[Elecraft] Roofing Filter question

[Andrew Faber]

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" <jim at audiosystemsgroup.com>
To: "Elecraft List" <elecraft at 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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