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[Yaesu] Filters for the FT-920

To: <yaesu@contesting.com>
Subject: [Yaesu] Filters for the FT-920
From: rick.morris@arris-i.com (Rick Morris)
Date: Wed, 13 Sep 2000 11:22:29 -0400
I am looking for anyone  with personal hands on experience with optional
filters for the Yaesu FT-920.    If that doesn't fit, or you don't care,
please delete this now.

I saw some earlier posts in the archives on the INRAD filters, but they
were from some time ago.  So I thought I would ask again.

It looks like there are a couple of ways to go.  Options are offered by
Yaesu and International Radio.  Prices are comparable.

I would like to increase the selectivity (or more accurately the
rejectivity) on SSB to eliminate adjacent channels during weak signal DX

and contesting.  Ideally, I would like to be able to use the NARROW
switch on the '920 to turn the more narrow filter on and off,
particularly since the filters affect both xmit and receive.  I would
also like to add a decent CW filter to get away from the huge 2.4 kHz
factory default.

(Yaesu's add-on filters are the YF-116A for AM and the YF-116C for CW.
The '116A is apparently just a 6 kHz filter for improved AM listening.
If you install it, it becomes the default BW and selecting the NARROW
filter setting actually just selects the factory-installed 2.4 kHz SSB
filter.  No gain there for SSB operation in DX, contests, or a noisy
band.  The '116C is a straight forward 500 Hz CW filter.  With it
installed you can either get the default 2.4 kHz BW, or select NARROW to
get the 500 Hz filter.  Seems rather common as CW filters go.

But I understand both are Collins Mechanical Filters, and I hear good
things about those.

Another option(s) is offered by International Radio with crystal filters
for CW, AM, and SSB.  INRAD apparently has a choice of 2 CW filters, a
400 Hz (701A) and a 250 Hz (708A).  Supposedly both are PC Board
drop-ins.  I guess that means that they fit into the '920's optional
filter slot without any radio mods.  Anyone know if this is true? Anyone
have an opinion (stop laughing) on using a 250 kHz filter for
rookie CW users?

Looks like the INRAD choice for AM is essentially the same as the
Yaesu/Collins offering, a 6 kHz AM filter (710A) that is a drop-in PC
board that apparently fits in the optional filter slot without any radio
mod.  Again, anyone know if this is true?  Anyone know what this offers
over the '116A?

For SSB, things get interesting.  INRAD offers a 2.1 kHz (709.1) , a 1.8
kHz  (711.1) and 2.8 kHz (716.1).  All of these are "solder in"
replacements of the Yaesu OEM filter.  I assume that means replacing the
factory-installed 2.4 kHz filter with one of these.  If that is so, I
don't understand replacing the factory 2.4 kHz filter with INRAD's 2.8
kHz filter.  Anyone know why they even offer that?  But wait, there's

INRAD also now offers a Filter Switch Board for the '920 that apparently
allows you to use either one filter, or two cascaded ones.  Selection is

done from a toggle switch mounted under the front panel.  But it is not
really clear on how this works, at least not to me.  According to their
web page, you can also add two of these boards to a '920 use one toggle
switch to swap between CW and SSB filters.  My assumption is that what
happens is that you replace the OEM 2.4 kHz filter with the switch board
and then add the one or two filters of your choice to the board.  The
switch selects if they are cascaded or not, and somehow it also lets you
choose SSB or CW settings.  There is no mention of using the NARROW
button on the '920, so no idea how this is affected or what it would do
with this mod installed.

My other questions are thus:
1) Would I really see a difference in SSB performance switching from a
2.4 kHz mechanical filter to a 2.1 (or even a 1.8) kHz crystal filter in
the OEM slot? At least enough of a difference to justify taking a
soldering iron to my otherwise perfectly-working '920?  What is the
impact on xmit audio to switch to the 1.8 filter?

2) How much improvement should I expect in cascading a 2.1 and a 1.8 kHz
filter?  Engineering school was a long time ago, but the performance
curves on the INRAD web page really don't tell you much either.  Other
than helping to try and eliminate filter blow-by, is it really going to
help much?

3) Anyone know someone actually using the INRAD switch board mod that
can tell me how the function of the NARROW button is affected?

Lot's of feedback on the ham reflectors and web pages give rave reviews
for the INRAD filter mods, but there is nothing bad about the
Yaesu/Collins filters either.    Yes, I could send all this into to
INRAD for comment, but I'd rather get unbiased hands-on from you.

If you care to respond, please do so to KD4VOJ@arrl.net.  That way it
will find me if I am on the road (which I generally am).

Rick Morris

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