[Elecraft] [K3] Noisy K3 receiver

[WILLIS COOKE]

There are two ways to hear noise that comes from the antenna.  If you are hearing it while hearing a CW tone, it is strong enough to compete with the signal and about all you can do is narrow the band width or mentally filter it.  If the noise is blanked by the key down signal, but you are hearing it in the pauses it can still be annoying and you can still perceive the receiver to be noisy.  In the latter case, changes in the AGC, or RF gain can be effective and reduce the annoyance.  This is primarily why I like my slope at about 6 instead of 10.  But, I am mostly a CW operator with some SSB.  I don't operate AM or FM with my K3 which would certainly have different requirements.  Also there is a difference in what is appropriate for weak signal operation or strong signal operation.  In a contest situation you repidly switch between strong and weak signals so you probably would prefer a compromise setting.
 Willis 'Cookie' Cooke 
K5EWJ 




________________________________
From: Don Wilhelm <w3fpr at embarqmail.com>
To: elecraft at mailman.qth.net
Sent: Sat, December 19, 2009 9:23:08 AM
Subject: Re: [Elecraft] [K3] Noisy K3 receiver

Maarten (and all),

There are two separate noise sources to be considered here, and it is 
important to separate them.  One is the internal receiver noise, and the 
second is demodulated noise that comes into the receiver via the antenna 
port.

For anyone who suspects that the K3 itself is noisy (because of internal 
noise), I encourage those owners to do an MDS measurement.  If the 
internal noise is excessive, the MDS will be greatly reduced - MDS is 
the minimum signal level that can be detected above the receiver noise 
floor.  The Elecraft XG1 or XG2 is an inexpensive signal generator that 
will do the task - and the instructions for measuring MDS are in the 
manual.  If your K3 is not 'up to par', then that problem can be fixed.

OTOH, if the noise is coming into the receiver on the antenna port, 
there is not much that can be done to eliminate it - it is just like any 
other "signal" coming in from the antenna.
The K3 does offer tools such as the attenuator and AGC adjustments that 
can better handle than noise.  Unfortunately, there is not a "one size 
fits all" solution because each source of noise is different in its 
character and amplitude.

I cannot comment intelligently to those who are comparing the K3 audio 
noise output with that of another receiver because I do not have access 
to the receivers they are comparing.  I can only guess that the 
difference may be due to differences in receiver gain, AGC action, 
bandpass width, or the shaping of the audio spectrum.  Without doing 
actual measurements, these variables cannot be quantified.

73,
Don W3FPR

Maarten van Rossum wrote:
> I hope that with the help of this topic on the reflector, I too am able to
> set my K3 correctly for my circumstances so I too can enjoy noise free
> reception.
>  
>
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html