Category: radio

Since I've been here at LeTourneau, I've had the chance to meet a few other ham radio operators. Problem is, none of us can have any substantial antenna setups in order to make many contacts, if any at all.

After speaking with a couple of guys, we decided to reorganize the LeTourneau Univ. Amateur Radio Club (LUARC) and host a special event station. LUARC was more or less disbanded once the old shack was torn down to make way for Glaske Hall.

Since none of us have been able to play on the air very much, our special event will be nothing more than a chance to get on the air and hang out. It just so happens that the day we chose will coincide with the opening of the Texas QSO Party. We will be meeting on top of the birm, in the center of campus. We will be putting up the antennas around 12:00pm on Saturday and operating into the early evening. Everyone is welcome to stop by and check out our setup or operate - no license is required.

If you're on Facebook, you can see our LUARC Special Event page for Facebook.

I just finished making quite possibly the world's most simple radio. I had read a few HOWTOs for constructing a crystal radio. Some links offered the basic formulas for figuring the specs needed for the coil if you wanted to tune various frequencies. I purchased 3 spools of "Enamel-Coated Magnet Wire" from Radio Shack for ~$5, and picked up a crystal ear piece while at EPO in Houston.

After reading that just about any round object will do for a coil-form, and not having an empty toilet paper tube, I settled on an empty fish food container. It was small, compact, and just the right size - plus with the screw on lid, I can keep the antenna, ground and ear piece inside. I rinsed out the fish food residue, tapped 4 small holes with a drill bit and started wrapping the 22awg copper wire around the bottle. Every 5 turns I would wrap around a toothpick. After wrapping the bottle - which took a while - I ended up using about 30ft. of wire. (FWIW: my coil came out to be about 118uH) The toothpick wraps were then scraped free of the enamel coating to make antenna taps for rough tuning. (how this works) After ensuring there were no shorts along the coil body, I hooked up the 1N34 diode, ear-piece, ground wire and antenna and was greeted with some shortwave radio broadcasts. The first station I heard ID was WWCR out of Nashville, Tennesee, although there are plenty of others I can hear.

The trouble with such a simple receiver (no variable capacitor) is that there is little selectivity and the listener is bombarded by 2 or more stations at once - a mixing of all of the signals within a range of frequencies. To fix it would add complexity, but it's not hard to do.

For my antenna, I just have an 8' wire tacked up to the wall. For my ground, I have an 8' wire precariously plugged into the ground on an electrical outlet (I wouldn't recommend it, but it does work).

In the picture, the toothpick is shown on the coil with the wraps every 5 turns. The green wire is my ground, the black alligator clip goes to my antenna wire (the clip makes it easily movable for tuning), the diode is at the top of the coil, next to the green spool, and then of course the white high-impedence ear piece. Also note that no solder was required, I opted to use springs to connect points, but twisting and taping would have worked just as well.

If you're interested in trying it out, gather the required parts and let me know how yours turns out.

Grendel sez: For my next trick, I hope to swap the diode out for a razor blade and safety pin! The best explanation of how crystal sets work, that I've found so far, is here.

update: Success! After trying for an evening, I got the razor blade and saftey pin combo to act as a detector. Here's a picture of the setup.
I used regular straight blades (found by more "modern" blades in the shaving section of most stores) and an ordinary safety pin. After reading about the "blued steel" of the WWII-era blades, I learned that the blue hue of the blade was due to a heating treatment that is done to the blade during manufacturing. I wasn't having any luck with my blade so I gripped the blade with pliers, held it horizontally in a flame until I saw the blue appear on top of the blade. I wiped away the black residue from the flame on the bottom and tacked down the blade.

Next, I got a small piece of lead from an automatic pencil, connected it to the safety pin via a small dab of solder, tacked down the pin and hooked up the radio. (Blade goes to the ground, pin goes to ear piece.) You have to be patient and fish around the blade for the right point but you'll find it.

It also doesn't help that I'm not very close to a strong station, so it took a while longer. I'm sure anyone near a 50,000W AM station won't have much trouble. The signal is very weak, even compared to the diode, so make sure you are getting a decent signal with your diode before attempting this method. (I hooked up my ham radio antenna and got alot stronger signal than the aforementioned 8' wire.)

Tip: Try in the top-center of the blade around the hole in the blade - that's my sweet spot.
I've also found out that florist's wire works just as well and is alot cheaper (and more easily found in stores).

update: To make it even easier try a Slinky!

For about the past month or so I've been eyeballing PSK31 for ham radio. It's one of the newest protocols for digital transmissions for ham radio. PSK31 allows radio operators to send text messages back and forth rather than morse code (CW) or speech (phone). It's like chatting without a network connection.

Granted, many of the regular readers on neodux aren't ham operators, but it is a very interesting aspect of radio that begins to border line on hackable projects. In the event you ever wanted to start with PSK31, here's a primer. There are plenty of freeware programs to allow you to decode PSK31. All you need is an HF receiver, a verymodest computer and an 1/8"-to-1/8" stereo cable to hook the radio up to the computer. Install one of the PSK31 programs and you'll see text streaming in from current hams conversing over a whole array of topics. It's amazing that the computer is able to pull intelligable data from amid a whole field of static. I was able to read text from a signal I could barely hear, but could only see on the "waterfall" display. Another cool aspect is the lower power requirements of PSK31. 100W is overkill to work the world! To transmit you might need a slightly more advanced setup than a single wire, but nothing you can't build cheaply or conveniently purchase from plenty of vendors online.
While at the Belton Hamfest, I saw a DB9 model for Yaesu radios, I would've bought it if it would've worked for my Icom 706mkIIg.

update: I've now ordered a USB interface directly from Saratoga Amateur Radio which should be in shortly, and I'll post more on it after I've had time to break it in.

Also for the curious, here are a couple more links about PSK31.

If you really want to know, here is the PSK31 author's primer on how it works.

I just got back from a weekend in Austin that started with the Belton Hamfest in Belton,TX.
I took a few items that I wanted to sell. My AT-100Pro autotuner wasn't exactly what I wanted. The interface was a bit more "clunky" that I would have liked. (I received it as part of my trade for the Icom 706mkIIg.) I also sold the Yaesu FRG-100 receiver, as well as my Yaesu FT-2800 2m mobile that I had in my car, (I bought it almost 2yrs ago at the same hamfest for $95, I sold it for $120!) and a couple of other things.

After selling I went shopping. I bought the LDG Z-100 autotuner which does the same thing as the other tuner, with one antenna and is a bit smaller; and it looks nice atop my radio. I also got the seperation kit for the 706 so I can mount the radio under my seat and have just the control head in view. On my way out I grabbed a few small 2-3W solar panels for $5. The convention center wasn't as full as I'd seen in the past, there were some neat items, but nothing remarkable. I did leave with some good gear and more money in my pocket than I came in with.

I've finally got back on the air in the HF bands. After over 6 months of not having my radio reach any further than the local 2 meter repeaters (maybe 20mi away max), I finally have an antenna that lets me talk outside the state.

I bought a used Bilal Isotron 40 meter antenna from W6KIP off eham.net. I received the antenna after over a week-and-a-half long trek through the incredibly slow USPS shipping machine. That was on Friday, February 3. I assembled it and began thinking exactly how I wanted to mount it. I finally decided to mount the short "mast" (if you'd call it that) on one of the 3 vent pipes on the roof. I'll post a picture of it soon.

Part of my reason for using Isotron was the small size (only 22" wide). Looking at the antenna, you wouldn't even know it was an antenna, it looks more like a weather vane or birdfeeder. Being on campus, I didn't really want a very conspicuous antenna if I could help it. I haven't quite finished fine tuning the antenna, but I can do that as soon as I get my hands on one of the local ham's antenna analyzer.

I haven't made any contacts on it tonight due to an overwhelming amount of static on the 40-meter band. I've listened to a couple of nets, one on 7.2335 said that this is the worst noise they've had all month - what luck!

Update: Well, it turns out the noise isn't just on the band, although that particular night was particularly bad. It seems that the high level of noise (aka static) that I'm receiving is due to a local area thing. Most likely due to the power lines nearby. If I can pinpoint the source of the interference, the power company is obligated to resolve the harmful interference.

Update #2: It turns out it must be the power lines, I was able to go to the front of campus, shove the antenna in the ground and it received beautifully (for an antenna shoved in the dirt). Now, to find that pesky power line pole.

Update #3: Wow. So I called the power company and, not surprisingly, the service rep didn't have a clue what I was talking about. She tried to tell me that the power company has "the right of way" and that I just had to accept the interference. As politely as I could, I told her I didn't and that it was the power company's responsability to at least investigate the interference. She asked what kinda of amateur radio antenna I had, as if it mattered. She asked if any of my neighbors were experiencing problems on their radio. (wtf?) I told her I'd like to hear back from someone that understands about radio interference and what causes RFI on power lines. We'll see...

Update #4: The power company did send a guy out today. He called before he visited. I told him I'd be in class. After explaining the issue to him, he said he knew where my apartment was, and that if it's the powerlines I described to him, they belong to the university, and not Swepco. I had to get to class, but he said he'd leave me a note on my door. He came out, and it wasn't their powerlines. (I'm pretty sure he was right about the university being in control of the lines in question...) Now, to find the person in charge of the campus powerlines and go about getting them fixed in a way that won't get me evicted.