[amsat-bb] TranSystem 3733 Performance

["Colin Hurst" <hurst_cj@xxxxxxxxxx>]

Some recent posts have identified improved performance 
with the WC0Y modification. I can confirm that here also.
Prior to the addition of the capacitor the unit was "consigned" 
to the  waste bin. 
Apart from the Sun and UO-11 I have no test equipment as
such and of course AO-40 performance.
Some facts.
Normal convertor SSB UEK-13
2 dB of Sun Noise with a 750mm aluminium dish.
UO-11 averages 9 to 10 dB above noise threshold.
TransSystem (modified) 
1.5 dB of Sun noise
UO-11 averages 6 to 8 dB above noise threshold.
I would add that UO-11 varies with orbit, attitude etc.
so it is a guide only, remembering that it is the opposite
sense polarisation.
In respect to AO-40 both units hear signals in the 
passband BUT a preamplifier is needed for both.
Definitely not armchair copy.
But my main activity is Telemetry. With the TransSystem I
can detect when the RUDAK is switched off and on 
(slightly increased error rates at different squint angles).
When RUDAK is switched on the S2 beacon drops a
nominal 5 db (as measured at this QTH). With the SSB
this is not noticeable, however with the 3733 it is noted
with slighlty greater error rates, around 1 to 2%.
I intend to reverse engineer the NF and Gain using the
various spreadsheets compared to the SSB UEK-13
specs of 1.8 NF / 20dB gain.
Ward WC0Y mentioned "brain surgery" to effect the mod.
I had a fellow amateur do the mod for me, one with steadier
hands and better eyesight. A sharp knife and a magnifier are 
strongly recommended. The results are well worth the effort. 
Colin VK5HI 

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