EME Q&A 30-DEC-2015
1. How much activity on 2304 Mhz ?
Not a simple answer. There is quite a bit of activity, but typically only during contests. I have 47 initials, but there are many more active stations than this. Occasionally there are "activity weekends" usually coordinated by G3LTF. Usually the only activity is on high declination weekends or sometimes low degradation weekends. Personally only the high declination weekends are of any use to me. Europe has by far, the bulk of EME operators so you need a good mutual window with Europe.
13cm band is complicated by various spectrum allocations. The VK's can only operate below 2302 MHz, usually around 2301.975 (+/-50kHz). JA is only above 2400. They used to be only on 2424, which is clobbered by WiFi RFI. They recently got permission to operate on 2400. Many European countries must be above 2320 MHz. So cross band capability is a must.
My own system is fixed transmit on 2304 (exact frequencies usually vary from 2304.050 to 2304.150 and this range of .050 to .150 pretty much carries to the other country's bands). I can receive on all of the various allocations.
2. What exact frequencies and modulations are in use?
I covered the frequencies above; so far I have only heard CW, SSB and JT65. CW is by far the most common.
3. What Doppler shift to expect for various moon positions?
Doppler can take getting used to. Moon rise to near zenith the Doppler is positive, i.e., your echo is higher in frequency, by as much as nearly 3kHz. From near zenith to moon set is negative.
4. Are there beacons on 2304 that can be seen in California ?Frequencies?
Currently there is no EME beacon on 13cm band. There are beacons on 1296 (ON0EME) and 10368 (DL0SHF).
5. Any published scheds ?
Only case-by-case. The best place to look for them is on the moon-net reflector. Also the HB9Q chat page.
6. I see a few tenths of a DB change in noise level when I go on and off the moon in any direction, varies depending on its position in the sky. This is as seen on the Flex waterfall display. Can this be considered adequate RX performance to detect signals and echoes ?
Hearing a few tenths dB of moon noise is pretty much a guarantee that you will hear EME signals. A single Spectrian will get you many contacts. That is exactly what I run.
7. “experimenting witha cassegrain feed system.”
That is a waste of time. They are fairly useless unless at least 10 wavelengths in diameter, which would be over four feet in diameter and on your dish would represent very significant blockage. Cryogenic cooling is also way more trouble than it is worth, unless you are just curious and have the time and interest to play with it. It is definitely not necessary to make contacts. WD5AGO is the only one I know who has played with cooling. He has written some papers on his efforts.
8. “Feed is an OK1DFC and am trying different choke rings.”
That is a very good feed design. A choke ring can give you between one and two dB better performance. I currently am using an OK1DFC feed with no choke ring. I get about 1dB moon noise. I do plan on improving my system eventually. Step one is a new feed, probably a round septum feed and adding a choke. I recently have acquired a major RFI problem on 13cm band. So filter design is another challenge for me.
9. LNA is a Down East Microwave 13ULNA. Any betterNF ones available?
I am using this LNA in one of my own enclosures. I have built many of these Down East LNAs and some have measured as low as 0.2dB NF on my HP8970/HP346 meter. They are quite adequate. I think G4DDK and WD5AGO make some good LNAs but you probably would not notice the difference.