switching from FM to 2.4 - RC Groups
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Apr 27, 2012, 05:16 PM
Registered User

switching from FM to 2.4

Hey all I am currently running an FM radio system, and really want to switch over to the 2.4. What all do I need to replace? Just the TX, the TX and RX, or TX, RX, and servos?
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Apr 27, 2012, 05:23 PM
Registered User
Toysrme's Avatar
just TX and RX. make doubly sure to range check the 2.4 systems. their range is not near what FM is and the frequency is generally crowded compared to FM. (tho local conditions determine this)

servos are compatible with anything. if it's a high end aerobatic model, quality digital servos may be a benefit if you're a good pilot.
Apr 28, 2012, 04:33 PM
Registered User
I'm pretty sure that 2.4GHz is also FM, it is certainly not AM nor pulsed CW. Perhaps you mean you are now using PWM or PCM (which is usually FM but there has been some AM PCM). Petty comments I'm sure but it does help to use the correct terminology.
Apr 28, 2012, 05:09 PM
Registered User
Toysrme's Avatar
Yes it is quite newbish to talk about it. You can say FM and save yourself and everyone else the trouble of having to write 27mhz 30mhz 35mhz 40mhz 50mhz 72mhz 75mhz radio systems.

It's implied & understood that FM refers to the dedicated rc frequencies that apply to that particular region & type of craft.
Apr 28, 2012, 07:16 PM
Registered User
If you have something like the Futaba 9CAP or Hitec Prism 7 with the plug in transmit modules, all you can keep the transmitter and get a Spectrum or Futaba FAAST plug in module and compatible receivers. If you got one of those transmitters and a "dial-a-crash" 72mhz module, and the 2.4 module(s), you'd have a transmitter than can do 2.4 or any 72mhz frequency by swapping modules and/or dialing a different frequency (takes only a few seconds).
Apr 29, 2012, 08:33 AM
Will fly for food
2.4 GHz range is fine, it is beyond the distance you can see. But they are less tolerant of poor installation (power and antenna placement).

Also, 2.4 does not have issues with a reasonably number of Txs on at the same time. IRCHA, which attracts over a 1000 fliers, does not control 2.4 GHz Txs and does not have problems. Some problems have been noted at other large fly ins. But we are talking HUNDREDS of pilots and Txs.

2.4 is proprietary, in that each brand makes you use both Tx and Rx from that brand. There are 3rd party Rxs for JR/Spektrum DSM2 and for Futaba.
Apr 29, 2012, 09:45 PM
Rocky Mountain High and Higher
PROACE's Avatar
Spread spectrum uses a linear recursive keying sequence, that is why when bound to a receiver that rx only decphers the bound tx code. Depending on manufacter or model of radio, the keying sequence will be added to another data stream to spread the signal out below the noise floor or the the keying sequence will be used to freq hop or a combination of both may be used.
The way this sequence is generated, there can be millions of possible code combinations and as long as there isn't two identical codes, these signals can be transmitted at the same time on top of each other and not cause interference.

So if there are some 2.4ghz radios that don't get along then the fix is easy. Shut down the China made off brands and only operate the Japanese or European made radios.

Don't believe me try it. Even though these radios can reject a lot of noise and interference, they arent perfect, especially when a cheap made radio that generates as much noise as it does signal is operating in close range.

I bet some of those cheaper off brand 2.4GHz systems interfer with themselves and cause a pilot to think he has a bad RX or servos.
Apr 29, 2012, 10:57 PM
Registered User
Hey there to a fellow minnesotan!

I started on fm last year (borrowed a radio) and before I bought to many receivers and crystals (they add up in a hurry) I decided to make the switch. As others have said, the servos and battery packs/switches are all universal and work. I picked up an aurora 9 and inititially thought about researching the 72mhz fm module and seeing if that would work. Due to cost and the pain of it....I decided it wasn't worth it for my 2 receivers. I can readily find receivers in the 40 dollar range which was what I was spending on a used fm receiver and crystals.

Btw....McDonald straws are perfect size for the hitec boda antenna. A little epoxy and voila! Beats the little mount piece it comes with.

May 03, 2012, 05:52 PM
I'm a pilot, 100 yrs too late
Thermalin's Avatar
40 dollar receivers? That are the geniunie article? I fly the el cheapos 10 bucks in my small stuff and never had an issue but 70 per nice plane is

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