Need help with FM vs PCM... Please help

[brianwestoby]

Ok I'm in the market for a good heli radio. I am fairly new to this and don't understand FM and PCM swapping. I have an electron 6 neg shift FM reciever. Do I have to use FM RF modulator, PCM, or will the spectra work? I may possibly change receiver some day and don't want to be locked into limited options. Any help would be great. I am thinking about the futaba 9chps, 7c, or hitec eclipse 7 any suggestions here would be great too....... I need to fly.. I'm wigging out :shock:

[spork]

I'll try and help. Your RX will be either FM, PCM, or Spektrum (I'm not aware of any RX's that can be changed). FM is swell. Flown it for many years (when we got away from AM). I still fly FM in my planks. PCM requires a PCM RX. PCM tends to be much more resistant to glitches. While the PCM signal is technically still frequency modulated (FM) it is essentially a digital stream. The 9chps and the 7CHP will both transmit either FM or PCM (just a menu setting). I personally like the price and functionality of the 7CHP - but there's no right answer.

If I were starting over though I have to admit I'd be tempted to go the Spektrum route. This system uses a spread-spectrum transmission. This is not only glitch-free; but there's no need to wait for anyone to clear your channel either. You can buy the DX6, the DX7 (which is just out and supposed to be a very nice unit), or you can "Spectrumize" certain radios by replacing the module. I'm not sure which ones this works with.

[Pinecone]

Also PCM is proprietary to each company. So while most FM rxs work with most FM Txs for PCM the Rx and Tx must be the same. For Futaba Tx requires Futaba PCM Rx, Hitec -> Hitec, JR -> JR, etc.

The one bugboo for FM is Hitec (although the Eclipse is shift selectable) and Futaba use negative shift, Airtronics and JR use positive shift (for US 72 MHz operations). But many Rxs nowdays are shift selectable, so will work with any FM Tx. Even Hitec has shift selectable Rxs. Bergs, Corona (aka Vampower and LightFlight) and others can work with any Tx.

[brianwestoby]

So if I choose the DX6 or DX7 I would have to replace all my receivers with Spectrum 2.4ghz. Right? If I go with Futaba 7c I switch between FM and PCM by just changing the settings, or do I have to change the modulator?

[BarracudaHockey]

So if I choose the DX6 or DX7 I would have to replace all my receivers with Spectrum 2.4ghz. Right?

Yes
If I go with Futaba 7c I switch between FM and PCM by just changing the settings,

Correct

[brianwestoby]

Thank you :D

[Pinecone]

You can switch the transmitter from FM (actually PPM) to PCM easily, BUT you need to have the right Rxs. If you want to run PCM you HAVE to buy Futaba PCM Rx. For FM you can buy any number of FM Rxs (Futaba, Hitec, Berg, Corona/Light FLight/Vampower, GWS, etc, etc).

Rxs don't switch between PPM and PCM.

[spork]

You can switch the transmitter from FM (actually PPM) to PCM...

To complicate matters a bit more - but a fact that can be completely ignored... the TX is always trasmitting an FM signal. But the data encoding on the FM signal is either PPM or PCM.

To make matters simpler... if you go with a Futaba, get an R146ip RX. It's a great little RX.