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When: 2/24/24 @4:30 PM Where: Five Guys, 7321 Atlas Walk Way, Gainesville, VA Who: Anyone interested in radio https://fb.me/e/6le81jZPo

Hello! First post on any forum and recently got my GMRS license too, So needless to say I'm excited to get out there! I have gotten a Kenwood radio for myself to adventure in GMRS thanks to this forum and it's been a good little unit. Now just a few days ago I was out at my states surplus sale where they sell old desktop pcs, furniture, cars ect. Well they had a Motorola APX7000 on the shelf with no battery, antenna or anything, and I bought it on its circulation sale for $500. Before I go crazy and get a battery, charger, antenna and have programmed by someone, I would like to ask if it would be a radio I can use on GMRS and repeaters. I know this kind of question gets asked a lot and I'd hate to add to that annoyance but I've done the better part of my do diligence in research but I'm still left asking. It doesn't have a front display or keypad for FPP, just the top screen like my Kenwood. I've tried to find any forum posts relating to APX on GMRS here and on other websites but I've come up short. It operates on UHF in the lower band, 380-470mhz. I mainly got it because of the price and if I can use it, then great! If not, then I can try to sell it for a profit. Win win for me. If I need to give more details then I can try my best to, otherwise let me know!

I've noticed some things that people are not looking at in relation to their mobile based repeaters. So I got bored and started playing around with Matlab and made a few graphs concerning common mobile radios that are used to build repeaters. This isn't a very extensive list as it only consists of most of the Motorola Radius line (includes Radius, Maxtrac, GM300, SM50/120, and M1225) as well as GE Custom MVP's. All of this was built off of data that is available in the service manuals. Even though I do own some Kenwood and Icom radios (I even have the data for Icom F221s and F420s that I measured off mine before my tablet crashed) I just don't have the service manuals currently. As I recover data or fix my tablet, I'll update with the F420 and F221 info for building Icom CY-420 and CY-221 repeaters. These graphs show how transmit power relates to duty cycle (something that should honestly be considered when building repeaters). Figuring out the required duty is for the owner/builder of the system to decide. The duty cycle is a percentage of a 100s time period (as stated in both GE and Motorola service manuals). The slope of the lines represents the efficiency of the transmitters, this can be used by both those building off-grid systems and for calculating heat produced. These numbers can be changed with other methods of cooling (air flow, heat sinking, etc.) but represent the environment the manufactures designed the equipment to operate in. Motorola Radius Motorola designed the 40W radio for a 15% duty cycle, which translates to 2000 kJ of heat for the chassis. Giving duty cycles as follows. The efficiencies for the different power levels are as follows: 25-40W = 23.2% 10-25W = 24.1% 1-10W = 18.1% GE Custom MVP GE designed the 35W radio for a 20% duty, which translates to 2160 kJ of heat for that chassis. The 25W and 5W radios are lacking something…the heat sink on the back of the 35W radio (it can be replicated with a P4 or similar CPU heat sink). As such there are two graphs for the 25W radio, one for a factory radio (20% duty @ 25W = 1160 kJ of heat) and one for a system with the heat sink. The efficiencies for the power levels are as follows: 21-35W = 24.5% 7-25W = 29.1% Again, all these were taken off numbers available in the service manuals.