Competition Radio Interference Solution?

[Al Skierkiewicz]

OK, some weird data coming through in this thread.
The 900 MHz band that the radio modems use in a part of the shared Amateur and FRS band just above 900 MHz. Although close to cell phone frequencies they are not exactly crossing but, any high power transmitter close to or adjacent to your frequency can produce spurious signals on your frequency. Common wireless microphone frequencies in this country are designed to operate in the VHF TV band or on the now unused channels at the high end of the UHF band, ch 65-69. I have seen some in the 900 MHz band but they are pretty scarce at this point. However, second and third harmonic radiation from these radios can occur in the 900 MHz range. In particular, wireless microphones in the presence of metal produce out of band response as the RF is affected by the rectification of the metal to metal contact. Often, hanging jewelry, metal belts, even metalized fabric places havoc with wireless mics. (not to mention brush noise from DC motors) Regardless of the error checking that takes place there is still so much in the way of interference that can affect modem communications and since we can control it by not using the radios in the pit let's do it.
I am a big fan of adding a tether extension so that the tether can be connected to the outside of the robot, not directly to the RC. (Don't use the locking hardware for this when you connect to the outside tether.) When using the tether in the pit, should the robot act erratically, you just yank the tether out. Robot comes to an immediate stop, simple and effective. Also highly recommended is the use of a disable switch on the OI port. These are easy to build and you need one to enable the robot and autonomous mode during build. Info is on the IFI website.
If you think you can get away with using your radio in the pit, be advised that the IFI monitor at the field table, can tell every robot that is fired up and what the status of things like battery, backup batt, etc. They know when you are sleeping and they know when you're awake.