[Elecraft] Re: Magnetic fields and phase noise

[Bob Evans]

Fraser,

I would also be interested in a solution to magnetic field sensitivity in my
K2/100.  I found that a Radio Shack Optimus speaker placed within 8 inches
of my K2/100 caused distortion on both transmit and receive.  I'm not
technically astute enough to call this "phase noise", I just thought it was
one of those undocumented features similar to beta software product
releases.  I have not seen the distortion problem occur when using my amps
(one Ameritron AL-80B and one Dentron Clipperton L) as Earl, K6SE has, but
they are both a couple of feet from the rig and are not as potent as an
Alpha.  Since I'm not really a QRPer, I simply bought the K2 because it has
such great specs in the areas I was interested in; i.e. close in
selectivity/descernability (I know everyone in the UK cringes when Americans
hammer the Queens English) for contesting.  In fact, I would like to build a
second one to complete my SO2R (Single Op 2 Radio) contest station, but I
would like to raise my comfort level with the magnetic sensitivity issue.

Lastly, as far as the phase noise limited tests shown for a K2 in some of
the published comparisons, I saw a "nice" (meaning = understandable to the
technically challenged such as myself) post on this reflector that described
the K2's design itself as being max'ed out with the phase noise limitation,
so I am not expecting anything further to be done to improve the phase noise
issue.  The K2 handles contest conditions MUCH better than my pair of old
Icom IC-765s and that means I'll probably have to learn to live with an
idiosyncrasy or two in the magnetic field department.

Bob K5WA

K2/100 #4687

 

Message: 5

Date: Sat, 19 Mar 2005 10:26:05 +0000

From: "Fraser Robertson" <g4bjm at hotmail.com>

Subject: [Elecraft] magnetic fields and phase noise?

To: k6se at juno.com, dbarker at visioncomm.net, elecraft at mailman.qth.net

Message-ID: <BAY102-F2771B7E88B7AC86D24D792F94B0 at phx.gbl>

Content-Type: text/plain; format=flowed

Interesting Earl, the non exhaustive tests I've done indicate that it is not


due to magnetic fields. But if indeed that is the case, there must be a 

relatively easy, if perhaps not elegant, way of significantly improving 

this.

Has anyone else investigated this?

73 Fraser G4BJM

>From: Earl W Cunningham <k6se at juno.com>

>Over a year ago I noticed this problem, which occurs only when my K2 is

>driving my Alpha linear. After extensive testing done by me to determine

>the cause of the problem, is was found to be caused by hum from the

>magnetic field of the linear amplifier's HV transformer getting into the

>PLL circuit of the K2. In my case, 6 feet of separation between the K2

>and the linear was not enough to eliminate the problem, however with 30

>feet of separation (with the K2 and amp in separate rooms) did solve the

>problem. This answer is unacceptable, of course.

 

Bob Evans
(713) 937-9013