dspurg7310

Looks like I'm late to the party on this particular thread, but for anyone who may need info about this topic, This absolutely can be done. For a repeater, you can program one radio with an analog conventional RX channel (upper frequency for the GMRS pair) and the other radio for the lower TX channel. In the CPS (Customer Programming Software) under General > Accessories, scroll down to the 'GPIO Physical Pins' section (this correlates to the accessory connector on the back of the radio). You need to assign a pin to be 'Ext Mic PTT' (on transmit radio), and another to be 'PL/Talkgroup Detect' (receive radio) - which is the same as COR label on other radios. I usually do GPIO 1 as PTT and GPIO 2 as Detect. This will make PTT physical pin #17 & Detect physical pin #19 on the back of the radio. Active level low and no debounce. You will need Motorola accessory connector (part #: PMLN5072A) for each radio. Crimp pins on wires (22 awg is fine) and insert into the following pin locations on the connectors; RX Pins [14, 16, 19], TX Pins [11, 16, 17]. If you are connecting each radio to a controller, you may want to use all 5 pins below on each radio depending on what functions you would like to controller to be able to do. TX Radio Side: 11 - Mic/Audio In [this connects to receive radio's pin 14] 14 - RX Audio Out [not used on TX side for 1-way repeater] 16 - Ground [connects to receive radio's pin 16] 17 - PTT (Program GPIO 1) [connects to receive radio's pin 19] 19 - PL/Talkgroup Detect (Program GPIO 2) [not used on TX side for 1-way repeater] To connect the radios and use them like a repeater, you will need to order some accessory connectors (Motorola part# PMLN5072A) to build a cross-over cable to allow the receiving radio to key up the transmitting radio. You can accomplish this with a single cable connected between the radios, unless you have a separate repeater controller you would like to use to add additional features like DTMF, time announcements, CWID, etc. Note that if you are using this 'repeater' on GMRS channels, if you are not regularly identifying your callsign yourself, you will need a controller to do it for you. Most controllers will identify your callsign with morse code, some will also air voice. Even if someone else is talking on your repeater and you are not part of that conversation and not transmitting, your repeater is still being used under your license, and therefore is required periodically identify with your license. There are many simple controllers available on the market that are made just for airing identification (the IDoMatic has been mentioned a few times already), so I would recommend to at the least get one of those ID controllers and work it into your cable interface if you just plan on connecting two mobiles together with no other advanced controller - so you stay legal. Depending on if you use a controller and what controller you use, the custom cables you will have to build will differ. Another programming feature you will need is Wideband, since you will be using it for GMRS. The radios come with the ability to program as wideband, but because of the narrowband mandate, you don't automatically get that feature. You will actually need to go through the "training" from Motorola (to cover their butts in case you use wideband on frequencies you're not supposed to), then you actually have to purchase the wideband feature for your programming software only. Once purchased and activated in the software, your software will be able to program wideband on any Mototrbo radio. Again, you only need the wideband feature license for the software on the computer you intend to use and NOT for each radio. If you don't have a Motorola account and access to MyView, etc. this will be harder to accomplish and you'll want to talk to an authorized Motorola partner who can help you purchase and activate the feature. These are great radios and I use the XPR series often on both GMRS and analog/digital business frequencies; 4550, 5350, 5550, 7550. I own my own licensed digital & analog business systems and GMRS systems. I also have a Motorola account to access CPS, firmware, etc. One of the issues you might run into with used radios is that the codeplugs could be password protected and you may not know that password, so you can not read/program the radio. In this case, you will need to use the same or slightly later firmware version package to 'Recover' the radio in the CPS. This will delete the whole current codeplug in the radio, and load the firmware back to the radio with a blank, factory codeplug, so you will not be able to copy any of the current data/channels, etc. that were on the radio before you started, but it will re-flash the radio with a blank codeplug allowing you to program it and start over. The latest firmware for the 4550 is version 1.12.17. If you need to rackmount your mobile repeater, there is a great company out of Canada called Alberta Radio Supply who makes 19" mounting plates in a variety of different configurations. You could get one that will allow you to mount two 4550's side-by-side. They also have some that will mount power supplies, scanners and other makes/models of two-way radios. They also sell on ebay (where I got mine).