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Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Hi, for a 10 kW VTTC project I'm looking for an air cooled externally heatsinked directly heated triode or tetrode, with a plate dissipation of 3 kW or more. Some examples of such tubes are the GU-10b, GU-39b, GU-47b, ITL 3-1, ITL 5-1, 3CX3000 (5000,10000...) or 4CX... and many others. I have some dinner-plate sized RF power caps to go with this project. The plate transformer is yet to be wound so will accomodate any plate voltage.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Hi Jan, surely you mean 3kW anode input power, not 3kW anode dissipation - why would you want to throw 3 kW away as heat? Anode dissipation is that power lost by the transformation of electron bombardment energy into heat, a loss we should always try to keep to a minmum for any given value of anode input power.
The value to look for when choosing a valve for a power oscillator would be RF output power - often written as Pout in English language datasheets.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Hi PM, The design input power into the coil is 10 kW, from which no more than 2.5 kW should be lost on the plate with the oscillator properly tuned, that's why I said 3 kW or more for some safety margin.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Hi DDC,
sorry, I don't have anything like that at the moment - an industrial valve, I suppose. The largest triodes I have are Marconi ACT28 UHF Disc Seal Pulse Oscillator triodes, 550 kW peak power in 5μs pulses - but only 1.5 kW average DC input power. I haven't tried them out yet, because of all the metal work and machining needed to build a micrometer tunable co-axial cavity to fit them, but I'll learn how to do it one day.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
PM, No problem, I understand that you don't see such tube every day and it might take quite a while until I find a tube like this for a reasonable price.
Some time ago I bought a GU-39b for a funny price of $25, but it had damaged one of the parallel running filament wires, which might have happened during the transport. It still works, with 85% emission but I won't use it because of the risk of the broken filament bits shorting something inside.
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Dr. Dark Current wrote ...
Hi, for a 10 kW VTTC project I'm looking for an air cooled externally heatsinked directly heated triode or tetrode, with a plate dissipation of 3 kW or more. Some examples of such tubes are the GU-10b, GU-39b, GU-47b, ITL 3-1, ITL 5-1, 3CX3000 (5000,10000...) or 4CX... and many others. I have some dinner-plate sized RF power caps to go with this project. The plate transformer is yet to be wound so will accomodate any plate voltage.
Thanks for looking, -Jan
Hi Jan
I'm just curious, why do you prefer a directly heated tube over quite superior oxide cathodes? They seem like quite ancient bits of technology to me, actually I've never even seen one myself yet.
Pulse tetrodes are actually quite superior tubes for VTTC's, as far as I recall huben panev built a VTTC with some GMI7's and it was pure awesome. So why not just pull out your GMI32 and pwn all noobs with it?
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Marko, The directly heated cathodes are used in majority of transmitter and industrial oscillator tubes. They don't have such high emission, but they are very rugged and can stand overcurrent and overvoltage conditions with little effect on their life, the indirect cathodes are very sensitive to these conditions. I've never seen a power CW oscillator tube with an indirectly heated cathode...
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