[TenTec] Redesigning the filter section of the Orion IF

[NJ0IP]

Lee,

Great job of thinking it through, but too much work for too little gain.

The ORION is great as is - better than anything else.

If you want to improve it, do as Bill (W4ZV) suggests (not as he does) and
remove the 500 Hz filter and replace the 1000 Hz filter with the 600 Hz
filter.  This is the best solutions for those who work a lot of SSB (not
just 1 contest per year) and want the best performance for CW.

As it turns out, the 250 Hz filter is not so bad.  It seems to be only the
500 Hz filter which deteriorates performance.  When you think about it, you
don't need 1000 Hz for SSB and it's quite wide for CW.  Replacing it with
600 Hz has no downside.

In reality, the "normal" ham who is not a die-hard contester, probably turns
the rig off on heavy contest weekends.  For the rest of the time of the
year, you will never even hear the small decrease in performance that the
500 Hz filter brings, but it will do the job of eliminating the QRM for you.

I think this whole Inread thread is only interesting for die-hard
contesters.  There are only a few weekends per year where you will actually
be able to "hear" a difference.

Me?  I'm replacing my 1000 Hz filter with the 600 Hz and then getting on
with enjoying the radio as is. (I'm a die-hard cw contester).

73
Rick



-----Original Message-----
From: tentec-bounces at contesting.com
[mailto:tentec-bounces at contesting.com]On Behalf Of Lee Crocker
Sent: Thursday, July 15, 2004 1:42 PM
To: tentec at contesting.com
Subject: [TenTec] Redesigning the filter section of the Orion IF


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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