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audioguru fm transmitter


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from which technique the RF cops will get any transmitter?
some one tell me that they use Radar ?

Radar won't work.
RF cops are alerted by people complaining about radio or TV interference. The RF cops use their van with a directional antenna on top and their receivers to find the transmitter causing the interference. The interference will occur if your transmitter operates at the same frequency as a radio or TV station or if its harmonics do.

if any one "ON"(start)any illegal transmitter they will caught him in minutes or it takes time?

If they are listenng for the interference with their van and at the same time you are continuously transmitting the interference then they will catch you.

i use trimmer but they are little big. i want to use like urs.

Mine are nice and small, from a local electronic parts store. Digikey also has them.
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this is the only(directional antenna) technique, or other military or other secret sevices use different  techniques and equipments.
i m asking you these things because in my country there is no good law for these things :( for example if some one make tansmitter for hobby, educational or leaning that how it works and transmit & if they (police or RF cops) catch him they dont listen or understand any argument they dont see who is he student or learner, they catch them and put in jail for many years :( :( there is no law for students:(

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Here in Canada, the RF cops don't put anybody in jail and they don't chop off heads like the cops do in some crazy countries. They would explain about interference and ask that the unlicenced transmitter be turned off. Just a warning the 1st time.
The 2nd time they would probably take away the transmitter and the owner would need to go to court to explain about it.

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The RF cops use their van with a directional antenna on top and their receivers to find the transmitter causing the interference

this is the only(directional antenna) technique, or other military or other secret sevices use different  techniques and equipments?
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  • 4 months later...

to mr. Audioguru,
I want to build this, but I have some questions about it ( how the schematic compares to the picture)

I see 14 capacitors in the schematic, but I seemed to only counted 13 capacitors in the picture of the completed picture

I see some bigger power? precision? resistors on the picture. What power rating, etc should they be?

What do the 2 vari-caps do?
I'm also really unsure about what capacitors to use.


Thanks really much

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I see 14 capacitors in the schematic, but I seemed to only counted 13 capacitors in the picture of the completed picture

C2 and R6 are on the bottom of the circuit board. I didn't make a new circuit board but I modified the mod3 circuit into the final mod 4 circuit instead.

I see some bigger power? precision? resistors on the picture. What power rating, etc should they be?

All resistors are 1/4W, 5% carbon film. My 220 ohm resistor is longer because it is about 40 years old.

What do the 2 vari-caps do?

I used two 5pF to 35pF trimmer capacitors. C6 tunes the RF oscillator to the frequency you want to use and C13 peaks the output at that frequency.

I'm also really unsure about what capacitors to use.

The uF capacitors in my schematic are electrolytic, nF capacitors are metalized poly film and pF capacitors are ceramic disc.
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