Archive for the ‘Uncategorized’ Category

2m Spring VHF Sprint

Tuesday, April 12th, 2011

I went up to Brush Mountain last night (EM97sg) to take part in the first spring sprint this year, on 2m. I used my Kenwood TR-9000 rig along with the Mirage B-108 80W amplifier, and operated out of the back of my Jeep. For an antenna, I got my Cushcraft 13B2 up and running, which seemed to work quite well. All in all, I made 14 QSO’s with the farthest being FN01xt up in northern PA.

Now off to get my 222 Transverter (W7BAS variety) up and running again for next week!

What’s Really In The TV Bands?

Wednesday, February 2nd, 2011

The TV Bands in the United States get a lot of use, despite what you might think based on the White Spaces proceedings in the past few years. Some of it may be obvious, but other users might be downright surprising. This post is an attempt at a comprehensive list of users of the TV Bands in the United States.

Before we begin, here is a list of channels and what frequencies they correspond to:
2-4: 54-72 MHz
5-6: 76-88 MHz
7-13: 174-216 MHz
14-36: 470-608 MHz
38-51: 614-698 MHz

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222 MHz, The Homebrew Way

Monday, January 24th, 2011

I’ve had an interest in getting on bands above 6m for quite a while, but for various reasons I’ve tended to stall out in the process and never complete the projects. This time, though, I set a hard deadline of January 22nd to have a working 220 MHz SSB station.

The project started when a friend found a transverter board online by W7BAS that uses a 144 MHz IF. This is convenient because I just got a Kenwood TR-9000 2m rig for Christmas this year, and it’s of the variety that can be easily modified for transverter operation. I purchased the board, and got it about two weeks ago.

I have to complement Bruce for his board design. Unlike some boards out there, significant thought was put into the kit design to make it easy to assemble. Not only does the board have labels for all components, but the kit comes with all components in individually labeled containers so that one can keep track of parts really easily. No components were smaller than 0805, which made assembly extremely easy with a SMT solder station. I’d imagine it would be much harder without a fine tip soldering iron and magnifying glass, though.

W7BAS Transverter Board

W7BAS Transverter Board

I had few problems with the board after assembly. I discovered later on that the receive MMIC amplifier was not receiving bias, but that was due to a mis-soldered RF choke.

The board is designed with performance in mind. The receive path has a 222 MHz three-stage helical filter immediately following the mixer to filter out LO and IF leakage (though the third harmonic of the LO is still a potential issue at 234 MHz), and the LO, RX, and TX paths have small filters inline after each amplification stage to keep the signal path clean. I have not done a formal spurious response analysis, but undesired signals appear to be at least 25 dB down from the fundamental at 222 MHz.

After fixing the receive preamp, I found sensitivity down to CW signals (as measured by ear with the TR-9000) to be good to at least -136 dBm, and possibly better though I did not try. Drive from the transverter is also very good with output power better than the specified 10 mW, though I did not record actual CW values. I will do this next time it’s on the bench.

A transverter isn’t much good with drive in the milliWatt range, though, so I purchased an M67712 power module from RFParts. It cost around $85, and can in theory make close to 30W with linear amplification (Class AB, not C). The module is easy to use, with RF in, RF out, bias, and ground terminals. I used a specially designed board with it, but I don’t know that it would be strictly necessary for good performance. Due to drive issues from my Kenwood TR-9000 (read: too hot!), I can only get to about 4W output before I run the risk of damaging the transverter.

I found that the entire system, with the power module, makes about 20 dB gain from IF drive power. That is to say that the 222 MHz output power is 20 dB higher than the 144 MHz IF drive.

To complete the package, I used a G6Y relay with a W1GHZ board for T/R switching, and bundled the thing in a metal box I got from a friend.


Amateur Satellites

Tuesday, November 24th, 2009

I’ve always had an interest in making contacts over amateur satellites. Not only did the idea of talking to someone over a satellite seem really cool, but it can be done with basic equipment that almost every ham has. So, this week I decided to make an honest attempt at making a satellite contact–and it worked!

For receive, I used a handheld 440 MHz cubical quad antenna that was built for foxhunting, not satellite work. That said, it makes a pretty awesome satellite antenna due to its light weight and compact size. To transmit, I simply used the whip mounted on the top of my Jeep. The antenna probably provides somewhere around 3-5 dB of gain, but not necessarily directed upwards. I set my mobile to output 10W.

My first contact was on Friday, November 20th and I made it from the Chicken Hill parking lot on the campus of Virginia Tech (Grid Square EM19), on satellite SO-50. Sadly, I didn’t buffer the call of the other station, so I was unable to log it correctly. My second and third contacts occurred on Monday night, November 23rd, and were also on SO-50. The first contact was ZL7VX, who I believe was stateside in FM18. I then spoke with N9AMW in EN52 in Wisconsin.

Working the bird at night was definitely a pleasurable experience as I didn’t feel rushed to make the contact and get off the bird; there was plenty of time to slowly exchange calls and say a few words as well.

I’m looking forward to continuing to work satellites in the near future, and look for updates here on this blog as to how I’m doing with that.

Transverters

Tuesday, October 13th, 2009

I’ve always been interested in the upper UHF and microwave amateur radio bands (900 MHz and up).  Unfortunately, nobody actually makes full-on radios for these bands (save for 1.2 GHz, and they’re expensive).  This leaves the curious amateur with two options:  build a radio, or build a converter to allow common radios to operate at higher frequencies.  The second option, obviously, is simpler and the route I decided to take.

I recently discovered W1GHZ’s multiband transverter project.  Essentially, his goal was to build inexpensive transverters that worked “well enough”–and ones that had an interchangeable LO to keep costs down.  Since I already own commercial 900 MHz gear that works on the 902-928 amateur band, I decided to order the 902 MHz transverter kit.  I should get the boards and parts in soon, and I’ll post again once I get it assembled and tested.  Here’s hoping it works well!