28.2. Transmitters

28.2.1. What is the difference between an airplane transmitter and a helicopter transmitter?

For most transmitters, there are only two differences:

  • An airplane version will have a ratchet on the throttle. A helicopter version has a smooth throttle with no ratchet.

  • An airplane version has the idle-up switch on the right side, and the throttle hold switch on the left side. A helicopter version has the idle-up switch on the left side and the throttle hold switch on the right side.

For Futaba transmitters, there is no firmware difference betweeen the airplane and heli versions of the transmitters, so the two physical differences are the only difference.

Some JR transmitters have separate airplane and transmitter versions where the airplane version does not support CCPM modes. The JR transmitters known to have this problem are:

  • JR XP783 airplane (CCPM unlockable via service menu)

  • JR X-388S airplane (CCPM unlockable via service menu)

  • JR X-347 airplane (CCPM unlockable via service menu)

  • JR 10X airplane (CCPM not unlockable)

For more information on transmitters see Chapter 9, Transmitters

28.2.2. Can you give me your transmitter settings for helicopter X?

This is a meaningless question, because the transmitter settings for a helicopter are dependent on:

  • Servo type. Different servos have different ranges of movement.

  • Servo horn type and hole used. If the servo horn is not exactly the same, and the same linkage hole used, then the range of motion will be different.

  • Servo rotation direction. Different servos have different rotation direction

  • Linkage length. The settings will be different depending on the length of the the linkages from the servo to the swashplate and from the swashplate to the main rotor blades and the flybar.

  • Transmitter type. Different transmitters use different ranges for servo movement

So therefore, unless all of these different factors are exactly the same as your helicopter, the transmitters settings will be significantly different.

28.2.3. Which receivers are compatible with my Walkera transmitter?

None of the standard receivers from Futaba, JR, Hitec, Airtronics, etc are compatible with Walkera transmitters.

28.2.4. Which transmitters are compatible with my Walkera receiver?

None of the standard transmitters from Futaba, JR, Hitec, Airtronics, etc are compatible with Walkera receivers.

28.2.5. Which transmitters are compatible with my E-flight Blade CP receiver?

The E-flight Blade CP transmitter uses negative shift, so any transmitter which can transmit with negative shift, such as Futaba, Hitec, Airtronics and Multiplex, are compatible.

28.2.6. What is the difference between FM, PPM, and PCM?

Basically, FM is frequency modulation, which is the method used to send the data.

PPM is pulse-position modulation, which is an analog method of encoding the data to be sent.

PCM is pulse code modulation, which is a digital method of encoding the data to be sent.

Both PPM and PCM send the data using FM, but encode the data differently.

For more info see:

www.aerodesign.de/peter/2000/PCM/PCM_PPM_eng.html

davesrcflight.mysite.wanadoo-members.co.uk/frame_pages/radio_control_topics_frame2.htm

28.2.7. Can I use a JR/Graupner/Futaba/Robbe PCM reciever with my JR/Graupner/Futaba/Robbe transmitter in PCM mode?

The Graupner transmitter/receivers are manufactured by JR so they are compatible with JR equipment. The Robbe transmitter/receivers are manufactured by Futaba, so they are compatible with Futaba equipment.

The Futaba and JR PCM standards are not compatible, so JR/Graupner PCM equipment is not compatible with Futaba/Robbe PCM equipment.

Futaba has two incompatible PCM systems: an older PCM512 (9-bit) system and a newer PCM1024 (10-bit) system. The newer Futaba transmitters only support PCM1024, and not PCM512.

JR has two incompatible PCM systems: an older Z-PCM (9-bit) system and the new S-PCM (10-bit) system. The newer JR transmitters support both Z-PCM and S-PCM standards.

28.2.8. Can I use a crystal from manufacturer X in my receiver from manufacturer Y?

It may or may not work. If both manufacturers use the same intermediate frequency in their receivers, then the crystal may work. However, if the intermediate frequency is slightly different, then the receiver will work erratically. Therefore, it is best to use a crystal from the same manufacturer as the receiver. Why risk a $100 crash to save $10?

See this URL for more info:

www.torreypinesgulls.org/Radios.htm

28.2.9. Can I use a single-conversion crystal in my dual-conversion receiver?

No. Single-conversion crystals are not compatible with dual-conversion crystals.

See this URL for more info:

www.torreypinesgulls.org/Radios.htm

28.2.10. Can I change the transmitter channel by changing the transmitter crystal?

An R/C transmitter is carefully tuned to a specific frequency. If you change the transmitter crystal to a different frequency, then the other components in the transmitter will not be tuned properly and the transmitter may generate interference on adjacent channels.

In the US, this change is covered by FCC section 95.222 Rule 22. It is illegal for the user to change the transmitter crystal to change the operating frequency.

If a transmitter does not use a transmitter plug-in module, then it must be sent to an authorized service center to change the frequency. However, if the transmitter does use a plug-in module (such as some Futaba models) then it is legal to change the module to change the operating frequency.

In non-US countries, it may be legal to change the transmitter crystal, but it is not recommended to change the channel by more than two up or down (from the original channel) to avoid detuning the transmitter and generating interference on adjacent channels.

See these URLs for more info:

http://www.rcgroups.com/forums/showthread.php?t=94580

http://www.torreypinesgulls.org/Radios.htm

28.2.11. Why are channel 20 and/or channel 21 not recommended for use or banned at my flying field?

If there is a strong television channel on TV channel 4 nearby, then a transmitter on R/C on 72 Mhz channel 20 or 21 can cause interference on all 72 Mhz R/C channels.

For more info, see this URL:

www.rchelibase.com/radiofaq

28.2.12. Can I use brand X servos with brand Y receivers?

Yes. All R/C servos are compatible with all R/C receivers. However, some manufacturer's servos rotate clockwise, and some rotate counterclockwise. This can be compensated by reversing the channel, however.

28.2.13. When should I move from an FP helicopter to a CP helicopter?

It is best to buy a CP helicopter after you have mastered everything which can be done with an FP helicopter.

Basically, you should be able to hover in all four orientations, do forward/backwards flight, stall turns, and slow pirouettes in both clockwise and counterclockwise directions.