[TenTec] "Low Note" 221 250Hz Filter Problem

[Dr. Gerald N. Johnson]

On Sun, 2007-03-04 at 10:23 -0700, Peter Hoon wrote:
> Fellows,
> 
> Have the model 221 "low note" 250 Hz 9MHz IF filter.  On my Xceiver, an Omni
> 6 Plus, late serial number, it is in the "N-2" position. Am aligning my S
> meter with a 50 uV signal from Calibrated Sig Gen as described in operators
> manual.
> 
> Have checked gain jumper (correct), and have reheated all solder connections
> on the 221 filter circuit board.
> 
> All of my other 4 filters are fine, and are properly compensated for
> insertion loss:  when engaged, and passband is set correctly, I get an S9
> reading on S meter.
> 
> But my 221 filter is one S meter unit low, at S8, or 6dB low.
> 
> When examining the 221 filter, I note that one .001 5% capacitor (102J), in
> series with the third crystal in from one end, is missing.
> 
> Could someone check their 221 filter and let me know if a similar capacitor
> is missing?  It could be that it was the manufacturers intent to remove the
> capacitor from this position in the filter. Or, it could be an inadvertent
> omission, and thus the cause of the insertion loss by one S unit.
> 
That sounds like way too large a capacitor for trimming a crystal to
frequency, and too important to be missing. Unless there is some other
coupling a missing series capacitor ought to increase the insertion loss
much more than 6dB. Is there a jumper shorting out the capacitor
terminals?

> Thanks,
> 
> Peter
> VE1CHS
> 
> 
> _
-- 
73, Jerry, K0CQ,
All content copyright Dr. Gerald N. Johnson, electrical engineer