WRKC935

Well if you are looking to 'do your own thing' I will say this. It's not as hard as you might think, but there is some knowledge required. Since no one wants to reinvent the wheel so to speak, it's really going to be easier to use what others have done and adapt it to your own use. All that is being done with mygmrs and gmrslive linking is a 'rebranding' and repurposing of something called All Star Link or HAMVoIP. The basis of that entire system is a open source IP PBX called Asterisk. This is a office type phone system that someone wrote to replace his ageing PBX in his office and then decided to put the source code out in the open for others to use. Another gentleman wrote the 'rpt' part add on for Asterisk that created a manner to connect radios and repeaters into the PBX in what could be defined as a conference call. So when you link two repeaters or radio's together, it's like two phones, with one calling the other. THere is a bit more to it but that's the really basic way it can be described. When you connect a number of radios and repeaters together it's treated as a conference call at that point. The limitation is the amount of bandwidth available for the traffic being shipped from place to place and the processing power of the computer it's running on to process and ship the audio and telemetry (PTT and COR) from site to site to site. Now that's established. ASL or All Star Link is open source. You can go download the servers, hubs and all the manuals and set about modifying it to do what YOU want it to do. There are a couple things that you need to know. First is that the typical downloads are setup for non-computer people to use. So they are preconfigured for the databases of the HAM nodes out there and the info for them to connect together. All that needs to be removed or modified to make it work in YOUR specific application. And although there is no specific requirement for Internet access, linking sites together must be done with IP for this to work. Now you can use microwave links between towers that have LOS or Line Of Site between them and forego the Internet all together. But that might not be what you are desiring to do. But it's going to require someone with significant ASL and Asterisk experience to get this all going. It's not a plug and play solution. USING ANOTHER SYSTEM There is the possibility of using a preexisting system to do the linking where you just create nodes on the system for each repeater and then connect the nodes together. You do NOT want to create loops while doing this. So the easiest way is select one node to be the 'hub' and connect all your other repeaters to that node. Then you are allowing others to do the 'heavy lifting' on the back end so to speak and riding their system. SO this is a possibility. Now, I will say this. There is a way to go into the rpt config files and ONLY allow certain nodes to connect to your node. So it you want to like 5 repeaters together, with node numbers of 1 thru 5 and node 3 is the 'hub' you set repeaters 1,2,4 and 5 to only allow connection from node 3 and node 3 you limit to the other 4 node ID's. Then if I get to playing around with my node that's numbered 10 and I attempt to connect, I will get rejected because I am not in your allowed node list. By default, most systems update their node lists every 10 minutes, so that would need turned off or a different node list would need created that was static (not updated) and the rpt.conf file location would need modified to point to that list and and not the master list for the system. And there are other ways to go about that as well. If' it's a few repeaters, you can just set the system up to not connect to anything and then go back and individually allow the specific nodes you want in to have access. So there are a couple options that are out there and are NOT crazy expensive. If you want to look at third party hardware, I would advise you to look at the nx2-u units from JPS. I THINK that those can be configured for point to multipoint connectivity. which would fit into what you are talking about for a small system but those ain't cheap.

Motorola does have RAC for analog, but it's can be scanned. A better option is to spend the money and get a part 90 license then you have better options. First is you can run DMR (MOTOTRBO) and run a digital RAC and run basic encryption. It would also allow you TWO talk paths on the same frequency. Something that's no possible with analog radio. And the other thing with a part 90 commercial license is if others come in, outside of your family unit, they can use the license under your authority. You can 't grant a non-family member access if they don't have a GMRS license.. so day workers and laborers that are not family can't use the radios. The basic encryption will also keep your radio traffic semi-private. The 6 digit numeric RAC code will keep all but the most determined off the repeater. And it really sounds like it would be a better option for your specific application. The issue is that you are so limited with analog radio. And there is a greater limitation with the lack of encryption due to the regulations of GMRS. I know that someone brought up using a trunking controller that would look at radio ID's to grant or deny access to the system, but there again, I don't know the regulations specifically for GMRS would allow that. Would it work, sort of, until someone with a scanner that could display the LTR data was used to pick apart the information and then it's going to be screwed with if you are really expecting issues with others trying to gain access. I wouldn't typically go to these length's but you seem adamant in you post about it to the point you foresee issues before you even have equipment on the air. And in truth, if you haven't bought any equipment for this yet, now is the time to look at other options that better match your listed requirements. Personally, I am a P25 and AES encryption guy all the way. That will always work and NO ONE gets to listen in. But none of that fits within the rules governing GMRS.

I am thinking that the national HUB's are just what's established. That being said. For a statewide hub, or group hub, you have a couple options. First is to just use one of your NODES as the 'hub'. Link all the other repeaters in the group to that NODE and run it that way. Second option is to build out a Pi without the audio interface and attached repeater. You will need to register it as a repeater on the site and then assign it a node number once it's created. This could also act as a NODE, but I will warn you that you will get people requesting access to it thinking it's a repeater. I took mine 'down' off the site becasue of that. I kept getting requests for access since it displays as a repeater. People will not bother to read the listing first and verify what they are requesting access to. Now, if you are a Linux guru and a ASL guru, you can in theory download the image, and load it up on a Pi and then look at the changes to ASL and see what's been done to it and mimic those changes on a Debian instance with ASL loaded on it in a x64 platform. I have had no luck with that but I am not even versed on either Linux or ASL. So your mileage may vary. If you are knowledgeable on both, and get it working I would LOVE to know what the steps are to making that happen.

Going back to the idea of GMRS for communications. If you are looking to map coverage of a repeater in the area, try RadioMobile. Just google it. That will generate coverage maps. Be sure to use LOW GAIN repeater antenna's if there is a lot of up and down or you are placing the antenna significantly higher than any part of your expected coverage area. High gain antenna's will cause issues when close into the repeater if it's a lot higher in elevation. If you are looking for this to be a solution when cell is down, you need to consider why cell service would be down. Cell towers require a couple things to operate. First is power. If the cell sites have no power, will your repeater. If not, it's is not going to work unless you power it off some other source, or have a backup source when the power is out. Second is connectivity to the outside world. Cell sites can't communicate with the phones if they have no connectivity to the outside world. Think of it like an Internet outage. A repeater in local service would NOT be effected by an Internet outage, but a linked repeater or repeaters will have issue if they are reliant on Internet connectivity to link between the different sites. Now the HAM and NVIS stuff is all great for base to base communications. But that is HF frequencies. You are NOT going to build an NVIS antenna for GMRS and have it work. The problem is that the UHF frequencies will NOT bounce off the Ionosphere. They will just go right past it and out into space. So NVIS doesn't work for GMRS.

Does anyone have a VMWARE instance of the ASL mygmrs linking software up and running? If so would you be willing to share it? I am working on configuring a State level HUB for Ohio. Have an ID and all that, I just need to get the Raspberry Pi software off the ARM platform and on to an X64 platform so it's easier to manage and run. And I would rather save my Raspberry Pi's for repeaters, which this isn't going to be, at least I hope not.

I am wondering how you would seal with receiver at the subscriber level. If you put a transmitter on the air in the same band as another radio in receive with 30 feet of each other, the transmitter will overload the receive of the other radio and it goes deaf. GMRS isn't just in the same band, the whole thing is only 175 Khz wide for the repeater channels. There isn't a UHF duplexer made that will deal with that sort of spacing. So how would you even think that it was possible? Full duplex can't exist at those tight channel spacing. Just not reasonable to build the filtering for it. Cell and other technologies had Megahertz of channel spacing available to pull it off. The analog 800 band is 45 Mhz. The 700 band is 30Mhz, and the 902 ISM band is 27Mhz for ham and I believe it's more for the commercial users. It's simply not possible to do on GMRS.

Yes, but I don't believe that you have an ERP limitation on 15-22 that you are required to meet. That being said, it's always a 'best practice' regardless of regulation to only use the minimum amount of power needed to establish a solid communications path with the other party. Using power levels beyond that can cause interference for other users of the service. But there is no specific regulation stating that requirement.

There is just SO much wrong with this. Gonna go full on with the math here so it makes sense. And this is gonna be based on that if the antenna in question has 11dB of forward gain that it has an 11dB null off some part of the pattern, most likely the back side off the corners. Second assumption is the repeaters in question are running full legal limit power of 50 watts minus a standard combined loss of 3 dB for feedline and duplexer losses and a 6dB gain antenna. So conversion of 50 watts is 47.0 dBm for ease of the math. Real conversion of 50 watts is 46.9897dBm so I rounded up to save time. Mind you that a 3dB change is a doubling or halfing of power. So, 47 dBm minus 3dB is of course 44dBm OR 25.11 watts. Getting that out of the way. So we have a 44dBm signal going into a repeater antenna with 6dB of gain. So that's 50dBm or 100 watt's ERP if you want to go that route. ERP is Effective Radiated Power. Look it up for a better explanation. Now we need to consider path loss. Path loss is the amount of signal drop between the two antenna's ( repeater transmitting antenna, and your receiving antenna). The path loss calculator used for these calculations. https://www.pasternack.com/t-calculator-fspl.aspx?utm_campaign=Power_Combiners&keyword=&gad_source=1&gclid=Cj0KCQiAkKqsBhC3ARIsAEEjuJj7ApOIs_PMeM7_yH6hraxqwaoC9i42tDkgTTaSKcF2Q5qN0GSO0coaAtBGEALw_wcB Path loss on a 9 mile path for 462.550Mhz is 109dB. So we take 50dBm and subtract 109dB which leaves up with -59dBm. Your receiver will open with a tight squelch setting at about -110 to -105dBm signal level. So lets add the null to the -59dBm signal level and we get -70dBm. This is when the signal null is the greatest when the antenna null is turned to face the transmitted signal. So your radio will open up at -110 to -105dBm and you have a signal level of -70 dBm at the antenna. Even with another 3dB of signal loss in your coax feeding the receiver, you STILL have a -73dBm signal level hitting your receiver. To put into contrast the difference between -103 and -73 dBm which is 30dB of course. If you have a 1 watt transmitter, and you amplify the 1 watt by 30dB, you now have 1000 watts. It's THAT BIG of a change in signal level. And your receiver is hearing that much more signal than it needs to in order to open the squelch up and hear the signal. So, is your yagi defective? I am gonna say NO. And this is the math that proves it's working. If you ever worndered how the FCC can sit in your neighborhood and gell how much power your CB radio is putting out without needing to walk in and test it with a watt meter, these equations are it. You measure signal level off of a calibrated antenna into a signal level meter or spectrum analyzer and calculate it back. Your antenna of course is clearly visible above your house, and it's design will indicate a reasonable gain number to apply to the math to figure out just how much fire you are putting in the wire. And mind you, don't take my word for all this. There are two RF engineers on this board, One has posted in this thread. If he chooses to pipe up he can verify this math is correct and why you are hearing the signal off the side of your beam. And also verify that even if the repeater output was reduced to 1 watt, you would STILL hear it off the side of your beam. The math don't lie. I would ask him, if he reads this, that if it's the case, that he bump the answer over on the top left of the post here. It makes my numbers look a bit better. And I will continue to do that for him as well. Gonna toss this link in here too, gives a better explanation of a yagi and how it effects signal pattern for both receive and transmit.

While SOME might think that you need to bring your own group to the party so to speak, and chatting it up with other users isn't the thing to be doing, there are those of us that believe that's a lot of BS. While don't have near the number of repeaters that some do in Indiana or Illinois, I am growing the system in Ohio as I can. And our rules are pretty simple. Some ask that you gain permission for the use of their repeaters but grant to all comers, and then there are others like me that take the approach of it you have a license, by all means use it and I will speak to you if you are NOT using it correctly otherwise have at it and enjoy. Mind you that repeater system reaches across 4 states and covers most of Indiana, much of Illinois, and parts of Ohio. And we all work together to make sure it's available for all that are willing to use it and have a license to do so.

A lot of that is going to depend on the bonding more than the surge suppressor. As mentioned elsewhere, the BONDING is done for safety reasons and to keep all the equipment at the same voltage potential. So single point grounding of all equipment on the operator position is KEY in keeping the equipment running after a strike. If you have a strike hit any piece of the equipment , it should ALL jump to the same potential as the gear next to it. If that happens, you stand a better chance of it surviving. If one piece of gear jumps to 10KV and the rest stays at 0 volts, POOF. And you get a big fireworks show on your desk to boot. And one of the things that I had a hard time with when discussing grounding was how does a number 2 or number 6 wire really deal with a hit. It's tens of thousands of amps and millions of volts. But what was explained to me is there really is no way that you could pass that amount of current across a conductor that size for any length of time. But if the time was short enough, it would hold that sort of current. The other part was once you are in the structure, and the site has proper grounding, those smaller conductors are NOT exposed to those sorts of currents and voltages. If a single DC floating antenna takes a direct strike, the maximum voltage across the cable from center conductor to ground is the breakdown voltage of the cable. You can't put 100KV across two terminals that are 1 inch apart. The voltage will arc over and limit due to the arc, and that arc will short the rest of the voltage to ground. And that breakdown voltage is only present until the arc starts. Once an arc starts, it's no longer an open circuit. You have current flow and therefore a load against the potential. Welders will recognize this with simple stick welding. You have to fight to get the arc to establish. And a typical stick welder open circuit is about 60 to 80 volts. Once the arc is established, the welding voltage drops down to about 20 volts. And you can pull up several inches from the welded material and maintain the arc, still having a really low voltage present between the welding electrode and the material. Same thing with a coax cable on a tower that is hit. The center will arc over to the shield and the voltage gets limited between the shield and the center conductor. Of course the shield is grounded to the tower at the base of the antenna, where it transitions off the tower to the structure, at the entry point of the structure on the outside and then at the surge suppressor just inside the structure. At least that's the way it's done on commercial towers. In addition, it's grounded not less than every 100 feet coming down the tower. Back to the number 2 wire and the 100K amps and a gazillion volts. Lightning is swift. It's a LOT of power being dispersed very quickly. So the wire will heat up, but it's not an instantaneous thing. And since the duration of the voltage drop across the conductor (which is the actual voltage across the wire and NOT the total voltage present during the strike) is so quick, the relatively meager conductor size in actually ample to pass the voltage across it and into the ground. Now, something else that's NOT being considered. Since the cables are all grounded to the tower and everything else and all that is bonded together, the tower carry's a LOT of the power to ground via the metal structure and the metal in the concrete base of the tower. In other words, the single antenna cable of the antenna that gets hit, never really see's the entire blast of lightning, it's spread across a number of other conductors to ground.

Grounding bonding and the like are NOT to deal with a direct strike. The first and foremost reason to ground and bond is safety for the operator. And that is where the bonding part comes in. If you install a tower, toss a couple ground rods in the ground and connect them to the tower and do NOTHING else you create a bigger issue than if you just did nothing. And here's why. Your house, building or whatever has an electrical service connected to it. Part of the code for that service being connected is there is a safety ground. So that service has one or two ground rods connected to it (newer builds require 2 rods). You radios are plugged into that service and that ground. That ground is connected to the case of your radio and then the antenna is ALSO connected. That antenna is connected to the tower and the tower is grounded with a second set of ground rods. A ground strike that hits neither the tower or the electrical service will induce a pulse that will spread out across the ground as it disperses. Since the two different grounds are at different places, they are at different voltage potentials as the strike disperses in the ground. But you have connected them together with your radio being the fuse in the middle. So it goes poof. If the radio is NOT connected to the electrical ground, but is connected to the tower, but other equipment is sitting there on the desk that is connected to the electrical ground, then it will arc across from one device to the other, OR if the radio is connected to a computer or some other device that is on the electrical ground via data cables, then one device has a different voltage potential than the other across the data cable,,, again POOF. None of these are 'direct hits' They are all ground strikes that fry your gear due to lack of proper bonding between the different pieces of equipment connected to the different grounds. Specific to tower grounding. For a small tower for GMRS / HAM radio use, and NOT a big commercial tower, the reason for grounding the tower is NOT to deal with a direct hit, it's more to prevent the hit from coming at all. As we have all been told over and over. Lightning will take the path of least resistance. If you have an ungrounded tower, that tower can build a static charge on it with reference to ground. The tower is more conductive than the tree's around it, and it's now at a higher potential due to the static charge. That makes it the path of least resistance and therefore the most likely target for a strike. Anything connected to that tower is going to become part of the dispersion of that strike. So you ground it. Grounding the tower brings the entire tower back to the same voltage potential as the rest of the surrounding earth and therefor makes it no more of a target than anything else there because the grounding pulls the static charge off the tower, and in reality will not let it build up to begin with. Lightning suppressors. Lightning suppressors perform two different tasks when they are properly installed, and don't do anything if they are not installed correctly. They first and foremost need to be grounded. That ground needs to be right at the entry point where the cable enters the building. But the shield of the cable needs to be grounded on the outside of the building just before it enters the building as well. The surge suppression part of the device is to short down any voltage higher than the trigger voltage of the suppressor in use. This is typically about 100 volts. If any part of the tower is hit, every part of that tower and anything connected to it will have a voltage induced on it. That induced voltage will create a magnetic field (like a transformer) that will induce voltages on any other conductor near it including the center conductor of any coax on the tower. The suppression is to short that to the shield of the cable and then to the grounding system it's connected to. It's NOT to deal with a singular hit on a specific antenna on the tower. If that happens, the radio connected to that antenna will go POOF. BUT if the grounding is done correctly and the bonding is right, that will be the only radio damaged. If not, then the lightning will come down and tear up lots of stuff.

Try the Johnstown600 repeater if you have an elevated outdoor antenna. It's possible to make it but it's gonna be difficult.

I mention the rules thing for one reason only. If it's not brought to to the forefront in the initial discussion, then it will be discussed, debated, and pontificated by a number of folks that may or may NOT have a solid understanding of it and possibly convey partly or completely incorrect info that then needs corrected. This always seems to turn into a thing, threads get hijacked, dead horses beaten. It's just a thing that happens with online forums. Nothing new or exciting, just a continuance of the norm. Unless you are connecting your .5 watt radio to a 30dBi gain 20 foot dish and purposely creating interference for others I seriously doubt that the FCC is gonna come knocking. That being said. You mentioned both dBi and dBd gain numbers. Gonna give a quick explanation of each, because it's not common knowledge. dBi is gain over an isotropic radiator. This is the default 'paper' reference antenna that radiates RF in all directions at all angles equally. It's basically a free space radiator that has a sphere of RF eminating from it. I know that I used a lightbulb as an anology, and it's not quite correct since it can't radiate out the bottom of the lightbulb, but it's a good point of reference for most all other directions. dBd is gain over a dipole. Dipole is simple, and does exhibit gain over an Isotropic radiator since it's pattern doesn't include significant radiation off the ends of the antenna. That power has to go somewhere, so the increased radiation at certain angles give the antenna some amount of gain over the paper antenna in those directions. One of the other interesting things with antenna's an gain as opposed to amplifier gain which of course is an active component of the RF string is the amplifier is typically uni-directional with it's gain. Take a typical amplifier with a 10dB gain design. You put in 1 watt and 10 comes out. This will make you be heard farther than before. But it does nothing for your receive. Now, gain in an antenna doesn't so much 'boost' the receive signal. The signal is what ever it is at the antenna. Once again, we bring in the light source. The light isn't brighter for the directional antenna vs the onmi directional antenna. It's the same level. I am not going to bore you with math and what is referred to in the big antenna college text books as power density. I am gonna go back to the simple light source. So what a directional antenna does to increase your ability to 'hear' a signal is it darkens everything else out other than what it's pointed to. Take a flashlight outside at noon, you can see it at 100 yards. But you can't see a candle at the same distance. There is too much other light source (noise) to see the candle. But take the same candle out at midnight, and it can be clearly seen as a light source at the same distance. The directional antenna does this by ignoring the light (signal) from every other direction and only looking at the candle. A receive amplifier can't do that. It's going to amplify the signal some, but it's going to amplify all the other signals that we don't want as well.

Yeah, there have been 800Mhz radios that were produced with PL-259 connectors. Sure there is some loss. The N connector is a better option, but it's a situation where the performance difference isn't significant enough to matter in most real world situations. There are people that believe that little bit of loss is going to keep them from being able to communicate, or give them an edge on getting some rare DX contact in the case of the ham radio guys. But the truth is you would never notice. But I will say that installing PL259 connectors on RG-8 sized cables is a pain as opposed to an N connector. We use the Times Microwave LMR400 / LMR600 EZ connectors and that specific cable at work as a standard unless heliax is used, and the connectors go on quickly with the proper prep tool.

So there are some issues using a beam specifically with simplex operations. First issue is beamwidth of the antenna. Think of an onmi-diredctional antenna as a bare light bulb, the light comes out in all directions pretty much equally. Then we get into a short yagi of 3 or so elements. That's like having a flashlight. It's a directional beam of light that spreads out as the distance increases but is still very directional as compared to the bare light bulb. Now we get into the longer boom yagi's. And while 7 elements isn't really a big beam as opposed to some of the 30 element ones that ham's use for Satellite work, it's still significant forward gain. That's gonna be like a cheap red laser that up close is just a dot, but at a distance, the dot might be a foot or two across. You need to point that dot at the other person you are trying to communicate with and hold it on them throughout the communication as it progresses. And the more elements, the smaller that 'dot' is that you need to hold on the other party. Because once they are out of the dot, they are no longer able to communicate with you. Second issue is more of a regulation thing. While the repeater channels are NOT ERP regulated and any sort of antenna system can be employed for these simplex channels, some of the simplex channels are indeed ERP regulated and the ERP is a calculation of antenna gain and input power to the antenna. A 10 watt radio into a beam with 3dBi of gain is the same ERP as a 20 watt radio connected to an antenna with 0 dBi of gain (typically an omni-directional antenna). If you get into 6 or 9 dBi of gain, your .5 watt radio is no 2 watts, or 4 watts, when you are regulated to .5 watts of ERP and FRS is always regulated on ALL channels hence the reason an FRS radio has an antenna that can't be removed and connected to a different antenna.

BTW, I believe that the XTL and APX will address up to 4 heads. There is a way to set the head number on each head and they get daisy chained from head to head. The power would be a bigger issue at that point as I don't know I would want stand along power supplies running each head creating a ground loop on the data cable between the heads and the radio.

This is true. Dual head was available on the Spectra, AstroSpectra, XTL and APX lines of radios. Now a dual head setup for an APX is going to be in the thousands of dollars, so I don't know what your budget is, but it's certainly out of mine. Another option couple of options. First is a tone remote setup where there are remotes that look like a desk phone sitting in different places throughout the house, and areall wired back to a tone remote panel that is connected to your radio. The audio is routed to all the desk sets and you simply lift the receiver and hit the PTT to talk. This stuff is around on ebay and could be used. This is going to be easiest if you use a commercial radio for the interface, they are designed for it. A Motorola CDM is a really good choice here. And if you find the right stuff you can change channels from the remotes. Second option is a Zello / RoIP setup where you connect an interface to your radio and then your phone connects to the interface that is available via WiFi or Internet to the radio gateway. This gives you access most anywhere your phone can connect to the Internet. Another option that is going to be a bit more costly, but has a LOT of additional abilities is CTI Products Radio Pro. This is going to require a Motorola XPR radio and a Radio Pro Gateway to function but you have full control of the radio via either a computer running the 'Dispatch' Software or a smart phone running the app. With this setup you can use the Phone for mobile comms and if traveling, you can load the client on your laptop and have full control for radio use while abroad as long as you have a WiFi connection.

Get over yourself dude. Never said I blocked you specifically. Hell I'm Batman and your the Joker. We need each other. It's a love hate relationship. Where on a rare occasion when the stars align, we might actually agree on something. But we do have a symbiotic relationship where one of us is the host and the other is the parasite. We just can't agree on who is who. But that's all right. You'll keep making my butt itch and I will keep giving you headaches. It's all good.

Well, news flash, YOU have been lied to. There are indeed dumbass ham operators that believe this crap and a number of GMRS guys that fall into this as well. The biggest believer in this BS about SWR by far is CB operators. I have also come across the ones that think that any amount of cable loss that's not an absolute necessity is sinking an installation and the radio system will never talk without more than X dB of cable loss. And these moron's will die on that hill as well with their beliefs. There was a time that being a ham operator actually meant that you had some level of technical ability and knowledge. In fact it was a requirement to prove that knowledge during testing for a ham license. That's not been the case in years. Once the FOIA became a thing and the question pool for the tests were made into study guides for passing the test, there was no longer a need to have specific knowledge of radio, you just had to be able to memorize enough of the questions and answers to pass the test. And these folks that get licensed now did just that and then through a total lack of any real knowledge, listen to wives tails of Whoa when it comes to cable loss and SWR and treat those lies as gospel and preach them to all that will listen. And the reason they believe? Because the dolt that is preaching the good word of SWR has been licensed for 6 weeks longer than they have. I don't understand the 'importance' of the length of time that someone has walked around with a ham license in their pocket. Old people have had drivers licenses for far longer in some instances, it doesn't mean that grandma should still be driving when she has run over 12 curbs, 4 dogs and a shrub or two in the front yard. Does it mean that you are some how a master of bating when you have been playing with yourself for 30 years? No, it just means your old and lonely. And not much different mentally than most teenage boys. Other than they might get some at some point down the road. The guys that had to actually construct a radio at the testing office to get their ham license (yes it was a thing once) are about 3 days older than the dirt that they will be buried in any day now, if they haven't been already. I will have been a ham operator for 30 years in April or 24. And that don't mean crap. Other than I got a ham license long ago. It doesn't prove anything past my ability to fill out a forum every 10 years and send some money to the FCC with that forum and renew my license. It's the same method used to renew a GMRS license, a commercial radio license or many other certificates that someone might have. What does prove out that I know something about radio and electronics? Two years of electronics in high school with a state certificate of completion. Three years of college with a degree in electronic repair and a degree in industrial electronics. Fourteen years as a communications field technician designing, installing and repairing public safety communications system and 911 phone systems. That would be a good starting point. But, any skill that you are being paid to use, and have been paid to use for more than 2 years typically means you must know something about it, because most employers would have fired you in that time frame if you weren't any good at what you are being paid to do. Again, just my personal opinion.

The way to do this right is two radios. One radio that was a 1 to 25 watt radio set at the lowest possible power in each position for inner vehicle communications. These would only be for the operators of the 'train'. A second radio on a different channel for escort and spotter operations. These could be 1 to 25 watt versions as well but turned up to 10 or so watts to communicate with the escort vehicles and the train vehicles. There are two equally important sources of radio traffic when running a setup like this. First of course is from the other operators on the connected vehicle. The second being from spotter / escort ops that are running all around the vehicle. And a front lead vehicle may be a 1/2 mile or more in front of the load vehicle to spot traffic, road conditions or other issues that will effect the navigation of the load vehicle. Being able to hear BOTH is important, to the point two radios are all but a requirement. Licenses can be simple itinerant nationwide frequencies but multiple channels are also a must if you would happen to run into another license holder that would cause interference. If that happens everyone switches to a different channel and the issue is averted. And escort / spotters are NOT on the same channel as the vehicle operations for the same reason. Something as simple as changing speed is a group effort here. All power units have to be doing the same thing at the same time. And that 'team effort' for lack of a better description is why NO ONE else is on their channel. CB radios and other 'distractions' shouldn't be present in the load vehicles either. If CB or other radio monitoring is needed, that needs to be a function of the escort / spotter team. They can then relay important information to the load vehicles across the spotter radios. At least that's the proper way to do it in my mind.

So the first issue that they may be having is the fact the radios they have are in the Part 90 allocation. And do you know what frequency they are on? Could be VHF. could be UHF. Hard to say. All this has to do with the noise floor of the area around the facility. Rural area noise floors are typically going to be lower than urban areas. The type of license they have is also a consideration. If they are saddled with an itinerant license, their neighbors across the street may have the same frequencies as they do further limiting their ability to talk. Lastly, the squelch level of the radios they have, which is programmable only and not user adjustable may have a hand in the lack luster coverage they are experiencing. GMRS and HAM UHF frequencies are typically fairly quiet and the noise floor there is very low typically. Much lower than the noise floor in the part 90 allocated frequencies. But what I can tell you is this. There are a number of different radio services out there that are for different applications and users. FRS radios that are sold in a big box store in bubble packs are meant by the service they are attached to to NOT be used for commercial / government entity applications. Just because you can buy them across the counter doesn't mean they are for every application you can imagine. FRS specifically stands for FAMILY radio service. Meaning they are for family use in a similar way that a child's walkie-talkie is meant for that application and NOT as a radio system for public safety. Could you use kids walkie-talkies in a public safety situation? Sure, if the range was limited, and the interference was minimal, police could use them to communicate. But that's not what they are for, and if a police department was to use them for law enforcement activities and the FCC caught wind of it there would be some fall out over it. Same goes for FRS radios being used for school communications. It's not what that service was intended for. And improper use of a radio service is technically against the regulations. Now, mind you seeing any sort of enforcement with this is pretty far fetched, BUT if the FCC were to get wind of it and decide to levy fines to the schools for using the FRS service as their communications system, those fines could reach over 10K in short order. So messing about with things of this nature, not being aware of the regulations could get them in hot water. And while the FCC can't really come for you for violations, the school could seek to create a civil case against you for sending them that direction.

Correct, the payload is the only ting typically encrypted, but the 'repeaters' in a conventional system are also transparent to the data stream. They look at the signal to see that it's P25 and nothing else. If it's a 'system' then the data stream is further processed to see that the talkgroup ID and radio ID are encrypted before allowing the traffic to pass. But if you stand up a stand alone Quantar repeater in P25, and run encryption on the subscribers, the repeater doesn't care or even have the ability to look at the data stream. Now the headers which carry the ID are NOT encrypted typically. This becomes apparent when you have a radio that isn't encrypted listening to the secure traffic. The transmitting radio ID will be displayed, but the audio is muted since there is no way for the receiving radio that's not encrypted or doesn't have the proper key in it to decrypt the radio traffic. As mentioned, to have 'wireline' control of the repeater, it requires a DIU with encryption in the DIU to communicate via wireline encrypted. The repeater isn't encrypting the traffic, that is done by the DIU and the encrypted data stream is fed directly to the repeater and it puts that stream on the air.

You might have heard that someone had to 'buy back' an entire system over the issues with the interference that it was causing and getting from surrounding agencies. I have first hand knowledge of that system. Those issues were also why the APX line of radios never received the ability to do DMR. That family of radios were built for public safety in mind of course. And Motorola didn't want to even go down that road for interoperability. I know of a Motorola shop owner that did setup a TRBO system after all the mess happened. He told me that M said if it didn't work, they would pull his dealership from him. He was a very accomplished RF engineer, and his system did work without issue. But it was not a case of just taking out the analog repeaters and dropping in DMR on the same frequencies and power levels. Some of the original frequencies were reused, but some couldn't be. And the whole thing was re-engineered. Different antenna's at different heights, and power levels were all significantly reduced. But DMR requires a different mentality and effort than old school analog radio where you run as much power as allowed as high on the tower as you can. This is another concern that I, to this point, have been reluctant to bring up with DMR on GMRS. GMRS users typically do subscribe to the 'height is might' mentality with strong reliance on power. We hear guys complaining that there 50 watt radio only does 48 watts on their meter (coax loss in the test jumper is the typical cause) and wanting those extra 2 watts. With that line of thinking, dumping DMR into GMRS in a suburban or urban environment WILL cause interference problems of course. And getting the max power thought process out of peoples heads isn't going to be possible. So there is yet another reason to steer clear of the whole idea of DMR on GMRS.

yeah, i made a list finally

A sort of limited explanation of ERP vs power. Where the power or watts measured from a power meter, which is where the 50 watts thing comes in. There is something called ERP or effective radiated power. This has to do with antenna gain. Gain is typically figured off of an Isotropic radiator, which is really a theoretical antenna that radiates power in all directions evenly. All directions meaning up, down and every degree of a circle around the radiator at all angles evenly. It's not an antenna that really exists except on paper as a reference. To achieve gain in an antenna, the elements are configured in such a way that the power that is radiated up and down is redirected more toward a flat plane horizontal to the center of the vertical radiator (vertical antenna). Since even basic quarter wave antenna's have some amount of gain over the reference, it's better to consider those as a reference point when trying to figure out performance gain. But it works like this. 3dB of gain, either from some type of amplifier or an antenna is going to effectively be a doubling of power. If you consider the 3 dB of gain against the reference antenna, the antenna in question will perform at a level as if the reference antenna had double the power feeding it. So an antenna with 0dB of gain will talk as far with 100 watts as an antenna with 3dB of gain will talk with 50 watts, as long as you are considering the antenna radiation pattern. Meaning since the antenna is taking radiation away from the higher and lower angles off the horizontal plane across the center of the antenna, it will talk farther across that plane, but you LOOSE coverage in the higher and lower angles of radiation. Yes, this is a difficult topic to really understand. And not having radiation pattern diagrams posted here make sit harder to see. All that being said. There is no 'limit' to antenna gain in GMRS. Part 90 licenses do have a maximum TX power and a maximum ERP. We luckily are not saddled with a max ERP. So we can run right up to the 50 watts of maximum power, and if we so desire to get totally crazy, we can legally put up a 20 foot dish and feed that dish with 30 dB of gain with our 50 watts of limited power and have 5000 watts of ERP. Now there are some safety issues that need addressed with that sort of ERP, and of course, a dish is gonna be pretty tight with the radiation pattern, but it's still technically legal to do it. As a side note to that. We are NOT allowed to operate with those antenna gain levels on the 467 interstitial frequencies and I don't believe we can do it on the 462 ones either. So bear that in mind when getting crazy with an antenna system.