150 Watt Linear Transmitting Amplifier

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All that is stopping me, is Im not sure how to modulate my message unto multiple FM frequencies with the laptop so I can transmit on all stations at once, if that is even possible with my setup. I've heard stuff about GNU Radio, but I would need some help setting it up as Im not familiar with it at all. Maybe if one had the right software, he could pre-record/modulate his message, and copy it onto an mp3 player for later use.

This is all hypothetical fiction, btw.

I think you'd need a transmitter for each frequency, and a means of mixing them if you're going to use them with the same amplifier. You probably don't want to transmit the results of heterodyning, so you'll need some filters as well (both low-pass and high-pass).

Yea, I think you'll need a transmitter for each frequency. I'm sure there are only 5 or so "main" radio stations in your area so that shouldn't be so hard.

Yeah. A couple hiphop stations, a couple country stations, and a couple top 40/rock stations. Quite sad really. Can I use the same amp for all the stations?

Can you recommend a good transmitter or refer me to a schematic for one?

You should be able to use the same amplifier if it's got a wide enough bandwidth to cover the FM band. Just be sure to filter the mixed output of the FM transmitters.

How long do you intend to operate for? If you only want to go for a few hours at a time you can just use the common "FM bug" plans. For longer-term operation you'd want something a little more stable, of course.

I think it's a VHF amp, so it should cover everything no problem. I got it second hand, so Im not sure what the specs are.

Does this look like a decent transmitter design? http://www.aaroncake.net/circuits/fmtrans.asp

That transmitter should work for short-term use (a few hours at a time). It won't be terribly stable in frequency as it warms up, but if you're only using it for relatively short periods it should be OK. (Components like caps change values when they get warm -- heatsinks or fans might increase the usable period of the circuit.)

VHF is a very broad portion of the spectrum. It should list its frequency range on it somewhere. If it can handle approx 85-110 MHz it should be alright in most countries.

You'll need a VHF mixer circuit to add the different transmitter outputs together, and a bandpass filter for approx 85-110 MHz to prevent signals from interfering outside the normal FM range.

So hypotheticaly, what are you planning on doing?

Whatever I need to.

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