Simplex repeater dual antena seperation

[truevil]

Hello all, this is my first post.

I am newly licensed and just into this for just over a week. I was thinking of building a small simplex repeater to cover the 180 acres I live on.

My question is what is the proper distance I need to place the two antennas from each other?  Any and all help would be greatly appreciated. I have read many threads on here over the last few days, but I have yet to find this answer.

 

Best regards.

[PastorGary]

Hello John, and welcome to MyGMRS.   There are some technical factors that dictate spacing without using a duplexer, so if you can give us an idea of the brand and model of repeater and the antennas that you are considering, we can look at the RF characteristics of that equipment and be a bit more precise in our answer. A "general" rule is 30 feet, but that may vary with regard to specific installations using specific equipment. Thanks.

[JohnE]

https://forums.mygmrs.com/topic/292-duplexer-tuning-distance-without-duplexer/

 

[zap]

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.

[truevil]

Thanks for all of the answers.

The setup I was thinking of was two of the Baofeng BF-F8HP's with the Baofeng controller, two runs of LMR400, and two of the Ed Fong antennas. I was able to price all of this out for under $300.  From what I can determine is that these radios should put out about 6 watts on the GMRS band, and I think that is enough to cover the area I want to cover.

So from what I read above, I need to separate the antennas by at least 30"?

[JohnE]

horizontal 30' vertical or inverted vertical ~10'

[zap]

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

[truevil]

Zap,

I looked and looked and could never find anything that inexpensive or something I could just plug and play. If you could post some links I would still buy it and use the H/Ts I already bought for something else.

[gdavis316]

ebay always has something.  i think there is a R100 for sale now.  I have two GR1225 that work great.  one with a small footprint for the farm, and one with a larger footprint on a commercial tower.  A half duplex repeater is the way to go.  

q

[zap]

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.

[quarterwave]

Welcome. 

 

If you are still talking about a simplex repeater (simplexer, parrott, etc) you don't need to separate the antennae at all, since neither receives and transmits at the same time, and in the case of a simplex setup...you would only need 1 radio, as it is store and forward.

 

These projects are cool, a guy has to touch and see this stuff, get a feel for how it really works. 

 

I would ask what the terrain is, seems like 180 acres would be easy to cover with just portables and no repeater. I have used them on my family farm for years. 

 

The down side of the simplex repeater setup like that is durability. The TX radio is working twice as hard, carrying transmissions from both sides of the conversation, plus you have to wait for your message to repeat, and then the other guy talks, and his repeats. Make for a slow conversation. They have their uses, so it's not all bad. I made a "heavy duty" one once using a 40 watt mobile, a PC, custom interface, and Echo Station software. Still have the parts, but don't use it any more. 

 

If coverage is the real issue, I would lean towards a 10-25 watt repeater with a duplexer. It's just cleaner, easier and more reliable in the long run. But, by all means, if you have the means and desire to "tinker" like most of us, don't be discouraged from building a simplex machine, best way to learn is try, and try again. 

[truevil]

Thanks for all of the answers.

I guess I was thinking of sort of a duplex repeater, since one radio will receive on one channel and the TX radio till transmit on another channel. I will have 2 antennas, so do I still have to have them 30' apart?

I am looking at an R100 with duplexer for $80. Is this a decent price? http://www.ebay.com/itm/121460445228?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

 

Again, thanks for all of the help, it is most appreciated.

[quarterwave]

If no duplexer, then yes, you must have vertical and/or horizontal antenna separation. Not always easy to do, or do right. 

 

That R100 looks ok, but you never know if it works and for how long, I am always wary of a reseller like that ("I bought it from XXX or an auction....was in service, untested, not tested, etc.") 

 

It is usually best to buy from someone who can test it (beyond plugging it in!) and at least for frequency, power out, and audio, which doesn't require a radio shop if a guy knows what he is doing. Also, on something as old as a R100 (they started making those in the late 80's and stopped in the early 90's) you want to be sure someone can program it. It takes a cable (or cable and RIB) and a PC that can run DOS, as well as a copy of the R100 software. 

 

So, not to discourage anyone from buying an R100, but I don't want anyone to buy a boat anchor either. Sometimes you can find repeaters on eBay that guy's build them selves, and while they might not be able to warrant the equipment, at least the put it together and generally had some means of testing it.

 

If worse comes to worse, a simple controller from MRE1032 like  http://www.ebay.com/itm/RA-1-Repeater-Adaptor-Motorola-GM300-CDM-1250-RICK-/350465888363 and then a couple of M120, Gm300, Motorola Radius or Maxtrac radios with 16 pin connectors will work fine. I have one of those I built right now. All you need is a mobile duplexer off Ebay and then get the radios programmed and the duplexer tuned and you are ready to roll. 

[zap]

If no duplexer, then yes, you must have vertical and/or horizontal antenna separation. Not always easy to do, or do right. 

 

That R100 looks ok, but you never know if it works and for how long, I am always wary of a reseller like that ("I bought it from XXX or an auction....was in service, untested, not tested, etc.") 

 

It is usually best to buy from someone who can test it (beyond plugging it in!) and at least for frequency, power out, and audio, which doesn't require a radio shop if a guy knows what he is doing. Also, on something as old as a R100 (they started making those in the late 80's and stopped in the early 90's) you want to be sure someone can program it. It takes a cable (or cable and RIB) and a PC that can run DOS, as well as a copy of the R100 software. 

 

So, not to discourage anyone from buying an R100, but I don't want anyone to buy a boat anchor either. Sometimes you can find repeaters on eBay that guy's build them selves, and while they might not be able to warrant the equipment, at least the put it together and generally had some means of testing it.

 

If worse comes to worse, a simple controller from MRE1032 like  http://www.ebay.com/itm/RA-1-Repeater-Adaptor-Motorola-GM300-CDM-1250-RICK-/350465888363 and then a couple of M120, Gm300, Motorola Radius or Maxtrac radios with 16 pin connectors will work fine. I have one of those I built right now. All you need is a mobile duplexer off Ebay and then get the radios programmed and the duplexer tuned and you are ready to roll. 

 

 

 

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

[truevil]

Wow! Thanks guys!

Looks like I have a lot more reading to do.

I decided not to bid on the R100.

[gdavis316]

there is a GR1225 on ebay that is seller refurbed.  He can program and tune.  occassionally the power amp will fail, and i mean after years of service and lots of traffic.  Sometimes at the pa its just a cold solder joint.  mine have worked great.  He wanted $350 or b/o.  

[gdavis316]

seller ucsmoto(350)

unit has new pa, he will program and tune, and the band range is 450-470.  looks like a good unit to me

[quarterwave]

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

 

Appreciate the counter points. I wasn't suggesting the R100 was not a good unit, it was good for what it was built for, which was not to be a 100% duty cycle heavy duty repeater. We sold alot of them when I worked for M, and they generally were great. I did see some melted down because the customer needed a MSR2000 or MSF but didn't want to spend the money. I would hate to see someone buy one that may essentially be salvage, and may not be working....but buying one from a seller that can test, and would take it back if it wasn't what he said it was, would be better. Especially if you are are just-getting-started radio guy. 

 

I would disagree a bit on the Radius and Maxtrac....I have seen many a small repeater made from them, and they are a reliable, well made mobile. I have some that are 20+ years old and work just like new. 

 

I do understand that everyone's experience will vary, we each like what we like. 

[zap]

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. 

[quarterwave]

Yes, once you find your way around M equipment, like I did working for them in the early 90's, its is cool to see what you can get into. Our shop built alot of interesting things back then. 

 

I run a pair of M208's as a small repeater, I have it set for about 15 watts, and it works just fine. Celwave mobile duplexer and a MRE1032 RA_1 interface. I used the interface to get the audio adjustment and drop out delay. I also keep a couple of my own cables around to make a quick repeater if I have to. 

 

My main machine is a 100 watt 100% duty cycle MTR2000 turned down to 50 watts....with a Zetron 37. Love that thing. 

[truevil]

Quaterwave, You asked about the terrain, well it is flat but we have a lot of trees. My wife and I did a test two evenings ago, and with her standing in the middle of our property we could not communicate at the farthest corner. A repeater may not be necessary maybe just a roof mounted antenna, but it still seems like a fun project to put together.

[gdavis316]

Goodmorning,

my wife and I have a small farm and we purchased a Motorola GR1225 and also got the comet gmrs base antenna.  we get great coverage, and its our system.  i mentioned in an earlier post that on ebay ucsmoto has a gr1225 for sale, he will program, tune, and has refurbished.  it will be a plug and play unit, and he is a good seller.  we like our system that cover 5-7 miles.  i put another on the air that cover a couple of counties.  also, for mobiles i got several pm-400's that are wide band.  the reason, when you get hooked, you may want to get your ham ticket.  these are good little radios.  you will have to get someone to program them.  there are several on sale on ebay.  it will add up, but it is good to know you have reliable comms during any emergency.  

[zap]

Goodmorning,

my wife and I have a small farm and we purchased a Motorola GR1225 and also got the comet gmrs base antenna.  we get great coverage, and its our system.  i mentioned in an earlier post that on ebay ucsmoto has a gr1225 for sale, he will program, tune, and has refurbished.  it will be a plug and play unit, and he is a good seller.  we like our system that cover 5-7 miles.  i put another on the air that cover a couple of counties.  also, for mobiles i got several pm-400's that are wide band.  the reason, when you get hooked, you may want to get your ham ticket.  these are good little radios.  you will have to get someone to program them.  there are several on sale on ebay.  it will add up, but it is good to know you have reliable comms during any emergency.  

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.

[quarterwave]

I like the M1225 and P1225...I have a couple of each. I also have a new 4F M1225...in the box! 

 

Most of my mobiles are older, but work reliably. Most of them are in Farm equipment. 

 

What I am working towards with my system is eventually making it a primarily handheld system. The coverage I have is fine, if I can improve it, I will, but with the cost of equipment and they way I use it outside of some farm coordination now and then, just doesn't warrant needing mobiles. I will keep one for my pickup truck, but other than that I want to focus on a portable radio coverage system...just like cell phone use...more of a carried device than a fixed, or fixed in a vehicle thing. 

[gdavis316]

we used the m1225 in boats for years and they always performed.  i love the pm 400's since they come loaded with all the pl's.  Great for gmrs.  quaterwave, i've got a saber, sva or ava, and amp........thats what you need.     

[zap]

we used the m1225 in boats for years and they always performed. i love the pm 400's since they come loaded with all the pl's. Great for gmrs. quaterwave, i've got a saber, sva or ava, and amp........thats what you need.

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.