Posts by SM6PGP

    there is nothing infront of the feed cavity/waveguide opening. The entire "RF-head" is under a rain cover and have some heating to keep it 10-15 deg above outdoor temperature just to avoid humidity.




    73 - Hannes - SM6PGP

    ..and yet another one, a Coaxial cavity feed like the OM6AA feed. The 2.4 GHz part is fed with two probes which simplifies the feeding compared to OM6AA feed. I only need one 90 deg hybrid , Anaren XC2500-3. Less prefect symmetry is the price to pay.


    In the 10 GHz part I have vertikal and horizontal probes so I can easily switch between NB and WB transponder with a SMA-relay.

    My 10GHz RX setup is NOT based on an LNB - it is scratch built with SMD MMIC:s.



    The feed is designed by SM6FHZ and is of course a compromise and not as efficient as the EME-feeds.

    I use a 2.3 m dish, f/D = 0.31 , it is actually a1.8 m dish extended to 2.3 m.


    https://sdr-radio.groups.io/g/…/0/S_X_Dual_Band_Feed.pdf





    Any one else using something like this or OM6AA feed ?


    73 - Hannes - SM6PGP

    Receiving WB transmission (now 10.20UTC) at 10492.5 MHz , SR=2000kS, DVB-S2, H264

    (1468.5 + LO at 9024 MHz = 10492.5)


    MER increased to 8 dB from previous 2-3 dB



    73 - Hannes -SM6PGP

    Hi ! I used 20mW into my 2.3 m dish (estimate 33dBi gain) for CW QSO with good signals. Could not get down to the noise floor ;) have to remove some gain. It is interesting to see how low it is possible to go with the power. In sweden we are limited to 100mW, but with a 2.3 m dish it is not a problem.

    73 - Hannes - SM6PGP

    Hi !

    Power control built into Up-converter.

    I have a step attenuator in the RF chain in my up-converter.

    The mixer is followed by som BPF:s and amplification an then fed into a HMC624, a 6 bit attenuator with 0.5 dB steps so max attenuation is 31.5 dB. Using 5 bits so I have 1dB steps. Up and down stepping is controlled by up/dwn counters (2 x 74HC193) feeding the HMC624 parallell input.


    The upconverter (and down converter) will be mounted at dish focus behind the feed, so I have remote control of the attenuator by pulses to the up/down counter inputs.


    Attenuator/counter setting is read by a DAC and feeding a DC-voltage back to the shack, 30V = 30dB attenuation.


    Thus I can control my output power from 9 dBm up to 37 dBm without the need to change anything like at the IF rig like MIC gain/RF power. It will always be running the same settings. IF (TX) rig is IC7600 running at 28MHz + xverter to 144 MHz fed via 25 m cable to the up-converter at the dish.


    At the power amplifier output I have a coupler feeding a log detector AD8313 with some signal conditioning so I get 5 V for 40 dBm, 4V = > 30dBm and so on, this will show the actual RF power feed to the antenna port.





    73 - Hannes - SM6PGP