Greetings from a lurker -- Dick has an interesting idea here and I enjoy pretending that I know how to play the numbers <g> so here goes...
Let's use the 200w figure with a car amp with a bridge amplifier powered by the car's 12v battery, and for the moment we will neglect the losses. The amp's output transistors will produce a maximum output voltage swing of 6v peak (12 v peak to peak.) With a sine wave, the rms voltage will be about 0.707 x 6vpk = 4.24vrms. The AC rms current at the 200w output level will be about 200w/4.24v = 47.2 amps to drive an impedance of 4.24v/47.2a = 0.0898 ohms. So now all we need is a couple or three big honkin' car batteries, several feet of car battery/starter-motor cable,a 200w rms car amp that is actually capable of 200w (which will be much larger than what most manufacturers CALL a "200w" amp), and a 200w modulation transformer with a primary impedance of 0.0898 ohms. Oh, and don't forget what Larry said about DC current through the secondary of the transformer... and we still haven't figured-in the losses. So, is it doable? How much money do you have Dick? <g> The guys have presented some good options, that are most definately doable. But if your heart is set on ss high-level modulation, there might be a better way to go... Here is an amp that uses +65v/-65v for power instead of +12v/0v: http://www.apexjr.com/Cerwinfullrange.htm With this amp, the max sinewave output voltage is 65v peak, or .707*65vpk = 46vrms. For 200w output the rms current will be 200w/46v = 4.35arms to drive a load of 46v/4.35a = 10.6 ohms. When you figure in the losses, the load will probably need to be closer to 8 ohms -- just perfect for that off-the-shelf 200w audio output transformer. <g> In reality, I suspect the transformer will be a problem -- but not an impossibility. I think it's worth a shot Dick! Al disclaimer: I have no connection with apexjr.com other than being a satisfied customer. Dick wrote: >I have over the years built several low power AM transmitters. I would like >to build something a little bigger say in the 400-500 watt plate modulated. >I have been kicking around the idea of using one of the solid state >amplifiers made for car audio driving a reverse connected audio >transformer. I have seen these audio output transformers available in the >200 watt range. I understand that the RF output stage would have to be >designed to fit the impedence of the output transformer. Does this sound >like it could be done? > > K6KWQ Dick > Amps by "MORE POWER" ______________________________________________________________ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html