Friday, November 24, 2017

Forty Years of Personal Computing - First Steps

As my present for Christmas of 1974, my older brother gave me a one year subscription to 73 Magazine, starting with the January 1975 issue. This was pure genius on his part. He knew I was showing an interest in amateur radio, plus he would have the opportunity to read my copies, so he didn't need to continue his own subscription. I enjoyed the magazine so much, I continued my subscription until the magazine's demise in 2003.

1975 an exciting time in the world of the electronic hobbyist. MITS introduced the Altair 8800 in November of 1974, and other vendors soon jumped into the market. Microprocessors and related components were coming available, and 73 Magazine was writing all about it.

With the February 1976 edition, 73 Magazine added a special section called I/O, to talk about the developments with these Microprocessors. To my teenage mind, I just had to have one of these machines. They were expensive, but I slowly saved my money from my paper route.

By the spring of 1977, I fell prey to a surplus equipment advertisement from Verada 214. The ad promised a complete system with a keyboard, display, microprocessor and dual cassette decks -- the Viatron 2111 -- only $699! It seemed like a perfect way to enter into the budding world of microprocessors without spending a fortune. Although the equipment arrived as advertised, there was no microprocessor to be found -- nor any way to program the device. After studying it thoroughly for a week, I decided the purchase was a mistake. My father managed to convince the company to refund my purchase price for the cost of shipping it back.

My father could see the seriousness of my interest, so he signed me up for a summer course at the local college where he worked. This was a six week course, and the first three weeks were spent on learning about VCR and other television technology. (It really is too bad that Quasar Alpha-wrap video cassettes didn't catch on -- but they were HUGE) But the last three weeks included plenty of hands-on time with a KIM-1, the 6502-powered single-board computer. Forty years later, I can't remember what programs I wrote, but I thoroughly enjoyed that first taste of programming.

About this time, a computer shop had opened up in Morgantown, WV, about 20 miles away from my home. My parents took me there a few times. I was fascinated to see the MITS and IMSAI equipment I had read so much about over the last couple of years. But the prices were beyond my reach. These systems cost upwards of $2000, much more than I had to spend. I'd have to wait for something more affordable.

Saturday, October 7, 2017

WARC Dipole Repair Complete

Yours truly mounting the antenna near the
top of the tower.
Well, if that didn't seem like it took forever. Back in early September, I took down the WARC Dipole. Although I quickly determined that one of the 17m traps was irreparably damaged, I didn't think it was going to take more than a month before I got the antenna fixed and back up in the air.

I made two new traps using identical lengths (35.5") of RG-58 coax. I didn't bother to try to trim these to any precise frequency. I just made the two traps as identical as I could, and that seemed sufficient.

With the traps back in place I didn't want to re-mount the antenna until I was sure all three bands were squarely in a useful part of the SWR curve. To accomplish this, I used the rope and pulley I had attached near the top of the tower. I used a carabiner through the U-bolt to lift the assembly near the top of the tower.

This actually worked pretty well, as I was able to get the apex of the antenna within a foot of it's mounted height. A 55 foot piece of coax allowed attachment to my MFJ-259 antenna analyzer.

First measurements showed the antenna to be off on all three bands. That wouldn't do. Since I had originally hacked in the 12m traps to a 17/30m dipole, I hadn't done a good job of making the wire lengths symmetrical. This was contributing to bad SWR at resonance. So my first trimming was to make the two legs equal, and subsequent trims were to both legs.

The process goes something like this. Attach the antenna to the carabiner, haul to top of tower. Take rope from one leg and attach it to end of old playground. Pull the other rope through a pulley on the other side of the house until it is above the roof line. Attach the coax to the antenna analyzer, take measurements of resonance and the 2:1 SWR points. Loosen the rope on the side of the house and get the antenna past the roof line. Untie the other rope from the playground. Lower the antenna to the ground. Untangle it all and drag it into the basement so it can be trimmed. Repeat this process.

Honestly, I didn't think I would have to do this eleven times! Both 12m and 17m were resonating slightly low, so I carefully trimmed the 12m portion until resonance occurred in the band. Then repeated the process with 17m. Once each band was in the right place, I soldered the connections between the wire and the trap. Trimming past the trap does not appear to affect the inner doublet, which is what we expect.

30m was a problem. It was resonating slightly high. I ended up splicing in about 14" of wire, split between the two legs. This was too much. In the end, I only needed 3 1/2" added, and that only to one unbalanced leg.

Managed to work ZD7BG just a few minutes after getting this antenna back up on the tower. It's really nice to have a working antenna again. Now the next repair is to figure out what's wrong with the A3S.

Friday, September 22, 2017

Life after 5BDXCC

For the last several years, I've started off the late summer thinking about my plans to complete 5BDXCC. This has meant figuring how who to make more DX contacts on 80m, whether that meant improving antennas or just being on the air more.

But, this June, I managed to wrangle enough confirmations to qualify. I'll likely submit these in November.

As that time of the season rolls around again, I have to think - what's next? What comes after 5BDXCC? It's a good question.

I still have a few other bands to add. On 17m, I have 87/87 confirmations, so that's likely next. It will be easier now that I've identified the problem with my WARC dipole. ON 12m, I have 73/73 confirmations is not that far behind, although old Sol is not likely to be active enough to sustain much propagation on that band for a few years.

160m seems less likely, where I have 42/41 confirmations. Given how hard 80m was, it may take quite a while to add many more entities there.

The DXCC challenge is still unclaimed. I have 835 current credits, and my unapplied LoTW confirmations will bring me up to 1125, if I applied them all. Plus at least five more QSLs I'll submit this year could get me all the way to 1130. I've decided a couple of years ago not to push for this too early. The 80m DXCC submission this year, plus all the band endorsements should get me over 950 credits. I'll make it over the 1000 credit requirement as soon as I complete another band.

And, of course, there's the DXCC Honor Roll. At the moment, I have 259 current confirmations, which puts be 80 away from the 339 total. And 71 away from the 330 required to make Honor Roll.  That may take quiet a while. I have two cards that I'll submit this year, and there's a dozen more entities I've worked that I need to obtain confirmations from.

Naturally, some of these remaining entities are increasingly rare. The good news is there are several exciting DXpeditions this year. I'll have to make plans to work them when I can.

So, yeah, still a lot of challenges left in DXCC.

Monday, September 4, 2017

Back in the Harness Again

Yours truly on the tower.
When I moved back from Floyd County a couple of years ago, I did a tower inspection. When I got to the top section joint, about 10 feet above the roofline, I lost my nerve. I checked the bolts, then came slowly down the tower. I haven't climbed since. Until today.

I really had to. All the antennas on the top of the tower show signs of being messed up. Mission today was the WARC dipole. While still resonant on 12m, 17m showed no match, and 30m was way out of band.

I took the ends of the dipole loose, you can see two of the traps around my foot level on the tower. Then the climb to the 44 foot level of the tower. The center of the dipole is a NEMA box U-bolted to the tower leg.

Being up there is a little unnerving at first. You try to stay as still as possible, because each move causes the tower to sway.

Of course, as soon as I got up there, I find I don't have a screwdriver. This is why you always use a ground crew. My daughter Lauren did an excellent job in this department.

With the lid to the NEMA box off, took off the U-bolt, and lowered the dipole to the bottom of the tower.

Once back on the ground, a quick inspection showed what was wrong. One of the 17m traps had a clear open, and it wasn't something that was easily fixed. After 12  years on the tower, the shield braid from the trap coax had disintegrated. The trap needs to be rebuilt. It's companion doesn't look much better. In the interest of keeping them symmetrical, I decided to rebuild both the 17m traps. The 12m traps are a couple of years younger, and look to be in good shape.

After I get the traps rebuilt, it will be back up the tower to re-install. And then I need to lower the A3S down so I can check out the driven element -- figure out why I've lost resonance on 15m and 40m is so messed up.

Monday, July 24, 2017

Forty Years of Personal Computing - Prelude

1971 Logix 0-600 "Electronic" Computer kit
When you are young, you rarely realize how smart your parents were. Mine bought me all kinds of educational toys. One birthday, I got an  optics experiment lab that culminated with building a working 35mm camera. I did every step in that lab, and eventually built the camera. OK, it was inexpensive plastic, yes. And while I never did manage to buy film for that camera, I learned all about concave, convex, chromatic aberration and other principles of optics.

One of my favorite educational toys was a subscription to "Things of Science." Every month, I'd receive a little envelope or a blue box with science stuff. There would be a small booklet, often with plastic or cardboard parts in the box. The people who came up with this were geniuses, as they managed to package a lot of science into a tiny, inexpensive kit every month.

It was hit or miss each month. Sometimes, the article wouldn't interest me, or I'd just not be patient enough to do the experiments. Sometimes, it would be really cool -- like they'd send enough chemicals to grow a small plant hydroponically. Or send some plastic lenses in cardboard holders to do optics experiments. I played with those lenses for months and months.

And while not every kit was a hit, it at least got me to study some element of science for a few hours each month.

The actual "computer", sans wiring.
A couple of years ago, I found something from my childhood in my father's basement. It was a 1971 Logix 0-600 "Electronic" Computer kit. I use the quotes only because this kit contained no electronic components. It's just a battery holder and ten lamps, a SPST pushbutton, and ten ganged ten-way SPST switches. The switches provide data input, the lamps show the output, and the switch connections are wired by sticking pieces of wire into holes that make contact with metal clips -- very much like a modern solder-less breadboard.

The first part of the manual contains assembly instructions. These are easy, provided you can turn a screwdriver and strip a wire. I must have been 11 or 12 when I received this kit, and I did the assembly entirely myself up in my room.

The manual is the brilliant
part of the whole kit.
This kit was really brilliant. Despite the lack of any electronics, the manual shows how to build 39 different "programs." The switches were used to enter the input, and tissue-paper overlays are slipped into the transparent amber lamp cover to label the output. Each program had a clear wiring diagram.

All you had to do is read the program description, and follow the diagram.  So long as you wired it up correctly, the program would work as advertised. The ganged switches were sometimes a little flaky, but not enough to detract from the experiment.

Through the series of programs, the kit teaches some of the basic logic and computer principles -- AND gates, OR gates, NOT gates, Addition, Counting, binary numbers, Venn diagrams and more.

I do remember working through all the programs, and even trying to develop a few myself. At one point, I figured out how to wire up a program, but realized it required a 12-way ganged switch, instead of 10-way. It was beyond the capabilities of the 0-600.

After I ran through the programs in this kit, I don't remember using this machine much more. But it was a real learning experience. The experiments taught me a number of important logic and computer concepts that I later used in my education and in my career. Having it now brings back fond memories.

Friday, June 16, 2017


For the last four low-band seasons, I've been hoping I'd capture enough confirmations for 5BDXCC. I had already confirmed 40, 20, 15 and 10m DXCC, I just needed to get to the magic 100 entities on 80m. As I wrote in the fall, I just needed a few more to put me over the top.

At that time, I had 91/90 confirmed on LoTW, plus a couple of cards.

Today, I received a confirmation on 80m from CE2VMF, bringing my totals to 98/97 on LoTW. Plus, I have THREE cards with additional confirmations, which brings the overall total to 101/100.

I remember talking to Jim Streible K4DLI (who now, unfortunately, is a silent key) about his 5BDXCC plaque. Jim said he had spent 35 years earning that award. And Jim earned it back in the day before electronic confirmations, too.

So, when I apply for DXCC awards later this year, I'll be petitioning for 6BDXCC (got 30m, too!).

I'll have to seriously consider ordering the plaque.

Tuesday, May 23, 2017

PIC-based Push-button K9AY Controller

Push-button K9AY controller works!
I can't believe I have been working on this project for three years. I wrote about it earlier, describing the project and how it didn't work, because of the bouncy mechanical switches.

Yes, I bought the PIC16F1503 chips. It also took a while to figure out how to program them.

Conceptually, the software is simple. I program the Timer1 timer to fire every millisecond. Then the cpu loops and waits for an interrupt.

When the interrupt fires, I gather the state of all four of the direction buttons from PortA, and shift each into a byte in memory. This gives me the state of each button for the last eight milliseconds.

When a button is pressed, even if it bounces a bit, it will eventually transition to an on state. If it holds that state for seven milliseconds, it will result in a distinctive pattern: 01111111.

That's what I look for. If a button has this pattern on any interrupt, I consider it to be on. Otherwise, it is off. Take the value of all four buttons and jam them together side by side, and you have a number between 0 and 15. Sixteen values in a lookup table. Look up the current value. If it is zero, do nothing. If non-zero, I write the value out to PortC. The PortC bits control the LEDs on the buttons as well as the control lines for the two relays which select the control voltage for the K9AY loops.

All the work is in the lookup table. It has all zeros except for the four entries where one button has been pressed -- one each for the four directions.

It's all less than 100 instructions.

Most importantly, it works!

My prototype has wiring that's a little flaky. The board flexes a little bit when the buttons are pressed and sometimes the wiring moves a bit and shorts out. I'm thinking that now that I have something that works, I should make a printed circuit board.