[TenTec] Omni VI+: low TX and RX on 12 meters

[MadScientist]

More likely than alignment as an issue, would be the switching diodes for 12 meters, or, again, bad soldering of the circuitry around those diodes and associated coils.

You can check the continuity of the tuned coils in-circuit since the shunting paths are say to account for.

Also, try connecting a 0.01 uF capacitor across the entire bandpass filter (Cathode of D21 to Cathode of D22 will accomplish this) and see if receive level reaches near-expectation level. This will prove that you are looking in the right place.

Do not transmit under this condition1

Gary

> On Dec 29, 2018, at 2:40 PM, Phil Erickson <phil.erickson at gmail.com> wrote:
> 
> Hi all,
> 
>  More investigation has narrowed the problem to the BPF/front end board
> 81593.  We'll use 15 and 10 meters as our "working normally" and 12 meters
> as "working abnormally" for this discussion:
> 
> - LO input from the XO-LO board at connector 26 is at exactly the right
> appropriate frequency for a 9 MHz IF, and nearly constant voltage for
> 15/12/10 meters.  That eliminates the XO-LO board as the problem (relief!).
> - TX input at connector 27 is also nearly identical on 15/12/10 meters.
> - However, the output at connector 24, which goes off to the low level
> driver board, is not the same for all three.
> 
> Using a 1 Mohm input impedance on a Tek 2465A scope:
> 
> 15, 10 meters:  in TUNE mode, signal increases with PWR knob up to
> about +/- 2V at three dots up from minimum (10:30 am clock position) and
> then essentially saturates
> 12 meters: in TUNE mode, signal increases with PWR knob but only up to
> about +/- 0.12V at three dots up from minimum and then essentially saturates
> 
>  Not sure why the signal is saturating at the 10:30 am position as I would
> have figured it would go up as I turned PWR up further.  (It does go up to
> a clean 90 watts or so on 15 and 12 meters when everything is hooked back
> together.)  No matter; the problem is clearly in low output at 12 meters
> from 81593.
> 
>  Since 81593 has individual BPFs for each band that are used for both TX
> and RX, my guess is that the BPF is off frequency for 12 meters which would
> explain why I have a relatively deaf receiver by 20 dB on that band as well
> as low TX output.
> 
>  Now the next question to this group: does anyone have the alignment
> procedure for a 81593 BPF/front end board?  The manual does not describe
> one.  I am also very careful about adjusting slugs as like many of you,
> I've had inductor cores snap in two with too much pressure, so I want to do
> the minimal amount of tweaking to fix the problem and not do too much
> "golden screwdriver" wiggling back and forth.  Knowing what to inject and
> where to inject it would be great.  (I have HP signal generators and the
> like available.)
> 
>  This list is really terrific - and thanks to Gary W0DVN and Pete in
> particular!
> 
> 73
> Phil W1PJE
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