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Thread: ASTRO25 Waveforms

  1. #1
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    Default ASTRO25 Waveforms

    I have an XTS-5000 programmed for ASTRO wide mode on a repeater channel.
    Now when switching between repeater mode and direct talk around mode I noticed that
    the transmitted waveform looks different every time.
    Any ideas about this?


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    the wave forms should look identical, ie same deviation and general appearance. if you descibe the differences I maybe abkle to identify the issue. I am assuming the radio works fine in both modes.

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    They definitely don't. In normal repeater mode the waveform looks like a mix of different sinus waves.
    In "talk directly" mode it looks like 3 rows of superimposed eye diagrams.
    On a monitor receiver they also sound slightly different.

    I have seen this on 3 different XTS5000 UHF low range.

    Btw: by changing the pulse filter from narrow to wide on a quantar I've seen the same effect.
    Any hints?

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    Wide pulse changes the filtering from a RRC filter to a motor proprietary one, and also the waveform is modified to give increased "dwell" at symbol time so the FM capture effect aids symbol recovery in simulcast systems.

    I'm really not sure why it's different on the subscriber, I thought the uplink from radio to infrastructure was always C4FM.

    In any case getting details on WIDE is difficult as its Moto proprietary and I don't think is used much anymore on new systems.

    LSM is the new simulcast and is defined in the P25 standards, so maybe putting some effort into figuring that out might be worth while also. Max, KA1RBI has done awesome work on writing a high quality decoder for this in OP25, and he has some excellent pages that describe it in detail.

    I'm at a BBQ right now (yep you can tell it's winter in Australia - I'm outside, cooking a BBQ surrounded by Russian friends lol) but ill post some links when I get home.

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    Hey Matt,
    thanks for this very informative reply.
    No much info available about these Moto waveforms indeed so I would be grateful for any additional info's or links.

    Still wonder why my XTS radios change TX waveforms while toggling between repeater mode and direct mode.

    Hope you enjoyed your BBQ down under!

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    Thanks Matt for the info on the dwell time modifications to the incomming data.