Thanks for the input guys.

I am using a Buxcomm rascal interface (I had forgotten the make, but have
been reminded since), which apparently has excellent isolation.

The problem occurs equally on all HF bands, so is not really frequency
specific.

If its a stray RF problem, which I am very willing to accept, I'm surprised
that it effects two very differently designed computers in exactly the same
way.

Jack VK2CJC wrote:

If its a stray RF problem, which I am very willing to accept, I'm surprised
that it effects two very differently designed computers in exactly the same
way.

Do they perhaps have the same CPU chip, in spite of their very different
design?

"Steve Bonine" wrote ...
Jack VK2CJC wrote:

If its a stray RF problem, which I am very willing to accept, I'm
surprised that it effects two very differently designed computers in
exactly the same way.

Do they perhaps have the same CPU chip, in spite of their very
different design?

Not the CPU's fault. It is almost guaranteed to be the "brick"
power supply. Note that the problem goes away when you
disconnect the "brick" and run on the internal battery supply.

I bought a used "brick" power supply for this Dell laptop on
eBay and it came with an intermittent (3-pin U-ground) mains
power plug. So I chopped it off and replaced it with an after-
market, 2-prong plug and I don't have problems with ground
loops and RFI from the garbage power supply anymore.

Yeah, yeah, green-wire "protective ground", etc. etc. Well,
I don't see what exactly the "protection" here is doing, and
if the green-wire ground WAS supposed to be there for RFI
shielding purposes, then why does it *go away* when I
disconnect the green-wire ground? Riddle me that! :-)

Yeah, yeah, green-wire "protective ground", etc. etc. Well,
I don't see what exactly the "protection" here is doing,

Well it will be double insulated so doesn't really need an earth at all.
I'm surprised there was one.

Jack

On Nov 25, 11:57�pm, "Richard Crowley" wrote"

Yeah, yeah, green-wire "protective ground", etc. etc. Well,
I don't see what exactly the "protection" here is doing, and
if the green-wire ground WAS supposed to be there for RFI
shielding purposes, then why does it *go away* when I
disconnect the green-wire ground?

The green wire isn't there for RFI purposes. At least not primarily.

It's there mostly for safety purposes. In case something fails inside
the power supply, the system cannot become hot-to-ground.

RFI prevention is secondary.

73 de Jim, N2EY

wrote:
On Nov 25, 11:57�pm, "Richard Crowley" wrote"

Yeah, yeah, green-wire "protective ground", etc. etc. Well,
I don't see what exactly the "protection" here is doing, and
if the green-wire ground WAS supposed to be there for RFI
shielding purposes, then why does it *go away* when I
disconnect the green-wire ground?

The green wire isn't there for RFI purposes. At least not primarily.

It's there mostly for safety purposes. In case something fails inside
the power supply, the system cannot become hot-to-ground.

RFI prevention is secondary.


RE the misbehaving unit:

Jack, you probably have a number of problems going on, so I'll outline
some things you can try, and try them one at a time, so you can
troubleshoot which one might cure the problem. Some you may already have
done.

Pull the audio out cable from the laptop and have a listen to the signal
while transmitting both with and without the power supply attached.
Sound okay - the same- both times?


Get the computer and transmitter on the same mains line.

Isolate, isolate, Can you get a line isolator on that power supply, or
possibly make up a cable to run the laptop off a good power supply?

I don't know how the power plugs are in your QTH, but if you are 2
pronged no neutral, you can try reversing the plug on the Power supply.

This probably isn't the problem, but some clip on ferrites on the DC end
of the power supply can't hurt.


Can you try another laptop PS?


- 73 de Mike N3LI -