Well Ken,
Remember that I have past experience with both the 500 & 250 Hz CW filters
in a Corsair, so I'm somewhat used to them both.
Granted, the 500 Hz filter saw the most use. I found the 250 very useful,
though, under a handful of particular situations. Two that come to mind
off-hand:
(1) Rare DX or a DXpedition sending CW who is getting interefered with. If
the QRM wasn't zero beat (and often it's not quite) that filter was enough,
sometimes along with some gentle nudging of the PBT and such, to pull the
signal clearly out of the muck.
(2) In major CW contests, especialy CQ WPX CW, when my old call was a
semi-rare enough prefix to be a minor advantage, the 250 Hz filter would
help me separate signals under crowded band conditions. Especially on 40 &
80 CW.
Now I should add that in the past, I've used external filters (on other
rigs) to perform the some of the same functions. (Somewhere I still have
that old external MFJ filter! But my external DSP filter on the TS-140S
does a better job these days) I've found a setting of 350 Hz (+/- 50) is
narrow-er enough than the 500 Hz filter, yet wider enough than the 250 Hz,
to serve my purposes. If I could find a compatible 350 Hz filter at a
reasonable price, I'd try and get it. But unless I did something like
custom order one, or get a bare board and try and get the crystals to roll
my own, it's not going to happen.
And I will admit that one of the reasons I'd like the filter is just to make
the rig "complete." It has everything else (OK, the Corsair PS & Remote VFO
don't quite cosmetically match a Corsair II, but electrically they're
identical, so I can live with that!), so it would be nice to "finish the
job."
It's not something I must have today. I can afford to be patient until the
right one comes along. Soon enough, I'll find one!
73, ron w3wn
-----Original Message-----
From: tentec-bounces@contesting.com
[mailto:tentec-bounces@contesting.com]On Behalf Of Ken Brown
Sent: Sunday, October 21, 2007 6:36 PM
To: Discussion of Ten-Tec Equipment
Subject: [TenTec] Purpose of 250 Hz 8 pole filters
> Another viewpoint: I have both filters (500 and 250) in my Corsair
> II, and found that I never used the 250. Too narrow for comfortable
> tuning, and if I couldn't isolate a signal in the 500 hz bandpass it
> wasn't worth the aggravation anyway.
>
>
This is sort of my experience too. I do use the model 221 six pole 250
Hz filter in the 9 MHz IF a lot. However the model 282 in the 6.3 MHz
IF never gets used . Using the 250 Hz 8 pole filter "interferes" with,
or detracts from, my own ability to discriminate between
noise and CW signals. I found I was also not using the 250 Hz filter in
a FT-1000 this weekend for the same reason. It seems like the main
purpose of a 250 Hz 8 pole filter is to use it to demonstrate that you
don't really need a filter narrower than 500 Hz. This is for human
copied CW, there may be practical application of the 250 Hz filter for
other modes.
DE N6KB
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