Stabling frequency of RF oscillator

[svetoslav belchev]

I have a smal RF UHF oscillator with antenna, for use like sound
transmitter. It is colpits osc. How to stable it's frequency ? Because
when I touch it or antenna or simply move the device it's frequency
untunes. I want to be able to move with hands while it transmits my
speach.
Many thanx forwadly.

 

[Andrew Holme]

svetoslav belchev wrote:

I have a smal RF UHF oscillator with antenna, for use like sound
transmitter. It is colpits osc. How to stable it's frequency ?
Because
when I touch it or antenna or simply move the device it's frequency
untunes. I want to be able to move with hands while it transmits my
speach.
Many thanx forwadly.

You could try adding a buffer/amplifier stage (or two) between the
oscillator and the antenna, AND mount it in a screened metal box, but
even then you'll still have temperature-related drift. This became
more of a problem with the advent of PLL-controlled receivers which
remain dead on-frequency. Older receivers had AFC which could track a
drifting transmitter. These days, you need a crystal-controlled
transmitter too: either with frequency multiplier stages, or a PLL to
generate the final output frequency.

 

[svetoslav belchev]

You could try adding a buffer/amplifier stage (or two) between the
oscillator and the antenna, AND mount it in a screened metal box, but
even then you'll still have temperature-related drift. This became
more of a problem with the advent of PLL-controlled receivers which
remain dead on-frequency. Older receivers had AFC which could track a
drifting transmitter. These days, you need a crystal-controlled
transmitter too: either with frequency multiplier stages, or a PLL to
generate the final output frequency.

I want to try simple circuit with one ampliffer stage, where to find circuit ?