UHF Radio Interference

Submitted: Monday, Sep 23, 2002 at 00:00
ThreadID: 2028 Views:4267 Replies:5 FollowUps:0
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Hi,
I have a GME TX3400 in my NM Pajero. It has a ground independent RFI aerial. Unfortunately I get an incredible hum (described as sounding like a helicopter in the background) when I transmit. The radio is under the dash and the face plate is in the console. How can I identify the problem. It is no where near as bad with the ignition off. The power is from the accessories. Any ideas what to do about it. Thanks
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Reply By: Member - Nigel - Monday, Sep 23, 2002 at 00:00

Monday, Sep 23, 2002 at 00:00
The cheapest and most effective option is to run 4mm cable from to battery to the radio for both 12 volt and earth leads. The battery is the best filter against noises generated by vehicle electrical systems.
AnswerID: 6840

Reply By: ben - Monday, Sep 23, 2002 at 00:00

Monday, Sep 23, 2002 at 00:00
maybe a silly reply, but did you connect your aerial and more importantly did you do it correctly. i connected mine how i thought was correct but later found out through some problems that i didnt do it right. repair costs from the repairer was $10 . so maybe get it checked out. good luck.
AnswerID: 6846

Reply By: Eric - Monday, Sep 23, 2002 at 00:00

Monday, Sep 23, 2002 at 00:00
Phiem.
Sounds like the radio is not earthed solidly to the body, the best earth is the shortest wire posible the thichness of the wire is not critical. the inbiult filter on the positive input should be able to handle the vehicle noise if it is earthed properly. Check the outer of the coax is soldered at both ends.
Eric.
AnswerID: 6851

Reply By: Rob - Tuesday, Sep 24, 2002 at 00:00

Tuesday, Sep 24, 2002 at 00:00
Try these links for good information on mounting, tuning & problems

http://www.mobileone.com.au/tune.htm

http://www.gme.net.au/land/choose_ant.html

http://www.alphalink.com.au/~parkerp/cb.htm

Rob
AnswerID: 6888

Reply By: Guy - Wednesday, Sep 25, 2002 at 00:00

Wednesday, Sep 25, 2002 at 00:00
Philem what is in your view a "ground independent RFI aerial"? an other marketing term to sell the antenna at a higher price. Your hum comes from a capacitance problem between your aerial and the "ground"/chassis of the vehicle. As it has been said previously some parts of your vehicle are NOT ALL grounded together. One of the main problem is the petrol tank usually being insulated. Ground all your UHF cable. ( I mean the external part of it, NOT the centre core). Guy
AnswerID: 6897

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