Friday, August 2, 2019

Demise of the 80/40m Dipole

Sad to say, I recently lost my 80/40m trap dipole. Which is too bad, because it was a good antenna. I used this antenna from four different locations in Georgia: Gwinnett, Floyd, Walton and Fulton counties. I made thousands of contacts on this antenna. It had been the first antenna I put up at Floyd and Walton counties, and the only antenna at Fulton county.

It was last up at the parsonage in Fulton county. Apparently a group of teens was doing some volunteer work near the parsonage. They saw the rope tied off to the parsonage fence and thought it was something other than it was, so they untied it.

After this, half the antenna fell down to the ground and was left there. When the landscapers came by to mow the grass, they ran over it....

So, about 80 feet of rope, insulator and one of the traps was completely destroyed. The other half of the dipole is still intact, up in the trees. But most of one element is gone -- clearly the landscapers threw it away.

Plan is to design an 80/40/20m trap dipole, using traps made with coils and capacitors, since they have much higher Q than the coax cable traps. I'll also place the traps on frequencies well off the operating frequency.

Tuesday, March 26, 2019

Uh Oh. Not Good.

Well, if it isn't one thing, it's another. After celebrating getting the A3S/A743 rotating again, I've found a problem. The SWR shifts I mentioned? On a dark night, I went outside and looked up at the antenna while WSJT-X was transmitting on FT8 trying to contact someone. I tried this on 40 and 20m.

I observed one of the 20m traps on the driven element light up with arcing using 100 watts. It was visible in the drain holes and end caps of the trap.

At the very least, I'll need to take the driven element down and rebuild it.

Update: I've tried this experiment on 15m, and I see no SWR shifts even using 500 watts. I think the problem may be confined to the 20m trap(s).

Monday, March 25, 2019

Rotating Again!

Well, it didn't take months after all. As I wrote last month, my A3S/A743 had been stationary since December. But with the beautiful spring weather here in Georgia, I managed to get to the top of the tower and finish the installation.

It's now rotating freely, as expected. It's really good to be able to use the beam as intended, and not have it fixed roughly east.

I do wonder if the A3S/A743 needs repair, however. I'm still seeing occasional SWR shifts at 100 watts on 40 and 20m. I'll need a gin pole to take the antenna down to refurbish.

Thursday, February 28, 2019

Back on the Tower Again

During my December vacation, I started a rather ambitious project on the tower. Since its installation, my A3S/A743 has been about eight inches from the very top of the mast. My intent was to put the beam at the very top of the mast, in order to give more room to stack an A50-3 under it.

It had been a while since I climbed on the tower, and any work at the very top is always nerve-wracking. As I've written before, sometimes you get up there and decide you've had enough.

Anyway, back to the December project. I conscripted my daughter Lauren to be my ground crew. I ascended the tower, removed the rotator and hung it from a couple of nylon loops off the side of the tower. Then I lowered the mast into the tower, until the A3S/A743 bracket was right at the top of the tower. The mast and antenna are somewhat heavy, weighing about 50 lbs. I relied on a pulley at the top and bottom of the tower and a haul rope to get support from my ground crew.

The tricky part of this operation was going to be moving the antenna higher on the mast. I had two options. First, I could loosen the bracket U-bolts, lift the antenna higher, then retighten. This would only take me about five hands, and I was only born with two. Second, I could loosen the bracket U-bolts, then lower the mast into the tower. While this seems easier, I had visions of the mast going too low and the antenna falling off the tower. Plus, I was afraid that we'd drop the mast and it would fall some 40-some feet into the base of the tower. And then the antenna would fall off the tower.

Plus, my daughter was having a lot of trouble getting sufficient leverage on my pull rope, which was 1/4". After being at the top of the tower a little over and hour, I decided to continue the project later.

Little did I know that it would take two months before I could get back up there!

In the intervening time, I had purchased 120 feet of 9/16" braided black poly rope. Our first order of business was to replace the existing 1/4" rope with this much more substantial lanyard. Once again with my trusty ground crew, we set out to complete the project.

With the bigger haul rope installed, I surveyed the top of the mast. I had thought that perhaps the antenna had slid down the mast in the 18 years it has been up. But a close examination of the mast showed no evidence of that. It had always been at that level.

Standing there 40-some odd feet in the air, 20 feet above the edge of my roof, I wondered if loosening the antenna would get me into a whole new world of problems. I decided at that moment I wasn't going to mount the A50-3 under the larger beam. What we needed to do was hoist the mast back and up and put the rotator back in place.

This proved to be a problem. Despite all her hauling away on the rope, Lauren was unable to raise the mast any significant distance. It was only with me grabbing the mast with two hands and pushing we were able to move it at all. I ended up locking down the mast with a couple of bolts in the tower and climbing down to solve the problem.

I had a ratcheting come-along, but hauling it up and using it on the tower was problematic. I ended up tying the come-along to a support pole, then hooking it into the haul rope via a tied loop. This would allow Lauren to use the come-along to provide lift, and I could manage things at the top of the tower.

After climbing back up, things moved a little more quickly. The come-along provided plenty of tension, but I found that I had to move the mast with my hands to get it to budge -- there's just too much friction and too much stretch in the poly rope. In a few minutes, we had the mast nearly back up into position. I had to re-position the pulley to get the last few inches to make room for the rotator.

With the mast locked down again, I hauled the rotator back into position. Thereupon I discovered two problems. First, one of the four nuts on the U-bolt that clamps the rotator to the mast was missing. In the two months on the tower, it apparently shook loose and fell off. Second, the rotator connection at the base of the rotator were loose -- one of the forked lugs had fallen off the wire and would need to be replaced.

Not having the necessary hardware at the top of the tower, I finished as much of the assembly as I could and came down the tower knowing that this project would be finished on another day. Hopefully, it won't take a couple of months to get back up there.

Friday, February 15, 2019

Mark V.5 Shunt Feed Matching Network (75 & 80m)

Additional capacitor for 80m at lower
right, relay is black box just above.
Three years ago, I improved my shunt-feed matching network for 75m by upgrading to a T200A-2 core and a way more beefy variable capacitor. It tuned my shunt-fed tower quite nicely to a 1:1 match around 3800 kHz. And it could easily handle a little bit of power.

However, when using the antenna on the low end of 80m, the match isn't quite so nice, reaching nearly 3:1 at the bottom of the band. I needed to be able to re-adjust the network when operating there.

It occurred to me that additional capacitance would do the trick, along with a way to switch it in. I found good capacitor of about 25 pF and suitable plate spacing. Switching it was more of a problem.

I wanted to use a large, 12 volt, open-frame relay. Unfortunately, I didn't have anything in my junk box, and couldn't find anything I liked at a hamfest. Eventually, I settled on using a PC board style relay. I figured it had enough of a contact gap to avoid arcing.

Mounting it, however, was problematic. I ended up just having it floating in the box, suspended by the wiring connections.

Side of box showing the control voltage wiring, the 75m
tuning control (upper right) and the 80m tuning.
After re-wiring, the network tuned up nicely on 75m, but there wasn't quite enough capacitance to bring the match down in the CW portion of the band. I ended up putting to 33 pF 6 kV capacitors in series across the 25 pF variable, essentially adding 16.5 pF to the circuit.

That did the trick, and I got a 1.1:1 match around 3570 kHz. VSWR at the bottom edge of the band was under 2:1.

The existing four-wire bell cable control lines were re-purposed to drive two relay circuits. The existing frame relay selects between the 75/80m and the 160m matching networks. The additional relay is energized to bring the additional capacitance online for 80m.

This works so well, I'm surprised I didn't try it earlier. With a better match at the antenna, losses in the feed line and antenna tuner are reduced.

Monday, January 28, 2019


In the center, the regulator that was spraying
water over my equipment. Note the ceiling
tile above it has disintegrated from the spray.
It's a terrible feeling. You're walking into the basement to grab some hardware right before going to work, and you are greeted with huge puddles of water on the basement floor. Looking for the source, you find the pressure reducing value (also known as the regulator) spraying water all over your ham radio gear. Oh no!

The next several minutes, I hardly knew what to do. I shut the water off immediately, then called my wife to see who our preferred plumber was. Then I mislaid my phone so I couldn't call anyone for a while. I had to get my daughter to look for my phone.

In any case, I got busy clearing out the shack, mopping up the shack floor and vacuuming up water from the basement. The first plumber arrived, I told him the water was spraying from the regulator. He said he'd have to see if he had a replacement. An hour later, another plumber arrived, an associate of the first. He looked at it, and said he'd have to check his truck if he had the right unit. He didn't. So, he disappeared for another hour and a half....

During this time, I'm working hard. I'd cleared out the shack and mopped up the water, vacuumed the water off the basement floor, thrown out the few soaked cardboard boxes.

Then it came to determine how to salvage my soaked equipment. I decided to take an ancient tip and placed my Elecraft K3/100, plus a few other pieces of gear in the kitchen oven for an hour at 150 degrees F. This temperature wouldn't hurt the electronics, but it would drive out any water that had gotten into the gear.

By about 1:30 PM, the plumber replaced the regulator, and lightened my wallet by $325. Later in the day I tested the K3, and it seemed to be working fine. I suspect, other than some papers I had on the desk, nothing will suffer any lasting damage.

That was Friday. Monday night, I'm putting the pieces of my shack back together. So far, everything seems to be working. Whew!

Thursday, October 25, 2018

VP6D on 30m CW

Odd things happen. During a long DXpedition, like the current VP6D expedition to Ducie Island, they are bound to happen. They happened during the K1N Navassa Island expedition, for example.

Last night I'm trying very hard to put VP6D in as many DXCC slots as I can. I hadn't worked them on 30m, and they were running RTTY. 30m is often tough, since everyone runs 200 watts, tops, and my 100 watt signal doesn't really stand out. RTTY makes it even harder. I called for a half an hour with no luck. And then VP6D disappears.

I continue calling for a little bit. It's a sort of anxious hope that sometimes works. Maybe they had a generator die, and the first thing the operator will hear when the generator comes back to life will be my callsign. Right? Well, it could happen.

After a couple of minutes I stop calling. I'm sitting there with the headphones on. The left ear is listening to 10142 kHz at about 450 Hz wide, the right is listening up around 10144.5 kHz, about 2 kHz wide. And, I'm hearing nothing. Nothing at all.

About three minutes after I stopped calling, I heard a signal. It sounds like a CQ. A CW CQ. It's off frequency, so I can't really tell. I'm not set up for CW. I'm in DATA mode, with settings all flipped around with wide filters. But - there it is again - in my right ear, it sounds like VP6D calling CQ, in CW.

Switch things around to CW, with a narrow filter, and then tune for the right frequency. I'm sure I'm going to miss it, but no, I find him. There he is CQ VP6D UP2. Plain as day on 10144 kHz. That's not where you'd expect him to be at all. No, the published CW frequency is 10105 kHz. This frequency is out of position for CW, but there he is, calling CQ VP6D UP2. And no one is answering. No one.

This is my chance. I go into split, up 2, and give him a call. But, again, CQ VP6D UP2. A couple of times. No answer. So, I figure, hey, maybe he's actually listening up 1 and doesn't realize his memory keyer doesn't match. I dial in up 1, and call. No dice. After a few calls, I wonder where he's listening really. Maybe he's listening up 2 from 10105 kHz. I give him a call on 10107 kHz. Nothing. Perhaps he's listening on his own frequency?

At this point, he's been calling CQ on 10144 kHz for two solid minutes and no one has answered him. I figure it's worth a try without being a DX lid. I turn off split and dump in my call: AA4LR. AA4LR 5NN comes the response. R 5NN TU, I reply.

And bam, quick as that, he's in the log.

He goes back to calling CQ VP6D UP2. I listen for a couple more minutes, but no one is calling him. I post a spot on and listen for a couple more minutes. Still no one. I begin to wonder if he's just clueless to where he is in the band, and that no one is looking for him there. So, I dare to send again on his frequency: FREQ? He responds to my question by sending 10144 twice. So, yeah, he knows where he is. I post another spot, hoping some other DXer will find him, too.

After about 10 minutes of this, he goes silent. A minute after, I find him down on 10105 kHz, once again calling CQ VP6D UP 2. And, people are calling him, and he's answering. Good, that's what's supposed to happen.

Looks like I'll may be the only one who worked VP6D on 10144 kHz CW. Cool.