I'm writing a detective novel, in which a series of terror attacks are carried out in the United States by a group of mercenaries using military grade, channel hopping radio to communicate.
I would like to create tension, in the lead up to a subsequent attack, by having my protagonist alerted to the activity and location of the mercenaries by picking up on these radio signals.
I don't need my detective to decrypt the contents of the comms (I assume this to be impossible without knowing their encryption keys), but the mere presence of channel hopping radio signals and the location of their source would be enough.
I read in another post that it's possible to determine the source of such radio signals, using a wide band receiver and directional antenna but I hope to determine if it's possible to have a system such as this set up to constantly monitor for these signals and to set off an alarm when it detects activity?
I don't intend to explain the intricate details of this system but I would like the idea to pass the credibility test and not have my readers pooh poohing it as impossible.
To give a little more background, the first attack in my story is the bombing of a dockside wharf which my detective is staking out on a case of drug smuggling and he's got support from police surveillance, who are monitoring the radio frequencies. This is how he first realizes he's up against people with military equipment.
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In answer to your query.. A/ the story is contemporary (excluding COVID19) and B/ my protagonist is a cop, therefore his assistance includes whatever surveillance gear a modern stateside urban precinct might have access to.
I appreciate your suggestion to modernise my tech scenario, which, I guess, might include cell phone tower monitoring.
On the plus side.. The first attack, at the wharf, happens in the dead of night in a deserted industrial zone, relatively free from local mobile traffic noise.
What I am looking for.. A self evident way to link a later terror attack back to the first one, so my protagonist realises that the perpetrators are one and the same group. I hoped that the military radio signals could achieve this but perhaps there are other unique attributes in the more modern tech scheme which could achieve the same thing?
Also, it's important that the unique identifier occur BEFORE the second attack, so that my hero gets a brief opportunity to avoid being blown to bits.
I've currently got it written such that my protagonist gets a phone call from the cop who's been running the monitoring system. Said cop announces excitedly that he's picked up a signal from the same mercenary crew as the wharf bombing. My protagonist asks where the signal is located and the reply makes him realise he's in immanent danger.
I hope this gives you enough insight to ruminate on a solution.
I really appreciate your expert insights here. I hate it when I see movies hinging important plot points on unbelievable technology...
"Hey, just stick this USB into the alien ship's computer and upload the virus to save the world" or "Zoom in to this wide shot photo of a massive crowd, to the engraving on the earring of that girl.. Enhance... Enhance..."