Mike, it depends much on which filter you have installed for CW in the N1 or
N2 position. If you've got a TenTec #221, that provides the best match with
the INRAD #765 as they both have center frequencies of 500hz. On the other
hand, if you have a Ten-Tec #219 or #217 filter, one or both of the optional
9 MHz. spaces, they are better matched for the INRAD #763 as they have the
same 750hz. offset. It's really a personal thing but the roofing filter
should be matched with the same offset as any optional 9 MHz. filters you
may have installed.
After much experimentation here, I found that what worked best for me is the
INRAD #765 along with the TenTec #221 in my N2 position. In my N1 position,
I have the TenTec #216 digital filter with an offset of 1500hz. and have the
roofing filter disabled when using N1 and enabled when using N2. I also had
a TenTec #219 filter originally in N1 and the roofing filter switched out
when it was selected. The option of bypassing the roofing filter is
available by means of a dip switch on the INRAD board that holds the roofing
filter. For optimal CW here I found the 765/221 combo to be optimal. If I
preferred a higher tone, I would suggest the 763/219 combo or the 763/217
combo. You have the ability to adjust the tone of the CW note to be as you
like regardless but the 765 INRAD should only be paired with the TenTec #221
as they are both centered at 500hz. Conversely, the 763 should not be paired
with the #221 as the different center frequencies would be a mismatch and
cause some undesirable additional attenuation, but would optimally be paired
with another filter with a 750 hz. offset. If that is clear to you, fine. If
not, I'd be happy to try again with further details. If you do not have any
CW optional filter in the N1 or N2 slots, I don't see much difference as to
your choice of roofing filters as it will act alone and I would choose the
one closest to the audio frequency (offset) you desire, but it should make
little to no difference.
The TenTec #221 (as well as the #216 for digital offset 1500hz) have been
out of production at TenTec for over a year now, but they both show up
regularly on this reflector for sale. I have a spare #216 as well as a spare
#221 that I bought "just in case" when I got word that they were being
discontinued. It may have been a poor investment but I have the spares
because at this point I don't ever plan to NOT have my model 564 Omni VI
Plus. If that changes, they are both new and getting more rare every day.
I've also got the briefly used #219 filter that I would consider parting
with but have never thought about advertising it until this very minute.
Ditto with a YK88-C1 500hz. CW filter I bought when I bought my TS-950SDX
new and preferred the narrower 270hz. YK-88-CN1 in that rig, which I am
hoping to install an INRAD roofing filter for CW into when it becomes
available, hopefully in the not too distant future. If anyone needs a near
almost new TenTec #219 or new Kenwood YK88-C1 filter, contact me off the
reflector at; K9RB@arrl.net $79 & $105 respectfully shipped and insured to
your QTH in the U.S.
73, and Happy New Year. -=Rog-K9RB=-
----- Original Message -----
From: "Michael Tope" <W4EF@dellroy.com>
To: <tentec@contesting.com>
Sent: Monday, January 02, 2006 3:02 PM
Subject: [TenTec] Fw: Inrad 763 vs 765
Hi All,
I just ordered an INRAD roofing filter kit for my Omni 6+.
Initially I specified the INRAD 765 (centered on 500 Hz
offset), but now I am wondering if I wouldn't be better
off with the 763 (750 Hz). I was just playing around with
the pitch control on my FT1000MP MKV, and I tend to
gravitate to a note that is between 600 to 650 Hz offset
which is right in the middle between the 763 and the 765.
Will either filter accommodate this note, or is one going to
be better than the other for this in-between note (I noticed
that the frequency response plots of the two filters aren't
exactly symmetric).
Thanks,
Mike W4EF.............................
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