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Can someone help me modding a FM transmitter? i cant find the antenna connection. Answered

I bought it over at dealextreme http://www.dealextreme.com/details.dx/sku.3102 (product).
I unscrewed it but now I can't find the place where I am supposed to attach the new antenna.
2 pics included.

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user
Re-design (author)2010-01-21

I have that same brand but a different model.

What do the white, black and red wires connect to?

What is the black socket with 4 connections in the second picture?

Where is your input from you mp3 player?

On mine the input cable has the normal 3 wires + an extra one labeled on the pcb "ant".  Your's is different than that though, not so lucky.

Answer my questions and I might have a better suggestion for you.

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user
Stevanov (author)Re-design2010-01-23

The red wite black wired connect to the audio jack where the mp3 player is conneccted.
The black socket on the back is the usb power input connector.
Thanks for your time

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user
Re-design (author)Stevanov2010-01-23

I think we're on the right track.  I think they use one of the input wires for the antenna.

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user

Is there any way to boost up the signals up to 1 or 2 Kilometers.......

I want to make my own transmission in Town?

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user
Re-design (author)Re-design2010-01-21

I believe that if you test it and very carefully touch a small piece of wire to one side of L1 that is the black rectangular piece next to the xtal marked "7.600" you will find the range much increased.  If not then try the other end of L1.

So how did it work for you?  If no increase then we didn't find the right place.

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user
Stevanov (author)Re-design2010-01-23

I cant find the L1 piece you are talking about.
Can you tell me if it's on the 1st or second picture, and then were it's located?

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user
Re-design (author)Stevanov2010-01-23

It's on the second photo.  Up next to where the wire comes in.  It's to the right of the metal can marked 7.600.  The pcb is marked L1 right next to the black rectangular part with solder on both ends.

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user
Stevanov (author)Re-design2010-01-24

I found L1 and tried both sides, it doesn't improve the range though.

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user
Re-design (author)Stevanov2010-01-24

Then, experiment.  AS long as you don't short anything out you can test all solder points on the board to see if any of them help.

From what I've found out in the past is that some of the modulators have more power than allowed by the gov'ment, so they have a coil or resistor between the output and the antenna.  If you can find that point then you can omit the attenuator and get full power.  May not be quite legal but at least it would work.  At least you can get a longer antenna if you can find that point.

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redhawkuk (author)2012-02-12

Most Wireless FM transmitters use the ground connection of the audio cable to transmit the RF signal this is where you should solder your wire.
To increase transmission range:
- connect a wire to your ground on the board and connect the other end to an old FM radio antenna or metal pole using a minimum amount of cabling.
- use a quarter wave dipole calculator to work out the optimum height of the antenna this depends on the transmission frequency.
- if you're using an external power source the cable should be looped a few times around a clip-on RF choke and the same for the audio cable.
The RF choke prevents the signal escaping from anywhere except the antenna wire this should minimise on transmission power losses.
As for your transmitter board itself (ZLK018??) there isn't much you can tweak it's pretty powerful enough considering the current consumption however there is the coil top left in the first photo.
By slightly expanding the coil you should get a little extra power but don't over do it else you’ll find the output power will drop down.

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user
steveastrouk (author)2010-01-21

Does it NEED an antenna, or is the earpiece cable not wired as an antenna ?

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user
Stevanov (author)steveastrouk2010-01-23

It doesnt have a wired antenna, i want to add a wired antenna.

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user
steveastrouk (author)Stevanov2010-01-23

What I'm saying is that the wires ARE the antenna - its quite possible to arrange, a bit like the car antenna built in the heated rear windscreen.

Does the thing not work at all ? 

Steve

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user
Stevanov (author)steveastrouk2010-01-24

Oh it's like that, the device does work, i just want to extend the range.

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user
steveastrouk (author)Stevanov2010-01-24

Try longer wires to the headphones then.

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user
lemonie (author)2010-01-21

Do you know that it has one? Did the new antenna not come with instructions?

L

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