I realize there is no stock filter that you can just
"drop in" to satisfy this modification, and that new
filters with appropriate loss/center freq would have
to be built. The fact that INRAD is comming out with
the new filter proves there is likely a demand
sufficient to sustain stocking a filter to satisfy
such a modification, especially if it improves the DR
on close signal work. My idea is to not use the
series 500/250 filter design as it presently exists in
the Orion, but to re-route the signal path so that the
filters would be placed in the same spot in the signal
path, as the other stock filters presently are placed.
I would continue to bypass the amplifier that is
switched in when 500 and 250 is chosen.
I would use the 500 and 250 steering signals provided
by the firmware to activate the "new" re-designed
filter path, and I would use something like a triphase
gate and some steering diodes to switch off the 1khz
position when the 500/250 filters were active. This
would basically eliminate the need for a firmware
change as far as the switching signals are concerned
if the signals from the firmware operate like I think
they do. It would merely then would require selecting
a filter with the correct bandwidth/loss/center freq
charactistic.
I presume there is enough interest to make this a
rational business choice for INRAD to develope and
stock such an item. Further it think it would be a
very low impact modification as far as what has to be
done to the radio. From what I can see it would take
a couple of peieces of coax to re-route the RF signal
path from the old path to the new path, making a
little external logic board to pick up the steering
signals from the radio, and a way to keep the amp that
turns on when 500/250 turned off. Further it keeps
the 1800hz slot intact.
If you can not make a filter with a low enough
insertion loss then this project as I've described it,
would not work. I don't know if N4PY's program or
another program could be developed to allow a database
table to be created that would allow you to choose the
roofing filter switching points, that could then be
ganged with a range of dsp choices, for each roofing
filter choice. If you also gang the Band, RF gain, IF
gain, PBT and ANT choices in the same databases you
could develope an optimized dynamic range for each
band/mode/filter/antenna. You could save these in a
profile as well. If you do that then you could also
make the 1800hz position more available to use since
you could choose the bandwith when this filter becomes
active.
Anyway that's my idea.
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