[NLRS] DEMI 10GHz transverter concern

[kb0mnk@visi.com]

With the two that I built the leakage was less than -40 dbc. I tuned the 
filters to peak above 10368 so that the desired output was just starting to 
fall a few tenths of a dbm. I was able to get good linearity up to about 8-9 
dbm with 1dbm at about 10mw out and saturated output of +12 to +13dbm. 

I also cut the "no-tune" filter on my 1296-144 to decrease LO feedthrough using 
my spec. an. (leakage was -10dbc before tweaking)

With a 141T I'd at your disposal I'd recommend just retuning the existing 
filters since they are marginally adequate at less than EME power levels.

Quoting "Chris Cox, N0UK" <chrisc@chris.org>:

> 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...
>   WWW Home Page: http://WWW.Chris.Org/   http://www.pingjockey.net
> Cultural observation:
> 	Europeans think 100 miles is a long way;
> 	Americans think 100 years is a long time!
> 
> _______________________________________________
> NLRS mailing list
> NLRS@mailman.qth.net
> http://mailman.qth.net/mailman/listinfo/nlrs