[Elecraft] K3 on-channel strong signal overload?

[Steve Ellington]

This "Duhing" is entirely unfair. Didn't you read what he said? The author 
stated that he had the pre-amp off, RF gain at minimum, NB off, NR off and 
ATTN turned on. What more could he do to eliminate the overload? Without 
looking, I believe the MDS of the K3 and the FT-817 are probably similar on 
60 meters. I believe he did everything possible with his settings. I still 
believe the problem could be the switching diodes producing IMD from that 
super strong signal and there may not be an easy cure.
Steve Ellington
N4LQ at carolina.rr.com
----- Original Message ----- 
From: "Jim Brown" <jim at audiosystemsgroup.com>
To: <elecraft at mailman.qth.net>
Sent: Monday, May 04, 2009 1:01 PM
Subject: Re: [Elecraft] K3 on-channel strong signal overload?


> On Sun, 3 May 2009 21:39:55 -0700 (PDT), orbarrett wrote:
>
>>I was joined while ragchewing with some friends on 5371.5
>>by two other friends locally, one operating HF mobile from the same 
>>driveway
>>and another operating from a base rig in the shack (using a backyard 
>>dipole
>>antenna).  When either of these two friends transmitted on the same 
>>channel
>>(at 100W), I observed severe signal breakup in the K3 receive audio.
> Why are you surprised by this?  This is entirely normal
>
>>To investigate further, I switched the portable antenna from the K3 to my
>>friend's FT-817 on the same operating table, and no audio breakup was
>>observed under the same conditions.  Returning the antenna to the K3, I 
>>then
>>got rid of most of the signal breakup by turning on the input attenuator 
>>and
>>turning down the RF gain to near minimum.
>
> DUH!  Why are you surprised by this? You had the K3 set for maximum
> sensitivity and then hit it with a 100 watt transmitter. OF COURSE it's 
> going
> to overload! You probably had the preamp on too, which is entirely un-
> necessary on 60M.  The 817 is probably a much less sensitive radio, and 
> may
> have a more brute force AGC. The K3 will outperform it by 40-50 dB in
> rejecting signals outside its passband.
>
> The K3 is doing exactly what you SET its controls to do -- pull very weak
> signals out of the mud. NO radio has infinite dynamic range. If you set it 
> to
> perform well on weak signals (preamp on, attenuator off, RF gain all the 
> way
> up), it's going to be badly overloaded by 100 watts ON FREQUENCY from an
> antenna 30 feet away.
>
> These are fundamental concepts of radio. It's too bad that they are seldom
> taught today. Most of us old farts learned them as Novices when we put our
> first rigs on the air. In those days, there were no transceivers. You had 
> a
> transmitter and you had a receiver, and when you transmitted your receiver
> overloaded.
>
> 73,
>
> Jim Brown K9YC
>
>
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