[Elecraft] K3: killing RX key clicks

Tue Dec 1 13:58:42 EST 2009

While on 160m a few nights ago I heard loud key clicks and tracked it down 
to a ham just 1 mile away who was chasing a DX station. When he transmitted, 
my K3 was rendered totally deft from any signal within 10 Khz of him! My 
200hz roofing filter, ATTN, preamp off and RFG down had no effect. I guess 
even the K3 has it's limits.
Steve
N4LQ
N4LQ at carolina.rr.com
----- Original Message ----- 
From: "David Gilbert" <xdavid at cis-broadband.com>
To: "Ron D'Eau Claire" <ron at cobi.biz>
Cc: "'Elecraft Reflector'" <elecraft at mailman.qth.net>
Sent: Tuesday, December 01, 2009 1:29 PM
Subject: Re: [Elecraft] K3: killing RX key clicks


>
> I'll accept all of that, but it still doesn't change the fact that there
> are some rigs out there that generate bad key clicks for no reason other
> than the fact that their users either don't realize it or don't care
> enough to fix them.
>
> When I first received my Icom 756Pro (now my backup rig) several years
> ago I discovered that the default rise/fall times (adjustable in one of
> the menus) was set to 2 msec (!). That's unconscionable, but I'll bet
> the majority of Icom users never bothered to check it.  Many of the
> Yaesu rigs generate horrible key clicks unless their users have
> performed a simple hardware modification on them (see the info at 
> W8JI.com).
>
> I operated about 36 hours in the contest this last weekend and made over
> a thousand contacts using the 8-pole 250Hz roofing filter.  Many times
> I'd be running a frequency within 200 Hz of a S9+30db station without
> even knowing he was there.  Other times I'd hear key clicks (loud enough
> to cover the dits in callsigns I was trying to copy) from stations I
> couldn't even find while tuning with the subreceiver!  One large M/M
> operation had great sounding signals on all bands except 15m, where the
> key clicks were objectionable two KHz away even when their signal was
> S5-S7.  At least in that case they have promised to find the problem and
> fix it.
>
> Actually, there is a third reason why some stations have bad key
> clicks.  They admit they do it on purpose in a contest because it gives
> them more elbow room.
>
> In my experience with the K3 in several major contests since I bought it
> last January, the very great majority of bad signals I've heard on the
> air have been due to the TX on the other end, not the RX on my end.
>
> 73,
> Dave   AB7E
>
>
>
> Ron D'Eau Claire wrote:
>> Key clicks can be generated by several different mechanisms within the
>> receiver itself. Paradoxically, it's easier to produce false clicks with 
>> a
>> high performance receiver than it is with a lesser receiver.
>>
>> These have nothing to do with the transmitted signal.
>>
>> The first line of "defense" is to turn off the Preamp and turn on the
>> Attenuator to reduce the overall strength of the signals. Next is to set 
>> the
>> AGC to "Slow" to ensure a strong signal isn't within the roofing filter
>> bandpass and triggering the AGC while the variable DSP filter is set 
>> narrow
>> so the beat note isn't heard. In some cases using the RF gain to control 
>> the
>> level helps a great deal. Another approach is to use a narrower roofing
>> filter or to shift your bandpass so the edge of the roofing filter is 
>> very
>> close to the desired signal on the side toward the interfering station 
>> and
>> as far from the interfering station as possible. Shifting the bandpass 
>> may
>> require you open up your DSP bandwidth to continue to hear the desired
>> signal or shifting the DSP filter position within the roofing filter
>> bandpass.
>>
>> And, remember, "clicks" are an essential component of a CW signal. They 
>> are
>> the sidebands created by modulating (keying) the signal. Very careful
>> shaping of the keying envelope, such as used in the K2 and K3, can 
>> minimize
>> clicks while maintaining an easily readable signal, but the only way to
>> completely eliminate clicks is to not key the signal at all. With a 
>> really
>> high-performance you can snuggle up very close to a signal, as many here
>> have noted. When you do that, you're much more likely to hear the 
>> essential
>> clicks required for good keying.
>>
>> Ron AC7AC
>>
>>
>> ------------------------------------------------------------------------
>>
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