My voice is so lopsided; it has peaks 2 squares pos on the scope for one square down. I've tried it on many scopes direct from many good microphones. When connecting the same mic to the rig, a 600 watt carrier output yields 5400 watts PEP output just as the carrier is pinched on the 100% negative cylce. If I switch the polarity of the microphone it all goes downward and pinches the carrier with only a PEP of about 700-600 watts. I was very careful to maintain the linearity and phase of the audio all the way through to the output of the modulator so that in the old days when we ran 1KW input and got 800 or more out of the high efficiency finals the PEP was 3 squared for me not 2. I am now toying with the idea of reversing the phase of the mic and increasing the carrier to about 1200 watts to yield 1500 PEP, just to see how it works that way. Same amount of sideband power just more carrier. It probably won't sound as heavily modulated nut I wonder if it will take out more noise and make diode detection cleaner.
About your modulator decks, do they each have there on modulation XFMR or is the modulation XFMR common to both. As for the different sounds for each one, there may be many variables I am not aware of. I assume the quad 100th modulator is AB2 of B and requires some driving power where as the 4X150 are probably AB1. so there may be different driving techniques. I don't know what the peak current capability for either of those tubes is for a given drive voltage. I used quad 4CX300s once for modulators and boy did that thing have the current swing capability, and in AB1 even. The sockets were a bear though. I had to make adapters with octal plugs on them. I was given the tubes and have no idea what the real socket even looks like. I now use quad 813s in AB1 although they will do AB2 just fine. They just never draw and grid current at the low level we run them these days. I run about 2500 volts on the plates and 800 on the screens setting the bias to idle total cathode current of about 100 ma. They show just a tiny little color on the plates. John, WA5BXO -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Brett Gazdzinski Sent: Tuesday, November 25, 2003 2:33 PM To: amradio@mailman.qth.net Subject: RE: [AMRadio] Re: Modulation transformer ID and repair 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
