900mhz MCS2000 receive sensitivity issue

This forum is for the discussions targeted at converting various models of Motorola equipment to operate in the 900MHz Amateur Band.

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900mhz MCS2000 receive sensitivity issue

Post by n3hfk »

After a long and successful run using analog Motorola spectras on 900mhz and UHF in my vehicle, I decided to modernize to MCS2000s upon getting a new vehicle. Due to space constaints, I selected model-1 radios and picked up a couple that appear to be ~2002 vintage. Thus far, I have spent most of my time working with the 900mhz MCS2000. After programming and carefully aligning the radio, I was suprised to find that the sensitivity was 5 to 6 db worse than my trusty Spectra. Thinking there was a problem with the radio, I checked T/R diodes and the front-end pre-amp and everything seemed OK. I replaced those devices for good luck with no improvement.

Recently, I have tested several similar-vintage model-1 900mhz MCS2000s with the same result. I have a friend who has a ~1998 vintage model-3 900mhz MCS2000 and that one had considerably better sensitivity, analagous to my trusty Spectra. It appears from the service manual that all the RF design is the same between model-1,2,3 radios. I'm wondering if perhaps there was some type of design change between 1998 and 2002?

Anyone had similar observations or any idea on what I'm experiencing? I know Spectras pretty well but am just getting familiar with MCS2000s.

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Re: 900mhz MCS2000 receive sensitivity issue

Post by Max-trac »

They do seem not quite as hot. But usually the squelch is too tight.
Set squelch with the tuner, usually the factory is too tight.
Set each channel for "standard", unmuting, that way it will receive wide open squelch and PL/DPL will unmute.
Uncheck the HUB defeats PL in the conventional/general tab, that way when you go off-hook, the squelch won't get tight.
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What radios do you own?: APX XTS XTL TRBO 900MHZ

Re: 900mhz MCS2000 receive sensitivity issue

Post by N4KVE »

Are they less sensitive at 927 mhz than 935-941, or the same everywhere? I have a 1999, & 2001 radio, type 3, & they are both hotter than a pistol, 927-941. GARY
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What radios do you own?: Syntor X9000, Spectras, EFJ...

Re: 900mhz MCS2000 receive sensitivity issue

Post by syntor9k »

Nothing like responding to a 4 year old message, right...

Anyway, I too have MCS2000, it has slightly more poor sensitivity on ~927 (0.45uV) and was also tested on ~935 MHz were its better, but still just about 0.40uV witch is as specified.

Anyone find a fix? If the early radios were better, there is likely a part change (do to NLA parts, this is common) or a wrong (mis-stuffed) part.
I cant find a service manual, so its kinda hard to fix or guess the problem...
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