George, I think I saw where you fixed your problem. I just wanted to
add something that I found out about many years ago from Eddie, W6/G0AZT.
The best way to rid RFI in just about any type of cable is to wrap the cable
around a ferrite rod. It has worked EVERY TIME for me. With my beam
directly above the shack, I have seen my share of RFI and this trick works 100%.
I've gotten into the practice of wrapping just about every cord around a rod.
Eddie and I were on a mini DXpedition to C6A one time (can't remember, might
have been '90 or so). Eddie connected his C64 to the television set that was
there, keyed up and the screen went practically blank. He pulled out a bad of
ferrite rods and wrapped each cable (including the power cable of the TV) around
the rods, keyed the transmitter and the picture remained perfect.
73, Don AA5AU
----- Original Message -----
From: "George Skoubis" <gaskoub@mhtc.net>
To: <writelog@contesting.com>
Sent: Monday, February 05, 2001 10:53 PM
Subject: [WriteLog] RFI and Audio Isolation Transformers
>
> Hi Everyone,
> I have a dumb question...
> I have an RFI problem on 20 meters when I connect my soundcard to the
> audio in and audio out jacks on my Omni VI +. I have grounded both the
> computer case and the transceiver with short direct ground wires to the
> common ground point (8 inch strap for the computer, 24 inch for the
> transceiver).
> If I unplug the phone plugs from the back of the rig the RFI hum goes
> away, when I plug them back in the noise is back.
> I bought a couple of audio isolation transformers from RS (273-1374) but I
> can't get them to pass the audio signals. I soldered the White wire to the
> center conductor on jack #1 then the Black wire to the jack #2 center
> conductor. I then soldered the Yellow wire to the ground tab on jack #1 and
> the Red wire to ground on jack #2.
> I used a non-conductive box since I didn't want the audio grounds from
> input and output to mix (I figured this would defeat the isolation part).
> No audio passes through when soldered this way and there is only
> continuity between center conductors when measured with a VOM. I have three
> of these "isolators" and so far all they're good for is isolating the audio
> signals from between the rig and the sound card.
> Can one of you tell me what obvious, dumb, "I should have remembered
> that!", mistake I'm making?????
> I want to get on for the contest part-time this weekend (I'm on-call this
> weekend so it will really be part-time) and I haven't ordered the new
> motherboard so I can do FSK (Longer Story, don't buy a FIC Athlon
> motherboard!!!!!) so a fast answer would be appreciated.
>
> Thanks everyone,
>
> George / KF9YR
>
>
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>
>
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