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Analog (CLB) Station
Multi-Coded Squelch (MCS)
Written by Robin Feil W7MSE
Compiled by Robert W. Meister WA1MIK
[Editor's Note: All PL codes (4A, 8Z, etc.) used in this article are the Motorola two-character codes. A conversion table for frequency vs. code can be found here.]
A group of friends and I operate a multi-repeater GMRS group. We currently have four repeaters on the air and are expanding the coverage area. I have always used tone 1A for my operations. The leader of our group selected tone 8Z for the common tone because most of the FRS / GMRS over-the-counter radios do NOT support 8Z, so it keeps interference to a minimum on the system. Tone 4A is loosely recognized as the "national travel tone" so we thought it would be nice to have this tone available to people traveling through our area. There are a couple of other tones used on a limited basis for specific people in the group to be able to contact their wives at home without forcing the wives to listen to all of the chatter on the repeater, you know, "happy wife = happy life" :-). Most of our repeaters have regular commercial tone panels (Zetron, CSI, etc.), so 8Z is not a problem. We have a few old radios without multi-PL (MICOR, Mitrek, etc.), which becomes a problem if we don't have a common tone between the repeaters. My radios are all commercial Kenwood and Vertex units, so I don't have the problem, but some of the others are a little behind the technology curve and don't have the money to buy newer radios.
I acquired a Motorola C74CLB7106AT, which is a 110-watt, UHF tone-remote-capable repeater with built-in filter/duplexer. It has the appropriate Multi-Coded Squelch board and power supply in an expansion tray. I want to use this for a GMRS repeater. I also have an R-1801 suitcase programmer with the appropriate firmware, cables, and adapters and plenty of EPROMs.
[Editor's Note: The MCS board has its own microprocessor and EEPROM to hold the code plug data. It performs its own audio filtering, tone detection, and generation. It can recognize and respond to several dozen unique frequencies and/or DPL codes. When this option is specified during programming, the station's internal PL/DPL functionality is disabled for repeater operation. The MCS board for the RSS-programmed stations is an entirely different unit and it gets its programming information from the station's code plug during the power-on self-tests.]
The suitcase programmer manual and the CLB Programming Sheet follow the same prompt order. Refer to those documents to see the various options, parameters, and choices.
Let Us Program (and Pray):
The best way to start is by entering the model number C74CLB7106AT and options (C0369 MCS and C0787 PL 8Z). By doing it this way, the R-1801 will default to MCS Enabled for channel 1 and put all of the other settings at reasonable defaults, except TX and RX frequencies, which are defaulted to 000000.00 kHz (not much use; I have a very good DC power supply on the bench for that particular frequency).
[Editor's Note: Even though option C0787 was specified, the MCS board is just incapable of decoding the following PL codes: 69.3 (WZ), 97.4 (ZB), 206.5 (8Z), and 229.1 (9Z). This is a hardware restriction on the older MCS option and although it doesn't make sense, there's no way to get around it. Even though there are four options specifically for those PL codes, they are ignored if you are using the C0369 MCS board. Although there is no option for it, PL code 254.1 (0Z, that's zero-Z) is not allowed by the MCS board either.]
Following the various prompts in the R-1801 programmer, I then:
All other parameters were left at default values. I burned the EPROM, installed it and powered up the station and all worked as expected except the 8Z PL tone would not activate the repeater.
I had programmed the MCS EEPROM before for PL 4A (141.3) and that worked as advertised. I got Decode and Encode lights on the MCS board and the station repeated properly with proper audio and tone. The CW ID also worked correctly.
Next I read the station's code plug with the serial cable connected to the programming jack on the MCS option board and the repeater Knocked Down to speed things up. I then went to the MCS code plug programming and added tone 1A (103.5) and tried to add 8Z (206.5). 1A TX and RX enabled worked fine but 8Z gave an "Illegal Entry" message. Well, 2 out of 3 ain't bad :-). I programmed the MCS EEPROM with the serial connection and tested the results. The short answer is that both 1A and 4A worked fine but I still couldn't get 8Z to work at all. (This change was due to my specific desire/need to use tone 8Z in my application along with 1A and 4A in the MCS. The tone really had no effect on getting the station to operate correctly.)
Now on to the tone remote stuff. I haven't had time to read the EPROM for the tone remote control board so I just went with a leap of faith and gave it a try with the service monitor generating the tone remote commands. Here is what I found:
The card is set up for two-wire control. Any PL that activates the repeater will pass RX audio down the line to the remote. With a 1950 Hz control tone, the repeater will key up with the PL tone that is programmed in the station EPROM, in my case right now 8Z, and pass remote audio to the transmitter just like any good tone remote should. I will have to look into the programming functions for the tone remote control to see if there is any way to get the RX audio to only un-mute with a specific PL tone. I really don't think this is possible but you never know.
[Editor's Note: Remote control for an MSF5000 is normally only used with base stations. Repeaters (at least in the amateur world) need on/off control, but they don't normally deal with audio on the remote wires. Wire line remote control comes in two flavors: DC (using various currents of both polarities) and tone (sometimes called high-level guard tone). The CLB station has one board for each flavor and only one can be installed in any station. The RSS-programmed stations use one board that, if present, can handle either tone or DC.]
The station appears to ignore the code plug programming as far as PL is concerned in repeater operation. All repeater operations rely on the programming in the MCS module. I will have to unplug the MCS board and give it a try that way. The only other thing I noticed with the default programming is that the repeater activation and hold seems to require the A (auxiliary) option set. I will have to investigate this further.
Right now, the station is in this condition:
It works normally with tones 1A and 4A from the MCS option board... Life is good :-)
It does NOT work with tone 8Z from the station EPROM... Life isn't so good :-(
I will have to do some more playing to confirm the operation of the station and the interaction of all of the various programming variables. I was hoping that the station EPROM values would work as the default tone pair. We would like to use tone 8Z (206.5) but the MCS documentation clearly states that tone is NOT supported. The station WILL support it although Motorola does not recommend using any of the higher tones due to the roll-off of the Low Pass Filters. I also don't know what the operating parameters will be for tone remote operation. I really only want the tone remote to respond to the 1A PL and the station to transmit the 1A PL when keyed by the tone remote. Hopefully this will be the operation if the station EPROM is loaded with this tone.
[Editor's Note: It seems that the MCS board is only used by the repeater, i.e. it decodes the coded squelch on received signals and properly encodes the transmitted signal. The coded squelch functionality programmed into the main Station Control Board (SCB) is only used when local or remote control transmit or receive is in use, i.e. when the station is used as a base station.]
Acknowledgements and Credits:
Motorola, MSF5000, R1800, R1801, MCS, PL, and a bunch of other terms are trademarks of Motorola, Inc.
The submitter can be contacted at: rdfeil [ at ] aol [ dot ] com.
The writer can be contacted at: his-callsign [ at ] comcast [ dot ] net.
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This page originally posted on Thursday 09-Dec-2010
Article text © Copyright 2010 by Robin Feil W7MSE.
Artistic layout and hand-coded HTML © Copyright 2010 by Robert W. Meister WA1MIK.
This web page, this web site, the information presented in and on its pages and in these modifications and conversions is © Copyrighted 1995 and (date of last update) by Kevin Custer W3KKC and multiple originating authors. All Rights Reserved, including that of paper and web publication elsewhere.