• Motorola Gr1225 Repeater Manual Transfer Switch
• Motorola Gr1225

Motorola Gr1225 Repeater User Manual - The Joint Boulder GR1225 prevents transmissions over your repeater with-out proper ID or “squelch codes”. Power is adjustable by channel Each channel can be programmed to a different power level, either 1-10W or 25-45W (UHF) and 1-10W or 25-50W (VHF) to meet your coverage needs. Motorola Gr1225 Repeater User Manual Motorola Gr1225 Repeater User Manual - The Joint Boulder GR1225 prevents transmissions over your repeater with-out proper ID or “squelch codes”. Power is adjustable by channel Each channel can be programmed to a different power level, either 1-10W or 25-45W (UHF) and 1-10W or 25-50W (VHF) to meet your.

Set the repeater on about 10 watts and use them for an exciter and they will last a very long time.(your going to put a pa on them anyway)you can pick just the r1225 (not the power supply are the rack) for around $600.00 to $700.00 and the Kenwood TKR750 is around $1500.00 and it to is not 100% duty cycle (but is a good repeater just a lot more. Gr1225 Repeater User Manual - thepopculturecompany.com This is a Motorola GR1225 UHF repeater, model number M44GRC90C2AA. These are 40 watt, 16 channel repeaters with a band split of 446-470 Mhz. Repeater comes mounted in a GR500 housing which provides continuous duty cycle (100%) and comes complete with internal duplexer. Using the GR1225 or GM300 with an IRLP repeater By Don L. Blanchard, WA7GTU. Note that the same software package (HVN9054 V4.0 CPS, runs on W3.1, 95, 98 and XP) is used to program the P1225 handheld, the M1225 mobile, the R1225 repeater, the GR1225 repeater and the RKR1225 repeater.

Note from the editor:

The R1225 is a continuous duty radio (about the size of a MaxTrac) that has two antenna connectors and will work in full duplex mode, and 25w continuous duty at that! The GR1225 is that radio in a box with a power supply plus two options: a duplexer and an advanced controller (the sales brochure is here). The GR1225 was designed to be the continuous duty model in the the GR300 / 400 / 500 line of prepackaged repeaters, all of which were intended for low-duty-cycle full duplex applications like a shopping mall security department repeater, or other low-end non-public-safety repeating applications. The GR1225 configuration parameters allow it to be programmed as a repeater or as a non-repeating full duplex radio and that, coupled with the continuous duty design makes it ideal as a point to point link, and much better than a Maxtrac or GM300 mobile, neither of which can duplex, or run continouous duty. The R1225 / GR1225 also has a fairly decent internal controller where the GR300 / 400 / 500 series required the RICK box to do that. The optional advanced controller could be one of four, and an autopatch was available (see the sales brochure link above).

The Internet Repeater Linking Project is a worldwide informal group of amateur radio repeaters that are linked using VoIP (Voice over Internet Protocol) systems. More information on IRLP is available at http://www.irlp.net. Each repeater in the IRLP network is connected to the internet through a PC running the IRLP system program, with runs on the Linux operating system. The computer is treated as if it was a link radio, with audio in, audio out (via the sound card), COR and PTT (via pins in the printer port). The IRLP interface board that plugs into the printer port has the necessary interfacing circuitry, including a hardware touchtone decoder. The board can be jumpered for simplex or full duplex operation, and if you have a full duplex environment you really want to set the jumper to match. A 'Node' in the IRLP system is one computer and repeater system.

The ideal IRLP situation is where you have an internet connection at the repeater site and can connect the node computer to the repeater controller directly (as if it was a second radio). Since very few repeater sites have an internet connection many connections use the second-best option: a point-to-point radio link (on UHF, 900 MHz or 1200 MHz link frequencies) between the repeater site and a location where the node computer and internet connection is actually located. Others use the third-best option: they set up the node computer and radio as if it was just another user on the repeater.

This article describes how WA7GTU set up a Motorola GR1225 radio as a local repeater, with an IRLP node connected to it. The same GR1225 if programmed differently could also function as a 'ground level' end of a point-to-point link, i.e. set up as a non-repeating full duplex base station.

There are pages at this web site that cover the RSS and RIB in detail.

IRLP Node 3574, located in Cedar City, Utah has been operating with a Motorola Radius GR1125 Repeater on the 444.900 ‑ 449.900 MHz frequency pair for a couple of years. There have been a number of inquiries as to how it was interfaced with requests to make the information available on the Internet. The following document is an attempt to answer those inquiries. It is believed that the mobile GM300 is basically the same radio and the following information should apply to both models, however the GR1225 will run full duplex, whereas the GM300 is a 'normal' PTT radio.

There are several models of the GR1225, and the product line includes models that cover both the 146 to 174 MHz and 444 to 474 MHz frequency ranges with differing power levels. The 146-174 models can be 'stretched' down to 145 MHz, and the 444-474 models can be stretched to 440 MHz.

The first thing that you need to know is that the GR1225 has to be programmed using the appropriate Motorola RSS software, so you either need to know someone with the hardware/software or have good rapport with your local Motorola dealer. The hardware/software is of fairly old vintage and hopefully it is still available in your area. The radio programming software is DOS based and will not even work on today's faster computers. The programming is done through the microphone plug with a computer interface called a RIB. There are diagrams of these interfaces on the Internet, but getting the software is a problem. Please see the RSS page in the Motorola section at this web site for details. The second thing that you need to know is that the 450 MHz version of the GR1225 will program no lower than 444.000 MHz without modification. The 3574 node repeater is operating within this frequency range, so no attempt was made to look into what modification would be required to go lower in frequency, but it probably can be done.

The GR1225 is a small self contained repeater (see photo below) that can be programmed to 16 different frequencies. The 3574 node repeater is also programmed to a second frequency of 444.500 - 449.500 MHz which is another frequency pair coordinated for this area. The built in duplexer handles this second frequency reasonably well with very little degradation, but this frequency is only there as a backup and adding it to the programming took less than a minute. The repeater operates from a built in switching power supply and there is a fan integrated into the housing for cooling. It often operates for hours at a time and there have had no temperature problems. The fan is temperature controlled and does not come on very often. The model in operation is a 10 watts version. The author also has an older 25 watt version as a spare, but has not yet tried it on IRLP. It is all programmed, but some of the connections on the Accessory Connector need to be rewired.

Below is a reproduced page from the GR1225 Service Manual explaining a bit about the available connections in the accessory connector on the rear of the radio. The fuctions of a number of the pins are programmable.

As mentioned above, a number of the accessory plug pins can be programmed for various functions. Several are electrically bidirectional but are programmed as either in or out. The manual says that Pin #8 defaults to COR, but on mine it was not, so that function had to be programmed in addition to the operating frequencies, PL, timeout timer, and identifier parameters (callsign and 10 minute spacing). The repeater also came with an existing interconnect cable and all that was required was to move two of the pins in the accessory plug and put the connectors required to interface with the IRLP board on the other end. See the Expanded Accessory Chart below.

The table below is from section four of the June, 1997 version of the R1225 manual, part number 6880905Z53-O.

The call sign identifier for IRLP can be programmed via software in the IRLP box, but this wasn't adequately researched prior to getting the radio programmed, so for node 3574 it is programmed into the radio itself. There is one inherent problem with using the built in radio identifier and that is if the repeater is keyed up before the identifier completes its cycle, it will start over again when the repeater is un-keyed. This is usually not a problem locally, but it is a problem when it is connected to a reflector and there is not a sufficient pause between transmissions for the identifier to drop out. Programming the call for higher speed helps in this case. There is also a programmable transmitter timeout timer which is currently set to 3 minutes and it gets timed out on occasion. A little longer time period might be preferable.

In my system the GR1225 Carrier Delay set to Off. This means that if you 'key up' you will not get a response back unless the identifier comes on. Our PL is set to 100 Hz. The use of PL on IRLP is HIGHLY recommended.

Just remember that if you need to make any changes to the configuration of the radio (i.e. the programming), it means another trip back to whomever has the RIB (the programming hardware) and the Radio Service Software (RSS), so try to get it right the first time. The author has a good relationship with the local Motorola dealer and was fortunate enough to wind up with a complete set of service manuals for the GR1225, but does not have the required software, progamming box or cable for programming the radio. If you end up with a GR1225 the two manuals that you will need are 6880905Z53 (the R1225 radio) and 6880904Z90 (the GR1225 cabinet, power supply, etc). The Radio Service Software has its own manual.

The figure below illustrates how the GR1225 repeater is interconnected to the Version 3.0 IRLP Board. Note that the IRLP board has its own DTMF decoder and the audio feed from the radio goes to both the computer LINE IN connection and also to the IRLP board pin 8.

A final note, please do not request copies of the Service Manuals from the author. Many of the schematics are very large and with both books the stack is about 3/4 of an inch thick. Pretty much all of what you need to know is in the information above.

Don L. Blanchard - WA7GTU - Nov. 2006

Three notes from WA6ILQ on the GR1225 units:

Motorola Gr1225 Repeater Manual Transfer Switch

1. The R1225 is a 16 channel radio. Adding the local 'test pair' to the channel list takes an extra minute as you are programming it, and depending on your circumstances might be a good idea.
   
2. The stock GR1225 power supply is the HPN90333A and is made by Duracomm. It is a switching supply and weighs about six pounds. The output is 13.8 volts at 15 amps continuous and 17 amps intermittent duty. The optional HLN9455A Battery Revert Kit adds a power fail/switchover/battery charger module that connects a user-supplied sealed battery to the unit, keeps it charged, and switches to it during a power failure. Don't bother buying one, just get the schematic for it and build it yourself.
   
3. One of the options in a GR1225 is an internal duplexer (part number RFE4000A, made by Celwave as their part number 633-2A-2N). It is a notch-only duplexer.The HKN9235 Internal Duplexer Cable Kit (about $40 from Motorola Parts) consists of two cables that have N-type male connectors on the duplexer end and mini-UHF male connectors on the radio end. The cables that Moto supplies are not fabricated to meet any technical requirement (i.e. length), they are simply made long enough to fit with only a little slack.
   The cheap plain-jane RG-58/U cable used in the HKN9235 Internal Duplexer Cable Kit causes some serious desense - more than 2 dB, in fact. RG-58/U coax is just too leaky to be used for duplexer jumper cables of any type.
   If you are ordering a GR1225, forget the duplexer. Pick one up off of eBay and make up your own cables, using only double-shielded RG-400/U cable, and install the correct silver-plated connectors on each end - and without any adapters.

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This page originally posted on 21-Nov-2006

Photos and article text text © Copyright November 2006 by Don L. Blanchard, WA7GTU
Artistic layout and hand-coded HTML © Copyright 2006 and date of last update by Mike Morris WA6ILQ.

Motorola Gr1225

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.