Was moving to put one of my hamshields into a repeater Tx roll on 224.000 MHz. Used HandyTalkie.ino (and later, FMBeacon.ino) to dev the setup and found that when transmitting with mic or pwm as the source, there is digital noise on the carrier and quite a bit of it. Not just the annoying phase noise we sometimes hear with cheap radios, this is full on unusable. Moving to 223.98 or 224.02 eliminates this. Anyone have insight into this? My guess is that there is an incompatible clock frequency either on the shield or the board. 224.000 is 14*16MHz and 28*8MHz, the two possible clocks of the Arduino. With that bit o' math in place, has anyone else identified other frequencies where there are birdies on Rx or noise on Tx? Oddly, Rx @ 224.000 is clean as a whistle with an RSSI of -137dBm.