Skitimberlake

My Feedback: (35)

Hi. This is an education question. Being stumped on this game of Are you smarter than a 5th grade RCer, I want to peek at RCD-Hitec support's answer.

Background - Recently was testing an older RCD receiver for use in a small sport flyer for a friend & student flyer. Receiver is RCD Platinum Model number PGP 21AM. It is dual conversion, ultra narrowband. (I did not notice the AM designation.)

To test, I hooked it up in shop (not in aircraft) with battery & 4 servos. ch 48. Proceeded to test it with an FM transmitter on ch 48. Found that all servos worked. No bleed over, all servos worked independently like they should. I noted the system was susceptable to antenna location and movement. Antenna could not be anywhere near the servos or lots of glitching happened. And if Rx antenna was moved, glitching occurred during movement, especially if reasonably close to servos.

These tests done in shop, Xmitter & Rx were close to each other. no range test done. But when antenna routed away from servos (sometimes difficult to do in fuselage environment), servos worked OK'ish.

In looking at the receiver to figure out what was going on, I then noticed the AM designation. PGP-21AM. Also on front in small print " Fut 'J' 72 MHz AM ". I assume the AM designates the modulation scheme and this receiver is AM ? Assuming this is an AM receiver, then:

Question - how & why could my low end Futaba T6As FM transmitter control it ? Also a Futaba skysport FM 4 channel "plain jane" non computer radio was able to control it as well.


Like I said, this one is just for educational purposes. I am definitely not smarter than a 5th grade RC'r... hence the peek.

Thanks

RSH

aka Skitimberlake

fizzwater2

My Feedback: (61)

There is at least one way - if the AM receiver is tuned slightly off frequency from the FM transmitter, or if there is enough ripple in the passband of the AM receiver's filtering, as the FM transmitter shifts in frequency, it will be "slope detected" in the AM receiver, and could control the servos. As you've mentioned, you wouldn't want to trust this combo, but with the particular signal strength you found by moving antennas, etc, this MAY have been the cause for it.

Bad_Daddy

Can an FM car radio receive signals from an AM radio station? Yeah, if you park your car under the AM station's transmitter antenna.
Otherwise, NO.

MikeMayberry

My Feedback: (1)

It's not uncommon for this to occure at short range.

Mike.