Source code for More Antenna Tinkering
--- title: More Antenna Tinkering date: 2010-01-30 13:41:59 tags: - amateur radio --- # More Antenna Tinkering __Dental school is taking a lot of time away from me.__ I try my best to compartmentalize dental school into a chunk of my schedule (a massive chunk), trying to use the rest of the time to spend with my family (wife) and when she's at work work on electronics (which seems to be radio these days). A few weeks ago I took the final amateur radio license exam and received my Amateur Extra license. It's a bunch of technical questions about radio circuitry, antenna theory, and other random stuff. You can see what I mean by taking an [online practice test](http://www.eham.net/exams/)! I applied for a new call sign (extra class operators can get shorter call signs). It seems the FCC gave me a VD. AJ4VD that is! Yes, my old call sign [KJ4LDF](http://www.qrz.com/callsign/KJ4LDF) has gone out the window as I am now [AJ4VD](http://www.qrz.com/callsign/AJ4VD)! In Morse code, that's `.- .--- ....- ...- -..` <div class='center border'> !(Ten_Tec_Century_21.JPG) </div> __I made my first Morse code contact__ from my apartment! This is the radio I'm using. It's a Ten-Tec Century 21 HF CW transceiver which puts out ~30W. I'm using a super-cheap but surprisingly functional homebrew base-loaded vertical antenna. The main vertical element is quarter-inch copper pipe from Home Depot (a couple bucks) cut with 1'' to spare from my 10ft ceiling. Therefore, it's a less-than quarter-wave vertical element, requiring a tuning coil (variable inductor at the base)... <div class='center border'> !(antennaBig.JPG) </div> <div class='center border small'> !(antennaBigger.JPG) !(antennaCoil.JPG) </div> __Here you can start to see the tuning coils.__ Briefly, I scraped a deep gash in the copper pipe such that a big glob of solder would adhere to it, and stuck a wire (yellow, coated) into that solder so it's a good connection to the pipe. I then started wrapping the wire around a few toilet paper rolls \[it's all I could find at the time!\] adding tap points (regions of exposed wire) every other turn. This functioned somewhat, but didn't allow for fine-tuning (pun intended). I therefore scrapped the bottom half of the cardboard cylinder/coil and constructed a slightly more elegant solution... __That's an [Olvaltine](http://en.wikipedia.org/wiki/Ovaltine) container.__ Yeah, I know, "More chocolaty Olvaltine please!" I used a rotary tool to scrape some measured/templated gashes on each side to give the wire (picture frame hanging wire from Target, 50' for $1.99) something to rest in. It turned out not to be enough, so I hot-glued the wire into the holes. This gives me a lot of exposed wire space to allow me to "tap" the coil wherever I want. By modifying where I clip onto the coil, I modify the length of wire in the coil that's used, therefore modifying the inductance of the coil, allowing for some tuning capabilities. Although it has a narrow tuning range, using the current setup I'm able to get my SWR down to 1:1 on 40m (nice!). __I made a couple of contacts since I got the rig last night.__ First was [K4KOR](http://www.qrz.com/db/k4kor) in central TN, who was calling CQ. I replied (slowly), and he came back to me (blazing fast Morse code). I was unable to copy ANYTHING he said (I'm not that good of an auditory decoder yet!) I'm sure he's incredibly nice and it wasn't intentional, but I had to give up the QSO. I know he copied my call, and I copied his, but I didn't copy ANYTHING else he said. Does that count as my first contact? This morning I fired up the rig at 9:15 and heard [W4HAY](http://www.qrz.com/db/w4hay) calling CQ from Northeast TN. I replied, stating that I'm new to CW so go slowly, and he was AMAZINGLY nice at sending me code at a snails pace. I was able to copy 90% of what he said, and will consider him my first solid contact!