I would appreciate a lead as to where I could find performance
curves for the Ten Tec filters say the 217, 218, and 219 optional
available for use in the Orion.
I believe the TT filters are "less" steep skirted close in, but are
actually more narrow further on out from the center frequency;
thus actually would perform "better" in the roofing filter application
in the Orion front end than the available Inrad models. Curves
for the Inrad filters are found at:
Couple of examples from the above site:
Inrad 400 Hz BW CW 9Mhz filter, the #759, is down 6 dB at
a BW of 455 Hz; and at 60 dB down it is 955 Hz wide;
their 250 Hz filter, the #760, is down 6 dB at a BW of
315 Hz; and at 60 dB down it is 700 Hz wide.
But, I have been told these actually "come back" up
and have less attenuation on beyond the close in curves
shown by Inrad at their site. I do not know if this is true!
Why, well "only" 60 dB down is really not that large
an attenuation in some ham band situations, and coming
back up again could really be bad.
But, I don't know how to compare to the "standard" Ten Tec
filters. I had an Omni VI+ in the past equipped with the Inrad
filters in all slots, replacing the TT filters. At the time I was
not apprised of the possible benefit of staying with the standard
Ten Tec units; that is, perhaps not as steep close in skirts,
but they "stay down", hi. Frankly, I cannot say that the
Inrad filters "really" made the Omni a better performer, but
I did not do a direct A/B comparison, for obvious reasons:
I only had one Omni, hi.
Any comments, actual data per this topic would really be
appreciated, should you have any or know of a source.
Would like my new Orion (coming in May?, lot #2 somewhere)
to have the best roofing filter performance possible, giving
the narrow IF-DSP filters the greatest opportunity to provide
super selectivity. BTW, have ordered the TT 1.8 kHz and
500 Hz optional roofing filters to be included with my Orion.
So far, have heard of no one replacing Ten Tec filters in
their Orion with the now available Inrad filters for that
radio; perhaps that is sacrilege!
73, Jim KH7M