I've seen several messages from individuals wishing to add
transmit/receive operation on 30, 17 and/or 12 meters to the
Omni-A, Omni-D and/or Omni Series B. I bought an Omni-D when it was
first
released around 1979/80 and later upgraded it to a Series B and
added 30 & 12 meter WARC bands with TEN-TEC modification kits.
The three models will receive 10.0-10.5 MHz as designed however
they lack the necessary coils and capacitors to allow transmit in the
10.0 bandswitch position. The AUX bandswitch position may be used to
add the 12 meter (24.5 - 25 MHz) band which requires a crystal as
well
as coils and capacitors.
The modification requires several hours to complete as you must
REMOVE the low pass filter, bandpass filter, oscillator/mixer and
receiver trimmer BOARDS from the chassis. This includes removing
shields and the bandswitch shaft. As I recall, no drilling is
required however the boards are not silk-screened and the
components must be installed with care. The modification
instructions were
about 11 pages long. A signal generator, RF power meter, dummy
load and common hand tools are required to install and align the
modification.
I'm unaware if TEN_TEC will sell modification kits at this time.
Although the instructions have you install each component, there is
NO parts list included. It MIGHT be possible to buy the components
as repair parts from TEN_TEC.
These models are single conversion superhet design using a 9 MHz
intermediate frequency. It is NOT practical to add the 17 meter
(18 MHz) band due to the strong spurious outputs that are too close
to
the desired signals with the particular mixing scheme used. I
believe this to be the prime reason TEN-TEC changed to a 6.3 MHz
intermediate frequency in the Corsair and Delta models.
The 'Series B" modification replaced the front panel, selectivity
switch and added the crystal filter switching and notch filter
boards. The SQUELCH control was replaced with a NOTCH control.
The WARC Band and Series B modifications are independent of each
other.
Either one or both may be added to the OMNI-A (Model 545) or the
OMNI-D (Model 546).
The OMNI-C was a considerably different radio. The above
modifications DO NOT apply to it.
73,
Bob Helms, AF5Z
af5z@inetport.com
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