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Output tubes for 30 meter CW xmitter	Reply
by W7ETA on May 9, 2008	Mail this to a friend!
Looking for output tube suggestions for a 30 meter CW transmitter. I've got a 750V-0-750V at 250ma xformer en-route. So far, my candidates are 12volt 6146B and 572B. Not too interested in having to run a cooling fan, or spending a lot on tubes or the socket(s). TU 73 Bob

RE: Output tubes for 30 meter CW xmitter	Reply
by W3LK on May 10, 2008	Mail this to a friend!
<< So far, my candidates are 12volt 6146B and 572B >> 12V? Both these tubes have 6.3v filaments. 73, Lon - W3LK Naugatuck, Connecticut

RE: Output tubes for 30 meter CW xmitter	Reply
by W8JI on May 10, 2008	Mail this to a friend!
Bad choices all around. A 750V CT transformer puts out over 1000 volts unless you use a choke input with heavy bleeder resistors. Then it would be about 700 volts and suitable for a 6146, but you would have to get a screen supply somehow and a driver/oscillator tube supply. 73 Tom

RE: Output tubes for 30 meter CW xmitter	Reply
by W7ETA on May 10, 2008	Mail this to a friend!
I'm not too worried about the screen xformer, or getting filament xformers, or about driving the tubes. Looking for suggestions for outptut tube(s) that aren't expensive and don't require expensive sockets. I've found most literature to center around the 6146 family of tubes. I have noticed that even used chokes are expensive and expensive to ship. I'm not hurried. This will be my indoor project once the temps go past the mid 90sF. I could even wait to put it all together until the temps are too cold for outdoor activity, when they drop into the 40s during the day, this coming Dec. I thought this would be a useful fun project to learn more about ham radio. 73 Bob

RE: Output tubes for 30 meter CW xmitter	Reply
by WB2WIK on May 10, 2008	Mail this to a friend!
A "transmitter" and an "amplifier" are two different things. I wouldn't use a single tube as a "transmitter" unless it were a low powered CW rig, like a cathode keyed 6V6 or something. (Egads, that was my first homebrew Novice rig 43 years ago!) If you have an exciter and are looking to amplify it, how much drive power do you have available? You can grid drive a 6146B to about 60W output with only 2W or so, but you need grid and screen supplies. You can cathode-drive an 811A to about 120W output with only a plate supply, but you'll need probably 25W to do it. What's your driver stage? WB2WIK/6

RE: Output tubes for 30 meter CW xmitter	Reply
by G3RZP on May 11, 2008	Mail this to a friend!
807 or 1625 would likely be real cheap. Three of them would give 200 watts out. A 6AG7 or even a 6V6 would drive them - even as tripler froma 3.3MHz VFO.

RE: Output tubes for 30 meter CW xmitter	Reply
by W7ETA on May 11, 2008	Mail this to a friend!
OK, amplifier section of a transmitter. This will only be used on 30 meters. I've got a few 6AG7s, 6V6s, 6L6 types, 6KD6s, 6KM6, 6JC6s, 12BY7s, quite a few replacement tubes for the Drake C-line and TR4CW, 6FQ7, 6SN7 types, 12Avariety7s, etc kicking around. I've got some 8877s, 3-500Zs kicking around, but I don't want to use them. I'm waiting for the Elmers to dry on the form I'm using for the 1948 HandBook power supply for both the one tube 6L6 and two tube 6L6 CW xmitters. As I layed out the parts, I decided to add fusing and an on-off switch. I was poking around for an illuminated switch, then I remembered the empty octal socket would be filled with a real rectifier. 73 Bob

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