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Tech Chat Project COHIRADIA

Illustrious V-Ratter Registered
Posts: 5477

Whilst looking for something else entirely, I stumbled across this:

From that page:

COHIRADIA is an acronym for CONservation of HIstorical RAdiofrequency bands by DIgital Archiving.

COHIRADIA has two main goals:

  1. to give interested radio enthusiasts and collectors the opportunity to play back original radio signals recorded in the past on historical radio receivers. These signals should not contain only a single station, but a whole frequency band (e.g. medium wave) with all radio stations contained therein on the correct carrier frequencies existing at the time of recording. This allows all stations to be tuned-trough on the radio receiver.
  2. to record currently broadcast radiofrequency bands, especially in the AM range, at various locations around the world. The goal is to map the still existing landscape of active stations in the form of archive files in time before the technology finally will die out.


Sounds fascinating.

Topic starter Posted : 06/05/2022 11:21 pm
LSmith, turretslug, Nuvistor and 2 people liked
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Posts: 528

That's a fascinating concept, and I was reminded that several times I have heard, purely anecdotally and usually "an older colleague mentioned it in the pub"-style that the US intelligence agencies had over the years dabbled in recording a whole chunk of radio spectrum at once and picking through it later for anything of interest. I'd even heard it suggested that the likes of Ampex's video recording techniques had been at least encouraged or even sponsored by intelligence agency motives, though have never seen anything directly confirming this- I can certainly believe that any very wideband high frequency recording technique would have been of interest though. There was a mention on the US Antique Radios Forum of a particular version of the widely-used Hammarlund SP-600 that had been devised as a wideband spectrum capture front-end device. I'd certainly be fascinated to hear any details of such technology from anyone informed on the matter, and no doubt if the US was doing it, lots of others were at least having a go.

Posted : 09/05/2022 9:34 pm
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Posts: 166


There are wideband capture cards but they are horribly expensive.

There are cheap video capture cards that could cover the bands, unfortunately they expect the input signal to be formatted in a particular way. Whether this is because of the chip set or software, I don't know.

I wonder if any open-source proponents have looked into using the cheaper hardware for this purpose. I shall have to take a look.

Posted : 10/05/2022 8:13 pm
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Posts: 166

Looks like I'm trying to reinvent the wheel. It's all been done.

Posted : 10/05/2022 8:22 pm