Sunday, 15 June 2014

More 10GHz tests

I substituted a three ring Chaparall feed and  DEMI 10GHz preamp (W5LUA) coax preamp into my DB6NTG3 transverter. Power was fed over the receive coax.
At the shack end the bias tee injected 13.5V.
One of my Anglian 144 transverters brought the signal (noise) down to 28-30MHz.
My SDR-IQ was then tuned to 29Mhz and dispersion set to 100kHz.
Using this set up I was able to measure 3.8dB sun to cold sky and 1.9dB ground to cold sky.

According to EMECalc these numbers are self consistent with the gain of the dish and type of feed, system noise figure of 1.2dB etc. at an SFI of 129 ( given for today) so I am quite pleased with my initial tests. 

The three ring Chaparall feed only gives, according to VK3UM,  45% feed efficiency. I know this can be improved upon so the next stage may well be to try and obtain a decent circular polarised horn feed for the dish, followed by an increase in dish size to 1.2 or 1.4m

Sam

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