G6GEI OSCAR-100 Solution

LNB modified from 25.000 reference to 25.787180 this drops the IF from 739.55 to 432.55 (70cm) (ref Freq x 390 is the LNB mixer frequency). I tried to get the IF into 23cm band but it cuts off at about 1Ghz so there must be a low pass filter in the LNB. (LNB came already modified by DXPatrol but can be done DIY). The 9700 supplies 12v to power the LNB via the ‘external pre-amp’ feature.

I found the Power Amplifier gets very warm, even on Rx, so fitted a cooling fan. The fan runs slowly (50-ohm resistor in power line) so makes no noise but keeps the whole thing cool.

I replaced the reverse polarity SMA connector on the amp with a standard polarity one to make cabling easier.

A length of 3m of 10mm Hyperflex connects the amp to the patch antenna with pigtails at each end. Tuning the radio tunes both Tx and Rx frequencies in sync. (antenna on wall outside shack)

Receive at 432.771 represents downlink 10489.771 uplink frequency of 2,400.271 MHz so easy.

The solution is stable (no drift) and so far, only good reports from stations worked.

(Above) The power amp with cooling fan fixed to box containing DXPatrol up-converter. 

(Above) the Patch antenna and LNB. The Patch was made from 1.3mm brass plate with hack-saw and file, 22mm copper tube and soldered. The sma connector is soldered to the reflector. The rubber bands are there as I was waiting for the silicone sealant to dry. The 'cone' was made by a friend of mine Laszlo Sanduly (2E0USS).

(Above) the 9700 showing the Rx and Tx bands with the spectrum scope below, listening to a station with a 5/9.  Reports I get from this setup are usually 5/9 good audio. It can be perplexing operating with headphones listening to your own voice with the satellite lag, but you can turn that off in settings (Set / Function / Sub-Band mute ) so you can operate without a headset.

Click here to download this document as a PDF Oscar100.pdf

The up-converter and modified LNB were sourced from dx-patrol DXPatrol