Monday, January 31, 2011

The J-pole is soldered together!

Tonight I soldered together the J-pole I mentioned in my last post.

Conditions were less than ideal for this. Not having a garage, and it being awfully cold outside, I had to work in a basement. On the plus side, the basement was relatively warm. On the minus side, it was awfully dirty down there. I kept things as clean as I could, though.

Another less than ideal thing was the flux I used. I purchased a kit from the hardware store that came with a small roll of solder and a small tube of flux. The tube of flux had a thick plastic lid, and I didn't have anything to puncture it with, so I ended up heating up a piece of scrap copper wire and using that to puncture the tube. I only managed this once, however, so the flux came out in a thin ribbon.

But, all problems and less than ideal conditions aside, the j-pole is together! Now all I need to do is find the 75 Ohm match point and I'll be good to go. Now, experienced hams might have noticed that I said 75 Ohms in my last sentence and be a bit confused. After all, most ham equipment is designed for 50 Ohm loads, and you generally want the best impedance match you can get, so as to maximize your power output. But as it happens, I have a bunch of leftover 75 Ohm RG6 that various cable installers have left with me, and I don't want it to go to waste. So I'm going to try and use that as feedline, and try and set something up to match that impedance as best I can. It was suggested in this thread on QRZ that if I make sure my 75 Ohm line is a multiple of 1/2 a wavelength, I can then connect a bit of 50 Ohm line at the radio end. We'll see how that goes. :)

Friday, January 28, 2011

Adventures in ham radio

In my quest to become a broadcast engineer and general polymath, I've started getting into ham radio.1. I got my Technician-class license in August of last year, and started operating on EchoLink, which provides VoIP connections to other ham operators and those repeaters connected to EchoLink. I made a couple of "Slim Jim"-type antennas, one out of twin-lead, the other out of ladder-line, but didn't actually get a radio until fairly recently.

My current radios are a Midland 13-505 that I bought at the last hamfest, and a pair of EF Johnson 9800 series radios that were given to me by a fellow ham. The Midland radio operates on the 2 meter band, which covers (for hams) 144 - 148 MHz. The Johnson radios operate on the 70 cm band, 420 - 450 MHz.

Neither of these radios is exactly ideal. The Midland is locked (unless I can find or build a synthesizer) to those frequencies for which it has crystals installed. As the Midland dates to the early 1970s, crystals to fit it are fairly rare. The Johnson covers the entire 70 cm band, but requires a special programming cable which I do not currently possess. I have, however, found two sets of plans on the Internet for building such a cable (here and here), so I think that I shall soon have that problem sorted.

As of yet, I have not been able to make a QSL (a contact) with either radio. Several times I have heard traffic on the Midland radio, but I have yet to be heard. I have heard nothing on the Johnson. I'm hoping all that will change soon, though, as I'm building a new antenna. It's another J-Pole (note that the "Slim Jim" is a special case of the J-Pole), but this time, I'm making it out of 1/2" copper tubing.

I used plans by G.E. "Buck" Rogers, K4ABT to get the proper lengths of copper tubing. I went to Westlake Hardware in Westport to buy the tubing, caps, tee, and elbow, and they were kind enough to cut the pipe in the lengths I needed at no charge. I haven't assembled it yet, as I don't know how to solder copper pipe together, but once I have, I plan to mount it on the railing to the stairs at the back of my house. That will give me a reasonable amount of height, especially compared to where I have my antenna now - hanging on the wall above a window in the rear of my house.

That's all for now, Dear Readers. I'll keep you posted (sporadically, of course) on my further adventures in ham radio. And I've still got all manner of things to talk about at KCUR. :)

1Before you ask, Dear Reader, no, I still haven't learned where the "ham" in "ham radio" comes from. I'm sure it's on the Internet somewhere.