Radioguy7268

Search up the Rodinia 2.3 chip used on some EVX & XPR Gen2 radios. That is a 12dB SiNaD reading I'm quoting for that -120 dBm - and it's easily achieved with those Rodinia receivers. Fully quiet at -120 dBm. I'll agree that real world factors play into this stuff. Noise floor is the killer in most urban environments. There's a ton of trash and hash out there in the real world. Nobody is designing a commercial system around the theoretical basement level of what receivers can do. Previous forum discussion on Receiver design

Yeah - the -120 dBm of the assumed average receiver is the true limiting factor. Google up EME (earth moon earth) contests - people using the moon to bounce/reflect signals. I've heard of people making it with 2 watts or less, but they're jacking up the receivers with all types of high end pre-amps and using CW. Voice would be problematic. There are real world receivers out there in UHF radios (Think DMR Digital Vertex EVX & Moto XPR's) that will go down to -125 without spending too much money (and still have decent selectivity). Those radio on a chip direct conversion receivers all the CCR folks love have some wild receive sensitivity, but they're also about as selective as a drunken politician spending someone else's tax dollars. The original Apollo comm's with the moon were all UHF with Yagi antennas. People still heard "One giant step for mankind" although how clear it was is debatable. Then again, those Flat Earther's would point to the limitations of UHF radio signals as proof that the landing did not take place on the actual moon. AI makes my eyes hurt.

I read about the rash of robberies happening to GMRS users, so I started using FRS instead. /s

Glass mount antennas suck for UHF. They are marginally better than using a portable inside a vehicle, and I do mean marginally. 800 & 900 MHz work better, but still not ideal. I'd tell you to look for other options before spending money on a glass mount. A 6" UHF hatpin can be mounted in plenty of locations where it's barely noticed. Shark fin antennas made by Stico & others mimic factory FM antennas for the entertainment radio.

I've got a concrete ready-mix company in the Mid Atlantic area with over 100 trucks using M1225 and PM400 radios in their fleet. They've been a customer since 1998, and they're still using some of the original radios that we sold to them. They go through palm mics & external speakers (which get clogged with concrete dust) but the radios sit in trucks that are parked outside all the time. They see temps from Zero to 90 every year. They get about as much use and abuse as any radio I've ever seen, and the M1225/PM400's are nearly bulletproof in my experience. The M1225 is Part 95 type accepted. The PM400 is not, but is just the updated version. Either one can be bought used all day long for prices similar to any of the CCR models listed above. Many sellers will program them for you.

There are 2 different radios being discussed here: The M1225 LS model was built by Motorola as a UHF Trunking radio that had the ability to program conventional channels in addition to LTR (Logic Trunked Radio) channels. There was no add-on board in that radio. The standard M1225 UHF mobile radio only did conventional channels out of the box. You could use an add-on Option Board (most made by Scholer-Johnson, but sold by others) to add LTR Trunking capability to the standard M1225. Removing the board (or just disconnecting the flex cable to the LTR board) would revert the radio back to conventional mode. The Scholer Johnson add-on board would be in the top left rear of the radio under the housing & secured with 3 nylon screws.

You would need to download and use RDAC (Remote Diagnostic and Control) program in order to see the internal repeater logs. The "logging" in CPS is software validation - nothing to do with operations. It just logs changes in the software & read/write operations. If you programmed the unit with CPS 2.0 & it was originally set up using CPS 16, you probably should have updated the repeater firmware prior to 'upgrading' to CPS 2.0 Assuming you read & saved the original log - go in and look at the Codeplug & Firmware info on the original codeplug, as well as the 'last programmed' date (which should be the last time it was set up prior to you touching it.) If you've got really old firmware in the box, that may be causing you some of your issues. A basic GMRS repeater does not need half the functions available in DMR. Keep it simple. Just add a new analog channel, then delete any previous channels, and program that new Analog channel with your basic channel info. Leave CWID and any other settings off for now. I'd be a little concerned if you had to 'blow the dust off' of a unit. That makes me think the machine was in use for a while without ever being touched or upgraded. The XPR's are a fine set & forget machine in typical single user campus type applications. They're not a high end repeater designed for mountain top use at RF dense locations for 24/7 operation. They are really just 2 basic XPR mobiles in a box with some special interfacing.

SMR's were the original business band analog trunking systems in the 1980's. You probably need to do a deep dive if you plan to try to build out something using 800/900 MHz freq's. Most of those original SMR's were bought out by Nextel (which implemented a digital cellular-like technology known as iDEN, and operated under an FCC waiver as an eSMR - enhanced SMR). Almost all of those old SMR freq's now belong to Tmobile. There's some limited Licensing opportunities in 800 MHz for smaller businesses, but it's a pretty steep learning curve to figure out what's available in your area, and what it might cost you to get up and running.

Nothing stops an individual from being in the 'wireless' business, and renting repeater airtime (or even airtime without a repeater!) to Part 90 eligibles (which is pretty much anybody except the Federal Government). You don't need to open your books, you don't need to claim a profit, and you don't need to prove much of anything to anyone, other than proving you can pay the Licensing and Coordination fees up front. Although, you would need to file a Construction Notice and certify that you're up and operating on the frequency(s) within a year of the License grant.

I was coming into this & expecting to tell you to use the LS version software, but seems you've already got that. Makes me wonder if the radios are actually standard M1225's with an LS housing snapped on ? Can you compare the model number to the radio that does read/write? I've also heard of some folks snipping the mic jack leads to keep people from messing around with 'their' programming. Take a minute or two and check that out if you bought the setup already programmed by someone else. You should also check the mic jack connection to make sure they are clean and not corroded. If the repeater was sitting without a palm mic plugged in the jack, it's possible that it's just dirty and not making a good connection.

I should also mention that if you have really old XPR8300 firmware, setting up your channel in Dynamic Mixed Mode will NOT allow for CWID to go out at all via the repeater. Set up a single channel as analog only - remove/delete any DMM channel, and CWID should work. If you plan to use it for GMRS, you probably shouldn't be using mixed mode. If you truly want to use DMM, you shouldn't be using a first generation XPR8300. Those had limited feature sets and limited memory. The later XPR8400 was the improved version.

Those settings will work, but you need to have the unit set as a repeater. If you use an external controller, you're probably setting it up as a Base, and allowing for external control of the repeat function. I'd strip PL for CWID transmit.

Motorola also makes the DLR version of 900 MHz license free radios. You may find some newer ones sold under the 'curve' designation. DTR's are expensive for what they are. Even the older DTR650 radios still carry a price tag when sold as used, working units. What's your budget? There are also some folks using older Nextel units on just the "direct talk" feature - and they're usually cheap since they no longer work with any cellular providers. Look for something like an i355, but realize there is zero support and zero cross-communication with anything outside of another Nextel unit.

The transmit light should come on. That's normal operation for a repeater that's being keyed with a hand mic. If you have a receiver (portable) listening on the 462.675 - then put it in Monitor (disable the PL tone). If your repeater is transmitting on that frequency, you will hear it. Even if the repeater has a bad amplifier, or the duplexer is totally hooked up wrong, you'll still hear the output if you're in the same room with a portable listening on 462.675 If you can't get that - then you are NOT transmitting on 462.675. There's a limit to the amount of help you're going to get online. At some point, you need to be able to troubleshoot step by step & figure out what you have, and what you don't have. Throwing darts at a virtual dartboard for tech help is not the answer.

According to that picture - your repeater is set to 467.675 Receive - but with a tone of 77.0 Hz. I believe you said your portable had a tone of 127.3 ?? The repeater needs to have the same PL tones as the portables. Your transmit appears to be set to CSQ (no tone at all) with a frequency of 462.675. If the portable radio you are using is set up with a PL on the receive, you would not hear the repeater. (You should still see a 'busy' LED when the carrier comes up on channel). It appears your frequencies are correct - but you need to match your tones on your portables and your repeater. If you can key the repeater with a local mic plugged in - the repeater will just be transmitting on the base of 462.675