DONE

Well, if we are gonna get into 'real' Faraday Cages, then lets actually talk about their construction. First off, they are layered. There is an outer and inner layer and they are NOT connected together. Hole size in the shielding material is what sets the minimum / maximum frequency that is blocked. In other words. A fine mesh will block a higher frequency than chicken wire will with 1 inch holes in it. Consider the holes with regard to frequency wavelength. If the hole is larger than the wavelength of the frequency in question, it will pass right through like it wasn't even there. A strong understanding of the signal level and the attenuation level of the Faraday Cage needs to be taken into account. A cage is not a perfect attenuator. It has very high attenuation levels, but a signal that is strong enough will get through at a much reduced level. Proper construction. A 2X4 or 2X6 frame is sufficient spacing to get a very high attenuation level with modest materials. Those being standard wood framing and aluminum screen. For an added sense of security, thin sheet metal can be used in place of the screen. You have an inner layer and an outer layer. of the conductive screen material. And remember they can't in any way be connected or you will loose attenuation properties. The other thing you need is a GOOD earth ground. This is not the 1 or 2 ground rods that are grounding your electrical service entrance, you will need to do better and it's advisable that the grounds be kept short as possible. So if you are planning on building a cage, do it on the first floor or in the basement near an outside wall so you can get the ground wires out the wall and to the ground field withthe shortest wire possible. Longer wires equal bigger antenna's and you don't want that. To put a door on the cage, you will need to ensure that the entire perimeter of the door be connected to the screens, both inside and outside. Couple ways of dealing with this is either finger stock, copper or other metallic door trim / weather stripping, or construction methods that taper the inner and outer screens in a way that when the door / cover is in place that a 100% seal exists in all locations around the door inside and out. Again, can't say this enough, the INNER shielding material is NOT connected to ANYTHING including the outer shielding material. For those that are looking to play around and build something similar to the professional level cages, this should be a good starting point. Sure you can locate copper screen and use that. It will work the best but it's also very expensive. Not worth the money to protect your Baofeng radios. If you are REALLY wanting to go for broke and build a large cage, and be able to occupy the space, there are methods of bringing power and RF into the cage, but special filters and methods are required and are put in place outside the cage and are bonded to the same ground as the outer layer of the cage. Remember that you need both layers of screening on all sides, including the roof and floor. There is no reason that you can't set the floor screen and then sheet over it with layers of plywood or other subflooring material as long as the screening isn't molested (floating floor material.And of course you can also drywall the walls and ceiling but it's advisable to use construction cement and not screws to fasten the drywall to the framing. Screws can be used sparingly to assist in placing the drywall until the adhesive is dry but will need to be removed after that happens to ensure the best isolation. If you bring electricity into the cage, do NOT bring a ground with it and you HAVE to use an isolation transformer with proper filtering right at the entry point on the OUTSIDE of the cage, DO NOT use conductive conduit to route wiring through within the inner shield. Detailed construction instructions are available on the web for building a Faraday Cage. Study those plans carefully and scale your project to your needs.

And that was my whole point. Thing is that the South Korea and China saw no damage either. And I was at a loss to find any information on damage done in the US from tests when they were conducted, which was the point of what I said. EMP is a real thing, and I am not trying to minimize the effects of it when it comes to things like the electrical grid. But to hear some people talk about an EMP is that anyone with ear rings in will be electrocuted by the voltage induced between them across your head. We had cars with computers in the 90's. No one seemed to be effected by the EMP from any of the testing in that era. Sure those detonations were below ground. But if the EMP is that powerful to effect every car in the midwest from a high altitude air burst then how is it that no one was effected at all during any of the testing. Or were those effects just not documented? I don't know.

Here's the issue with this. We don't know what we don't know when it comes to an EMP. And much of what we do know about it, or think we know comes from Hollywood where all the battery powered everything from automobiles to wrist watches are going to throw sparks all over the place and fry in a very dramatic manner. Yet it's said that old tube gear will be fine. Which honestly makes little sense. So here's what I know about it. And this comes from being an R56 certified installer and digging deeper into the bonding and grounding aspect of it. First thing is you can't 'prevent' lightning, you can only attempt to prepare for it and hope you have done all that is needed. We all know some CB operator that disconnects his antenna cables in puts them in a glass jar. News flash on that. Lightning jumps up to 9 miles during a strike. That little bit of glass, the 6 to 8 inches of rubber on a car tire or whatever is NOT going to stop the strike. And in truth, disconnecting the antenna cable if the cable and antenna isn't grounded at all past the shield being connected to the chassis ground of the equipment actually increases the chance of a strike. Glass jar be damned. The antenna has no where to bleed off the charge that builds up on it and it actually becomes a better path to ground because it's charged and other stuff isn't. Less of a voltage difference. Yeah, you may see some arcing on the connector in the jar, but that is an indication of the very thing I am talking about. You ground and bond everything to a common point to bleed off that charge. But you also bond it all together for when it does get hit. If you have a couple radios, a computer, power supply and such all connected together as a station, and your your tower gets hit. If EVERYTHING is bonded, then all that gear jumps to several thousand volts and then back to zero,,, but it all does it at once since it's bonded together. If you remove that bonding. Lets say on the computer you are using for HF packet and the power supply. Now all of a sudden, there is several thousand volts of potential difference between the power supply the computer and the radio. Guess what happens. So back to the EMP business. An EMP is nothing more than a light lightning strike. And if you think about that statement, think about lightning and the voltages and currents present you will realize that 10 million amps across a number 2 or even a 4/0 wire is going to be THOUSANDS of volts in the wire. Yet, towers get hit all the time. R56 is a standard used for 911 centers where they CAN'T unhook their antenna's and stop working during a storm. And if there is a tower at the center with radios connected to it and the dispatch console, then there is a direct DC path (considering the voltage potential of lightning) from the top of that mast to the headset of the dispatcher. So what do we really know about an EMP? Do we need to stick radios in Faraday cages to expect them to survive the pulse? What happened to all the electronic equipment (yes it was tube back in the day) when the US and Russia would test nukes in Nevada and the island chains they were known for? And when did the testing actually stop? Well the US's last test was in 1992. And the North Korean's was in 2017. Yet there is no information available about peoples cars stopping, radios dying, or any of that. So at what point would you need to store a radio in a Faraday Cage in order to protect it? And the answer is striking. If the EMP is that strong, the radio would need to be stored 30 to 50 feet below ground in a Faraday Cage to survive because you are close enough that the blast wave will destroy it at ground level. Now of course connected to the grid, and an antenna that distance increases, but not if you have proper bonding and grounding and correct surge suppression on the equipment in question. Antenna size and type will also play a role in this. A big HF antenna like a 40 meter dipole will take a bigger induced voltage than a UHF DC grounded folded dipole Like a DB-404 or other DB series base station antenna. This is due to the design of the antenna. Folded dipoles are closed loops with one end being grounded. HF type dipoles are open ended and typically are NOT grounded. In fact the standard half wave dipole is suppose to be a balanced design. So in theory a balun of proper design can be used with an HF dipole to protect the antenna to some degree when coupled with a proper surge suppressor. A good reference for this stuff is the Military grounding and bonding manual that goes into not only lightning suppression but EMP mitigation.

First off what is a 'channel block' forgive my ignorance. I have been a commercial radio tech for going on 15 years and a ham for 30. Never heard that term. I see things in zones and channels. If you are scanning the simplex channels with NO tone, and scanning the repeaters with tone the radio can stop on either one if a repeater is transmitting. If it's not looking for any tone, then any tone will work as well as no tone at all. Because it's not looking for it. No clue what radio you are using, so I can't even comment on the idea of priority scan. If it's a commercial radio, and it has priority scan running it will look at a channel, then the priority list, then the next channel in the scan list then the priority list again, then the next scan list member. This can slow scanning down a good bit, and commercial radios are NOT good scanners. They are not fast with standard scanning, and when you turn on priority scanning they get really slow. My advice, if you are gonna be scanning, buy a scanner. In fact as long as the stuff you are scanning is analog and not P25 trunking, buy several scanners. If you do have trunking stuff you are wanting to monitor, get a scanner for that too. Analog scanners are dirt cheap because they don't listen to the police any more in many places. But if you are wanting to monitor GMRS, ham or other analog stuff they work great. And trying to figure out what a radio in scan mode is doing by looking at percentages of when it stops and opens up isn't really gonna work out for you.

Oh it's possible. I can see a broadcaster buying / acquiring a broadcast tower from another broadcaster and getting it in the air and making money. But the key there is the money making. If you are in a good market and have a 2K per day income in advertizing dollars then spending 50 or 100K for a tower and that much again on a transmitter and studio gear to be on the air makes perfect sense. But it's gonna be rare that a HAM / GMRS operator is gonna be able to even relocate even 5 sections of Rohn 80 tower. Mine was almost 4 times that. Mind you the sections are 400 pounds for the top ones and the bottom and torque arm reinforced sections are 600 plus pounds. They are also 20 feet long which is a standard for medium rated commercial broadcast towers. Truly big commercial towers like Rohn 90 and above (some with 14 foot faces) weigh over 1000 pounds a section and are longer than 20 feet per section. But just so we are clear, I am not referencing the small TV and ham type towers that are in 10 foot sections and standing next to many houses with a TV antenna on top of them. That stuff can be lifted and moved about with one hand and only weighs 15 or so pounds per section.

My personal setup is a bit overkill for anyone new to radio. I run an APX8500 and a Comet 2X4 antenna. So that being said. A good starting configuration for the folks just getting into GMRS is gonna be an NMO mag mount with a unity gain whip. That is by far the least expensive option and will still give reasonable performance to get you on the air and talking on the local repeaters and some simplex as well. One of the things that people fail to understand, especially with mobile setups is the amount of available gain in mobile antenna's from unity gain to the highest numbers available is only about a 9 dB difference. Now while that sounds like a ton of gain, when you are looking at signal levels in a radio and what is receivable and whats solid copy all falls into a range of about 6 to 9dB. If your squelch is set to -118dBm which is pretty typical, could be as high as -110 dBm but that's pretty tight. When you are at -118dBm you are gonna be about 25% noise. But if you open the squelch up more and go down to -120dBm signal level you are now at 50% plus noise with your signal. So down at that level it matters. That being said. If you increase from -120 to -110, you are typically going to be perfect copy, and by the time you are at -107 you are solid. Any increase from there is NOT going to have any effect on your signal. You will sound the same from -105 to -50dBm. The reception just doesn't change. Point is this. If you have a local repeater that has a signal level of -100dBm in all the area's that you travel, putting a 9 dB gain antenna gets you NOTHING for increased signal. And UHF is finicky. Hills and valleys will block the signal no matter the antenna gain. I have two radios in my truck. One is an XPR4550 with a unity gain whip. The other is the 8500 with the 2X4 Comet. When I start loosing the repeater on either radio due to topography, both radios suffer equally. The signal is just blocked and there is nothing that can be done about that. And there are places that I can't talk on my repeater that are less than 10 miles from it, but there are places I can talk on my repeater that are 60 miles from it. So bear that in mind when your signal fades out and comes back and you feel you would be doing better to go drop $100 on a wiz-bang high gain mobile and antenna and mount thinking it's gonna cure all your problems.

Oh I can't afford free towers. Especially big broadcast towers. What you end up finding out is the towers typically will not pass a structural analysis and can't be used unless extensive reinforcement is done to them, if it's possible at all. When the power that be (local building inspectors) ask for the results, you don't be a permit to stand the thing back up. And that says nothing of the cost of dismantling a standing tower, transporting it and erecting in at a new location. I personally went through this with a Rohn 80 that was only 10 years old at the time. While it would still pass analysis, the concrete alone to put it back up was going to cost me 15K. With a total cost of about 50K to get the thing standing. I didn't have enough land to do it either, which of course is a concern. Point is if a tower that costs tens or even hundred of thousands to erect is FREE, free is TOO expensive for most.

You know they make a tool for that.

I see how if you want to split hairs here that it applies. What I am saying is that if I go down to the local TV station that has two UHF MSF5000's repeaters sitting on a deck at 750 feet. Yes, they are there I have worked on them. If I get permission from them to go up there and reprogram one for a GMRS frequency, lower the power to 50 watts (100 watt stations) then I am completely legal as far as the FCC is concerned. Now that's not going to happen since they use those repeaters. But, the FCC regulations regarding GMRS don't have any restriction on me doing it. That's the point I was trying to make.

So me in the part 95 regulations where it says you can't place an antenna above X height. It's NOT there... anywhere. What you can build for a tower is going to be limited by your location with regard to airports, flight paths and other factors. And yes, getting the proper permitting for a 1000 foot tower may not may not be possible in a specific location. You may be limited to 20 feet and be required to have obstruction lighting on it even at that height if you are right off the end of a runway. But that is still not a GMRS SPECIFIC height restriction. It's a general restriction that would apply to any tower including one for a TV antenna.

Yes, this is correct. But if you either have the structure already, permission to install on a tower owned by others, or have deep enough pockets to stand up a tower there is no limit to the height of a GMRS antenna. On LMR, the coordination body / FCC limits ERP, power out and height to maintain coverage only extends to your licensed operating area. Yes, we are limited to 50 watts out on power. But we have no ERP restriction outside the 467Mhz channels that are limited to .5 watt ERP. And while the FCC has the requirements in place for obstruction marking (tower lights) in their regulations, it's the FAA that sets these standards.

The only place in the rules where ERP is even mentioned is specifically posted above regarding the 467Mhz iinterstitial channels. So a GAIN antenna can NOT be used with a .5 watt radio on those specific frequencies. And since you grasp the concept of gain and such. Most fail to realize that while we are limited to 50 watts of output at the transmitter there is zero height limitation on a GMRS base station or repeater antenna. You can go as high as you want and can afford to. Here is the reason this fact is significant. Broadcast and LMR (commercial) radio are in fact height limited. And the reason is a realized gain due to height. That gain is about 6dB for every time you double your antenna height. So if you have a repeater at your home and it's on a 20 foot roof peak. You stand up a 320 foot tower next to your house and park the antenna up there. Cable loss not considered. You have a perceived gain of 24dB. Putting that into perspective. To put out the same signal at 20 feet would require feeding the antenna 12800 watts. Again, not considering cable loss. Go from a 3dBi gain antenna on the roof to a 6dBi gain antenna on the tower in the process and it's now 25600 watts. Antenna height, to a point is the most important thing to have with a radio system of any type if you want it to have good coverage. And antenna gain, both from design and height equally effect both your receive and transmit, where increasing power output only increases the distance you can be heard. It does nothing for your ability to hear others.

OK, explain your current setup. You said you can put an antenna up on your house. But you make no mention of current antenna system, placement, height or anything else. No idea here what you are working with so it's hard to point you in a direction.

Your spelling is Wong / Wrong.... sorry, couldn't resist

Yeah, add repeaters are EXPENSIVE, hard to support, and will either bring you constant complaints that the coverage doesn't go someplace specific they want it to or that no one will ever use the thing. But it's usually both issues that arise. Obviously need to cover radio operations, passing a conversation. Waiting on others to break in. Not trying to talk over the reset tone. Roger beeps are for CB and not GMRS.

Resistance of the heating element when cold too low for the FET's to drive without going nuclear? Transformer acts as sort of an impedance match so the elements can heat up? Purely guessing here.

Yeah, but at least in that case, you can go in the archives and grab the original design documents and put them in from of the guy and ask him how he's more familiar with the equipment than you are? Outside of one guy at work, we don't have that problem. We work together. The one boob.. I taught to tune a specific duplexer, and did it wrong. I went to him, applogized for the mistake and tried to retrain him. He was having none of that. The method that I taught him, mind you I am standing there telling this clown I had told him incorrectly, was fine and that was the way he was gonna do it. But that's the way this guy is. And he's scared of me. Like a LOT. Never really gave him a specific reason, he just is. And the other employee's can't figure it out. This clown will fart, burp, make noises, laugh in a loud and obnoxious way around anyone, except ME. Our boss included. I walk in the tech room and he pulls himself up to his desk, shuts his mouth and works. Minute I leave, he's right back at it. He did one day after I got on him for screwing off and not doing his job and butting into mine finally decided to muster the courage to tell me th 'go to hell' and called me an asshole. I IMMEDIATELY replied that my reservations for Hell were confirmed the prior week and as far as being an asshole, I appreciated the recognition of my continuing efforts. And it wasn't that he said it that was so funny.... It was the way he said it. Like he knew I was gonna pound him for it. So his voice was cracking and he was almost timid about it. When I fired back, the whole room got up and left. But of course as soon as they cleared the door they all busted out laughing. Gotta love co-workers

Yeah, I got involved with a forum that started as outdoor warning siren techs and manufactures. We would exchange info on different things we had seen, odd issues that we couldn't figure out and crap like that. Then the 13 year olds took it over. And they wanted to discuss leaning poles and what specific frequencies the sirens operated at and all sort of nonsense that had no bearing on keeping them running. Then of course they started disagreeing with people. Once case the guy that dude was arguing with was the guy that designed the equipment in question. He was the designer for that manufacture. And this clown is arguing with him about what he's saying about the equipment is incorrect. That was the beginning of the end. All of use that were in the industry left. And it was a shame, because at one point it was a very helpful took to reference. Now, not so much. But I actually am tired of stirring the pot. And any more, there is no need to stir it. It just happens on its own. And again, it just gets boring to see a horse beat to pink slime.

First off, I never said that keeping unauthorized users off a radio system was the only reason for trunking. But it WAS a sales point. Never heard of people using 'illegal radios to access a trunked system' Maybe not in your state... Ohio has had several instances of people being busted for selling radios that were programmed for the state wide system. Never heard of it prior to trunking? I have worked with the FCC and in one case the FCC and FBI tracking someone that was interfering with repeater systems that were County EMA equipment. All EMA's fall under Homeland Security. And due to that screwing with them can be considered a terrorist activity. And that's not some guess or interpretation, that was directly from the agents I was working with. We also figured out that the radio that was being used was indeed a cheap import. The 'roger beeps' on those radios are distinctive and the logging recorder that we had running did hear that specific set of tones multiple times in the case where the FBI was involved. The other times were fire and police repeaters that the FCC came out and tried to hunt the person or persons down but had no luck, other than whoever it was stopped doing it. But it was made public in the radio communities that the FCC was in town and that is what seemed to make it stop. Back to the trunking thing.. Yes, the primary reasons for trunking systems is frequency management and sharing. But interoperability, access control and radio resource management are also big parts of it too. And wide area coverage beyond the county level is a big piece of it was well. You simply couldn't use a single frequency across three or more counties that contained any significant population.

And this thread ladies and gentlemen is why some of us that actually work or have worked in the communications industry and might know a bit more about these topics than the casual user tend to steer clear of posts like this and giving technical answers to questions. There is always somebody that thinks that someone told them something else that they have ZERO first hand knowledge of will argue with guys that do this crap for a living. It gets old. And is one of the reasons that guys like me no longer bother with these forums like we did. But here's the sad part of all of this. There are some on here that DO know. And when they get driven off of here due to the BS, you loose that knowledge base.

Not really looking to 'microstamp' radios. Point I was making was back in the day the idea of fingerprinting was a thing. Now with the digital radios and assigned ID's it's really not needed. P25 standard has an additional feature called 'radio inhibit'. This fully disables the radio rendering it a brick. This can be reversed by the system admin that sends it out, but outside of that, the newest radios have to go back to the factory to be turned back on. And the factories require a pretty reasonable explanation of why the radio got that way to begin with before they will turn them back on and return them to you. In other words, it will be returned fully disabled, but only after the original owner according to their records and the system administrator of the system that inhibited the radio to begin with is notified. To that end. Technology has gotten us past the need of needing to 'control via regulation' radios abilities to transmit where ever. So even getting the regulations reviewed and changed pertaining to using a radio for multiple services is not gonna happen. And you need to remember that testing is done at the request of the manufacture by the FCC for a fee. If a radio is designed for LMR service, sure it could be used for GMRS if UHF or MURS / Marine if VHF. But those are additional tests that would need to be paid for at the time of testing. The manufactures are NOT going to build a radio for multiple services because there is simply no need. And if you think about the cost of a MURS or marine radio VS a commercial LMR radio, there is a huge difference. No one is going to spend the money for a commercial LMR radio when new to use on MURS when the LMR radio is hundreds of dollars more. And the manufacture see's no profit when the radio is sold used later on and the new owner wants to use it for something outside the original purpose.

Gonna expand on what I said a bit. There were / are technical reasons that the regulations were put into place that simply continue to exist even though the technical reason no longer does. I sort of spelled out the HAM VS everything else reason. And the real truth to that is if you had a radio that was full TX/RX from 400 to 500Mhz (UHF) and you started showing up on commercial and public safety parts of the band. The argument could reasonably be that the radio came that way and I just used it. Hence the TX block for the ham radios and of course the no end user programming for commercial and GMRS radios. It keeps people from doing dumb stuff and minimizes the calls about interference to the FCC. We as radio operators know that only goes so far. There will always be those people that will interfere with communications on any repeater they decide to. And that's part of the draw for public safety to switch their operations to 700/800 digital trunked radio systems that require a system key and assigned ID to communicate on the system. It's a more effective (not 100% effective) way of keeping purposeful interference to a minimum and offers ways of stopping it by disabling the radio ID from accessing the system. Some of this functionality has existed in analog for years in the signalling systems like DTMF and QC2 where the radio ID could be sent a stun command and the radio would disable transmit. That was effective for radios that were stolen or misplaced that were programmed to accept the command and be stunned. With the newer digital trunked systems, the ID can be disabled in the radio system. Since the radio ID is transmitted every time the radio is keyed, the system can ignore the radio and block it's access to the system regardless of the programming in the radio. This happens at a system / repeater level. This was looked at a number of years ago by some ham buddies of mine that were fingerprinting radios. Every radio as it goes into transmit 'rings up' as the transmit oscillator comes online and the modulation circuit becomes active. This 'ring up' is typically unique to every radio and can be used to identify a specific radio. That part they had down. The next steps were to compare that to a set of files that were banned radios and disable the repeater if a banned radio was attempting to transmit. The computers we had at the time were simply not fast enough for all that to occur before the person started talking. Of course this was all done in the days of 8 and 16 bit computers running DOS ( think Windows 3.1 time frame) and the first generation of SoundBlaster sound cards) Software was called XMITid. Written by Richard Rager.

OK lets look at the rules and start to tear this apart. First is HAM and anything else. Ham is the ONLY service that allows VFO access to any frequency that the radio is able to access. This applies to both transmit and receive. No other transmitting radio in non-government hands has this ability other than SOME Maritime and Avionics radios. They either need to be preprogrammed (CB, MURS, GMRS, Marine) Or they need to require programming with in their operating range in some fashion that doesn't give the end user direct access to program the radio without some key, or software (part 90 LMR radios). So that's reason one. As pointed out, ham radios don't need to be type accepted, but do need to meet certain criteria to be manufactured and sold by vendors. You can build anything you want for your own use. But radios from the manufacture have to ship with the ability to transmit outside of the allocated frequencies blocked. Of course, removing that block is simple enough usually, but it has to be there when it ships. So that's strike two. The third one, is the biggest and it exists in all services EXCEPT ham radio. No radio can operate outside the service it was designed for. So a commercial LMR radio can't be used for Maritime communications. It can of course be used for ham radio since no restriction exists but a radio designed for the ham radio service can't be used for any other service either. This is both regulated in the design criteria for ham radios that are manufactured and exists in the part 90 rules that a radio. This again is becoming a dead horse topic. It gets brought up and rehashed over and over again. So here's a better question,,,, why do you care? Are you gonna get a part 90 LMR license for VHF and want to use your Baofeng to talk on both VHF and UHF GMRS? Do you figure on running your modified ham radio on your boat? Or are you just complaining via a question that you don't understand the reasoning for what the regulations are and figured it would sound better if others were to complain about it so you didn't have to? Simple way to deal with it. Follow the rules. You obviously know them, or you wouldn't be asking why they exist to begin with.

I would be looking at drilling the rock and then using epoxy anchors to fasten plates to the rock face and then bolting the tower to that. We aren't talking about 'JB Weld' here either. THere are high performance epoxy products on the market for doing this sort of thing and they work well. But closely following the directions for the use of the chemical anchors is very important. But remember that light poles next to the highway may well be using this method for connecting to the concrete wall they are sitting on.

What frequency? Where at? You seriously can't come on here and ask that general of a question and expect an accurate answer. Could be ducting like Marc said. But it could be any number of different linked repeater systems. I was hunting around and just recently found a group that is using ham radio RF MMDVM hotspots on GMRS frequencies that are all linked together. If someone reasonably close has something like that you could be hearing it. Remember that there are other repeater systems out there besides this one.