Re: [RTTY] Help with keeping RF out of PC

[dj2pj@t-online.de (Hadi Teichmann)]

Hi everyone!

Grounding a computer (or whatsoever) does not necessarily mean grounding 
it from an RF-standpoint. And this is the more true the higher the 
interfering frequency is. Ground rods etc. are in the most cases too far 
away from components of your station, so that connecting wires possibly 
tend to function as radiators (with standing waves on them) rather than 
being ground wires for RF. John's advice may help - maybe it doesn't, or 
makes it even worse.

Please, first of all determine (after being sure (!) that the blocked 
programme IS caused by RFI):

1 Does it occur on all or on certain bands/frequencies? If yes, what is 
the _lowest_ frequency on which the interference occurs?

2 Does it occur on only one band/frequency?

If 1: Connect a wire of a quarter-wavelength of the lowest interfering 
frequency (e.g. for 40 metres, the wire would be 10 metres long) to the 
ground connection of your transceiver. If this only cures the 40-mtr 
interference, also cut quarter-wave wires for the bands which still 
interfere (they normally don't..., one wire should be enough).

If 2: Do the same with a wire of a quarter-wavelength of the interfering 
frequency.

The wire(s) can find its/their place anywhere in your shack, even 
bending around the room corners is allowed. They are not extremely 
critical in length. It goes without saying, that you should NOT ground 
the end of these wires! They are "hot" from an RF-standpoint. (I realize 
that wires lying somewhere in a room can lead to constant conflicts with 
housewives and the cleaning personnel...)

I assume that your computer has a short galvanic (!) connection to the 
transceiver, linear, matchbox, or what else you are using for 
transmission. I also assume that you have inserted an RF power line 
filter in the main power line from your station to the outlet (or a 
filter in each power line).

Did you ever try to find out if there were standing waves on the antenna 
low-impedance feedline? If there were, measures should be taken to 
especially improve this situation.

Giving remote advice (wthout having a closer look at the setup in your 
shack and making certain tests and measurements) is always a bit 
dubious. I feel sorry about that.

73 Hadi DJ2PJ


John- W4DJ schrieb:

> Ground the computer with an external ground flat braid to you ground 
> rod or ground bus.
> Don't rely on the ground power cord to do the job. Your symptoms are 
> exactly what I have had in the past and as soon as I grounded the 
> computer problem solved.
> John W4DJ
>
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