I would like to boost the power of this transmitter.

Thread Starter

leche

Joined Apr 1, 2011
14
Hello dear friends.First of all i am not sure if i am posting the problem to the correct page.Sorry for it.And the problem is, i bought a fm transmitter for my car.I can put usb disk, sd card or connect my phone and it plays the songs and shares them to the car's player by radio frequencies.But the problem is, the sound quality is really poor, maybe poorer than the regular FM channels.It has much of sizzles on the songs.So i wanted to solder a wire to the transmitter as an antenna to take some gain about the sound quality.But when i uninstalled the case i couldnt see a pad to solder for any antenna.Maybe i didn't see or there wasn't a pad to add it.So i am sharing the photos of the board, and i would like to know if i could do anything to make it better.I will be waiting for your helps about both the antenna or the others.Is there a way to do to make the transmitter work better?Thank you.






 

Papabravo

Joined Feb 24, 2006
14,659
I'm by no means convinced that adding a random length wire as an antenna will do anything for the sound quality. Where did you get such a fanciful notion?
A broadcast quality FM transmitter is actually an expensive piece of precision equipment.
 
These devices are sold to be within the legal specs of transmission power. Other wise, you need a permit to broadcast over a certain power level, and you could get yourself in trouble (with FCC?)
Increasing the transmitting power of your IC could burn it up. You need to read the datasheet and verify the Max Mw rating for it

Most likely, the IC has more POWER available, but the attenuator has dropped the output to a legal transmission level. However, that can be changed by using this calc:
http://chemandy.com/calculators/matching-t-attenuator-calculator.htm
This will NOT fix the QUALITY of your your sound, just amplify the signal to reduce drop outs.

This method requires you to follow the antenna back to the board, and look for and replace the series/shunt resistors in place.

Also in response to papabravo, im assuming hes been looking at dipole antennas, which will very length to obtain certain frequencies
If thats the case, then you could cut a length of wire for your selected freq by using this calc:
http://www.radiobrandy.com/dipole1.html

Edit: im not familiar with your device, as it may differ greatly from the bh1417 transmitter ive been working with. I hope this helps anyway.
 
Last edited:

Papabravo

Joined Feb 24, 2006
14,659
The TS/OP did say that he could not identify the antenna or the pads for attaching one. Is it possible to reverse engineer a schematic from the PC board? Can you tell us the purpose of the inductor, labeled L3, wound on the cylindrical bobin? Is it part of the power supply or is it an RF component?
 

Thread Starter

leche

Joined Apr 1, 2011
14
Thank you very much for all helps.As i understand, there is no way to boost the performance of the transmitter, right? :/
 

Papabravo

Joined Feb 24, 2006
14,659
Not without a great deal more information than has so far been provided. To be fair, that information may be either impossible or impractical to obtain.
 

wayneh

Joined Sep 9, 2010
16,400
...the problem is, the sound quality is really poor, maybe poorer than the regular FM channels.It has much of sizzles on the songs.
Is this true for ALL inputs at all times? I'm wondering if you are over-powering the inputs. You may need to turn down the source very low and turn up your radio receiver. Experiment with different combinations.

Oh wait, this thing plays the digital files all by itself. Does it have a volume control? Try turning it down.
 

Thread Starter

leche

Joined Apr 1, 2011
14
It has an ic which is called ATJ2009C on it.I tried to find some databe files to see antenna pin, but i havent fount it so far.Does anybody has the datasheet or pin wiring diagram?
 
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