Hi, I have seen some schematic diagram of amplifier, I found that the amount of 811As and 572Bs no more than four, Coud someone can tell me how much maximum amount of the tubes in parallel? Thanks! 7
Richard, I see, too much tube means much drive.Myebe I can not use the cathode drive. I have seen a very old Chinese military 1600W HF transmitter(final is FU-100F=4CX1000A) the pre-driver are 8*6P15
I have an article using 6 of the 811A's in parallel for 160 meters from 73 Magazine, early 1980's. I would imagine the output capacitance of more than 4 would be too much to tune the plate circuit on
Joe, I imagine your right. That's the problem with triodes if you want to parallel them. One needs to go to tetrodes or pentodes for smaller output C. I have built some though for 10 meters that didn
The real issue is feedback capacitance, not output capacitance. Amplifiers using two tubes are barely stable on upper HF because feedthrough capacitance is far too high. Four tubes actually require
Tektronix used to use c. 10 tubes in their O'scopes' deflection plate amplifiers. The story about paralleling more tubes having too much C is a large pooper scooper of taurine feces because if the #
If the number of tubes doubles, RL is divided by two, the amount of Tune-C needed doubles to main the desired Q, so adding more tubes only increases the drive and filament requirement. R L MEASURES,
Example: -- Goal: build a 12kW amplifier using a 4000v anode supply: To do so using 3-500Zs: c. a dozen would be needed. Since the feedback C is 0.15pF per 3-500Z, the total feedback C for a dozen is
If some may remember, we picked apart an 11 meter amp on here which was listed on Ebay that used six or eight 3-500Z's. Also, we picked apart one using eight 4CX250B's. There was one model using four
Yes, but do you get the same useful output power from a distributed amplifier unless you have two antennas to feed? Doesn't half the output go into a terminating resistor? Steve _____________________
Sweep tube amps were quite common in Germany in the past when our power was limited to 150W total dissipation in the final stage. I built several myself, one GG with 5xPL519 doing 2KW out on all band
Peter, The Galaxy 2000 amp used (10) 6HF5 sweep tubes. It was also grid driven, and was an amateur amplifier. It was made by the Galaxy Electronics Company in Council Bluffs, Iowa. One thing to note
Good point, Steve. I am not suggesting that a distributed amplifier be used for HF transmitting, I'm saying that paralleling tubes is possible but that additional effort must be made to reduce VHF ga