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newbie
08-27-2006, 02:03 PM
Thinking of getting a Futaba 2PL AM or 3PM FM but they've got 75MHz and 27MHz. What's the difference between the two frequencies and which one is better?

H8er
08-27-2006, 02:55 PM
There is no real difference, but if your friends or someone that you drive with uses 27 MHz, then I'd use 75, and vice-versa, as to not interfere with each other. I'd use 75MHz, just because 27MHz is so popular.

EphiDelt490
08-27-2006, 08:46 PM
Basically, if you run in an area where a lot of guys use RTR (Ready-To-Run) style radios, you'll want to run 75mhz FM radio gear to avoid conflicts. Easiest thing to do since you are just getting into it is pick up the Spektrum DX3 radio system, then you'll never have to worry about interference or crystals :).

newbie
08-28-2006, 03:31 AM
Thanks for the info!
Haven't touched any RC stuff for ages so had to ask... :D

Is the frequency (27MHz or 75MHz) associated with both the transmitter and receiver or just the receiver? I've seen 27MHz and 75MHz receivers but they don't seem to say the frequencies for transmitters.

If I get a 75MHz AM or FM radio system (with transmitter, receiver, etc), can I use the transmitter to control 27MHz AM or FM receivers just by changing the crystal in the transmitter?

I've taken a look at the Novak XXL receivers on Tower:
http://www2.towerhobbies.com/cgi-bin/wti0095p?FVPROFIL=++&FVSEARCH=novak+xxl&FVPROFIL=++
They don't have 27MHz receivers for both AM and FM. Is it like 27MHz is being phased out?

Also, I haven't used FM before. If I use FM, can problems like servo vibrations be solved instantly? The price difference is not that huge (if I get 3PM, not 3PK...) so if FM can solve those problems, it's good to get an FM in the long term.

soyverde
08-28-2006, 01:25 PM
The frequency is associated with both the transmitter and receiver...they have to be on the same frequency (27mhz, 75mhz, etc.) and modulation (AM or FM) to communicate with each other. With some of the higher-end controllers (Helios EX-10, Futaba 3PK, Airtronics M8/M11, to name a few) you have the ability to switch modules in order to switch frequencies/modulations, otherwise (as with the Futaba 2PL & 3PM) you are locked into the freq./mod. it is made to use. Nobody can guarantee that switching to FM will take care of any and all servo vibrations you are experiencing, but FM generally has a clearer signal than AM, so you will probably see an improvement. If you don't have loads of legacy gear to interoperate with (most RTRs come on 27mhz AM), you probably can't go wrong with 75mhz FM, as EphiDelt490 suggested. You will probably have a lot fewer conflicts with other drivers using the same channel if you go that way. :cool: