[TenTec] Issues aligning Omni 6+ (Mod. 564) FM TX carrier frequency

[Ken Brown]

I have Operators Manuals for the 563, Omni VI, NOT Omni VI+. The BFO
adjustments in the 563 are all variable capacitors, not variable inductors.
C12, C13, C16 and C18 are the variable capacitors to adjust the BFO
frequencies. There is some interaction between them, so the should be
adjusted in a particular order, and then readjusted until you get all BFO
frequencies correct. In my manuals L2 is a fixed inductor.

I'm pretty sure there is an error in the schematic diagram in my Omni VI
manuals. The line from the not grounded side of C12 should extend up to the
line connected to Y2 9.003, instead of being connected to to Y1.

Did Ten-Tec make big changes to the TX AUDIO BOARD (which is where the BFOs
are) in the + version of the Omni VI such that the BFOs are adjusted with
slug tuned inductors?

In any case, if you adjust the BFO frequencies in the prescribed order and
still cannot get them all on the right frequencies, then I would say your
guess of an aged crystal is a good guess. There are other possibilities.
Check to make sure that every mode CW TX, LSB, RX, USB RX, FSK SPACE and
FSK MARK has a different BFO frequency. If there are two modes that have
identical frequencies that would suggest that switching of the padding
capacitors is not working properly. There could be a shorted (or always on)
transistor keeping and additional capacitor connected all of the time. Or
one of the switching diodes could be shorted.

Good luck.

73 DE N6KB


On Tue, Nov 6, 2018 at 5:11 AM Sven Ladegast via TenTec <
tentec at contesting.com> wrote:

> Hello folks,
>
> I do have trouble aligning the TX carrier frequency on an Omni 6+.
>
> With no modulation applied, the TX carrier frequency shall be 9.00300
> MHz measured at connector 73 of the board. I used a TMP-BNC cable and
> connected it to connector 73 and connected the BNC connector to my
> accurate frequency counter using a T-connector and additional 50 Ohms
> termination.
>
> The TX carrier frequency is aligned by turning the core of L2 but with
> the core complete turned out of the coil I get a maximum frequency of
> 8.9965 MHz and cannot get to 9.00300 MHz. Do have anyone an idea what is
> going wrong? Aged XTAL?
>
> 73!
>
> Sven, DJ2AT
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