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Jack Schmidling wrote:
My new (first one in 50 years) is an 8000 modulated by a pair of 813's running as triodes. The RF deck and Pw supply are up and running and I am working on the modulator now. My plans are to drive it with the Ranger and eventually do a stand alone audio section. The Range gets poor audio reports in spite of months of trying to resolve it. I am wondering if anyone here as any experience using 813's as triodes and would also like some help on the audio driver. I bought a little solid state audio pre-amp and driver that puts out about 4W at 8 ohms. This is probably not enough to drive the 813's so I need more poop and some ideas on how to drive the modulators with the 8 ohm amp. There are some in progress pics of this project at http://schmidling.com/radio.htm Jack K9ACT If I have my numbers right, a peak envelope power of 1500 watts equates to a carrier power of 375 watts, which requires an audio amplifier to put out 200 watts (to round up a bit). If the 813's were wired as pentodes they could deliver 600 watts in AB-2 with less than a watt on the grids. I'm not at all sure of what you'd lose using them as triodes, but I'll bet they'd deliver 200W in AB-1 with no grid power consumed at all. Antique Radio Supply (www.tubesandmore.com) has a reprint of an RCA transmitting tube handbook that has extensive data on the 813 -- it should have enough data in there to figure out the design stuff, and directions in the front on how to use the data. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Posting from Google? See http://cfaj.freeshell.org/google/ "Applied Control Theory for Embedded Systems" came out in April. See details at http://www.wescottdesign.com/actfes/actfes.html |
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