Does the SparkFun RFM69 generate a radio signal carrier wave when powered alone?
No. If not instructed to do anything, the radio is in the deep sleep state.
Check the data sheet for the details.
The radio should never be powered up when connected via I/O pins to an unpowered microprocessor (or vice versa). That is a general rule for connecting digital modules.
After a quick read through the datasheet, it looks like a no to me. RFM69 sends data in packets, you would usually switch off the carrier when not actively transmitting data. (I do not have one handy to test with but I’ve used other similar modules and they don’t turn on the RF carrier unless they have data to send.)
Thank you. I am looking for a circuit card radio transmitter for a project I am working on.No need to receive, but small size and low power are needed. Any ideas?
What are your requirements for this transmitter? Frequency, power output, duty cycle, type and amount of data to be transmitted, etc.?
Low power, up to 1 watt. Constant tone transmit. No data. To be used as a target for radio direction finding exercises.
Be sure to check the legal power and transmit duty cycle limits in your area, for the frequency band you have in mind.
I used my eyes and determined the RFM 69 is not suitable since it has to programmed each time it is turned on. So still looking for a small circuit card type transmitter that puts out a RF signal between 300 MHz and 5 GHz when activated by the battery being installed. Can be analogue or digital. Ideal wold be about the size of the RFM69 but with header and footer mount holes.
For your application the 433 MHz TX modules (example linked above) would need a separate tone signal source. A 555 timer circuit would work well. Otherwise, search the web for “transmitter tracking modules”.