Omni V PBT/IF-AF Mod

From the Ten-Tec Reflector April 2, 2002

I received the AGC hiss modification info from T-T today. I haven't performed the modifications yet, so cannot comment on the outcome.

Here is the scanned text:


The purpose of this change was to "fine tune" AGC performance and reduce background hiss that can be noticed under weak cw signal conditions with extreme settings of the TONE and BP controls. The purpose of this bulletin is to keep you informed. The modification is not recommended because it fails the test of performance improvement vs. the effort required.


PBT BOARD (81460):

  • C40, change from 1200pf to 750pf.
  • C41, change from 360pf to 330pf.
  • C51, change from 5pf to 27uh in series with .0luf.
  • R46, change from 10k to 3.3k.

IF/AF BOARD (81462):

  • R5, change from 4.7k to 1k.


  1. Remove bottom cover and shield.
  2. Locate the PBT board (81460), right center of chassis.
  3. Unplug all cables from PBT board. (38,39,41,42,43)
  4. Remove the 6 mounting screws from the board/chassis.
  5. Remove and replace components as listed the summary, above.
  6. Re-install the board and cables.
  7. Locate the IF/AF board in front of the PBT board.
  8. Unplug all cables from IF/AF board. (43,44,46,47,48,49,50,51,53,54,55,56,57,0
  9. Remove the 5 mounting screws from the board/chassis.
  10. Remove and replace R5, as shown in the summary above.
  11. Re-install board and all connections.


  1. Power up radio. Inject a weak signal through the antenna connector. Adjust signal level so that the S-meter is just deflected with the receiver tuned to the signal frequency. Any frequency is fine.
  2. On the PBT board, adjust coils L18, L19 and L20 for maximum strength on the receiver S-meter. These coils will interact so you will want to go though the adjustment process several times.
  3. Calibrate input signal to 50uv. On the IF/AF board, adjust R45 for an S9 reading on the S-meter.


  1. Check transmitter and receiver for normal operation. If there are any malfunctions, re-check all cable connections.
  2. Install bottom shield and bottom cover.

1185 Dolly Parton Parkway
Sevierville, TN 37862
SERVICE……. 615-428-0364
SWITCHBOARD… 615-453-7172
FAX……….. 615-428-4483

Vy 73 Paul MW0CDO

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