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Author Topic: Cost of Building an HF Amplifier?  (Read 3711 times)
KX4QP
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Posts: 396




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« Reply #30 on: March 04, 2019, 04:15:12 PM »

One thing about "your price range" -- I built a telescope around twenty years ago.  I spent about the same money it would have cost to buy a similar instrument, but a) I never spent more than about $50 at one time, and b) I got an instrument that performed roughly as well as a slightly larger, much more expensive commercial scope.  Your "price range" can be much more flexible when you don't need all the money at once.
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MM0IMC
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Posts: 239




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« Reply #31 on: August 23, 2019, 07:34:22 AM »

Would starting off small scale with GI7B's, then progressing to a GS35B working, once I've got the confidence?
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W1VT
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Posts: 3350




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« Reply #32 on: August 23, 2019, 07:48:42 AM »

My guess is you want to start of first with the high voltage power supply, and then get tubes that will best use what you built.

There was a time where tubes were the hard part, and the HV transformer was the easy part, but I believe the situation is reversed for you now.
I could be wrong, maybe you live next to a benefactor with a collection of HV transformers he needs to find a home for, but many of those collections in the USA are now gone.
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KM1H
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« Reply #33 on: August 23, 2019, 08:26:45 AM »

Quote
Would starting off small scale with GI7B's, then progressing to a GS35B working, once I've got the confidence?

I certainly would not recommend that tube unless you are going for bottom cost and signal quality.
Here is an article from one of the best known real experts.

https://owenduffy.net/tx/GI7B/index.htm

Not mentioned is that the GI7B is a low mu tube and is designed for pulse type and industrial applications. Its mu is very low compared to all the well known triodes used for GG linears.

https://frank.pocnet.net/sheets/018/g/GI7B.pdf

Think of it as similar to the 5867/TB3-750 which are available dirt cheap but no ham amp uses them as a sub for a 3-400/500Z. It is a great tube for Class C AM Grin

https://frank.pocnet.net/sheets/089/t/TB3-750.pdf

Carl
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K6BSU
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« Reply #34 on: August 23, 2019, 10:20:24 AM »

I've built 3 amplifiers.  A 3-500Z, one with three 811's and one solid state.  I only did it because I didn't find a commercial amp that suited my aesthetic requirements.  For instance, my 811 amp has the three tubes just behind the front panel, which has a large cutout with glass and brass screen.  I like to watch the tubes glowing!
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MM0IMC
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Posts: 239




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« Reply #35 on: August 23, 2019, 11:53:25 AM »

I've built 3 amplifiers.  A 3-500Z, one with three 811's and one solid state.  I only did it because I didn't find a commercial amp that suited my aesthetic requirements.  For instance, my 811 amp has the three tubes just behind the front panel, which has a large cutout with glass and brass screen.  I like to watch the tubes glowing!

Gotta love that glow from a glass valve (tube).  Wink
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