I am curious. I have just gotten another 217 filter so that I
can build it into my Corsair I. While I was playing around with
the INRAD filters in my OMNI VI (gosh, they are truly wonderful)
I decided to plug the second 217 into the NAR 2 position just to
see the differences in the two. Well, there is about a 5 db
(on that inaccurate meter, I note) difference in loss, but the
center frequency is about the same, although it sounds like some
ripple in the lossier filter (different audio response through
the tuning range, all I have is my ear!)
I suspect that this is about right for "nominal" specs, that filters
can vary, and I may have two on the opposite ends of the spectrum.
However, the difference is quite apparent and helps me dig out
weak signals with the lower loss filter. I have found yet another
217 filter for my other project now.
Has anyone experienced this with a NS filter from Ten Tec? Does
it sound like one of the caps has gone south (would that cause some
strange ripple and a little extra loss?) I may just get some
NPO's of the same value on the filter and just replace them all
just to see what happens. I have reheated all solder connections
and played with the fit of the filter. This filter has several
caps soldered in parallel in single cap positions, NS must have
been out of the correct value that day.
Filters sure are fun.
AND, just for info, the INRAD filters (a 400 Hz filter and a 250 Hz
filter for the 6.3 MHz IF of the OMNI VI) have a noticeable lower loss
compared to the NS filters. When I installed them, and when I kick
in the 400 Hz filter, I can actually watch the S meter go up a little
as the Ten Tec amp that is to overcome the nominal loss of the NS
filters now gives me net gain.
I would really like to see INRAD come out with a 9 MHz IF 400 Hz filter
to match the one for the 6.3 MHz IF, a few less db of loss would be
just wonderful for weak signal work. I could toss the preamp.
George at INRAD says he needs to have 10 people interested as that
is his min order for a new filter. If anyone gets interested, contact
me, I would like to see this happen. I would plan to buy two of them,
so if somewhere near 8 other people are interested, we may have a go.
Clark
WA3JPG
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