[Elecraft] K3 receiver desensing on CW during contest

[Merv Schweigert]

Have to ditto whats been said,  I have to run with AGC off,  audio set about
3 o'clock and use the RF gain.   That seems to work fairly well,  I use the
400HZ filter most of the time.   Not sure what the problem is but the audio
goes to pot in a hurry in a pile up.  Sounds strange and no pure tone to 
the
signals.  Was beginning to chalk it up as my problem with old age,  not
knowing how to set parameters or ??
I have bought new headphones of several types thinking it was an audio
problem here,  but so far nothing works,  I agree mine does not seem
to be desense as I can get within a few hundred HZ of very strong signals
and copy a single weak signal fine. 
Merv KH7C

> I have the 200, 400, 1000 and 2.7
>
> I do not recall which one I was using at the time.  At least the 400hz.
> Keep in mind these signals were all s7 and below, most well below.
>
> I was fresh blood on 20m this morning and got spotted.  It was an ugly
> pileup.  The adjacent qrm was not an issue.
>
> When I could get one letter and had one or two people calling it was fine
> when 5 or more the signals all were the same strength and as Dave said mushy
> like.  I did have to rit off and pick off those not zero beat.
>
> All my pileup training goes against having super narrow filters as you want
> to hear those on your sides too.
>
> This issue had nothing to do with wide signals or clicks.
>
> I don't think it is desense either it is more of an overload of the audio
> circuitry where all the signal levels are being capped or captured to a
> specific level.  While the pileup was maybe S3 when I picked out station and
> he was all alone the signal would come up considerably.
>
> Why I don't know.  
>
> There was no local noise issues and no hams close by causing issues.
>
> Just passing on what I experienced.  Overall the radio is great on CW.  I
> worked so many very weak stations easily that I contribute to the fine
> receiver in the K3. 
>
>
> "A slip of the foot you may soon recover, but a slip of the tongue you may
> never get over." Ben Franklin
> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of wayne burdick
> Sent: Sunday, February 22, 2009 7:27 PM
> To: K2MK
> Cc: Elecraft Reflector
> Subject: Re: [Elecraft] K3 receiver desensing on CW during contest
>
> Mike,
>
> The K3 is virtually desense-proof, with a BDR of ~140 dB. But to take
> advantage of this, you need a narrow crystal filter -- the closer to the DSP
> bandwidth the better. This is exactly the situation that we had in mind when
> we designed the 200-Hz 5-pole filter. For CW pileups, you can't beat it.
>
> What crystal filter were you using at the time?
>
> Of course if the transmitting stations are "wide" due to key clicks, there
> may be situations where no amount of filtering can help (for any receiver).
> The DSP noise blanker and NR may be useful sometimes -- you might give this
> a try.
>
> Wayne
> N6KR
>
> On Feb 22, 2009, at 4:45 PM, K2MK wrote:
>
>   
>> I had a great time with my K3 during the ARRL DX contest. I do S&P and 
>> I was trolling around with my filter width at 50Hz. Absolutely 
>> outstanding.
>> The
>> auto spot is equally outstanding.
>>
>> At 50Hz width it was quite clear that many stations call off frequency.
>> Using RIT, I could see that it was typical for them to be 70Hz or more 
>> away from the DX station but I could not hear them in my 50Hz 
>> passband. The real problem was when one of them was S9 or greater. 
>> They completely swamped weaker DX stations.
>>     
>
> ---
>
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>
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