WRKC935

That right there is frankly terrifying. There are standards and requirements for encryption to keep it secure. At least for P25 equipment. One of which is the fact you can't see the key other than when it's typed into a key loader. Once it's in there, it can't be read by others. And it's never fully displayed on the key loader beyond that. From what you are showing me here, someone could take one of these radios and read it and have the key. In any compliant radio, if you open the radio and attempt to access the UCM (crypto module) the module dumps the keys in it. The backup battery for the memory actually gets grounded through the cover that protects the module. Removing the cover disconnected the battery from the module and the memory gets erased. Again, this is a P25 standard, DMR standards are not gonna be that high. There are a number of other standards and requirements for securing the keys in a compliant encrypted radio. It seems that this radio doesn't meet any of those requirements. But I am thinking these radios are DMR and not P25. I have not messed with AES on DMR. The MOTOTRBO radios in the US I don't believe are available with AES encryption. I know there are some that have it, but the ones I know of had it hacked into the radio . It is available in other countries however. All that being said. I would question if the Anytone radio does any sort of analog encryption AES or otherwise or if it's JUST for DMR specifically. Both DMR and P25 are both digital formats that a data stream gets transmitted and not analog audio. Both have added parity and other information in the data stream beyond the audio intelligence. But I also remember that DVP and DES OFB in analog would significantly decrease range because there was no error correction on it at all due to there not being any overhead data stream being transmitted for error correction to take place. And those were significantly less secure and complex than AES referring to the complexity of the key and the algorithm. It did require a full quieting signal and any interference on the frequency in use would stop the ability of the receiving radio to decrypt the signal. But being able to read out a radio and see the encryption key in that radio almost completely defeats the purpose of having encryption to begin with. I guess I should preface this with the fact I keep my encryption info and key loader in a vault located in my gun safe. So it's stored in a vault within a vault. The paper documents that have my keys written down on them are in the same place. While I do have keys that are shared outside my equipment with others, I load those radios and key loaders for those that have them and I don't share MY personal key with anyone. All my gear is multikey and the stuff I have in my inventory get keyed with a number of keys including my personal key that only exists in my radios. Do I have a specific reason to take it that far? Not really, other than personal OPSEC. But I can do it that way and the 'family key' isn't loaded on any gear that someone outside the family would have access to. But when I switch to channels that are strapped secure and say something on those channels, I have little doubt that no one else hears what is said.

Yeah, the only analog (WIDE BAND ONLY) encryptions that were available were DVP and DES OFB. Those would work through SOME analog repeaters and not in others. There was a 'SecureNet' encryption that Motorola had back in the day but your getting WAY back. To run AES (any version) you are gonna need a few things. First is radios that support that encryption algorithm. Then you will need a way to put keys in the radios (a keyloader or some hardware tool that will load keys) Radios will of course need to have the same keys in both of them to make it work. And range is reduced when running secure because the error correction works better with plain P25 and the added encryption will require a lower BER (Bit Error Rate) to function correctly and not pixelate. I run secure on a number of radios. I will not get into where these are run, but I have equipment that supports DES and AES on VHF, UHF and 900 Mhz.

Not sure how this has much to do with wanting to install a repeater. Other than maybe buy the property at the top of the 300 foot hill and install a repater there so you can talk on both sides.

OK, program your radio for the input PL of the one repeater that does need it and do NOT program a RX PL in your radio on that channel. It will hear BOTH repeaters. Both repeaters will hear it because you will be transmitting the correct PL for the one that needs it and the other one doesn't care about the PL. It's just gonna receive anything on the frequency regardless of the PL being used.

Wait, you HAVE a tower and building and want a repeater there? Is this YOUR tower site or something that belongs to others that you have permission to be on? If this is YOUR site, where is it, and how tall is it? Getting equipment can be difficult, depending on your financial ability to afford it, but there are ways to get money together to get it done. There might also be an option for others to provide some or all of the needed equipment if it makes sense to put a repeater on the site.

OK, there is NO WAY that can work. If there are TWO repeaters in the same area, and one doesn't have any input PL tone on it, that repeater would come up every time the other repeater was keyed up if the user could be heard by both repeaters. And if both repeaters could be heard by the user, their radio would howl and have very poor receive audio due to the frequency difference (slight mismatch) between the two repeaters. Now one of them might not have a TX PL tone. That is completely possible. But the receive PL would be required on both and both would need to be different to keep both repeaters from transmitting when someone keyed them up.

You are going to be looking for a MTR 2000/3000 or a Quantar. There is the GTR8000 but those are hard to find and very expensive, so I would consider them outside the realm of a hobby GMRS / HAM repeater in all but the most well funded groups / clubs. I would advise the MTR over the Quantar as they are a bit less expensive but are mostly the same electronically. Gonna see similar performance from either. I will say this, the MTR software will not run natively on Windows 7 or above. This creates a small issue that needs to be addressed. But finding a Windows XP laptop isn't a bad thing regardless as there are numerous other radios that you will need an XP or even a DOS machine for. An old laptop set to dual boot between DOS and XP is a very handy thing to have as a radio hobbyist. There are two versions of the MTR platform. One is 40 watt and the other is 100 watt. DO NOT get it in your head that the 40 watt units should be avoided since they will not TX 50 watts. The difference in performance between 40 and 50 watts is NOTHING. NO one will know the difference and it's not going to add any measurable distance to the coverage. If you don't believe me, go download Radio Mobile and run a coverage map from a tower site, run one with a 40 watt transmitter and then run the same map with a 50 watt transmitter. The second thing you need to be looking at is a GOOD duplexer. The little 'mobile' duplexer's work ok for a small setup that's not got much antenna height or is NOT in a high RF environment. Those will cost you coverage on receive due to allowing out of band RF into the receiver. That OOB RF will cause the first RF stage AGC to lower the gain of the first RF stage and make the repeater less sensitive to incoming signals. So you need to be looking for a pass / notch duplexer for a tower site install. I would advise against jumping into this with both feet straight away and instead setting up a repeater at your house or some spot you have access to. Get a feel for what it takes to do it and how much effort it takes. The other thing it will do is get you familiar with the money it takes to put together a system and get it on the air. EXPECTED COSTS for a large repeater system. I am looking this stuff up on eBay as I am writing this. So these are the expected costs for USED gear. MTR2000 UHF 100 watt repeater $1000 CELWAVE DUPLEXER $600 7/8 cable around 3.00 per foot used if you can find it. 7/8 cable connectors $30 each DB-408 antenna $100 - $200 another 300 in misc stuff Then a tower crew to install the antenna and line on a tower. Looking between 2000 and 5000 for that, at bargain doing yo a favor prices. Not Cheap.

No, UHF (GMRS frequencies) do not 'skip' like HF (CB frequencies) does. What you can experience occasionally is tropospheric ducting where a warm air mass gets in overtop a code air mass and creates a tunnel for VHF and UHF frequencies to travel in far beyond normal line of site. This is NOT a common occurence however and shouldn't be relied upon for consistent communications the way it is with HF communications. HF 'skip' is caused by the RF reflecting off the Ionosphere and back down to the ground where it's then reflected back up again, over and over until the path loss of the signal becomes too great for a receiver to hear it. With ducting, the greatest path distance that can exist only extend slightly past the area covered by the air mass inversion since frequencies above 50 Mhz typically do NOT reflect off either the ground or the ionosphere. VHF and UHF frequencies also do not have any 'ground wave' propagation like the lower HF and VHF frequencies do. Ground wave is a phenomenon where the RF wave 'hugs' the ground and carries long distances past normal line of site (past the curvature of the earth) by staying on the ground. This only works below 5 Mhz or so in frequency. There are several web sites and books including the ARRL Amateur Radio Handbook that discuss the propagation of different RF frequencies at length and might be a good source for a better and more detailed explanation than a half away guy posting at 4 in the morning while half awake.

Of course using RAC will require your users to have specific radios and not just anything that will program UHF frequencies. Same thing with MDC. It's of course a bit more supported but still not available on many radios that don't carry a Motorola label on them. Putting them on a logging recorder (do this myself on the non-linked repeaters I have) seems to be a good idea, but can you get an enforcement effort to proceed even with recordings? Lastly, how has all this effected new repeater owners joining your group? Are you requiring repeater owners to pay for access when they bring infrastructure into the fold? How do they feel about the rules? Are you linking your repeaters together to enhance coverage with significant overlap? Or are you limiting overlap and being good stewards of the repeater pairs by either not linking or ensuring that linked repeaters don't have a ton of overlap?

It wouldn't need to be directly on frequency. Could be a second or quite possibly a third or fourth harmonic (triple or four times the originating frequency) which would fall in that range. It would also explain why it's only being heard at that distance.

I guess my question would be did you put up a repeater to talk to YOUR family or for general use by all GMRS users? If you are putting up a repeater you need to decide what it's used for. No one in their right mind is gonna put up a repeater and link to one of the systems and then think it's gonna be a private repeater. Unless you are gonna leave the link down all the time. I just checked my repeater on MIDWEST. It's had over 6000 PTT's in the last 5 days. With over 24 hours of total transmit in that time frame. My other repeater does get some local use as well. And that's what it's there for, to be used. Both repeaters are for general use, and open to all licensed users. I certainly don't want to have equipment sitting dormant. If no one was on the repeaters, I would take them off the air and sell them. Now I would also not put up with it if there was some small group getting in there and keeping everyone else off the repeater tying it up all the time. But my personality allows me to be able to deal with that directly. I would just tell them they are not welcome. It's a shared resource and they can either figure out how to share or go do their thing somewhere else. I have in the past let others get under my skin. Get mad about the actions and behavior or others on my gear and then turn it off for weeks. Only to relent and fire it back up. I am not about that any more. If someone gets on my gear and acts dumb, they get told to grow up or go play in some other sandbox. As far as the original purpose of GMRS. I almost find those comments amusing. No one hardly uses GMRS for private family use any more, at least that I have seen. At least were they are ONLY using their license for family comms. I have no doubt that there are some that do. But I believe that is rare. And building repeater systems that cover 5 counties I can't see being for that specific purpose. And personally I see doing that as a waste of resources (the repeater pair being taken up). But we can do that according to the license rules. I just don't personally agree with it. But in saying that, far as resource utilization, is the reason I have my repeaters open to all and encourage their use by license holders. My crap does cover 5 counties. So I am not about to make it for private use. And I have other means that are equally robust to communicate with family in times it's needed. But that isn't a discussion for this forum.

I don't know. They filter 2175Hz out pretty well for the guys using tone remote control.

I typically use RADIO MOBILE (google it) for coverage mapping work. It has the ability to map both talk out and talk in from different subscriber configurations like mobile and portable with different power levels. Will pull down several different maps and create different maps depending on what you are asking it to do.

I 100% agree. Now, mind you I cheat. I have repeaters that are on both DMR-MARC and BrandMeister in my area. So I have multiple radios that are programmed for both systems. I have control of those radios via either tone remote (14 channel and one zone) MotoBridge, which has full zone/ channel control and TRBO-Vui / Radio Pro that also has full access to channel / zone programming. The TRBO-Vui is what I use with the Solo client on my phone to access those radios. Only have two currently configured for that. The VHF is all ham, the UHF is ham / commercial / GMRS. So that covers all the bases. The MotoBridge just switches zones, and has two radios for VHF and two for UHF, so I can get either system from either radio. I haven't seen or done anything with DMR Plus yet, But I do have an MTR3000 that I am currently running on 442.775 analog only. That repeater may get switched to DMR Plus if there is a reason to serve that system up locally. Most of what I do with it is monitor 3139 (Ohio TG) and the weather TG in Ohio. I don't see the programming being as much difficult as just plain tedious. But, I write code plugs for TRBO radios about twice a month at work for new installs, so I sort of have that down. I am looking at setting up my own RM server for TRBO since I have so many TRBO radios that I am managing for my own use. We have one at work, but I don't know how they would feel if I was sticking a bunch of my stuff on the company server.

OK in the ham realm here's who does what with digital. YEASU. Wires-X or Fusion which is C4FM, the same modulation scheme that is used in P25 but is not compatible with the commercial P25 offerings from any manufacture. ICOM. D-Star is their digital offering that is a fully ham system. The entire design of the system caters specifically to ham radio and has no commercial equivalent. This is a lined radio system that runs through various servers across the world. Call signs are registered and act as the radio ID. The system supports group and private calling (call sigh to call sign) across the entire system. The system is not band specific, meaning if an area has a full infrastructure roll out in place, users with VHF, UHF and 1.2Ghz radios call ALL talk to each other and anyone else on the system world wide. Kenwood has now adopted the D-Star technology as their digital offering for ham radio. Oddly, none of them are making a DMR radio that works with the MOTOTRBO DMR that is dominant in Amateur Radio currently. Those offerings are going to be commercial and the CCR's like BaoFeng, Anytone and Woxsun. Back to digital on ham and what's out there. I am gonna leave out discussion of hot spots. I know they are prevalent. I have one sitting here. But I personally don't consider talking 2 feet from my portable to my hot spot as real radio communications. So I will limit this to REAL (IMHO) radio systems with real infrastructure (repeaters with antenna's on towers). DMR is prevalent. Most hams know of this and many use it. Based on DMR repeaters, and a device called a C-Bridge there are two main systems. DMR-MARC and Brandmeister. These of course are both world wide systems using the Internet as a linking medium to connect the sites together. System is Talk Group based requiring not only the programming of a frequency and Color Code (similar to PL/DPL) in a Radio but a time slot and talk group ID as well to communicate. Bands supported are VHF, UHF and 900Mhz D-Star. Common in major metro area's. Build on all ICOM infrastructure. Specifically designed for ham radio from the ground up. Uses call signs as radio ID's to simplify management. System is also connected via the Internet. System is able to group and private call and has data transfer abilities. Bands supported are VHF, UHF and 1.2Ghz. P25. There is a lesser known P25 system that uses all Motorola infrastructure (Quantar repeaters) that is talk group based and Internet linked. This is the P25.link system. This system uses Cisco routers and software running on a Raspberry-Pi to link repeaters together across the internet. It uses reflectors similar to the MMDVM system (hot spots) for talk group support. This is a system requires more knowledge to connect to (must know Cisco router configuration and some level of Linux to load and configure the R-Pi. Has both internal Talk Groups that are PURE P25 and access to many MMDVM reflectors that allow for access for hot spots that can be configured for DMR, D-Star or any other digital mode supported by a hot spot.

Well, yes and no. And the FCC actually did the main one when issuing licenses in the PS band that had the emission designator for DMR. And that is significantly limiting ERP to pull the coverage footprint of the transmitted signal into a reasonable distance. Part of the problems that were created by DMR was the old school mentality of repeater systems for communications. That was put it as high as possible and run as much ERP as was legal. That mentality is why VHF low band is all but abandoned today. That stuff went up with 500 watt amplifiers to cover one county and it actually covered 8 or 10 counties. Then when the atmospheric conditions were favorable, you were talking to Arizona From Ohio and of course, the interference issue became a real problem. So, can you take a bunch of guys that have a CB radio mentality getting into GMRS that is further pushed forward by the guys that are already using the service where a 1.5 to 1 antenna match is TOO high, even though it's a .18dB signal loss and has ZERO effect on performance, to run a repeater with reduced power? And of course the answer is no. Because the rules say 50 watts, and by God, I can run 50 watts so I will run 50 watts. And I am not picking on the GMRS crowd here, this was an issue with professional radio techs doing it the way they always had done it, so there is zero reasonable expectation that hobbyist's are gonna do it the way it would need to be done. The FCC reacted to the issue on the public safety spectrum due to a glut of complaints they were getting from agencies and commercial radio shops fighting the interference that started as some agencies moved to DMR from analog. At one point they would not issue a license to any PS agency with an either a ERP or transmitter power level of 10 watts. I can't remember which it was, probably transmitter power level. For those that don't understand ERP (Effective Radiated Power) that is the realized effective signal level of a repeater SYSTEM including the feed line and antenna. So a system with a 50 watt transmitter, a 3dB loss in the cable and a 3dB gain antenna is 50 watts. But that same transmitter and line with a 6dB gain antenna would be an ERP of 100 watts due to the additional 3dB of antenna gain. GMRS and HAM radio doesn't have an ERP regulation, GMRS transmitter power is regulated at 50 watts and ham of course for most bands is 1500 watts. But a ham or GMRS operator can build any amount of gain into an antenna (as long as there is no additional active amplification) and have any ERP that system can produce. Ham's use this methodology to bounce signals off the moon and back to earth with large antenna arrays that produce ERP's in the ten's of thousands of watts.

This is only if we were to as ham operators shift our net to ham repeaters ( of course only those of us that have a ham license) that were AlStar linked. I guess I didn't specify that before. Lscott Pertaining to what you said regarding interference. I was specifically referring to the repeater pairs that were used multiple times in a similar geographic location. Obviously if two analog repeaters are close enough together they will interfere with each other. The issue really begins when the DMR modulation starts hitting analog signals on the same frequency and are close to capture in the receiver. DMR carries further than analog. I have tested this several times. These tests were against both wide and narrow band FM on VHF and UHF. With an analog receiver, the DMR signals were intelligible at the greatest distance, and the DMR radios would communicate a greater distance with all other factors (used the same repeater and antenna system) being equal. I have not tested the interference issues specifically. But We did have a DMR system in Fayette County Ohio and an analog narrow band FM system in Licking County Ohio. The FM system significantly interfered with the DMR system. The DMR system was built out to replace an FM wide band system in the same location in Fayette county. Both users had that same frequency for years and had never experienced issues with it prior to the conversion to DMR. At that point the DMR system had significant drop outs and the analog system was hearing the DMR digital transmissions in their receivers as the repeaters would drop (Licking county system was 6 site simulcast). I have never seen adjacent channel interference with DMR. Most likely since it's requirements for better frequency correctness than analog FM. (Can't remember the correct term here.) I have seen FM wide band radios off as much as 1200 Hz from center and work fine. DMR will exceed the acceptable BER long before the frequency drift gets that bad.

Lots to think on here. Selling spectrum as opposed to the continued increase of license holders and their money. I don't know what the agreements are for 'selling' spectrum. Is it a forever thing, as long as it's occupied or is it a lease with some fixed length of time? Reason I ask is this. GMRS and HAM are both a continuing revenue stream. This is from both new licenses and renewals of old licenses. If the sale of spectrum is done without a term then it's just done. Here's your money, and I can do as I please there as long as I want for no additional cost. Again, I don't know how that works. DMR on GMRS and interference. Would I like to see DMR made legal on GMRS. Yes, but I also realize, like others have and mentioned, the level of interference on the limited repeater spectrum could cause serious issues. I have seen the issues with DMR and analog trying to co-exist first hand on public safety frequencies and it didn't work. And the systems were several COUNTIES away from each other. There would be NO way that it could exist in the same county or city. Simply NOT possible. And they would interfere with each other,,, not just the interference from DMR to the analog, but the analog to the DMR as well. The interference from DMR is obvious, it puts noise on the air that the analog stuff would pick up. But the analog would cause increased BER on the DMR subscribers as well causing issues with pixelation of the audio and drop outs. How COULD it be addressed? Coordination would be a BIG part of it. Coupled with the DMR repeaters being limited to only PART of the repeater spectrum. DMR repeaters being REQUIRED to be high profile and FREE access to all licensed users would also need to be a requirement. In addition, because of the way DMR works, the coordination would not only need to be for the frequencies but the time slots, and talk group assignments as well. And that is where it would all fall apart. The equipment isn't hard to find. And groups could assemble to fund the repeater purchase. So, no big deal there. But Talk Group assignments and management would need to be figured out. That would most likely fall on the repeater owners to do. And ongoing management of that could turn ugly quick. As long as the person was available and willing to do it, things would be fine. But once that person wanted his life back, then the problems with getting ID's and talk group assignments would become a problem. And that's not something that anyone is going to want to do. We see this here to some extent getting repeater node numbers assigned. It's not automated, requiring ONE person to manage all that. And I am not complaining, but it's not a 24 hour process to get it done. Which is what people would want. And if that person sells off the repeater, then it's up to the new owner to manage it or NOT. They can very easily flip it to analog and it's just gone. Now if you bring LINKING into the mix, it gets MORE complicated. Not only can subscriber ID's not overlap, but repeater ID's can't either. So MORE management is required. If someone was profiting, then it's manageable. But we can't profit from it, because that's the GMRS rules. So it's just not even feasible to attempt linking. And even managing a single repeater in a big city with hundred's of users would be more than I would ever want to take on personally. You may have time for that. I don't. P25 on GMRS. Slightly more feasible. Can be linked flat (no talk groups but COULD be done). Still some management, but just at an infrastructure level. Could be relegated to one or two repeater pairs nationwide. Doesn't interfere as bad with analog. Still would create issues with analog repeaters however. Doesn't use the pulsed transmission that the subscribers do so the analog receivers don't have to deal with the constantly changing SNR that is present with DMR. Ham spectrum reallocated to GMRS. Yeah, not gonna happen. We don't even have a group to go lobby for something like this where the ham's have the ARRL. Then there are the technical issues that you would face with being 20 something Mhz apart and needing super broadband EVERYTHING to make that work. Too many reasons that will not work. Coupled with if you want MORE spectrum to communicate on, you can go get a ham license and do that. And once you have a ham license you can do MANY things we can't do on GMRS. But I will say this. If all the GMRS operators on this board were to figure out where their local AllStar node was and we were to link them all together and have a net some Friday night on that network, the hams would flip the hell out. It would be more traffic than their repeaters had seen in years. ANd it could be echo link or allstar. It would only require the linking. My guess is they would never allow it again due to the traffic load.

What? Creating a context so that you can create a platform to contradict someone? OK, since you said that, I will accept that as being the case. Not my specific intent here, but since you choose to point one that was your motivation, I can go with it. Now of course, context, presentation, and lastly grammar is EVERYTHING. You made that as a statement, rather than a question that would imply that I was the one taking refuge. But your presentation is all wrong. By taking what I said, out of context, and then making a specific statement about what I said, you in effect agreed with it. And in doing so implied YOU were the one taking refuge. Which of course is actually the case. And with reviewing other posts you have created over time, taking those into account along with this, it creates an even better context that it's indeed true that you like creating platforms out of thin air to contradict other's for no other reason than the act of doing it. But that's ok. We all are motivated by different things. And have different personality traits that don't always mess real well with others, but we all seem to be able to more or less get along. And how did a discussion about digital modes on ham radio devolve into this nonsense anyway? I had to go back and look and here's what I am seeing. LScott commented about hams complaining about expensive microphones and then dropping money HF gear. This was a reply to a comment about HHCH configurations which are a thing with commercial P25 gear. So still technically on topic. You disagreed and said cheap wasn't 'appropriate'. Couple comments of real world situations about hams, still within the overall subject matter. And again, you needed to contradict things and point out analogies being stretched. Couple more comments,,, then I posted and you again needed to contradict me, and LScott. And here we totally hijacked once again. I rebut, you again take what I said totally out of context and attempt to further your straw man position. And here we are. So I guess the question becomes, just what is it that motivates you to come in and hijack threads on here? ANd what exactly in this ENTIRE thread that you posted has ANYTHING to do with P25 on ham radio to begin with. I see you contradicting others. I see you create a context out of thin air to further your contradictions, but I don't see ONE DAMN THING that has anything to do with digital VOICE on ham radio.

Well, I was trying to keep stupid out of it. But yes, stupidity is certainly a factor.

I see the difference in the context that you are trying to apply to it. But that's not what he was getting at and you seemed to need to contradict him so you created that implied context so you could. And cheap tires are still regulated. I figured that someone from California, land of CARB and other 'additional' vehicle regulations would recognize that. For ANY tire to be installed on a motor vehicle that is used on any public road in the US it must be DOT approved. Your implications are they are buying farm tires or some other non-approved and untested equipment. That's not gonna ever be the case. Both of us were only indicating that some people are cheap. They spend money on certain items but even with spending incredible amounts of money on PARTS of their projects, they cut corners on other parts.

NO actually he's NOT. I have seen more than one setup where the radio and antenna system was a combined total of over 10K and they used RG-8X coax to connect it. That was ONE. Second was a big ICOM, huge money. Reused cable that the braid was showing connected to a Yagi that was missing elements. Thought the expensive radio would compensate for the broke ass antenna. It didn't.

OK, you are NOT going to get enough physical separation of the antenna's to get it to work correctly. So that's the FIRST problem. Second issue is you are using radios that due to their size have little to no filtering. If the thing was to talk more than 100 yards, you would be doing good. And your 'power robbing' duplexers are the ONLY way it could possibly work. Let me run this down in real numbers in a manner that will make sense. And the ONLY way you could POSSIBLY get it to work. If you can get the antenna's 20 feet apart on a vertical plane. Meaning one antenna 20 feet directly above the other then you will get about 15 to 20 dB of isolation. For every 20 feet increase you can add 10 dB to that. You need 80 to 90 dB of isolation for a repeater to work correctly. So if you can place the top antenna 200 or so feet above the other one, then you have enough isolation. Of course the bottom antenna that you are transmitting on is at ground level, and the receive antenna is 200 feet in the air so it will hear ok, but not be able to talk very far. Second issues is unless you dump a bunch of money into 7/8 hard line (with 1.5 dB of loss per 100 foot length) the loss on the receive side is going to be higher than the loss of a 'power robbing' duplexer. But it's STILL a portable with poor shielding, so the transmit RF is still gonna get in the radio and screw with the repeater function and desense the receiver in that hand held. You could of course run a 200 foot linking cable down the side of the 200 foot tower linking the radios together, but that will pick up a ton of static and electrical noise and cause other problems. Bottom line is this, you have never seen this work because it don't. ANd no amount of screwing with it is gonna get it to work. If you have a spot that has 1000 feet of elevation over the area you are wanting to cover and you have a repeater, move the thing. Install a LOW GAIN antenna, I would say 3dBi MAX. Reason is that an antena with gain is NOT an amplifier. If can't increase the signal level through amplification so it does it by concentrating the radiation pattern. A unity gain antenna has a pattern that looks basically like a donut from the side. A gain antenna flattens that donut on a vertical plane. So the pattern goes up and down in equal amounts. If you get too much UP then the area under the antenna has no coverage. Which does you no good.

Roger Beeps are a love it hate it sort of thing and everyone seems to have an opinion. I have heard guys that complained about MDC on the air, which is NOT a Roger Beep but a digital Identifier that will display on most radios if they are programmed to decode it. That would be the 'squawk' that you might have heard after a user talks, it you were wondering. A lot of folks find the Roger Beeps annoying. And I tend to agree with that myself. I do have a Roger Beep in one of my CB radios that has had significant modifications to enhance the 'loudness' of the radio when transmitting, it also has a double ping that plays every time I key up and an echo board to further enhance the annoying factor when I get on the radio. It's setup SPECIFICALLY to be obnoxious and to stir up hate and discontent. I use other radios when I am just trying to talk on CB in a friendly manner and not irritate everyone on the air ways. And as OffRoaderX mentioned. The ones you DO need to be concerned with are the repeater owners. They put in a TON of effort and money to keep equipment on the air for your enjoyment. And making them mad is a good way to not have a local repeater any more since they ARE the ones that can just pull the plug on the whole thing and sell it off on eBay. Don't be the guy that gets the local repeater unplugged. To the creating havoc with the repeater system. Not likely. I will say that there are some repeater controllers that can be configured to listen for DMTF and when it hears ANY DTMF it tries to do something with it. That can cause issues with a controller. But a couple tones played as a roger beep should NOT have effect on a controller.

Is this for a base or a mobile? IF it's a mobile, you are gonna be restricted to RG-58 or possibly LMR240 due to the size and flexibility of the cable. For a base you certainly have other options, but again the length of the run is going to determine whats needed and your budget is gonna be the other determining factor. Running the NEEDED cable length and not going overboard and having a big coil of cable someplace is the best way to limit losses. So figure that out and get what's needed and not some fixed length of cable. The reason I mentioned budget. If youget 100 feet of LMR-900 cable. The cable will cost more than the radio did. Average price on that cable is 8.50 a FOOT. So, 850 bucks for 100 feet PLUS 100 bucks average for ONE connector.... you will need two. So the cable run would be a grand. Guessing that you aren't ready to drop a grand on a cable run for a GMRS base station. But maybe you are. Here's the rub with cable loss and the CB radio mentality when it comes to wattage. Professionals in the two way industry all use dB for figuring the stuff out. ANd the really important part is receiver sensitivity. Depending in the radio, you need between -118 and -116 dBm to open a receiver. Typically -112 to -110dBm to reach 12dB sinad and -105dBm for a full quieting signal. SO to go from a noisy signal to a strong signal you will need 6dB of change. In watts, that's going from 25 watts to 100 watts. But there are other factors like antenna gain that play into that. And an antenna with 6 dB of gain over an antenna that has zero gain is going to be a LOT less expensive than 100 feet of that LMR900 cable that was mentioned and have the same perceived effect. Sure you can put that sort of antenna up on top of the 1000 dollars in cable, and have a really good setup. But again, that's a TON of money to spend for GMRS radio base stations. I have a repeater running 50 watts into a combiner network that has 6dB of loss. With the cables and such in the building I get 18 watts going out of the building to the antenna. Antenna is 8dBi of gain, and is 180 feet in the air. Cable loss is 3dB due to the length. The repeater in certain directions talks 50 miles. So, does cable loss have an effect, sure. But it's NOT as much as you would think. But antenna height is obviously more important than cable loss. And I am running LDF5-50 hardline which has similar loss figured to the LMR900 that was mentioned. But my run is over 300 feet due to the routing of the cable from the building to the tower.