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Thread: Astro Spectra S-Split 450mhz?

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    Default Astro Spectra S-Split 450mhz?

    I apologize if this has been answered before, I searched and searched but couldn't find a clear answer. Can a S-Split Astro Spectra work reliably in the 450mhz range? I don't have a S-Split codeplug to play around with otherwise I would try one out and see if the CPS will allow you to program down to 450. I assume I will need to do some hacking of some kind to make this work but wanted to see what others have found.

    Thanks!


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    It all depends on where the VCO loses lock. The Out Of Band (OOB) mods we have in another thread on this site will extend the 470 lower limit down to like 450 or 440, but where it will REALLY go is hardware-dependent. What you could do is get a regular R2 450-482 VCO out of an old analog Spectra and drop that in, then slap in an "American" R2 (450-482 codeplug). Then you are at the mercy of your RF front end and the RF PA in the TX as far as how much power it will produce and how sensitive the RX will be.

    Basically you will get at least 10 MHz out of band without much degradation, you can frequently go even more but with some loss of power or sensitivity. While your at it take that $50 analog spectra, and steal the PA and RF front end and voila'! You now have a 450-482 Astro Spectra!

    You have half of what you need to home-brew a franken-radio, which is an Astro Spectra in a useless split like Q or S. The other half of what you need is an analog Spectra in the right range (438-470 Canadian/Motorcycle or 450-482 American/R2). Then all you need is a codeplug and instructions elsewhere on this site...

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    Excellent, thank you for your help and insight this is very informative

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    standardmissile No Longer Registered

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    Motorola really did something right for once when they built the Spectra line (Spectra, Astro Spectra, Spectra Plus). It's a shame that they didn't continue to build on this great platform past the Spectra Plus.

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    If you are doing what I think you are trying to do, you can try the cut and paste method of taking the FDB portion of the 470 S record and pasting in the 450 or any other band s record.With this method you don't have to retune the radio and the radio will like it.Then you don't have to mod the software, or have to edit the serial number.

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    I think you're thinking of changing the lowest frequency the radio does APCO P25 at, which is normally 450 MHz without changing the actual base band split of the radio. You can extend that from 450 down to about 442 MHz without modifying the hardware by doing this mod:

    https://www.p25.ca/threads/3706-HOWT...-Deviation-Fix

    Actually, you want to copy the tuning values, not the actual FDB, as that will change the baseband of the radio from 450 to 470 and the VCO will fail to lock and/or you will have to modify the hardware to change the range (bandsplit) of the radio.