Filters and things...
Wed, 1 May 1996 16:38:25 -0700 (PDT)
Vernon -- I'll take a stab at some of your questions, but also refer you
to Chapter 17 of the 1995 ARRL Handbook which describes in great detail
the operation of the Omni VI which, i think, is very similar to the Omni
> Many of you out there had told me the virtues of running a 1.8 and .500
> filters cascaded together for CW work. Okay, I've tried this; what is the
> advantage? I have found myself using the .250 on crowded bands instead of
> the .500 & .500 combo.
I usually use 500/500. Using 500 in the 9 MHz filter has the advantage
of keeping a lot of noise and spurious signals out of the IF
channel...I'm not sure what the advantage of using 1.8 in the ( MHz
> Basicly what I am asking is this; (remember I'm a new HAM); how does the
> two filters (1st and 2nd IF) work together? Where does the passband tuning
> fit into this picture? Is the passband tuning in between the two IF's? I
> have learned how to separate two signals coming thru the filters using the
> passband tuning; but how does it work?
The 9 MHz filter is conventional, the 6.3 MHz filter has two mixers one
at the entrance and one at the exit. They are both driven by a common
local oscillator. As the frequency of the LO varies, the bandpass of the
6.3 MH filter is shifted relative the the bandpass of the 9 MHz filter,
thus affording bandpass tuning. On CW this is very effective if both
filters have the same bandpass.
Hope this helps...Ed
~ Ed Kleckner, N7YQR ~
~ email@example.com ~