No latency high response TX/RX possible?
 

Just some thoughts, no starting project.....

More and more racers are into low latency and high response.
Low or no latency is with the old 27/30/35/40/75MHz transmitters, the only latency was made by the low framerate of 20msec. Futaba came later with an HRS protocol that did speed up the frame to about 5 msec but was limited to that because the limit of digital servos and the need of 2 pulses (2 channels) behind each other.

Latency today is more made by computer chips in the transmitters and receivers as also the WiFi technology used on the 2.4GHz band which knows error protocols. This will make the transmission more reliable but with a (variable) latency that can go up to even beyond 10 msec.

What if we take an old style 40MHz system and speed up the framerate and shorten the pulse width? It should be possible to use SR/SSR servo's!

OK, you will lose some transmission reliability, but we have used FM transmitters in the past w/o any issues and you will gain the fastest transmission w/o latency.

Yes, it is going back to selecting frequencies, but today they are all free to use, no one is running a long antenna transmitter these days on the races.

Would people buy such an analog transmitter working with today's SSR/SR servos?

Roelof,

I guess that would be like the Transmitter Module being replaced? Is this correct? Similar I had the Radiopost conversion and then installed it from my 3PJ to my old 3PB. Surely If this is the case perhaps someone would be able to update / make similar modules then?

Herr is the Futaba 3PK one as a refference.
https://cimg4.ibsrv.net/gimg/www.rct...9ac01c3401.jpg

Some of those frequencies are illegal in some jurisdictions. I'd also hate to regress back to peg boards and interference issues.

Also you're wrong about there being no latency in the analog radios. There's always latency. Especially if you want features like exponential curve settings etc. The channel data needs to be processed before transmitting.

No, that is just a transmitter module so the PPM signal (the serial pulse signal with all channel pulses) is produced in the transmitter.

True, but the most latency comes from the transmission itself, coding into a language with error detection as also the transmission itself with error corrections.
Working from a prosessor calculating all kind of functions, you can do it realtime or calculate a curve diagram based on all the settings and use that table to translate the input to output, it is much quicker. With an oldschool trim and endpoint adjustment you can keep that realtime. Just a thought.....

Setting up an oldschool analog transmitter is possible with endpoint adjustments, subtrim and other basic settings without the need of a processor. I am no high frequency engineer so I would never start it although I do have the old 40MHz transmitter module of my T3VCS and even the FF3 with all the receivers so I could make a setup with a SR or SSR signal and see if it comes into the receiver. Probably not to the channels but high chance the PPM signal is somewhere before splitting the channels readable.

https://www.rctech.net/forum/radio-e...m-results.html

This disagrees with you, the latency is already approaching the limits of the servo. I'm pretty sure you've already read through this though since I found the link to it in an old post from you.

I know, he just made a a tool to switch something inside the transmitter and measure when the change comes up on the channel. I think some bad results will be better when doing it on the track and not at home where many wifi signals are in the air. But he is reading a total latency caused by everything between transmitter control to the servo channel output, it is very variable and can go beyond 10 msec of time, that is huge. That is the difference between hitting the Apex right up to launched by the curbs.

It never went beyond 10ms on the M12. It ranged between 2.2 and 6.5, which is a small range and close to the limits of the servo PWM. I'd expect the M17 with one of the faster servo modes and a faster TX protocol to be even better. But even then, a variance of ~4ms at 50km/h is only 5cm. When the fastest human reaction time has been measured at about 100ms, our servos are typically only around 50-100ms transit speed, and in general most ESCs don't support high speed servo modes, I'm not convinced 4ms is going to make a tangible difference.

I'm also not convinced that WiFi signals will appreciably impact latency. Our radios don't resubmit packets like a TCP network, it's closer to UDP where the packets are fire and forget. If a packet gets lost, the radio is still better off continuing to send the current input state. Even then a typical home WiFi network only has a couple ms of ping round trip, and most of that is in the router queues, not over the air transmission.

First of all, I think we need to find a way to accurately and reliably measure latency. I have no idea how such a thing might be accomplished. Only then can we appreciate the difference.

Measuring it is covered in the aforementioned thread
https://www.rctech.net/forum/radio-e...m-results.html