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Author Topic: Buffer amp  (Read 446 times)

W7CXC

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Buffer amp
« on: February 20, 2022, 03:35:12 PM »

Any schematics out there for a buffer amp to take the roughly 2 to 3 volt pp output of an 8640b up to say 20vpp so it can be used as a VFO for a crystal controlled  boat anchor? Discrete components perhaps? Dave
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WB6BYU

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Re: Buffer amp
« Reply #1 on: February 20, 2022, 03:46:05 PM »

Bipolar?

FET?

GlowFET?

W7CXC

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Re: Buffer amp
« Reply #2 on: February 20, 2022, 03:48:31 PM »

HiHi... not glow FET that gets complicated.
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KE0ZU

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Re: Buffer amp
« Reply #3 on: March 02, 2022, 05:53:18 AM »

Why not just a simple transformer?   No increased "power" requirements involved.
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W1VT

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Re: Buffer amp
« Reply #4 on: March 02, 2022, 06:09:51 AM »

There are designs for efhw transformers with a 7:1 winding ratio that may meet your needs.
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KH6AQ

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Re: Buffer amp
« Reply #5 on: March 03, 2022, 07:18:25 AM »

I think that KE0ZU has the simple solution. A 1:9 unun will transform HP8640the 4V P-P (into 50 ohms) output to 12V P-P into 450 ohms and a higher swing into a higher impedance. There are a few commercial designs or you can roll your own.

9:1 unun  https://www.balundesigns.com/model-9130sw-qrp-9-1-unun-1-5-54-mhz-300-watts/

HP8640B   https://www.valuetronics.com/product/8640b-agilent-rf-generator-used

If you'd prefer an active design I'll design you one, transistor or vacuum tube.
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