Sunday, 11 May 2014

144MHz

With the success of the Angllian 144MHz transverter kit I have started to wonder if I should get back on 144MHz and try to work some DX?

One thing that was always missing from my earlier 2m systems was a low noise mast head preamplifier. Thinking about the amount of cable loss ahead of the indoor shack transceiver/transverter it is obvious that I need some low noise mast head gain to obtain adequate sensitivity.

One possibility is to cut out the RF stage and filters from a now-unused Nacton transverter PCB to give a  low noise matched, low noise, preamp with a well matched on-board 144MHz output band pass filter.

From independent tests on the Nacton transverter the SPF5043 low noise front end is capable of better than +3dBm IIP3 with adequate out of band signal suppression, gain of around 20dB and good stability. I would expect a noise figure below 0.8dB. That is more than adequate for 144Mhz terrestrial use even in this formal area.
Conveniently, the RF stage and filters can easily be cut out from the Nacton PCB.

O
I will report results ( if it works!).

Sam



2 comments:

  1. How long is your 2m feeder and what loss?

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  2. Nearly 60m from mast via shack to the indoor shack. I would need to look up the various cable losses. Too much without the intermediate amplifiers, I'm afraid, Roger.
    Sam

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