[sdiy] wireless patching

[rsdio at audiobanshee.com]

On May 26, 2017, at 11:58 AM, mskala at ansuz.sooke.bc.ca wrote:
> On Fri, 26 May 2017, Tom Wiltshire wrote:
>> That doesn't sound too impossible given the 27MHz transmission frequency.
>> The standard 50Hz PWM seems like a pretty light load for such a signal. How
>> many channels can an RC controller handle? Are they multiplexed?
> 
> I described the protocol in my earlier message.  The number of channels is
> variable but typically eight.  Bandwidth would be a few kilohertz
> depending on how much resolution you want and how much signal/noise you
> think you can play with.  It is not a particularly bandwidth-efficient
> encoding.  I'm sure that the bandwidth in practice is limited by
> regulatory concerns - if you want a much higher sampling rate and you want
> to do it *legally*, then you're going to either be limited to flea power,
> or forced up into the UHF.

When you say "a few kilohertz," you're talking about the encoded signal, not the decoded signal, right?

I don't see how you can have 50 Hz PWM and get a few kHz signal out of that after smoothing.

On that note, what is the lag time for PWM? It may not be the same term as latency, but the necessary smoothing for PWM means that an immediate change in the PWM signal does not result in an immediate change in the DC Voltage output. If the PWM is running at 50 Hz, I'd imagine that the signal bandwidth can't be any higher than 10 Hz, and probably lower.

Am I missing anything?

Brian