From: rr (rr@dragonheart.net)
Date: Fri Feb 28 2003 - 08:16:16 EST
Stu,
I had noise problems that were horrid at one time reaching S7 to S9 at times.
Grounding is part of the problem but there are other areas you need to check.
Do ground your computer chassis to the same ground as the PCR1K.
Make sure you dont have any florescent lights nearby that are used in the
work area.
If you have a portable SW radio use it to help track down noise sources by
walking around waving the antenna near suspected object.
I used the PCR bandscope to show what frequency had noise peaks and tuned
the portable SW radio to the same frequency.
Check Electric over head fans.
I had to shield by computer by using that silver shiny metal air
conditioning tape over all holes and the used aluminum foil sheets to help
provide more shielding. I also cut out a square piece of metal screening
over the place I determined air could come into provide air for the
computer so it wouldnt overheat.
I have 3 servers in a closet 40 feet away in a shielded closet (used mylar
emergency blankets aka space blankets to line the walls before I put the
servers in) with metal mosquito screen used on the air intake also. But I
found a second very noisy source, the cable than ran from the server to my
hub was very noisy. Here the RF noise from inside the closet where the
servers are was traveling the cable to the hub that served my computer and
reaching the PCR. I solved that problem by using a ferrite rf suppressor
for ethernet cable in side the server closet on the cable to my computers hub.
I also found that a higher quality RS232 cable helped from picking up more
noise... a ferrite could help there.
And also have a ferrite on the power supply wire and audio to sound card wire.
This eliminated a good portion of the noise... but I still get noise
between 2 and 3.7 mhz... it was coming in on one of my long wires strung
from trees. This one was actually a little tricker to figure out... but I
did... I have a TV antenna (that Im not even using) that was picking up AC
RFI from an outdoor spotlight attached to the TV pole and was re-radiating
the RFI pointed towards my long wire 10 feet away.
I knew I knew what I was doing when I figured that one out... I used the
portable SW receiver to help locate most of the problems. I was sure it
was my neighbors swimming pool pump, but it wasnt.
I still have to shield my wifes' computer which is 5 feet away.... but I do
most of my listening after she goes to bed and just shut her computer off.
So in solving RFI problems tackle them as you find them and determine when
it is good enough.
Doing all the above brought my noise floor down to s3 or s4... I still have
to fix the TV antenna problem yet.
Robert Rathbone
KG4WKM
Tampa, Florida
>Message: 1
>From: "Stuart McMurtrie" <stuart.mcmurtrie@blueyonder.co.uk>
>To: <pcr-1000@mailman.qth.net>
>Date: Thu, 27 Feb 2003 12:16:37 -0000
>Subject: [PCR-1000] Computer Noise...
>Reply-To: pcr-1000@mailman.qth.net
>
>Blank
>I have dreadful computer noise around the 132Mhz + - area...
>
>any ideas how I can cure some of this ?
>
>Stu.
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