Spectra and MDC-Decoder

[wb4bsd]

I just replace a conventional sepctra with an Astro Spectra. I am also using a Motorola MDC Box that will decode and do radio checks and all that good stuff (model # B1667A).

My problem is that the MDC box will not work with the Astro. Is the pin out different on the Astro vice the regular spectra?

Thanks

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[Sundown]

I don't think it's simply a pinout issue. MDC won't run over Astro (there's no need) as Astro has it's own signalling built into the protocol that covers all of the things the MDC feature sets cover.

And they're two different beasts in terms of how they're modulated. My guess would be that there's no hope of the MDC box decoding Astro signalling.

[wb4bsd]

Well i understand that Astro does not use MDC. However, we are currently using our Astro Spectra in the conventional Non-astro mode. So it should work. The box simply needs to detect the mdc signal to decode it. I just need to know if the two spectras are the same as far as the rear serial connection goes.

[xmo]

We looked at the B1667 to Spectra cable pin out in the B1667 service manual and we also compared the accessory connector pin out diagram in the Astro Spectra manual.

There could be a problem with the following two signals: PTT on pin 13 and detected audio on pin 11. The Astro Spectra manual says that pin 13 is PTT and pin 11 is detected audio in "SP customer applications".

It would appear that this determination is made by jumper configuration [0 ohm surface mount parts] on the command board. To resolve this you will need the Astro Spectra Detailed Service manual [68-81076C25] and surface mount rework capability.

[jhooten]

It (and a bunch of other manuals) is availale for download at:
https://businessonline.motorola.com/Mem ... center.asp

You will have to register to access the member content. Takes about a ream of paper to print single sided.