New answers tagged

3

I get the impression that this answer is too long for many people, so here's the abstract: I presume your goal is to make a system that will automatically record a message when someone calls a particular operator on HF SSB and the operator doesn't respond, like an answering machine. Also the system will alert the operator to an incoming call for him or her. ...


1

You might consider looking at packet radio. It allows for this kind of message passing to reach recipients similar to BBS-style messages or email. Similarly winlink is worth checking out. Neither of these are exactly the point-to-point alert-style you mention above, but both are implementable on a RPi which can be scripted to have a klaxon or spinny light ...


0

After reading this question a few times, I think I have a good idea what you are asking. I am not familiar with the transmitter or receiver you mention, but you say they use AM. Using an AM transmitter, you can not easily (I mean, I guess it might be technically possible if you can vary the frequency of the carrier accurately, extremely quickly) generate FSK,...


2

A low-pass filter is one way to do it. Due to the interpolation done in the repeat block, you are representing a symbol with 1000 samples, and your sample rate is 2 million samples per second (the samp_rate variable). So your square wave has a frequency of: $$ \require{cancel} {2000000\ \cancel{\text{samples}} \over \text{second}} {1\ \text{symbol} \over ...


0

I want to mention that the technique described at the end of the accepted answer can be seen very clearly in the LuaRadio documentation: https://luaradio.io/examples/ Each of the examples defines a variable tune_offset, whose value is slightly larger than the bandwidth of the desired signal. In the first example, which is an FM receiver, the bandwidth of ...


Top 50 recent answers are included