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Part 95 Repeaters


commsprepper
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In a perfect world some boy genius would market a repeater package with the bugs already worked out. IMO the "perfect" repeater for many GMRS applications would be a weather resistant package consisting of the repeater and hardware hooked directly to an antenna with a short lead and a water proof AC power cord. It would be designed in such a way that it could easily be hoisted to the top of a 100 ft tree or mounted on a tower with the power cord trailing behind. No line losses to worry about but the equipment would need to be of a rugged design that can thrive in an outdoor shelter with no heat or cooling. The light weight exterior would be water proof but allow air flow for cooling. I've seen transceivers build into water proof packages with additional instrumentation and speakers, why not the whole repeater assembly? I'll bet that if someone builds it, they will come. 

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When code approved of my 55' tower, since the FAA required no light for it height, They said no residential 110v AC power could be affixed directly to the tower. Power for rotor is 24v and other devices use 12v. Unless you use a mobile duplexer, and a small repeater, it would be a large box. Not sure a 100' cord is a good idea. I do like the idea of eliminating so much feedline but it is more complicated as always. My current Hoffman enclosure is 24X24X18, I wonder what the wind loading would be.

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When code approved of my 55' tower, since the FAA required no light for it height, They said no residential 110v AC power could be affixed directly to the tower. Power for rotor is 24v and other devices use 12v. Unless you use a mobile duplexer, and a small repeater, it would be a large box. Not sure a 100' cord is a good idea. I do like the idea of eliminating so much feedline but it is more complicated as always. My current Hoffman enclosure is 24X24X18, I wonder what the wind loading would be.

Nothing is ever easy when it comes to actually doing it. Maybe the concept would lend itself to a low powered solar application. I've talked 17 miles from a mountain top with only 4 watts.

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When code approved of my 55' tower, since the FAA required no light for it height, They said no residential 110v AC power could be affixed directly to the tower. Power for rotor is 24v and other devices use 12v. Unless you use a mobile duplexer, and a small repeater, it would be a large box. Not sure a 100' cord is a good idea. I do like the idea of eliminating so much feedline but it is more complicated as always. My current Hoffman enclosure is 24X24X18, I wonder what the wind loading would be.

Was just re-reading your post, what is "my code"? Is that a neighborhood thing? We don't have any restrictions on towers unless they get into airplane territory out my way. 

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I have not doubt of that, when I hook my 4watt HT to my feedline, I easily get 15 plus miles. Height truly is King..  I think it could be done with a lot of forethought. I have deployed Cameras and DD-wrt routers like this. I have a collection of other enclosures none of them big enough for anything above a Parrot or two uv5r's and a rick. If you have 100' tower, try 2 HT's with a controller and separate antennas, at 4 watts and no duplexer, should fit in a standard demarcation box, I bet you get good propagation. Now you got me thinking of some testing of my own. hmmm...

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Had to have code approval with the city. but Our local Ham club made it easier, still took 6 months. glad to have it over and only one neighbor complained and she is across the lagoon and  in the garden club to which I also belong. She said "Were not thrilled about it" referring to her and her husband. I am digging thru my junk trying to find two old HT's for a simple tower mount two antenna repeater. at only 4 watts how important is antenna separation?

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Had to have code approval with the city. but Our local Ham club made it easier, still took 6 months. glad to have it over and only one neighbor complained and she is across the lagoon and  in the garden club to which I also belong. She said "Were not thrilled about it" referring to her and her husband. I am digging thru my junk trying to find two old HT's for a simple tower mount two antenna repeater. at only 4 watts how important is antenna separation?

If the distance between the antennas was a multiple of a wave length wouldn't you experience some gain? If we could work out the bugs it might be marketable as a package. I don't have a 100 foot tower yet but I do have two 100 foot trees (still working on how to climb them safely or launch a line to pull up a rope).  My understanding of how to make a HT into a repeater is woefully lacking. I'd still like to find a way to turn my Motorola base station into something that I can ping or that would parrot back my voice for testing purposes since I'm usually working alone.

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If I had a 100' tree, I wouldn't have spent so much money

I know that feeling! One of the problems is that the closest tree (an oak) is about 70 ft. horizontal and 100 ft. vertical from where my radio is located. Even calculating the side 'c' of the triangle (122 ft) that's a fair amount of line loss. That's why I think putting the repeater and antenna together in the tree makes some sense.

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It's doable. Right now you'd need a Maxon data radio with external sink for the transmit side and either another for receiver or a hamtronics receiver (about the best receiver that can practically be purchased right now). 30 ft of vertical separation and CAT5e to provide PTT, audio and COR as well as power (you'd want 24 or 48V for all intents and purposes). Still looking at $600 cost if the Maxon's were type accepted for GMRS.

 

Add the cost of a duplexer and subtract the extra antenna and combine enclosures, you'd have a decent TTR.

 

That's what it would cost with current tech in a reliable package though.

 

In retrospective, Motorola sells a P25 tactical repeater (battery, duplexer at 4W) for $22,000. Etherstack on the other hand has one they are bringing to market for (15-30W depending on configuration) for $30,000.

 

Sent from my iPhone using Tapatalk

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I know that feeling! One of the problems is that the closest tree (an oak) is about 70 ft. horizontal and 100 ft. vertical from where my radio is located. Even calculating the side 'c' of the triangle (122 ft) that's a fair amount of line loss. That's why I think putting the repeater and antenna together in the tree makes some sense.

run power to the base of the tree and get a quality enclosure

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"They said no residential 110v AC power could be affixed directly to the tower."

 

The reason they won't let you run direct household 120 volts up a tower is because one side is HOT in reference to ground.  If you are working on the tower, and you short yourself out to that wire, well... you get the idea.

 

The way around that is to use an isolation transformer, just like they use on professional towers that have beacon lights, only on a smaller scale.

 

Use a 1:1 isolation transformer inside the house.  Put a 5 amp fuse on each leg of the output line, and run it up the tower as a twisted pair of 14 gauge wires.  It will still be 120 Volts AC at the top, with enough current to run a 40 Amp 12 Volt power supply, but it will NOT be "directly affixed" to household power, it is connected to an inside, fuse protected, isolated "Power Supply" just like your rotor.  If it falls down, it will also be safe, as neither side is in any way referenced to ground.

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love this conversation, sorry to resurrect.   as a good radio technician (good not great) I like to use a rule of thumb of 2.5 feet of line for every watt of output power between a radio and an antenna.  This prevents finals from overloading.    Additionally, there are a number of HT duplex repeater units on e-bay for less than $20.  These are not FCC certified but many HAM groups carry these for disaster response.  As for separation of receive and transmit antenna's too little separation will destroy the preamp on the receiver.  I have tested and find my rule of thumb on the coax works.  2.5 feet for each watt of out put power.  Now some Real radio technicians will have various opinions, and these are opinions from trial and spend situations destroying stuff.  

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I recently contacted Midland to describe the need for a "plug-n-play"  GMRS repeater. I listed all of the features that I desired, and added that making it "portable" and operable on 12VDC would be a big plus.  I even suggested that they might spec-out an existing model being produced in the PRC.  I even have a name for the dream machine....the Midland MXT-R50. Front-panel programmable, 50W, integral duplexer, RF circulator,etc (if necessary). If you would like to see such produced, contact Midland!Also feel free to add to the features that you would like to see.

 

While you are at it, ask Midland to produce a GMRS/repeater-capable HT that is type-accepted!

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I recently contacted Midland to describe the need for a "plug-n-play"  GMRS repeater. I listed all of the features that I desired, and added that making it "portable" and operable on 12VDC would be a big plus.  I even suggested that they might spec-out an existing model being produced in the PRC.  I even have a name for the dream machine....the Midland MXT-R50. Front-panel programmable, 50W, integral duplexer, RF circulator,etc (if necessary). If you would like to see such produced, contact Midland!Also feel free to add to the features that you would like to see.

 

While you are at it, ask Midland to produce a GMRS/repeater-capable HT that is type-accepted!

Both truly excellent ideas!  I'll be hitting them up on Twitter and mentioning it in any relevant Facebook groups I can find…

 

Signal amplification for the win!

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When code approved of my 55' tower, since the FAA required no light for it height, They said no residential 110v AC power could be affixed directly to the tower. Power for rotor is 24v and other devices use 12v. Unless you use a mobile duplexer, and a small repeater, it would be a large box. Not sure a 100' cord is a good idea. I do like the idea of eliminating so much feedline but it is more complicated as always. My current Hoffman enclosure is 24X24X18, I wonder what the wind loading would be.

 

I do wind design for structures in Florida on a regular basis, and you would be looking at 40 psf up to 50 psf.  So for 4 sq. ft. (2'x2' box) you would be looking at about 200 lbs. of lateral force on the box.  Just as a general estimate.  How close you are to the coast and how high above the ground you are would also make the load higher or lower, just to give you an idea.  Of course any construction would need site specific calculations with local code compliance and approval.  These numbers are simply for conversational purposes.

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