Joe,
I agree with Jim's advice here. I have used my K3 several times in CW
contests from Aruba as P49Y, most recently on a 40m single band operation in
CQWW, on a very crowded band. For that kind of usage, I think the narrow
CW filter is advisable. With it, I was never bothered by signals even a few
hundred Hertz away (unless they had clicks extending into my passband, of
course), and I think the DSP along with the 2.7 kHz filter wouldn't have
stopped the loudest signals.
BTW, one think that makes the K3 such a great run radio is that in those
circumstances you also have a very clean passband, devoid of the kind of
digital artifacts that I hear, for example, on my 756 Pro2 on a crowded
band.
73, andy, ae6y
----- Original Message -----
From: "Jim Brown" <j...@audiosystemsgroup.com>
To: "Elecraft List" <elecraft@mailman.qth.net>
Sent: Thursday, December 18, 2008 8:52 AM
Subject: Re: [Elecraft] Roofing Filter question
On Thu, 18 Dec 2008 08:14:51 -0800, Joe Planisky wrote:
I recently added the 400 Hz
filter and so far, it makes virtually no difference EXCEPT in the case
where there's a strong signal within +/- 1 kHz or so of the station
I'm trying to work. Note that a "strong signal" might be another ham
station, a broadcast station, RFI, etc.
Yes. Remember that the IF in the K3 has EXTENSIVE IF filtering that
perform the function of crystal filters in older radios. Those filters
can be adjusted (front panel knob) to virtually any bandwidth between 50
Hz and 6 kHz, and are the equivalent of a selectable filter bank of 20
or more expensive filters! The roofing filter simply sits IN FRONT OF
these IF filters. It protects them from overload, AND provides
additional skirt selectivity.
The radio works fine for routine use with nothing more than the stock
2.7 kHz roofing filter. The roofing filters simply improve performance
under difficult conditions. I own two K3s, one with 400 Hz and 1.8 kHz
filters, the other with only a 400 Hz filter. I operated from two QTHs
during the SSB weekend of Sweepstakes. At one QTH I had the 1.8 kHz
filter, at the other I did not. The 1.8 kHz filter helped, but I was
still quite happy with the radio that didn't have the 1.8 kHz filter.
73,
Jim K9YC
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