More Sweet Tweets

Here are some more links to interesting Web pages I found by Twittering:

  • N3OX’s Remote Tuner Control. N3OX has added some servo motors and controls to a manual antenna tuner so that he can move it closer to the antenna, but still control it from inside the shack. Very inexpensive solution.
  • Band Plans for 900 MHz and Above. KB9MWR feels that the future of ham radio is above 900 MHz. I don’t know that I totally agree, but I do think we need to start thinking more about those bands. Give this a read.
  • Morse Code vs. Text Messaging. Chas Sprague, who’s not a ham, ruminates on how Morse Code could make text messaging more efficient. I wholeheartedly agree! Someone get this man his ham ticket.
  • Ham Logging as a Service. There’s been a lot of twittering about this KE9V blog post. I like the idea myself, and if I had more time, I might even take a crack at it. Anyone want to collaborate?
  • Planning a Digital ATV Station. After pondering a digital ATV station for the museum, I opted to go analog. If I’d seen this article first, I might have opted to stick it out and go digital.

Digital TV?

For our Ham Radio at the Hands-On Museum project, we want to set up a television station. My first thought was to buy a transmitter from PC Electronics that sends standard-scan analog TV. Then, I got to thinking, why bother with that? If our goal is to show that we’re at least up with current technology, then shouldn’t we be doing digital TV?

I have found a bunch of European hams doing digital TV using the European standard and one page of links on DXZone:

So far, though, I haven’t seen anything on ATV using the new US standard. Is anyone out there experimenting with this or even making gear that I can purchase?

German AMSAT First To Bounce Signals Off Venus

From the April 3, 2009 ARRL Letter:

On March 25, a group from AMSAT-DL bounced radio signals off the surface of Venus, marking the first time Amateur Radio operators have bounced radio signals off another planet. According to AMSAT-DL President Peter Guelzow, DB2OS, the Earth-Venus-Earth (EVE) transmission is another step in preparing for a mission to Mars.

According to an AMSAT-DL press release, the team’s transmitter was generating about 6 kW CW on 2.4 GHz. Guelzow said that signals were sent from a ground control station at the IUZ Sternwarte observatory in Bochum: “After traveling almost 100 million kilometers and a round trip delay of about 5 minutes, they were clearly received as echoes from the surface of Venus. This was the first German success to receive echoes of other planets. In addition, this is the farthest distance crossed by radio amateurs, over 100 times further than echoes from the moon (EME reflections).”

The EVE experiment was repeated on March 26 for several hours with “good echoes” from Venus, Guelzow said. “Morse code was used to transmit the well-known ‘HI’ signature known from the AMSAT OSCAR satellites.”

For receiving the EVE reflections, Guelzow said that the team used a fast Fourier transform (FFT) analysis with an integration time of 5 minutes. “After integrating for 2 minutes only, the reflected signals were clearly visible in the display,” he said. “Despite the bad weather, signals from Venus could be detected from 1038 UTC on until the planet reached the local horizon.”

Guelzow explained that with the EVE reflections, the high power amplifier “has therefore passed this crucial test as a final key component for the planned P5-A Mars mission. By receiving generated echoes from Venus, the ground and command station for the Mars probe has been cleared for operational use and the AMSAT-DL team is now gearing up for building the P5-A space probe. AMSAT-DL wants to show that low-budget interplanetary exploration is possible with its approach.”

Development, design and construction of this first German Mars mission have been achieved by AMSAT-DL and its partner organizations, Guelzow explained. “Already a third of the total project costs were performed. More work shall follow during the mission. AMSAT-DL would like to demonstrate that their approaches to low-cost space missions are feasible.”  

Information provided by AMSAT-DL. Pictures of the equipment used can be found on the AMSAT DL website.

New Year’s Resolutions

I know it’s pretty dopey to do New Year’s resolutions, but I’m going to do it anyway. Maybe if I list them, I’ll actually get some of them done this year.

  • Build more. High on my list of things to build is “A Simple Regen for Beginners.” I even have the PC board already. I’d also like to try some of the receivers described by George, G3RJV, at the two Four Days in May that I’ve attended.
  • Put up that 80m loop antenna. I’ve been saying that I”m going to do this for a couple of years now.
  • Get on 900 MHz. I’m throwing in an easy one. I’ve already sent off the check to get a 900 MHz radio so that I can get on the repeater here in Ann Arbor. Over and above just getting on, though, I want to explore some digital communications possibilities.
  • Work on some Mac software projects. It shouldn’t be too hard to come up with some simple ham radio software that will run on the Mac.

Space Station QSO a Success

Thanks to Ig, N0EFT, and his crew:

  • Tim, WA8VTD, back up radio operator;
  • Steve, KB9UPS, ARISS mentor and antenna and az/el rotor operator;
  • Olivia, KC8VGH, who handled the microphone and kids; and
  • Candy. KD8IPC, who made the initial contact and helped with the kids;

yesterday’s Space Station contact from the Ann Arbor Hands-On Museum was a success. Despite the low orbit (21 degrees), the contact lasted nearly nine minutes and they were able to ask 14 questions.

I hope to post video later, but in the meantime, here are a couple of news stories:

900 MHz??

Someone recently offered to give our club a 900 MHz repeater. 900 MHz?? Who uses that band Well, apparently, there is a lot of activity up there, and maybe the least of it amateur activity.

I got to thinking about how we might use it. The first thing to cross my mind was digital TV. Other kinds of digital apps, such as some kind of instant messaging, might also be interesting.

Here are some resources:

  • Exploring 900 MHz by KB9MWR. Some good basic information on the band and equipment you can use there.
  • AR902MHz Yahoo Groups Mailing List. This list has more than 1,400 subscribers and is relatively active.
  • San Diego 900 MHz ARC. General info on 900 MHz as well as specific info on what’s going on around San Diego.
  • GEMoto.Com. This is a networking group made up of mostly New England hams interested in converting and using GE and Motorola commercial radios. According to Ben, N1WBV, there’s a fair amount of 900 MHz activity around Boston because their use of 440 MHz is fairly restricted.

No VHF SWR Meter? No Problem.

On the HamRadioHelpGroup mailing list, a ham asked:

Will a CB SWR meter work on a 2 meter ham radio??

Mark, K5LXP, replied:

Yes and no.

I use a CB SWR meter to check 2M antennas all the time. There is a trick to it however.

If all you want to to is check SWR on your 2M antenna, you don’t necessarily have to buy a dedicated VHF/UHF SWR meter. What I keep in my toolbag for that is a cheapie $5 hamfest special CB SWR meter. They really don’t work well on 2M but there’s a trick you can do that will net a reasonably accurate SWR reading on 2M with one of these meters. What you do is connect up the meter as usual, key the rig with the switch in the forward power position, set the adjustment for full scale. Now, without touching anything, swap the coax connections so that the rig is connected to the “ANT” side of the meter, and the antenna is connected to the “XCVR” side. The reading you see on the meter will be very close to your real SWR. The closer to 1:1 your SWR is, the more accurate it will be. It would be more convenient to have a real SWR meter or antenna analyzer if you do a lot of testing, but for a quick antenna check after a mobile install or whatever, the $5 CB meters work OK.

When I asked his permission to use this, Mark said, “I don’t get the credit, I picked it up from some OF years ago.” (E-mail me if you don’t know what an OF is.) Well, Mark, you might not get the credit for thinking this up, but you certainly get the credit for passing it on. Thanks!

Find EchoLink, IRLP Nodes

From James, KB7TBT, via the HamRadioHelpGroup:

For those that wish to find a live on the air repeater or simplex node for either Echolink or IRLP.

FM Tutorial Online

TechOnline presents a basic tutorial on FM with descriptions of multiplex (MPX) signaling and noise improvement techniques, such as stereo-mono blending and soft mute. This paper was written by Lawrence Der, an engineer with Silicon Laboratories. Accordingly, it also introduces Silicon Laboratories’ Si4700/01 FM Tuner ICs.

If a J-Pole Antenna is Good for 2m, Would it be 3X as Good for 6m?

Nick, KD8IPE, one of the guys in my latest Tech class got interested in working 6m and asked me about 6m antenna. Well, having never worked 6m, I didn’t have a very good answer for him. Then, I thought about the J-pole antenna. I have built many 2m J-poles. They’re simple to build, and using my favorite set of plans, the SWR in the repeater portion of the band has always been 1.5:1 or less. So, I suggested he build a 6m J-pole.

Nick then turned the tables on me and suggested that we each build one. Then, he reasoned, he’d at least have someone to talk to. I took him up on that, and last night, we built one using plans developed by DK7ZB. This antenna differs from the 2m J-pole in a couple of ways. First, the radiator is made from antenna wire, not the 450-ohm ladder line, as in the 2m J-pole.

Second, the feed point seems to be at a different point. In the first set of plans, the feed point is approximately 20% up from the shorted end of the matching stub. In DK7ZB’s plans, the feedpoint is 5-10% from the shorted end. Since I’d had such good success with the first set of plans, we decided to go with the 20% figure and placed the feedpoint about 13.5-in. from the shorted end.

Third, the DK7ZB design uses a choke balun at the feedpoint. You rarely see this on 2m J-poles, although this is debated now and then.

After some discussion about whether to solder the coax directly to the ladder line or to install an SO-239 (we opted for the SO-239), we soldered it all together and then took it outside to hang it from a tree branch. We ran the coax inside and then hooked it up to my Icom IC-746PRO. I don’t have an SWR meter for 6m, but the 746PRO’s internal antenna tuner was able to find a match, so the SWR mustn’t be too bad.

Of course, 6m didn’t appear to be open at the time, so we didn’t work anyone. Heck, we didn’t even hear anyone or any of the beacons. Even so, it’s kind of cool to be able to say that I’m now capable of working 6m.

I do have some questions, though:

  • What’s up with the feedpoint? Why do the two designs differ as to where to place the feed point? I wish I had an antenna analyzer to make some measurements.
  • Is the balun necessary and/or useful? Does using a balun affect the feedpoint placement?
  • Does polarization matter? I’d guess if I were trying to operate a 6m FM repeater it would, but that it wouldn’t matter so much when working CW or SSB DX.