The Moon
Well, last Wednesday evening was the night. The moon was near Perigee, the sun was not in the way, and my 2m amplifier came back from M2 Antenna Systems and was reinstalled.
2m Amplifier And Sequencer
I got everything hooked up and tested before the moon came up that night. Our Earth-Moon-Earth (EME) system consists of an Icom IC-9100 Transceiver and a microHAM MK2R+ for our Sound Card along with a single M2 Systems 2M18XXX Yagi Antenna (18 elements on a 36-foot boom at 112 feet), a tower mounted preamp system from M2, and M2’s EME Sequencers along with their 1.2 Kw 2m amplifier. For software, we’re using Joe Taylor’s WSJT Application and the Ham Radio Deluxe Satellite Tracking software to keep our antenna pointed at the moon.
2m EME Setup
My first test was to bounce some echoes off the moon just as it came up. With the amp on and set for its rated digital mode output of 900 watts on 2m (it will do 1.2 Kw in SSB mode), I heard my signals coming back from the moon for the first time. The moon was between North America and Europe as it came up, and I noticed several European stations were on 2m EME. After a few CQ calls using JT65B (WSJT mode for 2m EME), S52LM, Milos in Slovenia came back to me, and I successfully completed my first EME QSO on 2m! I also worked two other stations on 2m EME from Europe – DK5SO (in Germany) and UT5UAS (in Ukraine). I suspect some of these folks may have had pretty big EME stations, as their signals were very strong. Here’s a snapshot of my first QSO with S52LM:
EME QSO With WSTJ
As you can see from the snapshot, the round trip delay to the moon and back was between 2 and 2.5 seconds. S52LM’s signal was pretty strong at -23 dB (he was also using close to 1 Kw on his end). At this level, I could not hear anything audible above the noise in my receiver. The following is what the WSJT waterfall looked like:
WSJT EME QSO – Waterfall
S52LM’s signal is the lines and dots between 0 and 200. These are fairly strong signals by EME standards. The WSJT software’s performance on such weak signals is pretty amazing. (The other lines on the waterfall are weak “birdies”).
Most of the bigger EME stations use an array of long boom yagi’s, so I am pretty lucky to get this done with a single antenna and no elevation rotator. Here’s a picture of a more typical antenna system for EME (this is DK5SO, the station in Germany where I worked):
DK5SO 2m EME Antennas
At this point, I am pretty happy with the performance of our 2m weak signal system.
I heard several stations in Australia a couple of mornings ago before I had my amplifier back. I will try to work them soon. Maybe someday an EME DXCC…. (3 down, 97 to go).
Fred (AB1OC)
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Hello Fred
I made my first EME QSOs on 432 back in the dark ages (1978). I’m not currently QRV due to a divorce, but I’ll be back! I’ve never been one of the ‘big boys’ but I’ve had a lot of fun! My last period of activity via the Moon was on 10GHz, but I’ve also been active on 2m (CW with a single yagi in the 1980s, and CW, JT44 and JT65 in the early 2000s). I was also briefly on 23cm EME in the 1980s. I’ve learnt so much from ‘playing’ EME, and made a host of good friends.
My reason for writing this is that I was struck by your enthusiasm. EME is amateur radio at its best. I do hope we have a QSO ‘off the Moon’ one day.
Vy 73.
Chris
GW4DGU
TU Chris, I hope that we can work a QSO off the moon sometime soon as well. Thank you for being part of our Blog.
73
– Fred (AB1OC)
Hi Fred,
Very nice setup! Could you tell me how many watts you used on the IC-9100 to drive the M2 Amp to 900 watts? Does the IC-9100 exhibit any overheating symptoms on JT65?
Since you’ve posted this article, can you provide a bit of an update on the IC-9100s performance long-term? Any hints for the would-be EME’er using the IC-9100?
Thanks, 73, Rich, K3VAT
Hi Rich,
You can make full power with the M2 Amp using about 50w in. This is well within the capacity of the IC-9100. I have not had any overheating problems with the radio/amp combo including using JT65.
A couple of suggestions on doing EME. First, get the receive setup working well. Consider using a tracking program to keep your antenna(s) on the moon. Anything that works for satellites will do the job for EME as well. Also, pay attention to the overall EME path degradation. I use a desktop gadget to monitor this. You can learn more about what goes into this index and about EME propagation here –
http://www.pe0sat.vgnet.nl/eme/
If you have feed-lines that are not short, you may need a low noise preamp close to the antenna. This can also help to improve overall S/N performance significantly over what you radio is capable of. I think I referenced a good source for such preamps in one of my EME posts. Once you have the receive and decoding setup working, try transmit. I have found that I need a little more power than the IC-9100 generate with my single yagi setup to make contacts. This is why I got the amp.
– Fred (AB1OC)
thanks Fred for the info and the informative link! These are very good suggestions and I’ve seen them made by other EME’ers.
One question that I have is that my proposed FIXED EL yagi has a 7 deg max take-off angle when positioned horizontally [zero degs]. Would that equate to having the best chance of delivering a ‘strongest’ signal to the moon when the moon is 7 degs above the horizon? Tracking software seems to indicate that at moonrise the moon climbs in elevation around ~1-1.5 deg over a 10 minute period. So a good window for me seems to be around 5 to 10 degs in elevation where I have a bit less than 1 hour to make an EME QSO. Additionally, it doesn’t seem like one would want to try an EME QSO when the moon is directly at the horizon [zero degs]. Am I correct in these assumptions? 73, Rich, K3VAT
Rich,
You will be utilizing the “ground gain” of your beam when it is pointed at the horizon. If the 7 deg angle includes this effect (which it probably does) then your best time will be when the moon is at this angle. I have found that I can typically work contacts off the moon about 30-45 mins on either side of moon rise/set. I don’t think there is a problem with the moon on the Horizon as long as enough of it is “up” enough to have a decent target.
– Fred (AB1OC)
Good data, thanks Fred! Didn’t realize one could work moonbounce when the moon is actually below the horizon. I found some excellent papers on K1JT’s website that I’m studying now. 73, Rich, K3VAT