Hi,

I have a Dx7 radio from Spektrum and I have several Spektrum RX's as well as OrangeRX from HK.

Because I use them mainly in multicopters where most of the flight controllers
have features that need the minimum and maximum throttle I'm starting to notice some differences between these two RX's.

I'm starting to do a detailed testing to confirm this but I wanted to check if anyone else have noticed the same. Just in case I simply had bad luck with the RX's I have.

Originally Posted by IceWind

Hi,

I have a Dx7 radio from Spektrum and I have several Spektrum RX's as well as OrangeRX from HK.

Because I use them mainly in multicopters where most of the flight controllers
have features that need the minimum and maximum throttle I'm starting to notice some differences between these two RX's.

I'm starting to do a detailed testing to confirm this but I wanted to check if anyone else have noticed the same. Just in case I simply had bad luck with the RX's I have.

I'll be interested to see your results and will do a bit of testing myself. I would not have expected the receiver to change the fundamental information, i.e., the pulse length. That should be set by the transmitter. Before the advent of receivers with processors, the question would have been meaningless, as the decoder just passed to info to the right servo. But now with receivers that are little computers, anything is possible.

Will give it a try and report back. I have several Orange and Spektrum receivers.

I think that different receivers have some variations between the signals.

Ok just made the first test, not very accurate but I'll do more.

As I have several multicopter boards with the Multiwii I used the GUI as reference in this case for Throttle maximum and minimum values.
The radio memory is the same I only bind each RX before each reading

Maximum throttle
Spektrum Ar6100e - 1894
OrangeRx 6ch - 1900

Minimum
Spektrum Ar6100e - 1102
OrangeRx 6ch - 1109

Here are my results. The transmitter is a DX7 with throttle set to 100% throw, Measurement is with an Ace RC Datamaster from the days when I built Ace Silver Seven radios for my friends. Timing is in ms.

Orange #1 1.12 1.90
Orange #2 1.11 1.90
AR6200 1.11 1.89
AR6100 1.11 1.89
AR6110e 1.11 1.87
RA61e 1.12 1.89

The last one is the clone of an AR6110e that HK used to sell. The readings should be taken as +/- 0.005, as you can get the last digit to change by one depending on how you push the stick to the stop.

If there is a difference its probably due to the CPU crystal in the receiver. Since the output servo pulses are generated by timers inside the CPUs used in these receivers, things like temperature stability, overall accuracy in PPM, aging effects and other crystal rating factors will affect the timing accuracy. I would not expect a batch of Spektrum branded RX's or the HK ones to all have exactly the same servo output pulse lengths if using a single TX as the source.

Originally Posted by hammer22

If there is a difference its probably due to the CPU crystal in the receiver. Since the output servo pulses are generated by timers inside the CPUs used in these receivers, things like temperature stability, overall accuracy in PPM, aging effects and other crystal rating factors will affect the timing accuracy. I would not expect a batch of Spektrum branded RX's or the HK ones to all have exactly the same servo output pulse lengths if using a single TX as the source.

Pretty close, though, as you can see from my numbers.
Thanks for the explanation.

Close numbers, the differences even statistically insignificant really.

They are closer than I had expected.
But the impact will differ according to the usage, for planes + helis it's none.
I just do the throttle range set on the ESC's and it's done.

For the multicopters that little change in the minimum value is enough to make me have different software versions , if not the FC won't arm.

Originally Posted by IceWind

For the multicopters that little change in the minimum value is enough to make me have different software versions , if not the FC won't arm.

As I said, the variation is within the tolerance of the throttle stick mechanism. I don't see how you can work with a setup that needs different software versions depending on whether you pull the stick down hard or soft.
Anyway, not my problem.
As far as I'm concerned, I've established the validity of my working assumption, which has always been that signal information issues are a function of what goes on in the transmitter, not the receiver. That's why, when people have problems with programming, I always advise them as a first step to turn off the model and look at the monitor screen to understand what's going on. I treat the receiver as simply passing the signal through to the servos (or ESCs). Nothing I've seen so far suggests that receivers normally change the control information in any significant way.

Yes, the numbers are pretty close. The difference equates to about 0.9% difference on the low end and roughly 1.6% on the high end. That makes sense because the differences in the crystals would show up more on longer output pulse widths. Probably if the pulse length increased to 4ms the difference would increase to 3%+.

Originally Posted by Daedalus66

As I said, the variation is within the tolerance of the throttle stick mechanism. I don't see how you can work with a setup that needs different software versions depending on whether you pull the stick down hard or soft.
Anyway, not my problem.
As far as I'm concerned, I've established the validity of my working assumption, which has always been that signal information issues are a function of what goes on in the transmitter, not the receiver. That's why, when people have problems with programming, I always advise them as a first step to turn off the model and look at the monitor screen to understand what's going on. I treat the receiver as simply passing the signal through to the servos (or ESCs). Nothing I've seen so far suggests that receivers normally change the control information in any significant way.

Well as simple as the reason that made me write this post in first place.
If I use the OrangeRX the FC arms if I use the Spektrum RX it won't.
Same software, same radio, same cables... only different RX.

So I decide to check if there was indeed any noticeable difference.

What you really need to do is pull the throttle trim down all the way so it arms consistently.

Andy

Daedalus66

Tried to send you a PM but your in box is full.

I saw this post where you use to build Silvers

https://www.rcgroups.com/forums/show...15&postcount=5

A couple of years ago I purchased a Fly Dream 2.4 unit to mount inside my Ace MicroPro 8000 SS
https://www.rcgroups.com/forums/show...81&postcount=1

and a couple of the plug in modules for my Hitec Eclispe 7 Transmitter and a bunch of receivers and all work great.

Question is if I wanted to use a plug in module with a AMP8K it appears to me that I would only use 3 of the 5 contacts.

PPM Battery skip one Grnd. and not use the last one.

The one I put in the AMP8K Single Stick (which I purchased in 1990) I set the switch to + ( looks like a U) . Would the Hitec plug in modules be correct for the Ace that is woulld they be +.

The reason for these questions is that I just purchased a couple of two stick AMP8Ks and I am going to either purchase the goes inside (hack) Fly dream or perhaps go the plug in module route.
I am thinking perhaps mounted the rear cover and hard wired instead of using mountind cavity with contacts.

Thanks in advance for your time and any help / advice you can provide.

Charles