W5JK wrote:
>There must be a more accurate way to calibrate the optional 250 Hz and
500 HZ for center frequency than to simply tune to a steady carrier and
peak the menu CF Adjustment control for highest S meter reading.
This is very simple requiring only a steady signal source
(i.e. no noise sources, Spectrogram plots, etc.)
1. Tune and zero beat Orion to a steady signal source.
2. Set DSP = 1000 or higher to take any DSP filtering out of
the adjustment. Enable and select desired filter in Filter
Menu. Do NOT leave it in Auto.
3. With C.F. Adj highlighted and not touching VFO, adjust
your Multi knob so that you see equal downward deflection on
the S-meter on both sides of the carrier. I would suggest
about 1 S-unit or 6 dB deflection, or whatever meter marking
is closest to that (i.e. not critical as long as you make it
the same deflection on both sides).
4. Write down the readings for each side of center. For
example, you might have something like -60 and +20. Add
these two numbers together and divide by 2 ([-60 +20] / 2
= -40/2 = -20). Set C.F. Adj. to that value. Your filter
is now properly centered, independent of any passband ripple.
5. Now check your work by first noting VFO zero beat (A=B is
a simple way to keep track), and tune VFO to both sides to
the same meter mark you used in 3 above, noting both
frequencies. If you've done it correctly, both should
be at an equal offset from the zero beat frequency.
BTW, if you install the Inrad 762 in the 1000 Hz
position, you don't need either 500 or 250 Hz filters since
it exceeds the IMD performance of both. Details below:
http://users.vnet.net/btippett/inrad_.htm
73, Bill W4ZV
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