Article by Pete K6TJ
Operators: K6MG, K6TJ, N9JIM, KA6Q, KD2SSL, AA6PZ, KI6CLA, NF2S, KK6JOL, K9TTL, KN6MYI
W6YX was active in the 2021 ARRL EME contest. Three stations were used, the 10 GHz with its 15’ cassegrain dish, the 1296 MHz 26’ prime focus dish, and the 144 MHz yagi station. The 432 station is under construction and we did not activate 2304 with the 26’ dish. The contest spans 3 weekends, in Oct, Nov and Dec.
10 GHz cassegrain subreflector on the 15’ dish
Over the decades, each station has had interest from a changing complement of students and club associates. Suffice to say we’re terrifically grateful for the additive effect which we enjoy now. We’re keeping a list of contributors, if you could drop me a line with what you helped with, that would be appreciated.
Like other contests, EME is competitive RF engineering, but because of the limited link budget, the complexity is significantly higher, and many key elements cannot be bought. This year saw unprecedented development, including a newly designed and fabricated (by Gary) feed horn that completes the conversion of the 15’ dish from 8 GHz with 4 pointing channels to 10 GHz optimized for gain. With Jim, N9JIM we installed this feedhorn and used lasers and rulers to confirm the dish shape is good to within 1/16” across the surface. Sun noise is measurably better, but there is more to go. The beam width was measured using the K6MG beacon on Mt. Allison, which is line of sight, and is about 0.14 degrees. Other smaller projects were undertaken for example the TWT uses a multivibrator for the helix and drain voltage which was having trouble starting oscillation. A LM555 tickler was built to address this issue. Also the in-shed power monitor was communicating intermittently with the power amplifier Arduino over an I2C extender due to bus blocking, and the bus was changed to RS-232. This year, Gary locked the brick in the transverter (and the IC-746 radio) to a OCXO to get the frequency stability required for Q65 digital mode.
The mighty 10 GHz station ready for action.
Gary K6MG and Jim N9MIM check into the T/R switch on 1296
1296 developments included reduction of RFI to 80m and 40m antennas by installation of a 3 phase AC power line filter and ground rod in the rocky soil. The Azimuth Selsyn digitizer drive was reduced to recover the 0.01 degree accuracy in Azimuth (beamwidth for the 1296 antenna is about 1 degree). New coax for transmit was temporarily installed – plans are to build a newer, higher powered amplifier for mounting on the dish, eliminating the need for a long run of coax at high power.
2m and 1296 focused on the moon
2m competitive stature was raised as well by re-aligning the 2m beams, repairing the coax feed, and additional guying for the weight of the coax phased feed. The beamwidth is about 10 degrees. The 1.5kW amplifier was debugged, as its controller was being confused by power supply spikes when the amplifier is keyed up. Limit switches were installed on the rotating Steel Pole (electrical integration is pending). New computers and SDRs were installed for the panadapters on all the stations. An adaptive polarization dual SDR is being built and implemented to improve RX performance further, as well as a new sequencer, the latter cost us points in the last hours of the contest. Again, Gary is the main driver for these developments.
One of the joys of a University station is to gather together like minded quick learners who may come to have a lifelong interest in ham radio that supports their careers and as an interesting hobby. Even though the last 2 weekends of the contest occurred just before two big holidays, Thanksgiving and Christmas, most of our operators were seeing EME for the first time: only Gary K6MG and Jim N9JIM had EME contacts already in their logbook. One student in particular, Samyak KN6MYI, made his first ever CW contact (and 2 more after that). They were on 1296 EME!! Also W6YX worked HS0ZOP, expat to Thailand, and this was Thailand’s first ever EME contact … with 70 W and a 3m dish.
Although conventional heterodyne mixer based radios were used for RX and TX, the audio input and output for digital modes comes from WSJT which uses advanced methods for modulating and demodulating the signals from the moon which are remarkably impaired by multipath fading from the rough moon surface and doppler from the relative motion of the moon and earth, and their rotation on non-parallel axis. Of course a human can be the modem too, in the case of CW. SDRs were also used for the panadapters which provide a spectral display of the band and a waterfall.
It was interesting to see the signals from local EME stations as they arrive directly (with no time delay nor doppler) as well as from the moon. They can be identified on the SDR waterfall, although the programs aren’t wise to the problem and often don’t decode.
EME is innovative competitive RF engineering, and is well supported by the associates of the club for shared benefit including students, the Stanford community and alums. Although not as popular as football, it serves to gather a community of resources which enriches all of their lives, not only in an engineering sense, as well as enriching the University’s target audience, the students.
Here’s our contest scoring, although the big win is the camaraderie and the pride in our University.
Additional photos and videos by William K9TTL:
Samyak on WSJT. He made his first CW contact ever, on 1296 EME. Samyak KN6MYI is a PhD student at Stanford U.
W6YX 4x28xp 144 (1.5kW) and 26' 1296 (500W) antennas.
Sarah NF2S and James KD2SSL on 2m EME. Sarah is a recent officer of W6YX.
Pete K6TJ, Sam KN6MYI, and Shri KA6Q debugging the 2m receiver.
Sam KN6MYI using a joystick to point the 2m antenna.
Checking that the 2m antenna is pointed in the right direction.
Timelapse of the 2m and 1296 antennas tracking the moon