The push pull parallel 100TH deck does take quite a bit of driving power, with the losses, likely close to 20 watts, which is what the UTC LS grid transformer is good for.
That may be part of the problem, but class B triodes always seem to sound less clean than a good AB1 amp. Brett N2DTS > > > I have been on vacation to visit the grandkids in Arkansas. > Sorry about > the late reply. > I agree on the blatant abuse VS occasional over the limit. I > feel that the main thing is to keep the signal as clean as possible on > bandwidth due to distortion and phasing products and just be > a gentleman > about all. Consider the other guys interests etc. These are > interesting thoughts though. > I have been altering the shape of the wave form at a low level > point to more equalize the symmetry. I have found it to be a more > soothing sound as most report when there is no QSB or noise but the > unmodified voice at full negative modulation and positive peaks where > the may be, has the most readability when the going is a > little rougher. > > I can't help but think the difference in the sounds of your > modulation decks must be in the flow of grid current VS AB1, plus just > because a triode has a low Rp doesn't necessarily make it as > linier as a > tetrode in the same application and load. As a matter of fact I think > tetrodes especially beam tetrodes make exception modulators. A > modulator doesn't have to work into a varying load over one > audio cycle > and should see the same load over all the audio frequencies (hence my > concern over having enough cap and choke for the modulation > reactor and > coupling cap). Since the load is near constant and there is > no damping > required then tetrodes should be superior modulators especially if one > could put a little inverse feed back on them. I plan on experimenting > with that in the future as well and with AB1 at the grid it should be > easy to do. > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Brett Gazdzinski > Sent: Wednesday, November 26, 2003 7:14 AM > To: [email protected] > Subject: RE: [AMRadio] Re: Modulation transformer ID and repair > > Both mod decks are hooked up to the RF deck all the time. > They both get high voltage, but I only turn one on at a time. > Both are driven by the same 120 watt 8 ohm power amp, into LS > output transformers (right and left channels), as is the 811 > mod deck in > the pp 812 rig. > All the transmitters should sound the same, since the same audio feeds > them. > The 4x150 (or 4cx250b) sounds best, in AB1. > Yes, lots of current, 500ma at 1000 or 2000 volts, 250 ma each tube. > > I have tried just two 100TH tubes, different plate voltages (variac in > power > supply), > yet it just never sounds as clean as the 4x150 deck. > > I can also run 100TL tubes, and tried them, same sound. > > People over the air cant hear a difference, they say, but its quite > audible in the mod monitor. > > My voice is also lop sided, but not as much as yours! > I get the best peaks on the 813/4x150 combo, I don't know what > the actual reading is, as the pep wattmeter only goes up to > 2000 watts, > and I have to guestimate by how hard the needle slams into the stop, > but expect its not much over 2500 watts at 600 watts carrier. > > If I was to run the rig at 2000 watts pep, would anyone know or care > that I was exceeding the power limit (by a little bit)??? > > In your case, I would try to limit the positive peaks, say equal > to the negative peaks, and run about 90% modulation. > This will give good audio percentage and a strong carrier. > Positive peaks are good, but I don't think they are effective > on the air, if you have to limit the negative mod and the pep. > better to make sure you go 90% negative at least, and > whatever positive, > lower is better to keep it under 1500 watts, although I doubt the FCC > truck will pull up outside the house if you go over 1500 watts pep. > If you ran 10,000 watts pep, someone might notice eventually, but they > Really should pay more attention to the intentional > interference on the > bands. > > I personally don't think they pay any attention to anything other than > Blatant abuse over a long time, and even then, they seem to > play games, > warnings, going to court, etc. > > > > > _______________________________________________ > AMRadio mailing list > [email protected] > http://mailman.qth.net/mailman/listinfo/amradio
