EME DISH

This dish was designed and constructed in late 1982 and early 1983. The dish was built from the ideas and with the help of SM6CKU, Ben. Tack Ba. It was used for EME on 23 cm (1296 MHz) and 13 cm (2304 MHz) from mid 1984 to 1989. The dish was situated at my QTH in locator JO66EW (or with the old locator system, GQ02c).

The dish was 5 m in diameter with a f/D of 0.6. I used W2IMU dual mode feed horns for both 23 cm and 13 cm. The preamp was mounted very close to the receive port of the feed horn. The pre-amp for 23 cm used an NE 720 FET and  measured a noise figure of 0.55 dB and the pre-amp for 13 cm used an NE 750 FET and measured below 1 dB NF. The polarization was circular, one rotation sense for transmit and one for receive. The cable for transmit power to the feed was 7/8" with a length of about 20 m in total plus 1.5 m of a more flexible cable for rotation and elevation axis's. The estimated antenna gain on 23 cm was 34 dBi and 39 dBi on 13 cm. The 3 dB lobe width on 23 cm was 3.2 degrees and 1.8 degrees on 13 cm.

A total of 29 different stations (initials) were worked on 23 cm and 4 initials on 13 cm. A first SM to ZL on 23 cm was with ZL3AAD on March 2, 1985. Graham was worked two more times via the moon on 23 cm.

The QSO's on 13 cm EME were the first QSO's ever from Sweden on 13 cm EME. Stations worked were WA2WEB, OE9XXI, OK1KIR and W3IWI/8. All QSO's were made in 1987. The QSO with WA2WEB was the first 13 cm QSO SM to W and the QSO's with OE9XXI and OK1KIR was the first SM to OE and SM to OK on 13 cm respectively.

The first QSO's on 23 cm were worked with a single air cooled 8907 (pulse version of 2C39) with 110 W output at the PA. Later a PA with TH338 was added (abt 550 W output).

On 13 cm the amplifier was a dual tube, water cooled 8907 amplifier with about 500 w input power and 120 W output. You could actually hear the water form air bubbles from the heat generated when you pressed the key down....... 

Water cooling is not always easy. When W3IWI/8 was QRV and I waited for my turn in the sked list, the PA started to leak water in to the cavity of the amplifier. While tracking the moon and listening to them I had to seal the leak and get the water out of the cavity. I managed to get it all fixed just in time to the sked and worked them OK.

One station I heard several times on 13 cm EME, but unfortunately never managed to work, was the grand old man of 13 cm EME, W4HHK.

The set-up on 13 cm gave consistent echoes off the moon on CW. I could detect about 11.5 dB of sun noise on 13 cm. My Tx on 13 cm was X-tal controlled with a frequency of 2304.267 MHz.

On 23 cm I also had consistent echoes on CW and even SSB echoes when the conditions were good. It is a odd feeling to hear your own voice coming back from the moon. When the echoes was at it's best the quality was so good that I could actually recognize my own voice from the echoes. When testing echoes on CW when the conditions were good, I reduced the Tx power to the point where I just barely could detect the echoes. The Tx power at the feed was then less the 25 W. On 23 cm the set-up gave about 12.5 dB of sun noise and 4.5 dB of cold sky to ground noise.

Updated April 10, 2006.             http://www.2ingandlin.se/SM6FHZ.htm