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Tuesday, March 1, 2016
- Spring is nearly in the air, the new HF rig is ordered and on the way.
The decision was made and the piggy bank shaken empty right down to the last penny. I came to the conclusion the best HF radio within my budget was the Yaesu FTDX1200. Negotiation was done on the phone with the friendly team down at ML&S, happ...
- Australian ham gives an insider's tour of his antennas
Rob Wagner, VK3BVW, gives an interesting and visually appealing tour of the antennas at his home in Mount Evelyn, Victoria, a small town in southeast Australia near the beautiful city of Melbourne. His backyard features mostly wire antennas — 3 are double bazookas (or coaxial dipoles) — and includes a Par SWL End-Fedz antenna. In addition to […]
- Single Yagi Moonbounce
After installing my new USB serial adapter and being able to key my 2m transceiver's PTT line once again, I noticed that a full moon would be coming up the following evening and thought it would be interesting to see if my old, but simple system, was still capable of working stations off the moon.
courtesy: JPL/NASA
In early 2007, I decided to try 2m moonbounce using WSJT's JT65B digital mode. Over the years, moonbounce has gradually drifted away from CW to the much less demanding weak signal digital mode, allowing smaller stations to still explore the excitement of exchanging signals via reflection from the lunar surface. I am fortunate to have an excellent QTH for such an endeavour, being located beside the ocean with a saltwater horizon favoring moonrises, especially during the winter months of more northerly lunar declinations.
Theoretically, the ocean horizon produces about 6db of added gain to my system, making my 9el yagi produce gains approaching 19dbd ... about 2dbd more than a 24 element yagi and similar to a box of four 9el yagis mounted in an H-frame.
Moonrise from front yard
I soon realized that the actual numbers appeared very close to predicted values and using an inexpensive 2m FM/SSB 'brick amplifier' (with built-in GasFet preamp) delivering approximately 140 watts, I was able to work 54 different stations over the next twelve months. All of the stations worked were doing the heavy lifting, with the majority running typical 4-yagi H-frame arrays using yagis from 6 to 17 elements each. I did work one station that was using two small yagis during a period of excellent conditions. Somewhat surprisingly, a large majority of the stations I worked were strong enough to be heard audibly from the transceiver's speaker.
I'm always amazed at the truly small amount of RF energy that is actually left, after the round trip to the moon ... yet information can still be exchanged. On 144MHz, the round trip losses are a minimum of 250db. Factoring-in my antenna's gain and ignoring the coaxial losses in 70' of RG213, there is a scant 1.56 x10^-9 W arriving at the moon ... that's .00000000156 W! Considering how much RF is absorbed in the lunar dirt and what's left over for the -125db home trip, it's a miracle that some signals are loud enough to be heard by ear at all. EME is really one of ham radio's most fascinating activities.
Reacquainting myself with the newer version of the JT65B software, and testing out the system, I was ready to go on the next evening's moonrise. Unfortunately the moon was rising just a little too far south to give me a really clear shot and I would be pointing into the next door neighbour's trees. Being unable to track the elevation, my operating time is limited to about two hours per session, over a period of several successive days (or nights).
Almost coincidental with the night's moonrise, I heard the strong signals of RX1AS (Alex) in St. Petersburg, calling CQ. I called him and he came right back with my signal report. His station is shown below, along with his large homebuilt strip-line amplifier.
The next station I worked was DL8FBD (Gerald) near Frankfurt ... a new 'initial' for me, #55.
RX1AS
The following evening, the moon was buried even deeper into the trees but initials #56 and #57 were worked ... YL2GD (Gunars), in northern Latvia and RX3A (Nikolay), in Moscow city.
YL2GD and his EME station 
RX3A's 2m EME array
Nikolay was worked with the moon at 11 degrees above the horizon. I'm not sure just what my upper limit for lunar elevation might be with this small antenna but the highest elevation I have worked anyone was at 18 degrees.
The third night found less activity on the band as well as a more southerly moonrise, burying my target even further into the neighbour's trees. Few signal were heard but one contact was easily completed with I3MEK (Mario), near Venice ... initial #58.
Mario's signal, shown here on the waterfall display, comes from his four 19 element yagi array and 1 kW amplifier. His signal peaked at only -21db, indicative of the poorer conditions and heavier tree line obstruction.
I3MEK's 4-yagi 2m EME array
I've contemplated building a small 500 watt amplifier which would give me another 6db ... really a huge increase when it comes to EME, but I'd still be stuck with the same receiving capability. Having more power might put me in the position of being heard better but not being able to hear other stations any better. At my present power level, there appears to be an entire new crop of stations within my present reach, that weren't around in 2007 ... but constructing the amplifier would be a fun project!
I3MEK's 2m JT65b signal
With so many larger (four or more yagis) stations around the world, a huge antenna is not needed to have success on 2m JT65B moonbounce ... nor is an over-the-ocean moonrise. I've also been able to work stations on moonset where I am pointing over hilly terrain and trees, nowhere near the ocean.
The WSJT (JT65B mode) software is freely available and very easy to implement, but spend some time reading the manual and playing with the software first, perhaps getting used to QSO procedures on 20m.
If you are running a small FM/SSB amplifier on 2m, such as the typical 'brick' I have been using, make sure to add a blower to keep the heatsink cool, as JT65 has a 100% duty cycle and these small amplifiers can get hot pretty fast. I use a small squirrel-cage blower from an old microwave oven to direct a blast of air onto the cooling fins.
Wondering where to point your antenna? One handy site that will provide the moon's position in the sky, for any time and any location, is the U.S. Naval Observatory's 'Sun or Moon Altitude/Azimuth Table'. As well, you can keep abreast of real-time activity or set up skeds, via NØUR's Ping Jockey JT65 EME page.
If you do decide to give this a shot, I'd be interested to hear how you do ... maybe your system is big enough already to let us work each other via the moon.
- Making the Palm Mini Paddle Stay Put
In my on-going quest to produce a lightweight yet good-performing kit of portable equipment to carry along on my exotic work travels, I set my sights once again upon the Morse keying paddles. When I was a student, I carried what I had: a black-base Bencher BY-1. This caught the attention of nearly every airport […]
- The Spectrum Monitor — March, 2016
Stories you'll find in our March, 2016 issue: 2016 TSM Air Show Special By Brian and Jo Marie Topolski Monitoring the action in the air at any of North America's many air shows can be daunting. You have to know where to listen and when to listen to fully enjoy the spectacle. Veteran air show […]
- Amateur Radio Weekly newsletter celebrates its 100th issue
Amateur Radio Weekly, a free curated ham radio newsletter, celebrated its one hundredth issue on Saturday, March 27. Cale Mooth, K4HCK, got the idea for the newsletter back in 2014. The Nashville ham had seen weekly e-mail newsletters from Cooper Press like JavaScript Weekly and wanted to create something similar for the amateur radio community. "Nothing like […]
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