Hi there . Here's my two cents for what it's worth. I have three Omni C's
and think they are the most fun. The 1.8 filter makes a nice cw band width
with the audio filter for those moments when the band is not too full. The
500hz filter is very good but if you don't have one , the 250 hz is very
usable and I have never found in line attenuation to be a problem. I have
all combinations of them and you really can't go wrong with the 250. Maybe
that is a repeat of old information and if so, indulge me. Good luck.
Yesterday, I got an Omni C off the shelf after not using one for a while and
moved my TS-850 and 870 aside and I gotta say, wow...still a very good
receiver. Steve, KU3S
----- Original Message -----
From: "Marinus Loewensteijn" <mjloewensteijn@hotmail.com>
To: <tentec@contesting.com>
Sent: Wednesday, April 30, 2008 3:17 PM
Subject: [TenTec] CW filters Omni-C
Recognizing a wealth of expertise on this mailing list I like to invite
your input on something that has kept me occupied for the past few days.
I like to add a CW filter to my Omni-C. TenTec has sold out of the 217
(500 Hz) and still has the 218 (1.8 kHz) and 219 (250hz). In planning is a
replacement manufactured by Inrad.
The consensus seems to be that the 500 Hz is more frequently used than the
250 Hz.
Have been looking at a few alternative options from Inrad, the 8 pole 1000
Hz #766, the 8 pole 400 hz # 759 and the 4 pole 600 Hz #763. Looking at
the curves on the old Inrad website I see that the 1000 Hz filter has
approx 4dB insertion loss, the 400 Hz approx 9 dB and the 600 Hz about 2.5
dB.
The Omni-C has a filter board that can take the 1.8 khz and the 500 Hz
filter. This board has an amplifier to offset the filter losses. The 1.8
kHz filter position has a 1 dB amplification and the 500 Hz filter
position has a 7 dB amplification.
(The 250 Hz filter has an approx 14 dB loss)
I am thinking about using the 4 pole 600 Hz filter: I feel it will provide
better IMD / dynamic range performance because it can go in the 1.8 kHz
slot. This should go well with the 500 Hz audio filter which is built in.
Am I missing something / have an error in my reasoning?
Many thanks, 73, Marinus, ZL2ML
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