Pippin

There were no information about packet rates available since those were proprietary to each manufacturer:

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

Btw, Futaba Fasst has 136kbps and Airtronics FHSS-3 has 125kbps.

AndyKunz

Yes, but they were all bound by the same laws of physics regarding bandwidth. How much data could they back then (remember, no multi-bit-per-change capability) when they had narrow band equipment?

Andy

Pippin

Somewhere I read that 15.6kbps gives greater range than the higher numbers. Don't know if that is true only for DSSS.

rmh

The odd part about these KBPS figures,is that IF one radio runs at 15 - and one at 135 , that a 9x difference..
One would think that this huge difference would lead to some easily seen difference in operational RESULTS
Yet the differences I have seen, are piddling.
The heli guys seem to be the most vocal about all this -yet the various systems performance in these is quite similar .
I did notice differences in precision aerobatics ,going from PCM2048 to Spektrum 2.4 running 1024
The 1024 Spektrum was far more responsive -requiring the use of inreased expo to damp the responses to familiar levels
same servo etc., it wasn't imagination.
In this example a 1024 system was quicker than a 2048 system -which sounds impossible but we were not comparing the basics - PCM vs 2.4
numbers can be confusing,till one sees the entire picture.

BarracudaHockey

My Feedback: (11)

Resolution isn't about speed its about precision. What you're seeing is the speed at which the transmitter input results in a servo output, or latency.

I can't tell the differnce between 1024 and 2048 resolution in the Spektrum systems.

I can by far tell the diffefrence between a slow 72mhz like the 9C and any Spektrum/JR 2.4 system.

rmh

The numbers by themselves don't tell a story
They simply mislead - that was my point
FWIW a non PCM system was smoother than the PCMs- I had the entire series - from the 512-thru the 2048 JR stuff

rexbirk

When I first went from 72 on my JR XP9303 to a 2.4 module I felt the difference right away. Can't explain it any way but that I felt more connected to the model. After reading some of these posts I see why.

I think 2.4 has been great for our hobby. I have never worried less about my radio. I have a JR XP9303 module based radio and an X9503 DSMX. Love them both!

Pippin

It's latency that makes the difference. The old analog transmitter were very fast. Then came PCM with more than 8ch.

Those kbps figures tell something different. Maybe something about range in crowded 2.4Ghz environments.

AndyKunz

In electronic communications 101 you'll often hear that lower data rates are better for longer range. For example, NASA uses very low data rates to ensure their signals travel the vast expanses of space reliably using the extremely low-power signals that are necessary for the life of the system. (They are working on increasing speed; just saw it in NASA Tech Briefs a week or so ago).

Andy

TimBle

that has more to do with available on board power limitations and error correction.
They could send higher data rate packets but then they need more sensitive equipment on the ground with better error correction

rmh

So a good system does 3 things:
!. it reliably transmits information with no losses in info
2. The operator inputs to received and translated time at the rx is minimized
3.The intervals in steps of information at the servo is minimized
which system does ALL of these things the best?
can most users see any real differences?
More opinions?