Assuming adequate core/wire sizing and airflow, can anyone think of a solid reason *not* to design a legal-limit HF amp output tank for 200 ohms, then use a 4:1 "un-un" transformer to step it down to
What kind of power? What plate voltage and current on the tube? 73 Jim W7RY I'm curious because doing so would bring the loading cap requirement for a 4000-ohm plate impedance down to under 1000pF at
Didnt the QRO 2500 have this format? 73/jeff/ac0c www.ac0c.com alpha-charlie-zero-charlie What kind of power? What plate voltage and current on the tube? 73 Jim W7RY I'm curious because doing so woul
1500 watts 4kV, 625mA Single 8877 at around 4000 ohms plate impedance in AB2. Tnx, Jim N7CXI Sent from mobile wireless -- Original message -- From: Jim W7RY <w7ry@centurytel.net> Date: 10/20/2013 6:3
Maybe it did because Ray Cronin and Pat Stein were partners in Command Tech years ago so perhaps that is true. Not 100% sure though. Didnt the QRO 2500 have this format? Didnt the QRO 2500 have this
ORIGINAL MESSAGE: (may be snipped) REPLY: If the only reason to do this is to use a smaller load capacitor, I would suggest instead to switch in some doorknob type padder caps instead. IMO, a pi-net
probably best done with a transmission line transformer, using a 100 ohm line - maybe 91 ohm coax? But I read somewhere that it is not as forgiving on SWR as the classical way, plus of course, the lo
Jim, Assuming adequate core/wire sizing and airflow, can anyone think of a solid reason *not* to design a legal-limit HF amp output tank for 200 ohms, then use a 4:1 "un-un" transformer to step it do
Thanks for the replies. Notables are: (1) Higher loading cap voltage (Gold Star Winner) (2) Loss, and what to do with the heat (3) Cost Thanks and 73, Jim N7CXI -- Assuming adequate core/wire sizing
Jim... To figure the plate load impedance: RP = EP / 1.8 X IP 1.8 = K factor for class AB1 (Changes with ZSAC) RP = Plate Resistance EP = Plate Voltage IP = Plate Current 1.8 X .65 Amps = 1.17 1.17/
The way I see it the 200:50 ohm bifilar xfmr reduces the loading cap value but doubles the voltage requirement and eliminates the need for a choke to ground in case the plate blocking cap(s) fail. It
THE COMMAND TECH HF-2500E THAT RUNS 3 3CX800 TUBES USES THIS UN-UN SYSTEM AND AT 3KW OUTPUT THERE SEEMS TO BE NO ISSUES WHATSOEVER. Seems to be a tried and true design. It's hard to argue with succes
ORIGINAL MESSAGE: (may be snipped) REPLY: Will that unit run at full legal limit with a brick on the key? The 2-holer version will not, and the weak link is the toroid. Guess how I know? Twice. :-) 7
That I don't know, I'll try to see what the manual claims. Will that unit run at full legal limit with a brick on the key? The 2-holer version will not, and the weak link is the toroid. Guess how I k
All 3 of the Command Tech amps 1/2/3 tubes used a single toroid switched for 40, 80, and 160 followed by the balun. It was the switched pi net toroid that caused problems. On the 6M amp they also use
Don't believe the 1.8. I found that this is far from the correct value for the 4CX1000A. Maybe it's closer for triodes like 8877s, maybe not. See <http://www.granta.g4axx.com/Linear_design_notes.php3
Assuming adequate core/wire sizing and airflow, can anyone think of a solid reason *not* to design a legal-limit HF amp output tank for 200 ohms, then use a 4:1 "un-un" transformer to step it down to
Ummmm... He's using an 8877. 73 Jim W7RY I found that this is far from the correct value for the 4CX1000A. Maybe it's closer for triodes like 8877s, maybe not. See <http://www.granta.g4axx.com/Linear
See below. 73 Jim W7RY Assuming adequate core/wire sizing and airflow, can anyone think of a solid reason *not* to design a legal-limit HF amp output tank for 200 ohms, then use a 4:1 "un-un" transfo
When Palstar bought the line they went to 3 seperate toroids and kept the balun. Is Palstar still building amps? 73 Roger (K8RI) Ive worked on several of all models from both companies and havent had