70 cm EME

I will be using an elderly array of 4 by 21 element Yagi-Uda antennas from Tonna

70cm EME antennas, ex GM3JFG
Array in Oct 03
Wot, no moon?


EME Antenna refurbishment.

The 4 x 21 el antennas were in very poor condition when I started this project.

There was not a straight element to be seen, and the coaxial cables were waterlogged. Some damage was evident to the driven elements, and these have been repaired. New phased leads, and some work on the preamp enclosure has brought the system back to life. Both rotators need a complete strip down as internal corrosion had taken its toll. A little work was required on the azimuth rotator, but the elevation rotator seemed fully operational. In the end, only 3 of the 4 antennas could be rebuilt, but thanks to John G3XDY, who had a spere antenna, more or less intact, I was able to restore the array.

The pole on which the antennas are mounted, and the hinged base plate, courtesy of David GM6BIG have been replaced with a self supporting steel mast base that can be assembeld in about 1 hour. The system is now able to be deployed, used and put away again as required, though reasonable weather conditions are required.

On 19 Oct 03 I worked JW/SM2BYA HB9Q and N2IQ on CW moonbounce. This was using a TH326 Triode PA running about 225W.


April 05

Problems with the elevation rotator and the power amp have kept me QRT since the first QSOs, I have run up GM3JFG's old K2RIW , but cannot get it stable so I am still short of power. More work to do!

Novemeber 05


After curing the instability problems with the K2RIW (one valve base needed quite a lot of cleaning up to make a good RF connection to the chassis.) I now see 700W from the amplifier with care, and 600W is easily obtained. The elevation rotator motor has had a major overhaul, and the preamp has been replaced with a new HB one, nf about 0.35dB

The new steelwork for the mast base was assembled just in time for the EME activity weekend of 20/12 November 2005

New mast-base for 70cms EME, with 23cms EME dish in background

New mast base Nov 05

With the array pointing at the moon, I was dissapointed to hear nothing (except the birdies that plague the band in this urban environment). A posting to moon-net yielded a few takers, and I arranged a test with SM3JQU (4 yagis and 1Kw)

Signals were immediatley heard and a QSO resulted. The system was obvoiusly working quite well to make it with a 4 yagi station on EME.

The activity during the weekend was a little low, but results were quite good.

Worked on CW

SM3JQU, O peaked 519:

K1FO, O peaked 529:

G3LTF, O peaked 529: Listen to G3LFT calling CQ (wav file filtered, 577Kb)

DL9KR, 559 559 Huge signal: Listen to part of the QSO (wav file unfiltered, 671Kb)

F2TU, O peaked 529:

KL6M, O peaked 539:

All initials, grand total 9 now.

Got aways, G4RGK heard at 419 just at moonset, RW1AW unreadable due to sever fading, SM3AKW, trace on spectran no positive ID, JH6AHB tried, not a trace in either direction, OZ6OL heard for 30 sec before I had to pull the plug :<(...


Problems .. During the weekend of 10/11 Jan, I put the sytem up, and was testing.. I was able to see my own echoes on spectran, weak but unmistakable.. occasional I could hear tones on libration peaks.

after about 3 hours of calling CQ and listening for echoes, I burned out the antenna changeover relay, replaced it and burned the new one out. I discovered too late that the sequencer had failed, with one of the relays stuck in TX giving a go signal immediatly on going to TX.. no delays.. I gave up for the weekend


Feb 5th

sequencer rebuilt and a new RF changeover relay (Thanks to GM0ONN)

Had 3 easy QSOs,

SV1BTR on Sked CW 529 429 First GM to SV on 70cms Initial #10

NC1I random CW 559 549 Initial #11

K2UYH sked CW 539 559 Initial #12 Audio sample from QSO 1 Mb in MP3 format

All super signals.. so I tried echo testing.. Much better echoes than befoe , Os sent in CW could actually be copied coming back!

Audio sample of own echoes 300kB WAV file

Sequencer failed again.. same sort of relay as before stuck, with the inevitable results . seeking replacement relay and I have change the relay in the sequencer for a different type.





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