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Controlling level of a low RF voltage

Qmavam

Oct 26, 2022
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Oct 26, 2022
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Not sure I'm in the correct forum, but I see nothing else that fits.
The circuit is for a Q meter, the commercial units have a very low drive impedance of 0.02Ω to 0.001Ω.
The voltage is 20mv to 30mv. The source voltage will be a standard 50Ω signal generator driving a 50 to 1 wideband transformer
The problem, designing a flat transformer for 50kHz to 30MHz and keeping output constant with the change of load.
I have wound a few transformers 50 to 1 (2500 to 1 impedance ratio, 50Ω in 0.02Ω out) with maybe a 4db drop at 30MHz, and considerably less drop with reasonable change of load.
So, I think the best way to approach these two problems is to control the input voltage to keep the output voltage constant.
I started by looking at the H11F1, but it has about 100Ω to 200Ω minimum resistance, I can't work out any way to get a minimum and maximum change to make those work.
Is there another chip that has a lower on resistance the will pass RF?
I posted a block diagram of my initial thought.
Any other approach you would take
Thanks, Mikek
 

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Qmavam

Oct 26, 2022
3
Joined
Oct 26, 2022
Messages
3
After a few measurements, even with a 0.5Ω load, my primary looks like 1250Ω, so I should be able to make the H11F1 do the the job.
I'll put some on order and get back to you when I have more questions.
Please feel free to add in incite into this that you may have.
Mikek
 

davenn

Moderator
Sep 5, 2009
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Sep 5, 2009
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14,241
Moved to radio and wireless forum :)
 

Qmavam

Oct 26, 2022
3
Joined
Oct 26, 2022
Messages
3
How did it help you?
Finding the H11F1, or something else?
What's your project?
Mikek
 
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