I need a HF link that will be (mostly hah) operational 24/365. Edit: at least at local daytime. The link is supposed to transmit a controlling signal (just one bit) in one direction for quite a distance (appr. 2000km Edit: appr.2500km) with the lowest latency possible. Due to the latency constrain filtering must not take longer than 1ms, if even 1 ms.
It may be a mistake, but I don't want to use any kind of FM, as it will require constant transmitting, and I only need to send the signal ~100 times a day.
- I can use directional antennas.
- I can not use more than 1kW transceivers.
- I can use several trancievers on differt bands in parallel.
What else can I do? How should I modulate the signal?
P.S. I considered other options, such as GSM, sat, fiber channel, etc, but unfortunately they are not fast enough.
Reliability of 0.8 would be supergeil. (If 0.4 is the very top, I'll have to take it as well)
P.P.S. About the nature of the link - you can think of an experimental setup that generates data, computer processes it in no time and generates an output - 0 or 1 (mostly 0's). On the receiving end there's other setup and it takes this 0 or 1 as an input.
UPD: I guess, I've chosen not the best question statement. Of course, the thing I'd like keep at minimum is the overall latency. As the propagation latency is fixed, we need to sort out the transmitting and receiving latencies, which I'd wish to cram into just ~1ms (however, I've mentioned only receiving part in the original question above). The question is titled as it is in order to avoid (in other cases useful) advices to extend transmitting time to the fantastic values and gain almost 100% reliability.
Add: Given the power, there seems to be a technical contradiction between the transmission duration (and therefore latency) and reliability. Well, I'd like to optimize them both :)
Another thing about the processing latency constraint is the test I made on a couple of Yaesu's that I told about below in comments. The test shown that it've taken about 4ms on the receiving end to process the SSB signal, which seems a lot to me.
Also, I'd prefer to keep the transmitting antenna complex on the smaller side to the possible extent.
UPD2: Now that I've received a couple of such wonderful and clarifying answers, I'd be more than grateful to receive suggestions about specific equipment suitable for making smaller-scale prototype – SDRs and antenna setups.