RF Module

[dhouston]

I can buy it from an international vendor, but, the problem is the delivery charges are like two times the cost of the modules itself...

That's only true if you're trying to buy in very low quantities. I bought non-standard (i.e. the frequency is not one listed in their catalog and required different SAW resonators) 310MHz TWS-A type transmitters from Wen Shing in Taiwan for about $3 each in quantities of 100 pcs. Shipping charges were about $25 for air express to the USA. On the other hand, they wanted more than $5 each for the RWS-310 receivers (which are in their catalog) and I can buy an identical receiver (of better quality) made by another Taiwan firm from Mouser Electronics for $5 in single quantities.

There are several excellent application notes on the Linx Technologies website.

• http://www.linxtechnologies.com/inde...ection=support

RF Monolithics also used to have some good app notes but I haven't checked that lately.

• http://www.rfm.com

If you are looking for lower quantities I think you are still better off to buy the TWS-434A transmitter available from 20 or more vendors around the world. Even Velleman sells it.

If you haven't read it, the third page of the PDF I referenced earlier in the thread gives a schematic, with component values, for a SAW controlled 433.92MHz transmitter that uses pretty much the same circuit, merely replacing the LC frequency components with the SAW resonator.