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FrSky questions

PostPosted: Mon May 10, 2010 1:07 pm
by Fly2High
I think it was said that due to the number of bits FrSky uses that some will find it not have the finest of control (not that most would notice).

I am paraphrasing there

I have an older XP 9303 which was only a 10 bit (1024) resolution. Since i do not have the 2048 of the newer radios, will I see any lack of precision?

I also have a X347. I would suspect it is 512 resolution. would the FrSky show it in this one or I would not even notice it?

I hope I am explaining it correctly....

Re: FrSky questions

PostPosted: Mon May 10, 2010 8:24 pm
by RCModelReviews
Because module-based systems have to convert an analog signal (pulse-width) to a digital form and then back to an analog signal again, there is always the potential for the total system resolution to be degraded.

For the most part, this loss of resolution is so small as to be inconsequential however, when using hi-precision digital servos they may not appear to be as smooth for slow stick deflections as was the case when running FM/PCM.

I fly fast models and I also fly 3D machines with BIG surfaces and BIG throws. Using the FrSky in a 1024-step RC system (JR9XII/9303) I've not noticed any difference in the air at all, and the same goes when using it in the 512-step Hitec Optic 6.

Re: FrSky questions

PostPosted: Tue May 11, 2010 4:16 am
by JMP_blackfoot
I have fitted an FrSky DIY module in my Supertef transmitter which has an 8-bit coder. I checked the channel outputs of both the 4-channel and the 7-channel FrSky receivers and find that when I move the stick slowly, the pulses do change in 4µs increments. This is exactly the same as the outputs of a regular 72 MHz receiver with the same transmitter. As far as I am concerned, the FrSky system does not introduce any change in the precision of the servo pulses.

Re: FrSky questions

PostPosted: Tue May 11, 2010 4:56 am
by RCModelReviews
Yes, if you have an 8-bit resolution then the 10-bit FrSky module will be providing 4-times oversampling so you should see no change in resolution at all.

Same goes for 9-bit (512-step) radios but you will notice a small difference with 10-bit (1024-step) radios although, as I mentioned previously, it won't be noticeable in the air.

Re: FrSky questions

PostPosted: Tue May 11, 2010 11:25 am
by JMP_blackfoot
FrSky specify their transmitter modules and their receivers with a resolution of 3072, which means they are 11 1/2-bit.

So, is it a 10-bit or an 11 1/2-bit system?

Re: FrSky questions

PostPosted: Tue May 11, 2010 9:21 pm
by RCModelReviews
I think it's some bad translation somewhere along the way :-)

11-bit is a strange level of resolution -- I'd tend to think that it's 10-bit but I'll query them and if they can't elaborate, I'll test it.

Re: FrSky questions

PostPosted: Wed May 12, 2010 8:17 am
by JMP_blackfoot
I've connected the FySky DIY module to an old Futaba FP-7FGH transmitter which has an analog coder and checked the servo pulse outputs of both the 4-channel and the 7-channel FrSky receivers.
In both cases, I was able to observe a minimum increment of alternately 0.6 µs and 0.8 µs. If moving the stick very gently, the servo pulse would increase by 0.6 µs, then by 0.8 µs, then by 0.6 µs, then 0.8 µs, etc...
This means that the total number of steps for 1 to 2 ms. would be approximately 1400, better than 10-digit resolution. Also, the servo pulse was never entirely stable, switching between two successive steps, as if some form of time averaging was in progress. Is this how FrSky achieves their 3072 step resolution?
For comparison, My Futaba 6EX 2.4Ghz system has a 0.66 µs increment, i.e. a 1500 step resolution.

Re: FrSky questions

PostPosted: Thu May 13, 2010 12:15 am
by Captain351
If FrSky is going to make much of an impression on the US market they are going to have to find some more dealers. I have been waiting for HiModel to get the 8 channel receivers in stock for a couple of weeks now. The problem is that I can't find a reasonable alternative to HiModel. Does anybody know of a dealer that has comparable prices and shipping costs for a US Buyer.


Re: FrSky questions

PostPosted: Thu May 13, 2010 12:27 am
by RCModelReviews
Yes, this is a big problem for the smaller manufacturers -- keeping up with demand!

All the Chinese manufacturers have had difficulty in meeting demand, which is good for them but bad for consumers.

I have emailed FrSky and suggested that they focus on their core products and not get too distracted by releasing new ones. There's little point in coming out with "something new" if you can't keep up with the demand for the products you already make.