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Thread: MC2100 - pin 24 acc connector modulation input

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    Question MC2100 - pin 24 acc connector modulation input

    Hi all,

    I want to use a MC2100 UHF radio as a transmitter for a digital voice ham radio MMDVM based repeater and I'm in a bit of a pickle. While on other radios like the GM900, or even the GM1200 that I've flashed the MC2100 from, pin 24 on the accessory connector - AUX TX IN2 works great as an input for the external modulation signal, on the MC2100 it doesn't. The thing is that for all the other radios, I could find somewhere in the RSS how to enable this input but in the MC2100 software it's hidden from my sight.

    So, hoping the question isn't (too) dumb, does anyone know how to enable the pin 24 - AUX TX IN2 external modulation input for the MC2100? Or maybe there is an alternative solution? I need a wideband, unfiltered, un-pre-emphasized input.

    And the most annoying thing is that in tune mode the signal gets through via pin 24. So, apart from putting the radio in tune mode or flashing it back to GM1200, any ideas?

    Dan
    YO2LLQ


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    You may have to do a hardware mod, if the RSS/CPS isn't allowing you to manually inject a signal on this pin.

    Do you have the detailed service manual? The MCS2000 is the North American version of the MC2100. Should be the exact same hardware; the difference being firmware.

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    In the MMDVM yahoo group, files -> hardware -> VRM.zip, is well documented how-to on using the mcs2000 (and varients) with mmdvm.

    In short, enable "VRM 100 Capable" under Radio Wide -> VRM. Then on the conventional personality, VRM tab, check "VRM 100" and "VRM 100 High Speed Data". This will enable the audio path on pin 24.
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    He's using a MC2100... the fimware and RSS structure is very different from US/NA MCS2000s. That option might not be available.

    I tried to configure a GM1200E (same hardware platform but uses yet another firmware/RSS package) as an analog remote base for repeater linking once, and got so frustrated trying to navigate the stupid Euro RSS that I gave up and walked away.
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    Thanks for all your replies. I'll take them one by one.

    @Mars: I will resort to a hw mod, if there's no other option. I have a service manual so I should be able to dig down where and how to inject the signal.

    @rainbowpenguin: If I had a MCS2000 that would have been great info, I saw it earlier, but it doesn't apply to me. RSS does not give me a VRM100 option or any other data modem options - like in the GM900/GM1200 and others. I've looked everywhere in the DOS RSS (GVN6011M) and Wookie (patched version). BTW - for the GM900 the data modem option is cleverly hidden in the tuning menu, not in the usual change/create/view radio data -> radio wide menu.

    @motorola_otaku: I'm afraid this is my case

    @Astro Spectra: thanks for the info, I saw that when I was trying to use a GM900 for receive, and it's good info as it makes a GM900 usable for receive, but I have found it still not comparable to a GM350/600/950 with DC coupling mod. Unfortunately it says nothing about where to inject signal in the transmit path, as the GM900 works out of the box.

    Otherwise, I know there are several versions of the skywalker radio upgrade utility for the 2100 series. I have now R06:11:00 - march 07, 1995. Does anyone know whether there are any differences between the upgrade utilities - aka perhaps another FW version allows the use of pin 24. I foggily remember having a different upgrade utility version some time ago - before the prehistoric HDD in the ancient laptop I used for flashing died (now I have backups, of course - didn't use to, back then).

    Otherwise 2, could/should I try to make it a different radio - one that definitely works? A MCS2000, GM900 perhaps? HW wise the radio is 403-470 MHz, 10W PA. Might be easier than digging out where to inject the signal.

    Dan
    YO2LLQ

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    If you can somehow manipulate it into a MCS2000, that would be ideal. Enabling VRM100 will give you what you need.

    I helped one of my cohorts set up a couple of VRM650s for what you're trying to do last week, using the instructions rainbowpenguin posted, and they do provide true FM discriminator output. We scoped the disc out line and were able to see the injected test signal start coming up at -125 dBm... not bad for a 450-520 radio.
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