RF coms

[Kane2oo2]

Hello
has been a hell of a long time since i was last on the forum, but im back

anyways the last time i was here i was learning to program pics and also built a few other small projects (fm transmitter etc)

im wanting to build something now with my new found knowledge (or at least some )
from the transmitter project although it worked..for about 5m ( :? ) it wasnt very stable. How could i make a "good" transmitter.. like the ones found in walky talkies etc ... what is different about these from the simple transistor ones?
grateful for any ideas

Thanks
Kane

 

[stevez]

Amateur radio operators are one of several groups who frequently design, build, modify and operate transmitters and recievers. As with other hobbies many document their work and share it via books, journals or magazines and via the internet. Some of these people are experts in their field - others, like me, have some formal training but much is self taught. You might look to publications and journals for designs and compare them to what you've been doing. American Radio Relay League is one organization and their publication is QST Magazine. I think the Radio Society of Great Britain's journal is QEX but I am not sure of that.

 

[Russlk]

You can improve the stability of a simple transistor FM oscillator by careful construction and use of a negative temperature coefficient capacitor to compensate for temperature changes in the inductor. Commercial walky-talkys use a crystal oscillator reference and a phase lock loop. For more information, look up "frequency synthesizer".