[TenTec] 221 cw filter insertion

[Bill Tippett <btippett@alum.mit.edu>]

>But doesn't  the Omni6 + have a similar gain adjustment for high loss
filters as the Orion? That is, for the optional 9 MHz filter there is 
a  jumper
plug that can be set to at least partially compensate for the 
higher  losses from
the 216,217 219 and ,yes, the 221  filters.

        It does, but suffers the same problem as in Orion.  You have a
fixed 12 dB preamp, but insertion loss differs by 5-6 dB between the
217 and 219 filters.  There is also a misalignment problem which
George W2VJN points out below (NOTE: This is from a new mailing
list on Inrad's website).

                                                73,  Bill  W4ZV

http://mail.inrad.net/mailman/listinfo/list_inrad.net

Thanks to W2VO, I have tested a Ten Tec 221 filter.  It is supposed to be a
250 Hz bandwidth filter with for a CW pitch of 500 Hz.  There has been a lot
of interest in low pitch CW copying on the Ten Tec reflector.

Here is the data:

Center frequency = 9000.468
-6 dB bandwidth = 278 Hz
-60 dB bandwidth = 792 Hz
Shape factor = 2.85
Insertion loss = -11.5 dB

Note that there is about 3 dB loss due to the 2400 Hz filter misalignment
plus about 8 dB loss due to the #763 600 Hz roofing filter misalignment, if
it's installed.

This happens because the 2400 Hz lower 6 dB point is 9001.5 - 1.2 = 9000.3
kHz.  It would be better if the SSB filter were switched out, but this is
not possible.

I have been asked to produce a 4 pole roofing filter with a 500 Hz offset to
go with the 221, but there will still be loss due to the OEM 2400.

Comments?

George, W2VJN

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