[TenTec] Date of manufacture

[Dr. Gerald N. Johnson, electrical engineer]

All crystal filter Tentecs up through the Omni VI use a 9 MHz IF
primarily. The 6.3 MHz IF is used ONLY on receive in Corsair (maybe
Delta) and later to allow for bandpass tuning. It has absolutely no
effect on the spurs at 18 MHz. The Corsair and later cure the LO spurs
by mixing the VFO to the high side instead of the low side which inverts
the normal sideband on 18 MHz. The spur problem is that with the
transmit IF of 9 MHz, the LO also needs to be on 9 for normal sideband,
but the second harmonic of the 9 MHz injections comes out of the mixer
nearly as strong (in a really good mixer) as the desired mixing product.
Moving the LO injection to 27 MHz cures the problem but it doesn't
appear to be a practical mod for the Omni C.

The Corsairs added audio CW and notch filters. The Corsair I had a
connector for band information for a linear that the Corsair II hasn't.
The audio filters may have been added for the Corsair II. The Corsair I
came with a 4 pole filter in the 9 MHz IF but that was easily upgraded
(plug in) to the more normal 8 pole filter.

73, Jerry, K0CQ

-- 
Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.