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MCS2000 Poor RX Sensitivity

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W3AXL
Posts: 108
Joined: Fri Sep 04, 2015 9:02 am
What radios do you own?: an unhealthy amount of them

MCS2000 Poor RX Sensitivity

Postby W3AXL » Wed Mar 28, 2018 9:03 am

Hi everyone,

I've been working on my base station, a HP VHF MCS2000. Over the past month or so, I noticed a few fringe repeaters started to sound much weaker than usual. After testing my antenna system to make sure everything was A-OK, I narrowed it down to the radio itself. First things first was to get the REFOSC in spec, but that didn't solve the issue. I also played with the bandpass filters without improvement as well.

I've actually found two interesting issues through my testing this morning:

1) In MCS2000 tuner, on the 146.0625 test freq, I can get 12dB SINAD at around -102dBm which is not great. With the radio in normal operation, on the same frequency, it takes until -85dBm to get 12dB, which is horrendous. So, there's obviously something changing between test mode and normal mode.

2) When closing out of tuner, just before the radio reboots, for a brief moment the test signal I'm feeding in becomes crystal clear through the radio speaker where before it was marginal and noisey. While I can't seem to figure out why, this leads me to believe these sensitivity problems are a software issue and not a hardware issue.

So I'm curious if anyone has seen either of these issues before, and how I can fix them if at all. I'm going to be doing some more testing up here today when I have the time, but for now I've got to get going.

Cheers!

User avatar
W3AXL
Posts: 108
Joined: Fri Sep 04, 2015 9:02 am
What radios do you own?: an unhealthy amount of them

Re: MCS2000 Poor RX Sensitivity

Postby W3AXL » Wed Mar 28, 2018 3:57 pm

Solution found, and an interesting one!

I opened the radio and tightened the torx screws holding the boards down. This was recommended by a p25ca member, and it actually worked to my surprise! Sensitivity went from -85dBm all the way down to -120dBm! Excellent advice that I'm filing away in my wiki.

fineshot1
Posts: 971
Joined: Wed Oct 12, 2005 5:13 am

Re: MCS2000 Poor RX Sensitivity

Postby fineshot1 » Thu Mar 29, 2018 4:58 am

Another thing i have noticed is that many older MCS2000 radios never had the 25khz, 20khz, and 12.5khz squelch adjustments aligned properly. I just went through a small pile like that and the receiver sensitivity was awful until I did them properly.
fineshot1
NJ USA


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