VHF oscillator circuit w/ large frequency range and change according to capacitance value

Thread Starter

Adrienboub

Joined Jun 15, 2020
5
Hello,

It's my first post. I'm new in electronics fields. I'm french and my english is not very good, excuse me.

I want to make a VHF oscillator(~ 30 MHz) that his frequency can change with the value of the capacitance.
I found in an another post the RF2506 which seems to works but it's difficult to found it and buy it because it is obsolete.
Do you know a circuit that can do the same or near the same ? Where I can buy it ?

Thanks in advance :D
 

Thread Starter

Adrienboub

Joined Jun 15, 2020
5
For general purposes, you can make a Transistor based LC oscillator that can be tuned using a capacitive trimmer.

View attachment 209807
(replace the Varactors D1/D2 with a Trimmer)

You can also buy Voltage Controlled Oscillator IC's.

https://www.minicircuits.com/WebStore/Oscillators.html
______________________________________________________________________________________________

Hello,
Thank you for your reply.
For the first proposition, where I can find the values of the condensators, resistances and self to put in the schematic ?

For the second, if I buy a VCO my frequency up/down with the value of the voltage but if I want to up/down my frequency with the variable capacitance what I must change ?

Thanks a lot !!!!
 

Thread Starter

Adrienboub

Joined Jun 15, 2020
5
Hello Bertus,

What range should the VCO cover?
There are many ready made VCO's that have large tuning ranges.
Box73 sells a whole series, this is the 25 to 50 MHZ version:
https://www.box73.de/product_info.php?products_id=738

Bertus
Hey!
Thanks for your reply !
This is not a VCO, I want an oscillator which varies between 30 Mhz and 40 Mhz because of a variable condensator.
This VCO have a good tuning range but where I can put my variable capacitor ?
I hope that i'm clear... my english is not great !
 

Thread Starter

Adrienboub

Joined Jun 15, 2020
5
Hello,

The shown block IS a VCO.
With a tuning voltage between 4 and 9 Volts the range of 30 to 40 will be covered.

Bertus
The shown block is not my message...
I understand what is a VCO and i don't want to do that
I want a system where the frequency change according to the value of an external capacitance.
Like the RF2506 . But I can't find it beacause it's obsolete.
Thanks for help
 
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