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  Configuring and Activating
Motorola Spectra MPL

By Robert W. Meister WA1MIK
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The Multiple Coded Squelch (also known as Multiple PL or MPL) functionality is available on some Spectra radios. It seems to be a function of the firmware version (in the MLM or the command board) or the radio model itself (A3 or HHCH radios do not have any provision for an MPL button on the control head). I have heard that you need at least firmware version 5.00 for MPL support. Note that MPL is only available on conventional modes. I tested all the Spectra radios in my possession for MPL support:

900 MHzD37KGA5JB7FK 6.06YES
900 MHzL37KGM5174AM 6.15YES
900 MHzD37KGA5JE7AK 8.12YES

MPL configuration is done with the Spectra radio service software. The various MPL parameters are entered in a list; then each individual mode must have the feature enabled. Finally, a control head button must be assigned to activate MPL. All of these changes are written to the radio's code plug using standard procedures. A couple of steps are necessary to actually make use of MPL when operating the radio. All of this will be explained below.

All function key sequences are shown in parentheses and are the keys you'd need to press to get to the appropriate function from the main menu.

Radio Code Plug Configuration:

There are several tasks that must be performed:

  1. Decide how many MPL entries you want (1-16).
  2. Fill in the MPL entries in the list.
  3. Configure each mode to allow MPL for receive, transmit, both, or neither.
  4. Enable one of several possible control head buttons to activate MPL.

Begin by reading the code plug, either from the radio (F3, F2) or from an archive file (F3, F3, choose desired entry).

Step 1:
From the main menu, choose Change/Create/View Codeplug Data, then Conventional Configuration (F4, F3). Tab down to the "Number of MPL" field; it will show "Disabled" or a two-digit count of entries in the MPL list. Use the Up/Dn arrow keys to increase or decrease this field. If it will NOT change, then your radio is NOT capable of MPL and you can go no further. In the following image I've set the radio to allow two MPL entries:

Step 2:
From the main menu, choose Change/Create/View Codeplug Data, then Conventional Configuration, then MPL List (F4, F3, F6 or just press F6 from the current screen). Here you can enter a displayable name for this combination, then you can select the receive, transmit, and talk-around coded squelch options: Carrier (no PL/DPL), TPL (tone PL), DPL (digital PL), or DPL-INV (digital PL inverted) using the Up/Dn arrow keys. If you select anything except carrier squelch, you must enter the PL or DPL code. The MPL modes fill in the same as the regular modes and the same function keys let you navigate through the list. Here's what the screen looks like for a blank entry:

I've filled in the first MPL mode, shown below:

Step 3:
You now have to tell each mode how or if you want it to use MPL. You can choose receive only, transmit only, both, or disabled. To get to this screen, from the main menu, choose Change/Create/View Codeplug Data, then Mode Configuration, then Mode Opt 1 (F4, F5, F7). Tab to the MPL Type field and use the Up/Dn arrow keys to make your choice. Use the normal mode navigation fields to scroll through all the modes that you want to be able to have MPL activated. Here's what the screen looks like after changing that field to allow MPL on both receive and transmit:

Step 4:
You still need to tell the radio which button to use for MPL. The left-most button above the display is the one recommended by Motorola. There are six programmable buttons available on an A9 control head, but only four buttons directly over the display window on the A2/A5/A7 heads may be configured for MPL, since these are the only ones with indicators under them. The button labeled SEL may not be reconfigured or assigned.

Ideally, you should obtain a button with the MPL legend and install it in your control head, but at about $2 per button, most people don't bother and use whatever is already there. The Motorola part number for the MPL button supposedly is 3805672X02.

From the main menu, go to the Control Head Keypad Button Configuration screen (F4, F9, F1). Tab around until you reach the desired button, then scroll through the available choices using the Up/Dn arrow keys. Stop when you see MPL. Here's a screen shot with a button configured for MPL:

Remember to write the code plug to the radio (F3, F8, F8) as well as save it to the archive file (F3, F7) before exiting the program.

Use and Operation:

MPL is activated and the desired parameters chosen with standard Spectra control head user action. Press the control head button assigned to MPL; an indicator under the button will turn on. This indicator is either a small green arrow in the eight-character display on A2/A5/A7 control heads, or an LED under the button on A9 control heads. The last selected value is momentarily displayed. That MPL value is now active on that mode.

To choose a different MPL selection, hold the MPL button down until a beep is heard and the indicator flashes, then use the MODE rocker or knob to scroll through the available MPL modes. (Alternatively, you can use the keypad on A7 and A9 control heads to directly enter the MPL mode number if you know it.) Press the HOME button to accept the currently displayed selection and return the radio to normal operation. That MPL mode selection will remain active on that radio mode until you turn it off. You can choose a different MPL entry on each of the radio's modes; the radio will remember each one and the indicator under the MPL button will be lit on each mode that is configured to use MPL.

To de-activate the MPL mode, press the MPL button again. The indicator under the button will go off and the radio will return to normal operation using the coded squelch values associated with the mode in use.

Acknowledgements and Credits:

Configuration information came from examination of the various programming screens from version R06.00.05 and from the Spectra Mobile Radio Service Software User's Manual, 6880101W48-K.

Usage information came from the Spectra Conventional Radio System Operating Instructions manual, 6881071C55.

Spectra, PL, DPL, MPL, RSS, and probably a bunch of other terms are trademarks and/or copyrighted by Motorola, Inc.

Contact Information:

The author can be contacted at: his-callsign [ at ] comcast [ dot ] net.

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This page originally posted 26-Nov-07.

Article text, photographs, and hand-coded HTML © Copyright 2007 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.