Need help

102

00:31:42

Hello, I need help at building an FM test sender which gets the MPX Signal from my PC and modulates it to FM. The Output should not be higher than 15 uV, because I want to connect it directly to the antenna port of the radio. The MPX is a standard FM one (You can find on Wikipedia or else).

I need this thing to test the stereo decoders of a few old radios. 

I'm happy about any help, the best would be a finished circuit. I hope, that is possible in EC :D

published 10 years ago

lmccoig

10 years ago

From PC Stereo Multiplexing Sound Card you want FM transmitter to FM Radio connected at 13 uV? You need FM stereo transmitter and attenuated or low power signal out at 13 uV. Any information on sound card out?

TheKuli

10 years ago

You got it, exactly this function I need. I think, when this finished MPX comes in, I don't need to think about stereo, because it is in the MPX? The Sound Card is a Realtek with ALC269. It supports the needed 192kHz. Also I need to correct myself: I need an Output voltage of 15 uV.

lmccoig

10 years ago

I'm on a busy schedule this spring. In USA, Walmart stores in car audio have simple FM transmitters. The 15uV I would control with distance from antenna. I do not know how low power can go and still be able to transmit FM signal. Antenna attenuation may be needed to connect and how ground connections are made to components may matter?

TheKuli

10 years ago

When I get such a cheap transmitter, where do I connect the MPX Signal?

lmccoig

10 years ago

If microphone input or connector on transmitter I would output from computer to microphone input to modulate as FM signal. I have never done this to know all signal levels. Great you are checking this out. Volume controls on computer or transmitter may need set to proper power levels. Hope someone local look over your set up.

TheKuli

10 years ago

I think, I'll try this or next week. Hope, it will work :)

add comment in editor

EveryCircuit is an easy to use, highly interactive circuit simulator and schematic capture tool. Real-time circuit simulation, interactivity, and dynamic visualization make it a must have application for professionals and academia. EveryCircuit user community has collaboratively created the largest searchable library of circuit designs. EveryCircuit app runs online in popular browsers and on mobile phones and tablets, enabling you to capture design ideas and learn electronics on the go.