|Low Pass Filter|
As expected, without the Low Pass Filter, the raw Propeller output fed into terminated 50 ohm load was full of trash and harmonics, which is VERY undesirable for a Amateur Radio Transmitter.
Without Low Pass Filter
|With Low Pass Filter Attached|
The Single Spike Is the Fundamental Frequency
This is what a Transmitter Output should look like
Jeff got the idea that it was probably radiated from the processor itself. We wrapped the Propeller, Battery, and Low Pass Filter in insulating paper and then in aluminum foil attached to ground. Now, only the radiated power of the fundamental Frequency passing through the Low Pass Filter and leaking from the Ladder Line could be seen with an open probe. The open probe received signal was clean, the same as when the beacon was attached directly to the 50 ohm load at the Analyzer.
|My Local View of My Beacon's Signal|
I have a previously built Homebrew Power Amplifier that I may try, it should boost the signal to 30mW, maybe enough to be received in Las Vegas.
I think the Propeller, with a Low Pass Filter, can be used for experiments with Amateur Radio Beacons. But as always, more experiments and data is needed to know how useful it will be. A report from a remote QRSS Grabber will help the investigation.