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Thread: Receiving Navtex and weFax

  1. #1

    Default Receiving Navtex and weFax

    Hi,

    I am wanting to do a small project with a raspberry pi or the like. I want to be able for it to run and receive Navtex (490 and 518 Khz) and Wefax (lower still). One simple solution would be to get a device such as a Tecsun pl-680/880 and tune to the relevant frequencies, but, that can mean leaving the radio and PI on all the time and I want to have this as a low consumption project. The PL-880/680 is also rather expensive and I have not found another radio that does 518/490. Many short wave radios but not all will do wefax frequencies, but I found no radio other then the PL680/880 that did the navtex and also even the wefax signal strength is poor on even a Tecsun pl606.

    Does anyone know a simple cheep radio that could be hooked up to an audio port that could receive on the relevant frequencies as a first step. I would also want this to be portable so this should be battery powered? I have considered kit radios or old transistr radios, perhaps modifying with a simple capacitor an analogue MW radio for the Navtex freq.s but, again this require more knowledge of the model's structure that I have at present.

    In principle a crystal radio would be fine if you could tune it. They are also attractive as they do not draw any power. Is there any suggeton for kits that have reasionable reception?

    I have also tries searching for radios for PI (for now ignoring the problem of power) with out success.
    I have also thought about SDR dongles, but, these can consume power and even sdr v3 only goes down to 500 Khz, a HF version (i.e. one with an up converter) is getting bulky.

    Any suggestions would be most welcome.

    3E0SVE

  2. #2
    Super Moderator 5B4AJB's Avatar
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    Default

    You could try building an external BFO for a small handheld-type MW radio.
    Tuning the radio on frequency would be the most difficult thing, but one thing to consider is stability - FAX requires a fairly stable tuner, or the colours fade.

    I can't find a circuit diagram on Google (amazingly) but I built one using a 555 timer IC decades ago which worked very well - look for a 455kHz beat frequency oscillator...

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