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Author Topic: 6AF4 tube GG QRP amp  (Read 2041 times)
9A5BDP
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Posts: 117




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« on: April 03, 2014, 01:44:51 PM »

I have few pieces of this UHF triode. My question is will be possible to make some qrp level linear in GG mode with this tube. My goal is to produce maximum 2w into antenna. Core VFO is based around 6AK5 tube.

What do you think about this idea?

73!

Dubravko

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G3RZP
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Posts: 4847




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« Reply #1 on: April 04, 2014, 01:29:10 AM »

Although it has a 2.5 watt plate dissipation, the amplification factor (mu) is very low at 13.5. This isn't surprising, as it was meant for UHF Class C oscillator service. Another difficulty,  if you want a working tank Q of 10, is that the low plate resistance limits the load resistance to around 220 ohms. That means a gain of just over 1.

The 6J4, 6AJ4 and 6AM4 have much higher amplification factors and so are more suitable for grounded grid use.
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W9WQA
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Posts: 136




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« Reply #2 on: April 09, 2014, 09:31:45 PM »

my first thought is always,,,try it!!  sounds like fun. i should do it on a tiny chassis beside my BIG 2x 813 gg amp!!
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G3RZP
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Posts: 4847




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« Reply #3 on: April 10, 2014, 02:25:36 AM »

Are you intending this for SSB, where you need linearity? If it's for CW, then a push-pull pair in grounded cathode and neutralised, running in Class C, would be a better circuit choice.
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