Posted by
John Lemay on
Mar 23, 2011; 8:18pm
URL: http://elecraft.85.s1.nabble.com/K3-Noise-from-P3-tp6201047p6201779.html
I've spent a bit more time investigating this noise, following my initial
response to David.
The noise sounds rather like a buzz saw. It is quite audible on the K3
speaker, it is strong enough to move the S meter, and it's visible on the
P3. There is not just one frequency, but the noise is every 19kHz (approx)
across the band.
The noise goes away if:-
1. I turn the P3 off
2. I remove the 2m antenna
The noise reduces if:-
1. I disconnect the BNC at the K3 IF Out connector.
I already have chokes on the DC lead to the P3.
I think at this stage I should also make it clear that I have a highly
sensitive 2m system with masthead preamplifier, and four eight element yagis
which are at present quite close to ground level.
Regards
John G4ZTR
-----Original Message-----
From:
[hidden email]
[mailto:
[hidden email]] On Behalf Of Jim Brown
Sent: 23 March 2011 19:20
Cc:
[hidden email]
Subject: Re: [Elecraft] [K3] Noise from P3
On 3/23/2011 11:56 AM, John Lemay wrote:
> It seems to me that the noise is being radiated by the screen itself, and
no
> amount of cabinet scraping will reduce this.
That's entirely possible -- but it's also possible that the cables are
involved. Many RFI problems have more than one cause, or more than one
component, or a combination of causes, both of which must be present for
the RFI to happen. In this example, a hand or finger next to the
display allows RF to capacity-couple to the body, and the resulting RF
current radiates the noise. Take the fingers away, and if there's still
noise, another coupling mechanism may be present. On the other hand,
I've never felt the urge to have my fingers next to the P3 screen. :) I
don't operate 2M for weak signal work, because I'm blocked by a high
ridge to all of North America, so I can't comment on noise from my own
display. :)
I don't recall details of the P3 construction, nor the display, but the
display is a potential break in shielding, and even a potential RFI
source. Ideally, the display should be bonded to the shielding
enclosure and be constructed in a manner that there is no break in the
shielding, and any current driving the display should flow in a loop
with very small area to minimize any magnetic field.
73, Jim K9YC
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