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 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 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.