> I think I will look into small transformers. Farnell list one from > "Block" that is 22mm x 22mm that looks suitable Sounds like the one I got from RS. Be aware that it saturates and you need a series resistor. Mine was nominally two 6V secondaries but put out 73Vp-p. The lowest picture shows two primaries in series to give the approximately expected V out http://home.clear.net.nz/pages/joecolquitt/block-tx.html Russell suggested, during [EE] Block miniature transformer in May '05, that "Placing a 0.5 watt load on the transformer secondary and a 24k resistor in series with the primary MAY produce approximately the desired result" Block themselves confirmed that the small Tx would generate less heat with a load I regret that that particular part of the project got sidelined during my battle with the F88 and I2C, but it is back on the agenda and I hope to do some experimenting ASAP -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist