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UHF interference - follow up to post 28548

Submitted: Saturday, Dec 03, 2005 at 10:24

ChrisB

In regards to interference on channel 20 on my TX3400 UHF. I have established that it is the car’s electrical system itself that is causing the interference. The UHF works perfectly when ignition is off. When the ignition key is turned, even just to the ACC position, interference is heard on channel 20 only, all other channels are OK.

I have a 105 series GXL cruiser, 1HZ motor.

MY questions are:

Does this happen to anyone else?
To those that have had the same or similiar problem, have you overcome it or just put up with it?
To the gadget people out there, any recommendations for a solution, can I try to block the interference from cars electrical system with something?

Thanks in advance,
Chris
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ThreadID: 28589 Replies: 10
Views: 607 FollowUps: 5
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AnswerID: 142234   Submitted: Saturday, Dec 03, 2005 at 10:30

Gunnell replied:

Before you spend too much time trying noise interference filters, wire shirldind etc, I suggest you just try moving the transceiver a few inches from its current location. I mounter an Icom transceiver in a Prado in a spot inside the glovebox, It was great spot,looked like it was made for it but got a similar problem. Relocation resolved the problem.

Regards,

Peter
Reply 1 of 10
AnswerID: 142240   Submitted: Saturday, Dec 03, 2005 at 12:19

Shaker replied:

When you turn to ACC is your A/C fan operating?
I have noticed that my A/C fan can interfere with the AM band in my stereo.
Reply 2 of 10
FollowupID: 395949   Submitted: Monday, Dec 05, 2005 at 07:09

ChrisB posted:

No fan is not on. When I turn it on it doesn't make a difference. Also checked the wipers and washers, and no problem.
FollowUp 1 of 1
AnswerID: 142241   Submitted: Saturday, Dec 03, 2005 at 12:30

Member - 'Lucy' replied:


Chris.

I have used a Uniden and now have a ICOM 400 with no problems in a Troopy with 1HZ.

Therefore I reckon you don't have to worry about the engine side of it.

It is picking up the interferance possibly via the electrical connections to it.

Check and see where it has been wired into the power. If it is connected to the wring loom somewhere try this:

Disconnect from the loom and wire direct to one of the batteries both pos+ and neg- and try it then.

If that doesn't work then the aerial and connectors are next port of call.

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Reply 3 of 10
AnswerID: 142245   Submitted: Saturday, Dec 03, 2005 at 13:11

Peter 2 replied:

anything with a cpu or a chip running in the car can cause that type of interference. My UHF picks up the cpu in the Barrett HF, and two different Garmin GPS's.
Putting power filters (used Pioneer stereo filters ) on the GPS's power connections sorted them out but am unable to screen the HF.
Is the car radio on? It could be the voltage regulator on the instrument PCB but wouldn't have thought it was on when in acc position.
Might be the clock?
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Peter
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Reply 4 of 10
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AnswerID: 142254   Submitted: Saturday, Dec 03, 2005 at 14:27

Footloose replied:

My experience has been that the 1HZ motor is almost silent RF wise. I'd be looking at your accessories. Pull a few fuses and you'll soon trace it.
Reply 5 of 10
AnswerID: 142288   Submitted: Saturday, Dec 03, 2005 at 20:17

geocacher (djcache) replied:

The other thing you could try if it's mounted onto plastic is to ground the case of the 3400's tx rx unit. Screw a ring terminal to the metalic part of the case and run a wire to body metal somewhere.

No guarantee but it may work.

Dave
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Reply 6 of 10
AnswerID: 142339   Submitted: Sunday, Dec 04, 2005 at 13:11

Member - 'Lucy' replied:


Oi! ChrisB

R U going to let us know how its going.???????????
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Reply 7 of 10
FollowupID: 395924   Submitted: Sunday, Dec 04, 2005 at 21:01

ChrisB posted:

I’ve taken it out of the centre console but it makes no difference and it’s already connected directly to the axillary battery. Will check power connections and antenna connections and let you know.

Chris
FollowUp 1 of 4
FollowupID: 395927   Submitted: Sunday, Dec 04, 2005 at 21:38

Member - 'Lucy' posted:


Here ia another simple test for you.

Turn UHF on.

Select channel 20. Make sure there is no interference.

Fire up the vehicle.

Now according to the script you now should have this interference thingy on channel 20.

NOW disconnect the aerial from the back of the UHF set.

Result (1) No more interference = its that mother of an aerial

Result (2) Interference continues = its comming up the 'wires' most probably.

Result (3) Its none of the above and maybe some 'harmonic' thingo directly interfering with that particular set.

If possibl, borrow another UHF, set different make. Temporary rig it up using your aerial and see what happens.

Regards

Ken Robinson

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FollowUp 2 of 4
FollowupID: 395948   Submitted: Monday, Dec 05, 2005 at 07:08

ChrisB posted:

Thanks Ken. I did exactly that last night. I got result 1. I'll re-wire the antenna connection to the radio. My only thought, if I didn't do this properly in the first place, surely I would be getting trouble with all channels and not just 20.

I've got the GME 4.5dB ground independant antenna that was already wired at the antenna end. Should I be checking that end too, as I've never touched it?

Thanks,
Chris
FollowUp 3 of 4
FollowupID: 395972   Submitted: Monday, Dec 05, 2005 at 10:00

Member - 'Lucy' posted:


Good Morning Chris

No! don't piff the aerial. Well not just yet anyway.

I don't want to depress you, but all that you have achieved so far is that you have excluded (2) & (3) as the cause.

The next thing to try if you can manage it is a different UHF set attached tothe exact same aerial you have now and as it is fitted now.

Or get hold of a hand set and try that on channel 20.

If both these work okay then I would respectfully suggest that its starting to look like the 'glitch in the set' scenario that John (VIC) just posted.

Regards

Ken
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FollowUp 4 of 4
AnswerID: 142374   Submitted: Sunday, Dec 04, 2005 at 18:59

Banjo 1 replied:

Yep - try moving it a little - or running a temp feed line and taking the power straight off the battery (+ and neg). Your vehicle and many others are bad for this (as we may have said) - I have heard direct reports about the 100 Tojos being a real pain on HF - your UHF issue should still be much easier to fix though.

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Reply 8 of 10
AnswerID: 142403   Submitted: Sunday, Dec 04, 2005 at 21:42

Member - John (Vic) replied:

Hi Chris
I have 2 GME UHF radio's in my vehicle, one is a TX 4400 and the other is a TX 6200 hand held that reside in a vehicle mount with external aerial.

I have the same problem with channel 24 on the 6200 when on scan, (does not occur on the 4400)
I tried everything to sort the issue, no good, so I just locked it out of the scan list.
I also have a Codan NGT HF and it is as clear as a bell in a moving vehicle (No vehicle electrical interference)
Sorry I can't shed any light on the problem, other to say your not alone. LOL.

Cheers
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Reply 9 of 10
AnswerID: 143180   Submitted: Friday, Dec 09, 2005 at 20:43

prado_95 replied:


Consider the power source.

A HT runs from batteries, the 3400 runs from car battery (along with a bunch of other things).

One cause on sone early LC was the oil pressure sender. Disconnect it and see if the problem still exists, otherwise start pulling fuese one by one until it stops, then track it doen from there.

Dave
Reply 10 of 10