[NLRS] DEMI 10GHz transverter concern

[Chris Cox, N0UK]

I was just playing with my new (old) HP141 analyser and having had enough 
of seeing which 144MHz repeaters produced a signal strong enough in the 
living room to register on the display (surprisingly quite a few!) I 
decided to take a look at the 10GHz transverter.  As most of you probably 
realise, that was the main driving force behind investing in the beast 
anyway!

So, with it running keydown, it produces a very nice, single-source 
carrier on the desired frequency.  Yippee!

However, with no drive applied, but transmit enabled on the transverter, 
it produces a full-power signal approximately 150MHz down from the desired 
output - the LO frequency.  Note, the LO leakthrough disappears completely 
in the presence of 144MHz drive.  This anomolous response is present on 
both SSB and CW.

There are no other spurs within +/- 500MHz of the desired output strong 
enough to register on the display, although there were two spurs evident 
about +/- 800MHz of the desired output, but they could be sporadic mixes 
with other signals in the low to mid UHF region - I was measuring across 
the room from the dish to an open waveguide transition on the analyser.

Has anyone observed this strong LO leakthrough in the absence of 144MHz 
drive?

I'm going to try fitting a pipecap filter between the transverter and the 
PA to try and squelch the badness.

-- 
73  Chris Cox  N0UK, G4JEC, ex-AB0CN, ex-G8PTC  RNARS #1157  EN34jv33

chrisc@Chris.Org        Ping Jockey's do it until they HEAR the burn...
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