What do I need to do? I need to send a radio signal and have another device receive that and output a voltage pulse, with the time between starting to send the signal and starting to output the voltage pulse as consistent as possible every time I do that (zero variation is perfect, picosecond or less is good, nanosecond is bad, millisecond probably means I'm wasting my time).
I need to know if it can be done, and if so what the likely timing inconsistency will be, whether due to circuits, or interference, or other - I need the order of magnitude of the inconsistency rather than an exact figure, though exact or a formula would be good.
- The frequency can be any that is listed as 'Amateur' in https://www.ntia.doc.gov/page/2011/united-states-frequency-allocation-chart
- While the response time could be slow, faster would be better.
- I believe I need that to happen with an analogue AM signal, and no digital clock in this part of the device (as those will add inconsistency in timing based on the digital clock's resolution, and/or require expensive or non-existent ultra fast clocks). I may be wrong about this - I figured I'd find out if it could be done like this, and if not then I would look for other, more complicated, ways that break these two requirements.
Imagine I have an analog AM radio transmitter, frequency 222MHz, which starts transmitting a full strength signal at time 0s, and have a standard analog AM receiver 100 meters away (tuned to 222MHz).
The receiver's output is passed (possibly via an amplifier) to a digital converter circuit that normally outputs 0V but, when the received signal passes (at least) 80% of the transmitted signal strength, outputs 5V. Note: the converter does not use a digital clock or timing signal.
My first question is this: I've been told that the time from the transmission starting (0s) to the time when the converter first outputs 5V (T seconds) will not be a consistent amount of time, because the received wave will not be exactly the same as the transmission - that interference (natural or artificial) will make the received wave have small perturbations that will subtly change the exact timing of when the receiver's input/output hits 80%, making that time different each time. While the effect will be small, it will be non-zero. Is that correct? Can anyone tell me roughly what the effect will be (in terms of time variation)?
My second question is this: is there some kind of circuit or other thing I can do to avoid this? I really need that timing to be entirely consistent (and I mean, down to picoseconds or less if possible).
I don't the circuits laid out yet, but I imagine the transmitter would be along the lines of https://www.electroschematics.com/2522/am-transmitter-circuit/ or http://www.circuitstoday.com/am-transmitter-circuit , and the receiver would be something like https://www.electroschematics.com/601/2-transistor-radio-receiver/ or https://www.electroschematics.com/9043/am-receiver-circuit/ - and I don't have the digital converter circuit but if I recall my electronics lessons of long ago, that's a pretty standard, simple thing.
EDIT: The key here is consistency, over multiple transmissions, within a short period of time (seconds, not hours). I don't mind delay if it is a consistent delay. I should also note that, for reasons that it breaks the basic concept, I can't use digital signals or a clock in the signal analysis (because the clock would add inconsistent delays). Optical or cables are also out.
I have asked the same question in Physics as there is some overlap and I welcome the different viewpoints - https://physics.stackexchange.com/questions/408378/consistent-radio-wave-detection-timing
Please note, this is related to https://physics.stackexchange.com/questions/401512/radio-wave-detection-timing but is not the same question - though I asked a version of the above in the comments.
Thanks in advance.
To a degree you are right. It probably doesn't help that I'm used to the programming stack exchange where a specific, limited question is generally more useful than a vague 'big picture' one, up to a point. However that doesn't mean that this question has no value, nor that I don't need an answer.
1) this is an attempt to do something a new way. So there are existing ways to achieve it but they are not very good and I don't want to replicate them. Getting back to the even bigger question than the above just leaves me with existing methods, and probably kicks it in to whole other areas (physics, for one). If Einstein had asked about gravity in certain circumstances, would you refer him to Newton's Laws? Or would you answer his seemingly XY question? (I'm no Einstein but the point is still valid)
2) there is a limit to how much more information I can give away without laying out my entire idea. Call me selfish but I'd like to avoid that for now.
3) when I asked a more general question I was basically told to be more specific. This was my attempt to do so.