Hi Scott
My xyl just brought me a bottle of Maltese wine as a present ... so
far I did not risk tasting it, but the hand-written label suggests it
might cure most things including noises from my computer ....
You are lucky if you only have a whine. I had a lot of video
interference from the rig, until I got a surplus metal jacketed
monitor with heavy internal shielding. The whine MAY be reduced or
even eliminated if you can arrange for the RS232 lead to be screened,
with the screening braid grounded only at one end. The frame (signal)
ground connection (pin 1, I think) must be connected at both ends, but
if the braid is only grounded at one end, you avoid making a common
ground loop out of it.
Over here, its also normal for noise to come from the switch mode
supplies. A common fix is to make sure the AC power connector (to the
monitor) is of the filtered kind, because monitors also cause
noise. Filtered AC connectors are often sold at hamfests and I had to
fit a couple of surplus high-grade switch mode supplies with them to
completely eliminate noise on the receiver. The supplies were supposed
to be "exceptionally well filtered", but I could still hear them on
the radio ... until I fitted the filtered power connectors.
Oh yes; those clip-on ferrite things are OK, but only if you can get
several turns of cable into them. I have tried clamping ferrite
gizmos onto the AC mains power cables, but it made no difference. The
local equivalent of the FCC tells me that they are no good unless you
have several turns. They recommend wrapping a few turns through a
ferrite ring as being more effective than clamp-on ferrite blocks.
I also try to keep the computer wiring as far from the radio wiring
as possible. Both my shack AC supplies are fitted with brute force
filters, using surplus commercial filter parts. I'm not sure if they
help any, but I installed them on the basis that they should not make
anything worse. Fortunately the main AC distribution box is next to
the shack and it had some spare outlets available. I use one AC line
for the radios and one for the computer/packet radios/tncs.
If I blow a breaker with the rig, the computer line does not get
trashed. I got very tired of having to re-boot Windows after a
power drop-out. Also, in theory at least, noise on one line should
not get into the other.
John G3JAG
On 12-Apr-99 Scott Howell wrote:
>
> I have connected my Omni V to my computer. I get a wine now, but
> isn't
> overly annoying, but is there nevertheless. Seems the filters make
> it go
> away, but I am wondering what could be the cause Its a standard
> serial
> cable and as soon as I disconnect it, the noise goes away. I tried
> a beed
> on there, but maybe not enough.
> Any other thoughts would be appreciated while I look for more beeds
> to try.
>
> tnx es 73 de Scott/n3byy
>
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Date: 15-Apr-99
Time: 00:07:45
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