Saturday 18 May 2019

23cm on the IC9700

I have been busy bringing my IC9700 on-line in place of my 23cm transverter based system.
It is not that straightforward. One of the problems is that the radio is on my operating desk whilst the linear is in the rack. They are either side of a door, so the cable route between them  is about 3m, at shortest. I do have coax and control cables running between the desk and rack. But, it is impractical to run large, low loss cables, so with Ecoflex cable the 10W from the IC9700 is not enough to drive my 200W SSPA to anywhere near full output. In fact just to 80W output. My answer?
I have a now rather elderly twin brick M57763 amplifier with about  30W output, when driven at 400mW. I have turned down the IC9700 to about 5 to 6W output, drive the cable to the twin brick, situated in the rack next to the 200W SSPA and then use a 12V coax relay to separate transmit and receive path. I have a 6dB/10W SMA attenuator in the twin brick input to bring the input down to about 250mW (don’t forget the cable loss). With this arrangement I can drive the main amplifier to around  150-180W output and I have some power control by turning down the IC9700 when required.
I’ve still got to tidy up the cabling, reset power levels and then connect to the dish antenna.
BTW, there’s a lovely bright, near full, moon out there this evening, but it is low in the sky.

Sam

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