RF output transistor in FM transmitter swap

[Firestreak]

Please could someone let me know if the 2SC1971 (T4) transistor could be substituted with a BFS22A in this circuit and what changes would be needed to the circuit

 

[rjenkinsgb]

It would likely work as is, due to the input and output being tuneable.
The power would be reduced, both by the lower power dissipation and lower gain of the BFS22A.

You would have to be careful with heatsinking to keep the temperature down.

 

[Firestreak]

Thankyou 'rjenkinsgb' that was my thoughts too. Its a simple RF power stage. Cheers !

 

[danadak]

There are a lot of considerations, like SWR, high voltage mismatch effects,
transistor construction and its parameters, bias current, class of amp.....

Its quite easy to drop in a RF power device not specifically designed for the circuit
and see it oscillate into oblivion, and take other components with it.

What power level is the transmitter ?

Try the OEM web site to see if they have a cross, do same for Motorola (now NXP, also
Freescale) to see if they have a cross list. Even post on their engineering web site.

Contact equipment website, see if they have a forum/tech support where you might get help.

Regards, Dana.