well all I can say is it works.. works well as a matter of fact, and has been for 6 years :) I typically run between 350 and 400 watts of carrier every day. It looks great on the scope. Modulation envelope is perfect. 100% modulation. In 6 years Ive only lost one tube, and I accidently broke that one.
Ronnie - W5SUM ---------- Original Message ----------- From: Gary Schafer <[EMAIL PROTECTED]> To: Discussion of AM Radio <[email protected]> Sent: Tue, 11 Jan 2005 14:34:26 -0500 Subject: Re: [AMRadio] AM Amps > By "legal power out of the 813's" I assume you mean 375 watts > carrier? If so there is no way the peaks are going to 1500 watts. A > pair of 813's will not put out that much power in GG linear > configuration. At least not very long. > > A pair of 813's in GG are good for about the same power out as 4 > 811A's. If you run them with more than 150 watts carrier out you > will be flat topping with modulation, unless you keep the mod > percentage very low. > > AT 375 watts carrier out at 33% efficiency that would require 1140 > watts plate input power. That would be a plate dissipation of around > 380 watts per tube! Cooked to well done in minutes! > > Now if you tune them so there is higher efficiency, the plate > dissipation will be lower, but then your mod peaks will never reach > any where near 100%. Even if your driver is modulated 100%. > > In AM linear service the efficiency of the amplifier must be 1/2 as > much for the carrier as it is for the peaks. This is how the voltage > doubles to obtain that peak power needed. > > Without that ratio you will have distortion and splatter. As you > noted when running 600 watts carrier out you must back the > modulation down. At that power level you have almost no headroom at > all for audio. You are at near maximum capability of the tubes with > just carrier. > > 73 > Gary K4FMX > > ronnie.hull wrote: > > This aint rocket science at my shack. > > > > I have a pair of trusty old 813's in grounded grid with 3200 Volts on the > > plates. I drive them with my Ranger all the time with no problems at all. > > > > I always tune the ranger up to full power into a either a dummy, or my > > dipole. THEN switch the 813's into the line and then quickly dip the ranger. > > It usually will dip back to about 80'mils. I leave it right there and get > > legal power out of the 813's. > > > > If I want to bring the Ranger back up to full power, I can and it will drive > > those 813's to 600 watts and sounds great. > > > > I have been using this combination for 6 years and many of you have heard me > > on it. > > > > If I DO bring the ranger back up to 120 mils, I have to be careful of the > > audio drive, as it will tend to start to distort if the gain is up to high. > > But if I leave the Ranger at 80 mils, it works fine and I work coast to coast! > > > > Gotta love those old 813's! > > > > 73's > > > > de W5SUM > > ______________________________________________________________ > > AMRadio mailing list > > Home: http://mailman.qth.net/mailman/listinfo/amradio > > Help: http://mailman.qth.net/mmfaq.html > > Post: mailto:[email protected] > > > > > > ______________________________________________________________ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:[email protected] ------- End of Original Message -------
