When FM transmitter is plugged in amps go crazy and play music even when turned down & buzz

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When FM transmitter is plugged in amps go crazy and play music even when turned down & buzz

Post by McDonalds » Sun Jan 22, 2017 12:26 pm

Does anyone else have this at all?
is pretty annoying as the TV does go but the speakers still play the music on the stereo even in the other rooms.
just wonder if there a way to make this better and stop it?

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Re: When FM transmitter is plugged in amps go crazy and play music even when turned down & buzz

Post by 3M amateur » Sun Jan 22, 2017 12:48 pm

How is the connection between the antenna and transmitter, which allows all output goes back to the transmitter via the antenna cable. Check up on the screen of the antenna cable is properly grounded and the antenna is far from the amplifiers and other equipment.

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Re: When FM transmitter is plugged in amps go crazy and play music even when turned down & buzz

Post by teckniqs » Sun Jan 22, 2017 12:53 pm

Probably being caused by aerial in an attic? RF flooding your house? Move aerial outside and as far away from TV antenna.

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Re: When FM transmitter is plugged in amps go crazy and play music even when turned down & buzz

Post by McDonalds » Sun Jan 22, 2017 3:08 pm

great I will try outside though its not going be no where near as high.

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Re: When FM transmitter is plugged in amps go crazy and play music even when turned down & buzz

Post by McDonalds » Sun Jan 22, 2017 3:09 pm

aerial is just a dipole and 50 cable plus 35 watts

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Re: When FM transmitter is plugged in amps go crazy and play music even when turned down & buzz

Post by Albert H » Mon Jan 23, 2017 7:49 am

How's it matched? What's the SWR (if it's inside a roof, it'll be lousy and vary when it rains)? Also, you'll get about 10dB attenuation, so your 35 Watts will actually be about 3½ Watts radiated - even if your antenna was properly matched.

If you can't get as high outside don't worry, just build a ground-plane-type aerial - this will have two immediate benefits: a slightly rising radiation pattern, and much less energy going downwards into the house. You'll also get a naturally unbalanced match, so your coax connects directly to the aerial. (A dipole requires a balanced feed or you'll get a substantial mismatch, and the braid of your coax will radiate).

The interference to your electronic gear inside your house clearly shows you that very little of your RF energy is actually being radiated.
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Re: When FM transmitter is plugged in amps go crazy and play music even when turned down & buzz

Post by McDonalds » Mon Jan 23, 2017 12:33 pm

its odd as SWR is 1.0 in the loft yet its 1.6 in my garden though the buzzing has stopped its only going about a mile though in the garden was getting out about 8 in the loft.
I made sure to cut to my frequency to.
I do not intend to be on all the time as its where I am and have no link.
but its interesting to see how far a signal can get out.

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Re: When FM transmitter is plugged in amps go crazy and play music even when turned down & buzz

Post by McDonalds » Mon Jan 23, 2017 12:38 pm

I will see if I can get a ground-plane-aerial

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Re: When FM transmitter is plugged in amps go crazy and play music even when turned down & buzz

Post by McDonalds » Mon Jan 23, 2017 2:51 pm

is there a chance a better power supply will help?
I am using this
Image
It can get pretty warm.
if you have any links to some which are all ready in the UK it will help.

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Re: When FM transmitter is plugged in amps go crazy and play music even when turned down & buzz

Post by Albert H » Mon Jan 23, 2017 4:20 pm

That power supply is 60 Watts out. Your 35 Watt rig will certainly consume at least that much and probably more. A bigger current PSU will certainly help, but won't stop RF getting into all your domestic electronics!
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Re: When FM transmitter is plugged in amps go crazy and play music even when turned down & buzz

Post by McDonalds » Mon Jan 23, 2017 6:43 pm

I also tried this one but it got even hotter yet is meant to be 90 watts out.
https://c2.staticflickr.com/6/5784/3026 ... dfea_o.jpg
of course the volts were set to 12.
in fact it seemed to reduce signal but at least can use this on other things.

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Re: When FM transmitter is plugged in amps go crazy and play music even when turned down & buzz

Post by sinus trouble » Tue Jan 24, 2017 12:13 am

As Albert said, I doubt the PSU is route of your problem? More like as Mr Teck said it sounds like an RF saturation symptom?
that aside, ive never been a fan of the external PSU! I like all my eggs in one box
I would suggest re-thinking your aerial position and keep feed coax well away from and A/V cables
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Re: When FM transmitter is plugged in amps go crazy and play music even when turned down & buzz

Post by McDonalds » Tue Jan 24, 2017 2:31 pm

I have seen this one
http://www.ebay.co.uk/itm/321860242503? ... EBIDX%3AIT

if I got would it be taxed though as got a phone and had to pay £32 back for it because it came from china.

or this one is in the UK

http://www.ebay.co.uk/itm/131829420694? ... EBIDX%3AIT

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Re: When FM transmitter is plugged in amps go crazy and play music even when turned down & buzz

Post by MiXiN » Tue Jan 24, 2017 10:57 pm

Every time I've bought from China, and I've bought from there at least 100 times over the years, no matter whether £1 or £100, I've never had to pay duty or tax on anything as the seller marks the item as a "gift" which evades it - so I'm not sure how you got stung.

I've never got away with duty & tax when buying from the USA though.

You can build a 1/4 wave GP with some thick enamelled Copper wire, and a SO239 socket for less than £5 - so I wouldn't bother with either of the links from eBay unless you don't mind paying over the odds.

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Re: When FM transmitter is plugged in amps go crazy and play music even when turned down & buzz

Post by McDonalds » Wed Jan 25, 2017 12:02 pm

any guess what length they would need to be for 87.5? to 87.9

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Re: When FM transmitter is plugged in amps go crazy and play music even when turned down & buzz

Post by Radio Garfield » Tue Jan 31, 2017 7:39 am

McDonalds wrote: Wed Jan 25, 2017 12:02 pm any guess what length they would need to be for 87.5? to 87.9
Wel, thats pretty basic stuff. Use basic calculation : 143/f, which means in your case: 143 / 87.7= 1.63 meters. That is total length for half-wave dipole. For GP antenna use this lenght: 0,815m (81.5 cm) for "live" part and 3 parts of same length (81,5 cm) for ground.

When You look GP from top, that 3 ground parts have 120 degrees between them and they look like Mercedes bonnet sign :lol: .

Or, You can do it this way:

http://www.pcs-electronics.com/schematics/gpaerial.jpg

Good luck.

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Re: When FM transmitter is plugged in amps go crazy and play music even when turned down & buzz

Post by MiXiN » Tue Jan 31, 2017 10:02 am

The calculation above is correct, but I've read in a few places that it's good to add 5% to the length of the radials - but I can't recall why.

It's probably a good idea to add a CM or so to the radiator too, then that way you can snip bits off to get the perfect SWR.

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Re: When FM transmitter is plugged in amps go crazy and play music even when turned down & buzz

Post by Radio Garfield » Tue Jan 31, 2017 10:39 am

MiXiN wrote: Tue Jan 31, 2017 10:02 am The calculation above is correct, but I've read in a few places that it's good to add 5% to the length of the radials - but I can't recall why.

It's probably a good idea to add a CM or so to the radiator too, then that way you can snip bits off to get the perfect SWR.
Yes, I have used that calculation for a GP antenna on 145 MHz ham-radio band, so the measurements were 49 cm for live wire and 51 cm for radials.

73 de E74D :tup

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Re: When FM transmitter is plugged in amps go crazy and play music even when turned down & buzz

Post by Steve West » Mon Feb 06, 2017 4:54 am

That's deffo RF feedback. Get a few of these and coil mains/audio cables inside them 4 or 5 times: http://www.maplin.co.uk/p/ferrite-ring-hem3016-qt26d

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Re: When FM transmitter is plugged in amps go crazy and play music even when turned down & buzz

Post by fmdx » Mon Feb 13, 2017 5:32 am

Wrap the loft in tin foil lol, it's will stop Rf getting into your shit acts as a reflector, trust me it work's, i run 50 watts from a loft with audio equipment just below the dipole, no buzzing or anything.

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