 10m (3), RTTY Round Up (4), NAQP CW (3), NAQP Phone (4), NAQP RTTY (3), WPX Phone (2), Georgia QSO Party (3), ARRL Field Day (2), IARU (2), CQWW RTTY (3), Sweepstakes Phone (2), ARRL 160m, Stew Perry (3), VHF Sweeps (2), ARRL DX CW (3), ARRL DX Phone, WPX CW, VHF QSO Party, CQWW Phone (2), Sweepstakes CW, ARRL 160m (2), CQ 160m CW, CQ 160m Phone. Some of them were just a few hours on a Sunday afternoon, perhaps a handful of contacts but there were several I set a new personal best score: George QSO Party, ARRL 160m, SS CW, Stew Perry.

Estimating from my logs, I have made over twelve thousand QSOs from this quiet little room.

Being more than 25 miles from Gwinnett County, I had to start over for WAS. During my brief three and a half years of operating, in Logbook of the World, I have confirmations for WAS several ways:
  • Mixed
  • CW
  • Phone
  • Digital
  • 40m
  • 30m
  • 20m
  • Triple-Play
As well as being very close on a few others:
  • 160m - 49 (AK)
  • 80m - 49 (UT)
  • 17m - 47 (AL, KY, SC)
  • 15m - 46 (DE, MS, SC, WV)
  • 5-band - 230 out of 250
A lot of that came from 10 months of very purposeful pursuit of the W1AW-portable operations in 2014, especially on the WARC bands. But most of it was operating a bunch of contests.

Yes, I have a lot of fond memories of this place. Like pursuing the K1N Expedition. It was so much fun busting pileups with just a wire antennas, or getting up at 4 AM to outsmart the competition.

The Micro-Shack wasn't always the most inviting place. In the wintertime, it could be quite cold. The digital thermometer would sometimes read about 45 degrees F on the coldest days. However, a small space heater would warm things up in a half-hour or so. Summertime was much tougher. When it is hot in Georgia, it is hot. I could open the door and run a floor fan to cool things down a bit -- but in the height of summer, it would just blow hot air around. I don't know how I operated contests such as Field Day or IARU in the heat of the summer.

The Micro-Shack wasn't convenient, either. Feel the call of nature? Well, you have to go out of the storage room and walk to the house. More than once I was outside operating late at night and my family would lock the door. Perhaps they were trying to tell me something. I told my wife the next place should definitely have a shack where you don't have to walk out of doors to get to the operating position.

Small, cluttered, inconvenient, often uncomfortable. That well describes the Micro-Shack. However, I will remember it quite fondly. It allowed me to stay connected to my hobby despite being a hundred miles away from my main QTH.

Farewell, Micro-Shack. You may be gone, but you will not be forgotten.


Friday, June 12, 2015

Things I've Learned about Antennas - Horizontal Antennas

I've been fooling around with radio for more than 40 years. Finished my first receiver January 1971, so I guess it's closer to 44 years. In those early years, I didn't know anything about antennas. My initial antennas were nothing more than magnet wire strung up around my attic bedroom. They worked - Badly.

Over the years, I've learned a few bits of wisdom about antennas. This article is about:
  • Horizontal Antennas
Be they dipoles, center-fed Zepps, yagis, quads, Vee beams or rhombics -- horizontal antennas share one key characteristic -- their most important dimension is height above ground in wavelengths.

The height determines the radiation pattern, impedance and much of the loss. I remember a few years ago on the QRP mailing lists there was a hot debate about one of W4RNL's designs -- the "88 foot" dipole. When LB modeled this antenna -- meant to be a secondary or spare antenna when your beam failed in the middle of a contest -- he did so at 100 feet and also at 70 feet. 

This design was supposed to give reasonable performance on 80, 40 and 20m. 88 feet worked out to be about right. Long enough not to have too crazy impedance on 80m, and short enough to not have a lot of deep nulls on 20m. At 100 feet, I bet it is a pretty good performer. At 70 feet, it wasn't a slouch, either. The odd-ball impedance would make for some loss in the feed line, but for a spare antenna, that wasn't a huge concern.

From the discussions, you'd like that 88 feet was somehow a magic number that made everything work better. Heck, if you have the room make it a full-size 80m dipole then add a couple of traps, for pete's sake. And do you think those QRP stations put up that 88 feet of wire at 100 or even 70 feet? Heck no, they were down at more practical heights of 20-35 feet. 35 feet might be passible for 20m, since it is 1/2 wavelength up. But it is only 1/4 wavelength for 40m, and 1/8 wavelength for 80m. 

Here's the deal: the pattern of a dipole is hugely affected by the height above ground. About 1/2 wavelength, it just starts to have a bidirectional pattern, and only that at pretty high angles. Lower than 1/2 wavelength, it's basically got an ice-cream-cone shaped pattern going straight up. This pattern is rarely desirable.

How high is enough? At some point above about 2 wavelengths, the dipole pattern looks a lot more like free space. For beams, at these heights, you can start to get nulls in your pattern at useful angles, so you have to be careful. Somewhere between 1/2 and 2 wavelengths is generaly the "sweet" spot for horizontal antennas. For specific applications, your best bet is to model the antenna at the desired height and watch for undesirable nulls.

Given that most hams don't have supports for antennas above 50-70 feet, it's likely that any antenna below 20m is too low. Get those antennas as high as you can.

Monday, May 11, 2015

Sunday Afternoon Dxing

It's mother's day. My wife is taking a well-deserved nap, I've watched all my shows on the DVR, so what to do? I decide I should mosey outside to the shack and see if there's any DX to work. I'm hoping maybe there might be a 6m opening, since it is the Es season.

A quick check of 6m shows nothing happening, so I turn to dxwatch.com and check out some of the bands. I see a spot for V73NS on the west coast on 12m CW. Hmm. Maybe I should listen. At first I hear nothing.  Then, barely above the noise, I definitely hear "73." Intrigued I listen further.

It's just before 5 PM local time. V73NS is definitely in there, and he's calling CQ with no answers. QSB has him coming and going. I drop my call in, he immediately comes back to AA4, but he doesn't have my suffix. A couple more calls, and it's clear he can't hear me as he fades back into the noise.

Noting the QSB, I keep trying. Eventually, as he come back up, he's giving someone a report -- 229. Pretty bad. Oh, wait, here he is again -- he's calling ME with that 229 report. I give him a 559 twice, at the top of the QSB. I get a confirmation. Bingo - in the log it goes.

Wow, just about ESP-level, but a definite contact running over that QSB.

And, today, I get a confirmation in LoTW. Marshall Islands now confirmed on 12m, and CW, and the DXCC Challenge.

It doesn't get any better than that.

Monday, March 2, 2015

Another Kind of Monopoly

Back in the 1990s and early 2000s, Microsoft ruled personal computing with market share. At their peak around 2004, more than 90% of personal computing devices ran some variant of Windows. Even before this, they wielded enormous influence. It took a long time to topple Microsoft from the top of the stack. All during this time I was a staunch Macintosh supporter. I felt that this sort of monopolistic market was unnatural -- that consumers would be better supported in a market with three or four major competitors, rather than just one.

I happened to catch this short blog article referenced from the Stocks app on my iPhone under AAPL. It states that Apple has captured 88.7% of the profits from the Forth Quarter 2014 Smartphone sales. Apple has no where near 80+% of the Smartphone market share --  nearly 20% in Q4 2014, but more typically around 15%.

Seems this is another kind of monopoly -- not of share, but of profits. Google Android captured the remaining  11.3% of the profits, and other vendors lost money.

I'm not sure how I feel about this. It doesn't have the permanence that Microsoft seemed to have in the late 90s, since profits can change from quarter to quarter. But, unlike Microsoft, Apple seems to be in a mode where it is continuously re-inventing itself. And with the Smartphone cash cow, it has plenty of resources to do so.

And yet, Microsoft's hegemony wasn't permanent either -- the market eventually pivoted out from under them. I wonder where the market will pivot next.

Monday, February 16, 2015

K1N - Fabulous DXpedition

My Results from K1N
Well, it's over now. The much-anticipated K1N DXpedition to Navassa Island is now over. Lucky for me, I made it into the log multiple times, which makes me quite pleased.

Granted, it was a pretty easy shot from here in northwest Georgia to Navassa Is compared to other parts of the world. They were quite strong on just about every band, with the exception of 10 and 12m. I never heard a peep from them on 6m.

The pileups in the low bands were completely crazy in the evenings. All of my contacts 30m and below were made in either the 0900z or 1000z hour -- 4 or 5 AM local. That's one of the secrets of working DX -- be on the band when others are not! The one exception was 60m, and, honestly, the channel was so crazy I'm not entirely sure how I made it into the log.

All of these contacts were made with 100 watts and wire antennas, either the Inverted-L or the 80/40m dipole. Working DX does not require huge amplifiers and large antennas.

The team on Navassa Island did a fantastic job handing out contacts despite unruly pileups, deliberate QRM and the usual craziness. I witnessed on CW pileups that extended over 30 kHz with people continuously calling. Finding the listening frequency in the second receiver was an incredibly difficult task, and quite often I was just guessing -- but a few times I got lucky.

As I told my friend Mike, W1YM, now that I have Navassa Is on nine bands, I'm planning to volunteer to operate the next time team heads to the island. Perhaps in 10 years....

Wednesday, February 4, 2015

K1N - in the Log!

From the Department of "OK, that was a little bit weird":

Just after the SuperBowl, I easily found spots for K1N on 40m - they had just started operating. He was quite loud on the Inverted-L. At that point, the challenge wasn't in finding the DX, but finding exactly where he was listening.

As a belated Christmas present for myself, I bought the KRX3 -- the second receiver option for the K3. After ten months of chasing all the W1AW-portable stations, I became pretty proficient at pressing the REV button and tuning around to find the split listening frequency. Months I spent thinking that this would all be so much easier if I could just hear both sides at the same time.

Adapting to the second receiver wasn't so easy. While I've had a little practice with two radio operation, it isn't easy concentrating on one signal in one ear, and perhaps a bunch of signals in the other. I've had a little time to practice with it, and while it is really handy, I find that sometimes its easier to just listen to one receiver at a time.

In any case, the bedlam I found surrounding K1N was a LIDfest in the extreme. K1N was clearly asking for European stations only, and yet there were thousands of K, W and AA-AL stations calling madly. More than 15 kHz of the 40m band was covered in signals repeatedly sending their calls. It was going to be very difficult to discover the DX stations listening frequency. Add to this mess the number of operators who could not figure out how to properly configure their rigs for split operation. Plus the frequency cops repeatedly sending "UP UP", clearly interfering with the K1N transmissions.

Please, guys. I have written about how to work DX before. You have to LISTEN. Stop transmitting, and listen.

After about 40 minutes of that mess, I turned the rig off. I'd work them later. I hoped. Well, I'd have nearly two weeks of chances.

The next morning, I woke a little early at about 4:30 AM. I felt rested, so I figured I'd go out to the shack and check on K1N.

I half expected to hear K1N on at least 40 and 80m. I had heard them briefly the evening before on 80m, only to hear the operator send VERY TIRED QRX 5 HOURS. Great. (Well, I'm sure those guys were exhausted from the trip and all the setup)

Nothing to be found on 80m, but K1N was hoppin' on 40m. And seems like most of the lids had gone to bed. About five minutes later, I figure out roughly where he's listening (only about 9 kHz of people calling this morning), and it's time to join the fray.

Wait. He's gone. For about five minutes, there's no transmissions from K1N. Then a series of Vs, and he's back - works a couple of Qs, then disappears. Hmm. I keep calling for a while. I figure the generator may have quit, or someone tripped over a cable or something. Might as well call as I'm listening.

That's when something weird happened. You see, I'm using that KRX3 module, listening to the K1N transmit frequency in my left ear, and my own transmit frequency in my right ear. Then, very clearly, I hear "AA4LR 5NN" -- in my right ear. My transmitting frequency. OK, that's not right. I figure it's just some lid out there that's heard me calling over and over, and is just messing with me. Or maybe I'm just sleepier than I thought. I glance up and confirm, visually, that I am indeed operating split. Yes, thank God I'm not a lid -- today.

But, he comes again "AA4LR 5NN" -- insistently. Speed, cadence and strength are about right -- but it is definitely in my right ear. Well, why the heck not: "R 5NN TU" and the reply comes "TU UP" -- again in my right ear. But nothing else.

Right about that moment, the operator must have realized something was amiss. Next transmission is in my left ear - "K1N UP". For a moment, I'm flabbergasted. Did I work him, or not? Well, if I did, I know exactly where he's listening - so I send my call exactly once. "AA4LR 5NN", "R 5NN TU", "TU UP".

There. In the space of 20 seconds -- less time than it takes to read about it, I'd worked K1N twice -- once simplex, once split. Once in one ear, once in both.

About an hour later, I find there's spots on 80m. He's very strong, but even stronger on the trap dipole. The pileup is fresh, and hasn't had time to get as unruly as 40m. In three minutes, I found where he's listening and he comes right back to me.

UPDATE: Looks like he logged me twice as well, as I have two 40m CW contacts in ClubLog. Fine operator!

Saturday, January 31, 2015

K1N - Pumped for Navassa

Back when I first got interested in Amateur radio, I remember an article published in 73 Magazine about a DXpedition to Navassa Island.

This was something of an unusual article for 73 Magazine -- which, at the time, generally focused more on radio technology and construction articles. However, since the publisher Wayne Green W2NSD/1 had been part of the DXpedition, it was no surprise the story was covered.

I don't remember why, but the tale of hauling equipment and personnel up a steel rope and angle iron ladder from an inflatable boat amidst all the waves, surging and swells captured my imagination. You can read an account here.

It would be over a decade later that I would join the Atlanta Radio Club myself, but for some reason I never asked anyone about this trip. It wasn't until nearly two decades later, when I happened to strike up a conversation with Jim Streible K4DLI that I heard the story firsthand. (Ironically, Jim was the father of one of my colleagues at Georgia Tech as well - something I didn't piece together until that conversation)

At lot has happened since those days. When the Desecheo Island DXpedition was active in 2009, I intentionally worked them on as many bands as I could -- since it was clear that it might be decades before it was active again. I logged them successfully on 160-15m, using CW, SSB and RTTY. Given my relative proximity to the DX, it wasn't that hard to work.

Needless to say, I am pumped about the Navassa Island DXpedition. The pileups will be huge, of course, but I expect to work them on as many bands. It will be great fun trying.