oakley

My Feedback: (71)

I have a question about a 10X. I want to upgrade to a 10X but in looking at the 10X manual on Horizon's website, I saw a listing of compatable receivers for the 10X. I have several planes using a JR R600 receiver. Will that receiver work in PPM even though it's not on the list? Does anyone have experience with this?

Scotty740

Hello,

I use R600 receivers with my 10X all the time with no problems.

visioneer_one

My Feedback: (506)

I have a mixture of JR, Airtronics, Hitec and FMA PPM receivers - they all work just fine with my 10X.

XCaliber

My Feedback: (104)

I also have a R600 RX that works with no prob. on the 10X

Crash_N_Burn

It seems that I remember reading somewhere (think it was in the 8103 manual) that when using PPM rather than S-PCM or Z-PCM the fail-safe mode is inoperable. Different FM receivers work fine but no Fail-Safe.

Do I have this right?

I just bought two JR 949's so I would be able to keep the Fail-Safe mode.

Does this apply to the 10X also?

XCaliber

My Feedback: (104)

Yes, Fail safe is operable in PCM only not FM or PPM.

MO_Radio_Tech

Fail safe requires special circuitry in the receiver as well as the transmitter. With PCM, Pulse Code Modulation, there is an actual digital code being received by the receiver, that tells the receiver where to send the servo horns. The same type of signal is sent out on a regular basis by the transmitter when using fail safe. The receiver gets this info and stores it in a capacitor-powered short term memory just in case the receiver no longer receives anything from the transmitter.

In the case of PPM, Pulse Position Modulation, an analog signal is sent as modulation on the transmitter's carrier. This is converted by the receiver's little IC into a seperate variable signal for each servo amp. Because this is an analog signal, there is no way for a fail safe to remember it.

If one wanted to produce a failsafe in a PPM receiver, one would have to include an A/D converter and probably a D/A converter as well as a fail safe IC in the design. This would be extremely cost prohibitive. Since the most of the industry now considers analog (PPM) receivers to be low-tier, they are not willing to put $$$ into R&D and production to produce it.

If you want fail safe, you have two alternatives. 1) Go with PCM. 2) Buy those inexpensive fail safe units that go between the receiver and servo.

Crash_N_Burn

Thanks M-R-T! Good explanation!

It seemed strange to me that manufacturers couldn't also produce fail-safe in PPM systems but as you said, they could, but won't for money reasons.

Many years ago I had a JR radio and a big ugly stick that lost signal and went into fail safe. It maybe did 30 or more tight flat spins at idle from 150'. It pancaked flat, busted the landing gear and prop...and that was it. Easy fix! That incident made me greatly appreciate the fail-safe mode, so I continue to buy receivers that support it.

Thanks again for the great explanation!

Happy Flying!

ftomteen4cat

Fail-safe in a PPM system could be done easily using pulse-widtch discrimination for error detection. There are a number of ways you could hold last position without going digital. My supposition is that it's not done (with the exception of multiplex) because it's poised as a feature of PCM.

MO_Radio_Tech

In this capitaslist driven industry products are prodced that will make profit. Most folks who want to use fail safe have moved up to PCM already. In fact, many folks who have PCM and Fail Safe don't even bother to use it. Why spend money to design and produce a fail-safe PPM receiver when it will cost as much as the PCM equivalent? How many folks would then pay the same money to buy PPM as PCM?

Also, would a fail safe system that only goes into a "last clear signal" holding pattern be good? The beauty of Fail Safe is that you can set up surfaces in a way that brings the plane back into range so it can be saved. In many cases the Fail Safe your propose could be more harmful than no fail safe at all.

With all that trouble, why not just fly PCM?

Ladyflyer

My Feedback: (2)

A good ,functionally similar ,for practical purposes IDENTICAL failsafe(not a real accurate term) for PPM would not involve any " exotic " converters stated above.
A simple look for missing reset pulses at the decoder input could trigger a set of individualy preprogrammed pulse widths to each required servo. Upon restoration of the reset pulse the output of the decoder would resume it's trip to the intended servos. No ,not expensive , but it would take away a huge incentive to move up to the PCM rigs.
Could a third party benefit by offering a receiver of this type ?

Hmmmmmm.....


BTW PPM does have advantages of it's own !


Hey F'tom ....Tentative but just a few more for now !
Thanks for the note !

Furyflyer2

My Feedback: (117)

WOW i'm inpressed Ladyflyer

ftomteen4cat

LF - I agree. I think that pulse-width discrimination would be more robust though, since it would handle spurious interference.

Simple pulse-width discrimination can be accomplished using a charge pump with upper and lower thresholds through a dual-comparitor setup. The output of the comparitor pair would be used as a gate signal. We're talking one IC, a couple caps, and a few resistors.

Regards,
scott-

MO_Radio_Tech

Or, just fly PCM.

Ladyflyer

My Feedback: (2)

Or good ,reliable PPM on clear frequencies
But if you want failsafe (so called) you CAN have it along with the benefits of PPM for everyday flying.
No where NEAR as difficult as some would have you believe