Well, the 813 rig seems to be clean in the audio department, and gets nice positive peaks, over 130% positive, and I can get 2500 watts pep out of a 600 watt carrier, but will try a bigger audio cap and see if it sounds better...
When I run the push pull parallel 100TH deck, the audio does NOT sound as clean, its not bad, its just not as clean as the 4x150a mod deck. Resting current and plate voltage does not seem to change the sound, I tried various settings and so on. Brett N2DTS > > > I agree on the explosion Brett! > > If the choke and coupling cap are both large enough > there should be > no change in the output waveform than if it were connected to > a resistive > load. Perhaps it is the capacitance of the choke windings > that is throwing > it off. It would be interesting to know what the free > resonance of the > choke is. Or perhaps too much RF bypass capacitance in the > RF deck. At any > rate I can't help but think that a smaller coupling cap would create > resonance which would put a reactive load on the modulator as > would too > little reactor. This would make the modulator to see a > different load Z > depending on modulating frequencies. In turn there would be > intermodulation > distortion. And a shift in phase relationships of frequencies > that make a > certain wave shape. > > Interesting subject! > > John, WA5BXO > > > > > > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Brett Gazdzinski Sent: Tuesday, November 25, 2003 11:03 AM To: [email protected] Subject: RE: [AMRadio] Re: Modulation transformer ID and repair I was talking about the pass capacitor, using a big one seemed to interact with the choke and mod iron, a big cap had the sound muffled, or something, I was disappointed with the results. I tried changing the size of the cap, and found 4 uf I think sounded natural. I had tried all the way up to 40 UF. The power supply has 70 uf or more in it... Now that I actually have a good mike and preamp, maybe I should try other values again. More farads in the power supply is always better, but you need step start or some way to bring it up gently. Some run the voltage on all the time and switch the cathode, I never tried that, easy with triodes likely, not sure about tetrodes.... WA3JVJ has a push pull parallel 805 mod deck with a huge string of computer type caps, gives a full farad or more, and he runs the voltage on all the time. I think its quite crazy, about 60 computer grade caps in series parallel, at 2000 volts or whatever, if one cap fails, the explosion and mess will likely be very nasty! Brett N2DTS t/mailman/listinfo/amradio _______________________________________________ AMRadio mailing list [email protected] http://mailman.qth.net/mailman/listinfo/amradio
