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  How to Determine the Range or Split of your Spectra Radio
By Mike Morris WA6ILQ
Photos are courtesy of Bob Meister WA1MIK
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The Motorola Spectra series were made in several frequency bandsplits, called ranges, or splits. You can't figure out what you have unless you read the radio, or lift the cover and look at a frequency-determining part. And sometimes when you read a new-to-you radio, it lies, because someone forced a wrong-range code plug into it. Or maybe someone sold you a Frankenstein radio (i.e. built from spare parts).

The quickest way to determine what you have is to look at the receiver preselector, usually called the front end or RXFE.

Let's start with the basic radio, with the top cover off. A mid power radio package is on the left in the photo below (the low power package is the same except for a shorter heat sink), and a high power radio is on the right. The particular mid power radio in the photo happens to be a front mount version, with an integrated control head; all high power radios were remote mount (trunk mount).
The silver rectangle with the black stripe on the right side of the radio is a shield cover over the front end. The black stripe is a plastic handle that is used to remove the cover. Remove the four T15 screws in the corners, slide your finger under the handle and pull it straight up and off.

The assembly number sticker could be located on the top or bottom of the module; it's wherever Motorola found the room to place it. Some radios have the sticker on the top of the front end module (on this UHF radio it's marked HRE6003A). If you look that number up in the tables below, you will find that the number translates to a 450-482 MHz non-preamp front end. Now you know the frequency range of the front end (and hopefully your entire radio; no guarantees here).

This photo of a VHF front end shows the sticker on the bottom of the module. You will need to unplug the input coax from the rear of the module, then you will find a push-in cable protruding out of the underside of the board which also has to be unplugged. Be careful as you remove or reinsert the module and its cables.

The 800 and 900 MHz front ends are identical except for the ceramic filter. This 900 MHz front end has the label on the top.

Below is a list of the VHF and UHF ranges that we know of. All front end part numbers have a letter suffix indicating the revision: A, B, C, etc.

VHF Splits
Board Range Frequency Range Non-Preamp With Preamp
1 136-162 MHz HRD6001 HRD6011
2 146-174 MHz HRD6002 HRD6012

UHF Splits
Board Range Frequency Range Non-Preamp With Preamp
1 403-433 MHz HRE6001 HRE6011
2 438-470 MHz HRE6002 HRE6012
3 450-482 MHz HRE6003 HRE6013
4 482-512 MHz HRE6004 HRE6014
There were a large number of radios made in the so-called "Range 3-and-a-half" that cover 453-488 MHz. The non-preamp front end part number for that range is HRE6003BSP01, if the pattern seen in the rest of the tables holds true the preamp version would be HRE6013BSP01.
There were also some radios made for the 512-520 MHz range.
If anyone has the part numbers of any additional front end modules I'd be happy to add them.

The 800 MHz radios came in one split that covered 851-869 MHz. The front end is part number HRF6004 and there was no preamp option.

The 900 MHz radios came in one split that covered 935-941 MHz. The front end is part number HRF6003 and there was no preamp option.

Acknowledgements and Credits:

The front end assembly numbers came from a Spectra manual. The HRE6003BSP01 part number was provided by a city two-way tech, and he reports that despite the "SP" part number this unit is not rare - his entire city police department fleet uses Astro-Spectra radios in that range (and the Spectra and Astro Spectra radios RF sections are very very similar).

Contact Information:

The author can be contacted at: his-callsign // at // repeater-builder // dot // com.

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This page originally posted on 29-Jul-2009

Article text, artistic layout and hand-coded HTML © Copyright 2009 and date of last update by Mike Morris WA6ILQ.
All photographs © Copyright 2009 by Robert 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.