[Elecraft] XV transverter switching

[Kenneth E. Harker]

     Let me rephrase my questions/concern.

     Let's say it's the ARRL June VHF QSO Party, and I have the XV50 and XV144
transverters in a daisy chain configuration with the K2/100 as an IF rig.  
Six meters is wide open and there are signals from 50.100 MHz through 50.250 
MHz.  There's a very loud station running on 50.200 MHz.  I am switching
back and forth between 144.200 MHz and various frequencies in the six meter 
band.

     The XV transverters have relays that disconnect the IF ports when you 
deselect that transverter (using the K2/100 as an IF rig.)  So, in the 
daisy chain setup, you are relying on this relay as isolation to keep the 
downconverted signals of the deselected transverters out of the IF.  So the 
limit of this isolation is the limit of the 28 MHz isolation figure for 
this relay.

     The relay is an Omron G6E-134P - Omron does not seem to publish the 
isolation ratings for this relay.  My guess is that it might not be enough 
for strong signals.  For instance, when listening to 144.200 MHz (28.200 MHz 
IF frequency,) a really strong signal on 50.200 MHz (also 28.200 MHz IF 
frequency) will probably bleed through.  Let's say the transverters are able 
to produce downconverted IF signals of +0dbm.  The Elecraft K2/100 can hear 
down to at least -130dbm.  So, doesn't this mean that the relay would need 
a 28 MHz isolation figure in excess of 130db to avoid having strong signals on
one band bleed through and sound like weak signals on another band?

     I can't imagine that these relays have that sort of isolation.


     Downeast Microwave transverters have the ability to turn their 
downconverter sections completely, while leaving the local oscillator on
(so as not to cause frequency drift) when you use appropriate external 
switching.  We've had to use this feature at the W5KFT and K5TR contest 
stations, where we often share a single IF rig for the 222 MHz and 432 
MHz transverters.  Is this something that the Elecraft transverters can
be made to do as well (hopefully automatically with the band-switching 
controlled by AuxBus?)

-- 
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Kenneth E. Harker      "Vox Clamantis in Deserto"      kharker@cs.utexas.edu
University of Texas at Austin                   Amateur Radio Callsign: WM5R
Department of the Computer Sciences          Central Texas DX & Contest Club
Taylor Hall TAY 2.124                         Maintainer of Linux on Laptops
Austin, TX 78712-1188 USA            http://www.cs.utexas.edu/users/kharker/
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