making FM Tramsmitter -- modifying Z-299 --


Japanese version here.


I found that FM transmitter was sold for about $10 including postage, so I bought it.
It was "ing Z-299" by TAMA electronics.

I've had a thought of making FM transmitter, but I couldn't get a IC such as NJM2035D, BA1404, BH1414, BH1415 and BH1416FM.
In addition to this, If I can get such IC, I wouldn't be able to acqure a IC which works PLL.
So I couldn't realize the thought.

I was just about to through up my hands when I found Z-299.
It costed lower than the IC of FM modulation and it was very handy.
It offers us to choose transmitter frequencies from 88.0, 88.2, 88.4 and 88.8MHz.
It seemed to be a hero for me.

listmarkdismantling Z-299

There was a screw on the bottom of Z-299.

I turned this.

Then I lost its guarantee from maker completely.

The IC which modulates frequency seems to be HY1417LP.
I didn't know about HY1417LP, so I searched on Google.
Then Chinese web sites appeared a lot.
I guessed that it was made in China but I couldn't find the datasheet of it.
It seemed to have a compatibility with BH1417 and modulate frequency by PLL.

Following the lines on its print board, power supply seemed to be pass through LPF which was consisted of C and L and switching regulator.

Considering this, we can use 9V battery of 006P.

Stereo phone cable was used as sending antenna.
The cable was as long as 90cm and this is about 1/4 of wavelength of 80-90MHz.

I think it is surprising that we can get such a cool device for $10.
It will be much more low cost and high performance.

listmarkmodifying Z-299

Z-299 has negative points of following.
1: its volume is small
2: its power of sending wave is low

1: will be improved to insert headphone amp between iPod and transmitter.

2: is troublesome.
For this solution, I put a circuit that amplify high frequency.
Being careful of the law of radio wave, I tried to make the circuit.

I used a IC, uPC1676G, which would amplify high frequency signals by 22dB.
It needs 5V as voltage supply.
It can amplify as high as 1.2GHz.
But this is very tiny IC.
It is as small as sesame seeds.
It wat tough to solder.

my circuit is following

(If you click, the figure will expand.)

I don't like recieving power from sigar socket because it is eyesore.
So I adopted 006P battery supplying.
(It is also be able to take power from sigar socket by setting DC plug in case of emergency.)

I used stereo phone cable as antenna.

Now it is the time to making actually.

It is very small.
It is smaller than cigarette case.

It is small because I bought a case which I had to insert print board slantingly.

I'm sorry for my bad wiring.

I put letterings.

Now it is complete.
It took about $10 in addition to Z-299.

It sounds well, but it is behind FM radio.
If I put it in the rear part of car, fine music will fill my car.

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