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Topic: RFI from voice system - shield it? (Read 630 times) previous topic - next topic
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RFI from voice system - shield it?

Yahoo Message Number: 72296
I've got a 2000 magna that has enough rfi generated by the voice system to make my cb radio almost unusable. I can also pick up the rfi in my Bose fm radio when I add a separate fm antenna. The interference comes in as a clicking sound. When I position my fm antenna under the center of the overhead dash area I get the most interference. I'm assuming it is coming from the voice system.
My question is, has anyone successfully eliminated this source of rfi and if so how?

Pete

2000 40' Magna #5892
Pete
 2000 40'  Magna #5892  CAT C-10

Re: RFI from voice system - shield it?

Reply #1 –
Yahoo Message Number: 72297
do you have the Bose speakers in the cargo bay ? If so check the zone 2 Bose hand held dialed full volume.
Just a ...WAG
AL

00 affinity #5851

Re: RFI from voice system - shield it?

Reply #2 –
Yahoo Message Number: 72310
Pete...

Suggest you first remove the power from the audio board and see if that eliminates the interference...
If it does, wrap 10 or 12 "turns" of the positive and negative wires (as near to the audio board as possible) on small toroid transformers...you can get the toroids at Radio Shack... Make sure all grounds are good at both the CB, the CB antenna, and the audio board...
If you still have interference after wrapping the leads on the toroids, bypass both positive and negative power leads at the input to the audio board with 0.01 ceramic capacitors... keep the capacitor leads as short as possible...

buck

k7wn, '99magna5653, Cat C10, Allison HD4060

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Re: RFI from voice system - shield it?

Reply #3 –
Yahoo Message Number: 72323
thx for the replies. I've shut off the house batteries and the interference goes away on the cb. I've put a rfi filter on the power leads to the cb and that didn't help. I guess my next attempt will be the toroid transformers. I'll post the results.

pete

2000 40' magna 5892
Pete
 2000 40'  Magna #5892  CAT C-10

Re: RFI from voice system - shield it?

Reply #4 –
Yahoo Message Number: 72334
Trouble is with shutting off the house batteries is that you shut down everything that might be causing the interference... you need to disconnect the power leads to the audio board to see if it is the culprit... if you still have interference with the voice board disconnected then you will know it is something else that is generating the rfi...
the CB will pick up the interference from the CB antenna, not from the power leads... if the voice board is generating the interference, it will be radiated by the power leads to the voice board... try taking the rfi filter off the CB power wires and put in in the power leads to the voice board (as close to the board as possible)...
if that doesn't work (since I have no idea what type RFI filter you have installed) do the toroid thing and then the bypasses if needed...

buck

k7wn, '99magna5653, Cat C10, Allison HD4060

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Re: RFI from voice system - shield it?

Reply #5 –
Yahoo Message Number: 72338
Ever since I have owned my coach, I have had RFI problems from the audio boards. So I located them behind the TV. Well they are unshielded. At the time, I contacted CC and asked about them and they offered no suggestions. Torroid cores should help some and same with the capacitors but to really get it, the boards should be either eliminated or shielded in a aluminum box and solidly grounded. We are not sure if they are radiating at 27 MHZ or just radiating broad spectrum.
When I asked CC tech support if the boards ever passed FCC, they had no idea what I was talking about.

Jon Baum

2K Magna 5923
 

Re: RFI from voice system - shield it?

Reply #6 –
Yahoo Message Number: 72356
I give. I pulled the fuse on the voice system and the interference does indeed go away. I put a toroid choke on the power leads (by the way, red wire #65 on my magna and a green wire marked ground) with about 8 turns of wire and did not get an improvement. The access to this board, at least for me, is so difficult that I'm not going to attempt anything else.
Thanks to all for your suggestions and should I stumble on a solution I'll bring the topic back up and share with everyone.

pete

2000 40' Magna #5892
Pete
 2000 40'  Magna #5892  CAT C-10