zap

That's actually a good question. Although, the only microwave links I can think of that are budget friendly are 2.4 or 5.8 WLAN links (maybe 900 MHz).

I've got a couple off single channel, two channel, and 6 channel. Most of them are VHF 7-25W models (backup repeaters is how I'll probably repose them) and then I have a couple of 7-25W UHF and one 21-35W UHF. They make great little repeaters. The 7-25W radios have a 29% transmitter efficiency...higher than almost anything I've seen to date.

You'll have to make sure you have the offset programmed in. Then just change the pl tones once you have permission to use a repeater in the area.

First, it depends on the radios you are using. Most consumer grade FRS/GMRS radios can not be used with repeaters (they won't do the splits). If you can hear it, you can try to hit it. If you can see it, you can definitely hit it. It really just depends on the repeater's location and your location relevant to it. Repeaters are fairly simple things. A receiver, a transmitter and some circuitry to mix it all together. They can be a single, full duplex radio, or they can be based off of two half duplex mobile radios, and in some instances you'll see them based off of hand held radios (generally avoided in the commercial world though). The things you need to know are the split (GMRS is going to be +5 MHz), and the PL tone (referred to as CTCSS commonly). When you are on a duplex channel on the end user, it transmits +5 MHz from the radios receive frequency sending a sub-audable tone (PL). If the repeater's receiver hears this tone, it unsquelches and keys the transmitter, re-transmitting the audio it hears on the output, which is 5 MHz below the receivers tuned frequency (because your radio is transmitting, the receiver is turned off, but everyone else will hear who is on the output).

Where should I begin? At last count I had 5 Micor stations (1 low band, 1 VHF high, and 3 UHF) with most of the parts to another. This a 12W UHF Micor that is going to be torn apart in the near future. http://i1245.photobucket.com/albums/gg586/zap_uh_lack/Mobile%20Uploads/FFABBC0E-30FE-4535-BB2F-558D1B297B96_zpstvp1x4g5.jpg R100's (One is actually a MCR100) http://i1245.photobucket.com/albums/gg586/zap_uh_lack/Mobile%20Uploads/DBB7C590-C3CA-4E9A-A83F-9F18FD69A209_zpsdofiqf3n.jpg http://i1245.photobucket.com/albums/gg586/zap_uh_lack/Mobile%20Uploads/1270C507-ADB4-48AC-874A-5CCB16E6F611_zpsk9yrpp02.jpg GE Mastr II (VHF, in a Micor cabinet) http://i1245.photobucket.com/albums/gg586/zap_uh_lack/Mobile%20Uploads/CB240EF4-4302-4A55-AEBF-B66559710CF3_zpsijkcjiqd.jpg GE Mastr II Exec (UHF, the one in the case tried to play submarine in when the car it was in took a dive, I'm saving it to pull the harmonic filter) http://i1245.photobucket.com/albums/gg586/zap_uh_lack/Mobile%20Uploads/8282129B-AC5F-45FC-B68B-6074C089479C_zpsdmgs3fkw.jpg GE Custom MVP (Most of these were pulled from service around 1995, going into repeater service) http://i1245.photobucket.com/albums/gg586/zap_uh_lack/Mobile%20Uploads/7D0A1BC2-0CC1-4A2C-B1EC-573082A94F2F_zpsnadqzkhi.jpg Need some speakers? http://i1245.photobucket.com/albums/gg586/zap_uh_lack/Mobile%20Uploads/C2F6A53E-1EB2-4D6C-9920-1791E70510A9_zps82k5ofv4.jpg

ICM is the only company in the US who is still making radio crystals. They are about $25 a piece. Depending on the radio you'll either need one or two crystals. They charge $50 to re-crystal a channel element (which includes temperature compensation so the radio doesn't drift). Repeater Builder has some heater circuits that can be built for stabilizing the crystals. Crystal controlled radios are good radios and often make better repeaters than compared to just sticking two mobile radios together but as of recently, they have begun to get expensive to deal with. I've got several repeaters and repeater conversions that are rock bound…most of them are 40 or 50 years old.

I believe a scrambler would fall under encryption.

UHF is mostly a line of sight band. For the most part, if you can see what you're transmitting to, you are pretty much guaranteed success. The greater the height, the greater the vantage point for the repeater's antenna to "see". In most instances, the greater the antenna height, the further the range of the repeater. As far as towers go, just how high up are you planning on going? What kind of environment is you're repeater going to be installed? The only reason I'd notify the FAA is if you are in an approach path for an airport. Otherwise, it really doesn't make much sense, especially if you're going to keep it below 100 ft.

I've not messed with them. However, some of them are for simplex operation (talk back repeater) and some are for duplex operation.

You need to find the input/output pinouts of the radios. Most of us build mobile based repeaters out of commercial Icom, Kenwood and Motorola gear. The input/output information of that gear is well documented. In you're application, you're going to need a controller of some sort (it can be a ID-O-Matic IV, Commspec ID-8, or some more expensive controllers) to interface between the two radios. Without the pinouts, you'd need two of these: http://www.409shop.com/409shop_product.php?id=122465 And a controller to put it together.

Power doesn't always translate to distance. A couple of things to remember, the biggest attenuator to FM communications is the ground. Path loss on a 50W GMRS radio, a commercial grade receiver, and 1/4 wave antennas is nearly 6000 miles. However, this number goes south quickly when you start talking about punching through urban environments, trees, hills, etc. With GMRS, you're pretty much guaranteed a successful transmission if there is unobstructed line of sight. More power means greater risk for desensing the receiver (what good does it do to have a repeater that can be heard for 100 miles but only talked to for 35?) which means adding extra filters, more antenna separation, etc. The 675 and 700 repeaters in Lubbock. The 675 repeater is on the tallest building for 120 miles. The antenna is 360 feet off the ground. It's running 50W at the transmitter and 40W at the antenna (which is a DB420).That's 477W ERP. It fizzles out about mile marker 41 on I27 (it's located at marker 4 roughly). The 700 repeater is a good 70 feet below it running 32W (23W at the DB420)...it fizzles out around mile marker 38. The two sites are 1000 feet away from one another. 70 feet is what mainly makes up that extra 3 miles. 95% of the time, you'll never notice the difference between a repeater running 200W or one running 25W if it's in a good location.

I've never seen a UV-5R that didn't have a FCC-ID number on it…I've seen some with Part 90 stickers on them however that doesn't actually matter. They still shouldn't be using your system…

Yea…not what I would've done. I would've shotgunned, especially on amateur. Shotgunning and full-time link repeaters are how I'd link systems together over RF.

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

Interesting…I've thought about setting up a couple of TK-880's and throwing the existing GMRS repeaters in a trunk group. Some of this reminds me of shotgunning repeaters… If I read what PastorGary originally stated correctly. The basic idea was (what I'm assuming) using two GR300's (or similar), sending a command to have the channel steering on one repeater (both begin on the same splits with the same PL's) to swap RX/TX frequencies (called reverse on Yaesu gear) so that the other repeater can be directly keyed. Did I miss something or am I in the ballpark here?

I believe we were using GP300 chargers. So I'm pretty sure those are only 3 pin (I'll go check though).

On a side note, Quarterwave, I've been told one can modify a charging base to program the P1225's…I have a friend who has several and the programming issue is what is keeping us from using them.

I would take it you are talking about user selectable PL. Motorola called it MPL. I think my TK-880s can do that...they are just setup for FPP. My systems are generally designed for mobile use (as much coverage as possible in national forest, school trust, and blm). I am working on getting some systems up at ski resorts which would be better optimized for handheld use.

I try and resale my stuff that will narrowband (except my prized NIB M1225's). I've been debating installing two repeaters near my parents place. After plotting some coverage charts, a R100 would work where I was thinking about using a Custom MVP completely off grid.

Being you're repeater…you have the right to kick them off. Especially if none of them have proper licensing or if you have not given them permission to use the repeater for that purpose.

The Radius line does make good, reliable repeaters. Low duty, and for most GMRS applications they are great. I was actually going to install one for a remote system until I came across the much more efficient GE Custom MVP's. I've got a GR300 and GR500 running locally. The heavy duty machine is a SM50/Maratrac combo for the local '675' repeater (which generally has a heavier use). I'd install my R100 and MCR100 if I had the stuff to program them, not even my local Moto shop has that kind of gear anymore though. Reminds me of a project me and some friends are working on. Actually several. Hacking apart a low-band Micor station and a 12W UHF Micor repeater, swapping the receivers, and converting the low-band station to a repeater which should create a low-UHF cross band and a UHF to low cross band for a split-site low-band repeater. Also have three 40W UHF Micors that I have to bring back to life. One just needs to be aligned. Another is going to a friend for a GMRS repeater behind his barn (it's in an outdoor case) and the other is going to be a personal Micor that I currently have no plans on using currently.

R100's aren't bad little repeaters. Motorola built them to last. They have thermal controls that actually turn the power down if the system begins overheating. On a 25W model, the e-power was 10W and on a 10W model the e-power was 2W. Though they are essentially twin Radius boards stuck in a case, they don't use a rib to program (its a special cable that generally has to be built these days) and the receiver has much narrower filters on it than a Radius mobile would. I do agree, if someone doesn't have the ability (in this case) to makes sure that the repeater is at least making power when it keys, it probably needs to be avoided. Radius radios are generally to be avoided (very few have the desired 16 pin connectors). Maxtracs occasionally have the 16 pin adapter (there isn't an easy way to tell without looking at the rear of the radio) and you generally only see it on later model and/or 16 channel radios. The GM300 (and M120, M110, etc) variants will have the 16 pin connector. The SM50/120 will also have the same connector. All of the above radios program in DOS. Not a command prompt window but Disk Operating System. However, unlike the RSS for the R100 (which does require a i486 or slower) the latest versions will all program on dual-core machines running FreeDOS with a real serial port. There is a Windows software for programming GM300s (be known it will not program Radius, Maxtrac, or SM50/120) but it will only read and write channel info. You can not adjust the power on the radio. These are what we generally purchase and they allow the adjustment of the hang timer. The only problem I've ever had with them occurred when I shot a rat that was chewing on the cable off the repeater cabinet with a 1911…I kinda hit him in the face so I haven't really diagnosed whether or not it was the rat that bit cable, or the 45 slug. (I was not the one who installed the repeater and left the covers off the cabinet). http://www.ebay.com/itm/like/381014847628?lpid=82 Anything you could ever want to know about the R100 can be found here (and the "page up"): http://www.repeater-builder.com/motorola/r100/r100-overview.html Anything you'd ever want to know about building a Radius line (the line includes the Radius family, Maxtrac family, GM300 family, CM family, SM family, etc) repeater can be found here (look under interfacing for more complex interfacing): http://www.repeater-builder.com/motorola/maxtrac/maxtrac-index.html

You generally have to build them. R100's make great repeaters, you just have to have someone who can program them. I have two of them and my main problem is that I don't have a 486 or slower to program them with. It's also not just programming, you have to realign the receivers after you program them so you might as well align the transmitters while you're at it. Best thing to do, buy two UHF GM300's (a wideband, 10-25W model should run around $30). Find someone who can program them for you (and turn the power down to 10W if you plan on using it a lot). Purchase a GM300 repeater cable ($10 on ebay) and a UHF notch duplexer ($80-100 on ebay) that will handle the power level you're wanting to run at. All you need now are the various coax connections, power supply (or batteries) and an antenna.

That's expensive...for $300 you could build a 25W mobile based repeater with duplexer.

From reading the OP, we are going after a simplex (talk back) repeater, right? As in simplex operation, single frequency, requiring a controller, radio and antenna.