Amplifier and other news

I finally realized a few weeks ago that I have way too many ongoing projects in my life. I've taken on various volunteer responsibilities at the rowing club (ironic since I almost never get down there to row), I have 3-4 repair projects to finish on the scooter, not to mention washing it, and I now have two ham radio projects on my plate. In addition to the amplifier, I have the ATS-4a kit which I bought in January, still sitting unbuilt. If you're reading closely, you may recall that I had posted that I bought an ATS-4b. Upon closer inspection of the kit recently, it turns out that what I have is a 4a. The seller was mistaken about it, but it's OK. The differences are very minor – the 4b seems to have a slightly better screen and an updated AGC circuit, neither of which is critical to me.

I've resolved to focus on one project at a time and try to clear this backlog of stuff, because in 4 months I'm going to become a dad, and then I suspect I will have almost NO free time! So 2 weeks ago Nick and I went to the rowing club to use the drill press there and try to do some of the metalwork needed to make progress on the amp. First I spent probably over an hour laboriously cutting a hole in the top of my steel enclosure for the amp PCB to attach through. By the time I was done I was firmly reminded of why an all-aluminum box would have been a lot better. I also managed to cut the hole slightly too wide on the ends, so the heatsink can't cover it completely. $#%#$%! It's not too big of a deal, I'll just have to cover it with some tape.

Next we marked and drilled all the holes in the heatsink, using a center punch to get us started. It would have been better to do this before assembling the amp for two reasons. First, I could have marked the holes more accurately with the PCB sitting flat on the board. Second, when finished I could have physically mounted the transistors and THEN soldered them to the board, thus ensuring that they sat flush on the heatsink. Now I'm probably going to have to rework or even remove them when I mount the board to make sure everything mates up properly.

With the holes drilled we started the process of tapping them for the 4-40 screws. I've never tapped holes before, so Nick showed me how and we did two of them, and then called it a day. I planned to do the rest on my own. There are a total of 12 holes to tap in the aluminum heatsink. I worked on the rest over a couple of evenings this past week, did two more this morning, and I have four to go. It has taken me a bit to get the hang of tapping, but I think I've got it down now. I just work the tap forward and backward a bit at a time, stop and go in reverse a few turns every now and then, and after 4-5 full turns I remove it and clean out the chips. I'm able to do a hole in about 20 minutes now I think, where it was taking me 45 when I started.

Once this is done I should be able to mount the amp to the heatsink, and then Nick and I can test it more and try to get it tuned and dialed in. After that, we'll need to integrate the LPF board and band select knob, and then whip up a keying relay.

Rob (AK6L) and I are talking about working field day together this year, possibly from the rowing club since it's right on San Francisco bay. Nick might join us as well. It would be great to have the amp in usable condition by then, but I'm not sure it's feasible given how much more work we have to do.

I've continued to try and practice morse code, focusing mostly on numbers since that's the main group of characters that I don't know well. It feels like it has gotten harder though, working with close to 40 chars. It's a real struggle to keep up and have any kind of accuracy, even at an effective speed of only 4wpm (20wpm character speed). I just need to keep practicing. Part of me feels like maybe I should just get on the air and start making CW QSOs, but I'd really have to rely on the computer to copy for me, so I'm not sure it would help me get better. Once the amp is done though, I'll want to get my ATS-4a built, and that rig can only do CW. If I can learn it, I'll be able to operate remotely from almost anywhere, with minimal accessories, and that really does appeal to me.

Once I make more physical progress on the amp I'll post some pictures!

This entry was posted in Uncategorized. Bookmark the permalink.