[TenTec] Problem w/Omni VI and INRAD filter

[Rob Atkinson, K5UJ]

Joel,  I don't know the bw of these filters by number but it sounds like the 
2.8 khz filters.

They are wide enough to where they are right up against the carrier.  This 
makes R3 and R4 nulling adjustments critical.  Not long ago someone else, or 
perhaps it was you--I can't remember--had a question about the 2.8 INRADS 
and i posted instructions on how to null the carrier.  they should be in the 
archive going back a few weeks.  the short version is renull the carrier 
using if nothing else, a decent separate rx nearby and watch the s meter on 
it while running the omni into a dummy load.  no need to use a lot of pa 
collector current for this.  just enough to get a meter reading.  key the 
omni in both lsb and usb getting the best compromise null for each with a 
minumum of power spikes on mic keying.  put the mic gain pot on around 8 or 
9 o'clock.   it will take some time going back and forth between usb and lsb 
and fiddling to get it as best as possible.  r3 and r4 are single turn pots 
and the null is real sharp so it's a touchy operation.
It is far better to replace them with multi turn pots from Mouser (assuming 
ur rig is thru hole).  They sell pc board pots for this kind of thing but 
with 10 to 25 turns.  Those make it much easier to find the null.

Rob Atkinson
K5UJ

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