Hi,
To all who wondered what the results of my new
IF filter plans might be (as posted a couple days ago),
follows a status report of first impressions:
The new, at least to me, INRAD 2.8 and 2.4 10 pole
IF filters came yesterday. Got them installed after
super last evening. Line up now is:
1. First IF @ 9.0015 MHz center frequency
1.1. Replaced the TT stock standard 2.4 kHz filter
with the INRAD 2.8 kHz unit #754. This filter accomplishes
two mods to the Omni. First, eliminates completely
any chance of a leading edge CW tone thump caused
in some VI's when the tolerance of the standard TT front
end filter is just a tad narrow; and second, opens up
the SSB bandwidth of both transmitted and received signals.
1.2 Into the N-1 slot placed an INRAD #756. 10 pole,
2.4 kHz SSB filter.
1.3 Into the N-2 slot placed an INRAD #753, 400 Hz
CW filter. Note that the center frequency of this filter is
set at 9.0006 or a 900 Hz offset from the first IF
center frequency, which puzzles me a bit.
2. Second IF, 6.2985 MHz center IF frequency
2.1 Replaced the stock standard TT "fixed" 2.4 kHz
BW filter with the INRAD #755 2.8kHz unit.
2.2 In the 1.8 slot, took out the TT 1.8 kHz filter, and
replaced with the standard TT fixed 2.4 kHz filter for now.
Will replace this in time with the coming INRAD 10 pole
2.4 kHz filter for the second IF, INRAD filter #757
2.3 In the Omni 500 slot, took out the 500 Hz CW filter,
and inserted the TT 1.8 kHz SSB filter removed from slot
above.
2.4 In the Omni 250 slot, took out the 250 Hz CW filter
and replaced with the INRAD # #750 400 Hz CW filter.
Note this filter is centered at 6.29925 MHz, or is offset
750 Hz from the second IF center frequency.
Even with the first IF CW filter offset 900 Hz, and the second
IF CW filter offset 750 Hz, I can not see any operational
difficulty. I thought perhaps the differing offsets would not
be compatible with, say 500, 600, or 750 Hz CW sidetones;
if there is a problem, I have not noticed it yet using the
two 400 Hz filters in cascade. So far today, the CW
bands have few signals, mid day now, so perhaps a better
test will come along later when 15 and 20 prop improves.
Even 40 CW seemed dead last night, at least as heard
out here.
Biggest difference with this new set up is with the SSB
signals, of course. Rcvd audio sounds more "hi fi",
obviously more bass in the tone and wider audio window.
Also, kind of like the winder band window,
and the tone is super for rag chewing and nets. Again,
bands not crowded enough to play with the difference
between the INRAD 2.8 kHz BW system, and the
2.4 kHz filter options. But, sure do like the audio of the
complete 2.8 kHz BW cascade! So far, if feel I need
to narrow the SSB BW bit, have found that the front end,
N-1 10 pole, 2.4 INRAD is better than the second IF
TT standard 2.4 filter. The TT filter is certainly much more
high passed audio, when switched in, audio heads toward
the telephone band pass sound, at least in caparison
to the INRAD "sound".
Just some initial observations, time in use will reveal much
more, am sure.
73, Jim, KH7M
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