Grain bin/silo repeaters

[VETCOMMS]

I'm curious if any of you have experience with installing repeaters on tall grain bins/grain legs or Harvestore style silos.  If so, how did you protect the repeater from the elements and were there any unique challenges to using a silo/grain bin compared to putting a repeater and antenna up on a tower?

[WRKC935]

Yep. I have done this many times.  Couple things to be mindful of. 

If you are on the side of a concrete silo with no roof, then it's obviously gonna be side mounted to the wall. 

If there is a metal dome on it you want on top if possible.  Of course you need to limit the antenna size due to the twisting moment at the base.  So no huge antenna's.

Easiest way to deal with the antenna cable running down vertically is attach it to the outside of the vertical bar on the ladder.  But you are going to need to fasten it to something more often than just the ladder mounts that are every 10 feet.  Needs to be 6 feet or less between the attachment points.  If it's a flat side unit, you could use Tek screws and one hole clamps for conduit when it was empty so you can get all the metal shavings out of it.  If its' ribbed, you are about gonna have to use the ladder.

Weather proofing the repeater.  Easiest way is a water proof box or put in in the head house in a fairly clean area.  I realize that clean in a head house is a oxy-moron, but it can be done if you are willing to maintain it and blow the dust out of it a few times a year, and about every other week in the fall when you are drying and putting away.  If you have silo's you know what I am talking about. 

QUALITY equipment here is a MUST.  You have to spend the money on a real repeater that's sealed.  I wouldn't consider any other repeater than an  MTR from Motorola in that environment.  The last system I out in was 3 XPR repeaters on a feed mill.  They got installed in a weather proof cabinet on TOP of the mill due to the dust.  Too much of a concern for the repeaters becoming an ignition source to have them in the building at all.  Mind you they run 10 million bushel a year through that mill.  It's a big operation for a large egg farm. 

But it can be done.  It's gonna be more expensive to put it in, just like everything else is that has power going to it, but at least you are not paying reoccurring rent on a tower site.  And I am gonna guess it will work well due to most farm's sit in the middle of pretty flat land.

 

[VETCOMMS]

Thanks for that WRKC.  I've got a couple farmers I still need to ask and the answer very well may be no but can't hurt to ask.

The local sheriff has a tower maintained by RA Comm so again, that answer might be a no as well but can't hurt to ask.  

The grain bins are the only other tall option around.

[gortex2]

RT97, 6' LDF and a DB404 is an ideal setup for a silo. Just run 110' (which is normally already up there) and plug it in.

[VETCOMMS]

19 hours ago, gortex2 said:

RT97, 6' LDF and a DB404 is an ideal setup for a silo. Just run 110' (which is normally already up there) and plug it in.

What do experienced installers do to choose which antenna for such application?  I saw an omnidirectional Laird 4505 and other antennas but there's a lot to weed through.  So how do you decide?

 

[BoxCar]

50 minutes ago, WRTZ750 said:

What do experienced installers do to choose which antenna for such application?  I saw an omnidirectional Laird 4505 and other antennas but there's a lot to weed through.  So how do you decide?

 

That is like asking which radio is best. It depends on what's desired and what's needed. As you are the first in your area, you'll want an antenna that gives the best coverage over the area. That's why many use a DB for its radiation patterns, gain and reliability.

[gortex2]

Well in the LMR world we find the needs of the client, then run propagation studies to meet the expectations of the customer and meet the license requirements. In the past I did many warehouses that had a 10 watt UHF repeater in them with hundreds of 4 watt portables. I have also put in multiple GMRS/SAR/Public Safety systems that covered many miles and counties. All designed and engineered before install. 

In the hobby world I try to do what I can and learn from mistakes of others. Spending a bit more money on a decent antenna normally is worth its weight in gold. Wind, Snow, Ice change the antenna some will use. Since moving south I dont worry so much about ice load on my antenna, but wind is still there. Also what can the structure handle for weight and loads. Wind loading is a thing. 

The Laird antenna is a great starter antenna. I use them for control stations, low power repeaters and temporary installs. The DB404 is a bullet proof antenna but weighs twice the Laird. But I have DB antennas on towers for 20+ years with no issues. Can't say that about my Lairds. 

[VETCOMMS]

Thanks for the replies.  So because I'm new to repeaters this may be a dumb question.

If I put a Retevis repeater on a grain bin would I be able to program it to operate on one set of frequencies for the farmer to use and a second set of frequencies for my family to use?

[Sshannon]

52 minutes ago, WRTZ750 said:

Thanks for the replies.  So because I'm new to repeaters this may be a dumb question.

If I put a Retevis repeater on a grain bin would I be able to program it to operate on one set of frequencies for the farmer to use and a second set of frequencies for my family to use?

No. It’s configured with one set of frequencies. 

[wrci350]

55 minutes ago, WRTZ750 said:

If I put a Retevis repeater on a grain bin would I be able to program it to operate on one set of frequencies for the farmer to use and a second set of frequencies for my family to use?

There *are* repeaters (that work on GMRS) that won't do that, but *will* allow you to set up multiple CTCSS/DCS tones on the same frequency pair.  That would allow you to use one tone for the farmer and one for the family and they wouldn't hear each other.

[VETCOMMS]

12 minutes ago, wrci350 said:

There *are* repeaters (that work on GMRS) that won't do that, but *will* allow you to set up multiple CTCSS/DCS tones on the same frequency pair.  That would allow you to use one tone for the farmer and one for the family and they wouldn't hear each other.

But to make sure I understand, the two different groups with their different tones could not transmit at the same time, correct?

[wrci350]

8 minutes ago, WRTZ750 said:

But to make sure I understand, the two different groups with their different tones could not transmit at the same time, correct?

Correct.

If the repeater were active for "group a" and someone from "group b" keyed up as well, none of the other "group b" radios would hear the transmission.

[Sshannon]

And if you didn’t program in a receiver tone at all, you would hear everything transmitted by either group.

[wrci350]

38 minutes ago, Sshannon said:

And if you didn’t program in a receiver tone at all, you would hear everything transmitted by either group.

Which pretty much defeats the purpose, no?

[Sshannon]

5 minutes ago, wrci350 said:

Which pretty much defeats the purpose, no?

It does. But it must be understood.  If WRTZ750 is hoping for something that prevents overhearing messages (rather than simply not being interrupted) tones aren’t the solution. 

[VETCOMMS]

I think Randy's videos helped me understand the tones keep me from having to listen to others but offers no privacy at all.

What I wasn't sure of was whether farmer group A and Wrtz family B could use the repeater simultaneously 

[gortex2]

No they cannot. Farmer A can talk to his radio and when that conversation is done Farmer B can talk to his units. Regardless of PL/DPL used. Thats how community repeaters in the LMR world used to work. We would use BCL so they could not talk over each other. The only way 2 farmers can use same repeater is by going to a DMR business system and all DMR gear.

[WRVD377]

Hi Terry,

Even if you look at a Bridgecom, when I asked, the answer is no also. But I have a thought the others can beat me down about. What if you placed 2 antennas, and 2 repeaters and both ends of the freq range and diff PL's far enough apart?  As the Retivis Is sealed does it matter where mounted other than power source / lightning? Does that not fix the issue at a less cost than a towers monthly cost?

[Sshannon]

18 minutes ago, WRVD377 said:

Hi Terry,

Even if you look at a Bridgecom, when I asked, the answer is no also. But I have a thought the others can beat me down about. What if you placed 2 antennas, and 2 repeaters and both ends of the freq range and diff PL's far enough apart?  As the Retivis Is sealed does it matter where mounted other than power source / lightning? Does that not fix the issue at a less cost than a towers monthly cost?

I’m wondering if you even need two antennas.  You would already have duplexers on both repeaters; maybe you can combine the feedline from the duplexers with a diplexer.

[gortex2]

You can put 2 repeaters at a site with proper combining and filtering. Its done every day in the LMR/Public Safety world. We have 3 UHF SAR repeaters at one tower site. Receive goes thru a Receive Multi coupler and TX thru a Transmit Combiner. None of it was cheap. I know another person on this forum has 2 or 3 at his site on GMRS with combiners. 

Theoretically you could use 2 RT97 and 2 Antenna's on top and bottom frequencies but I suspect some desence would happen just with RF that close. Guess it depends on how much separation on antenna's you could do. 

[WRVD377]

I think I read somewhere that a person can put one antenna higher than the other in order to make that work and not get the desence.  Again I am not an expert but I did find video about it in all my reading.  That person claimed vertical separation rather than horizontal less feet and was not specifically about GRMS.

Antenna Isolation (commscope.com)

 

Isolation between the repeater receiver and RF sources (repeater-builder.com)

Site noted in video.

Anyone correct me on this area as needed.

[tweiss3]

2 minutes ago, WRVD377 said:

I think I read somewhere that a person can put one antenna higher than the other in order to make that work and not get the desence.  Again I am not an expert but I did find video about it in all my reading.  That person claimed vertical separation rather than horizontal less feet and was not specifically about GRMS.

Antenna Isolation (commscope.com)

Correct, isolation can be provided by vertical separation. At 462MHz, you need a minimum of 25' horizontal space between top of lower antenna and bottom of higher antenna. Add in they must be direct one over the other, its a bit harder to do while thinking about tossing this up on a rain silo. 

[Sshannon]

3 hours ago, tweiss3 said:

Correct, isolation can be provided by vertical separation. At 462MHz, you need a minimum of 25' horizontal space between top of lower antenna and bottom of higher antenna. Add in they must be direct one over the other, its a bit harder to do while thinking about tossing this up on a rain silo. 

But do you need the isolation that comes from vertical separation if you have duplexers on each of the two repeaters and a diplexer where they join to the antenna feedline?

I guess I could believe that transmitting on both repeaters at once into a single antenna would cause each other interference. 

[gortex2]

Even if they have 2 antenna's they can desense each other. I had 2 GR1225 at the site I have SAR stuff at. Both were on UHF antenna with a flatpack style duplexer (Sinclair) and I still have almost 20db desnese when RPT 1 would key up testing RTP2 desense test. The antenna's were almost 10' apart. This is when I changed out to a receive multicoupler and TX combiner (and Quantars) using the same 2 antenna's. I can't imagine the RT97 is better than that. 

[tweiss3]

24 minutes ago, Sshannon said:

But do you need the isolation that comes from vertical separation if you have duplexers on each of the two repeaters?

I guess I could believe that transmitting on both repeaters at once into a single antenna would cause each other interference. 

It depends on a lot of things. A mobile duplexer, or the little duplexer that comes in the RT97, yes, you will need the isolation. The notch is pretty big and may not be specific enough to provide isolation between repeaters. On sites that have multiple same band repeaters, some have combiners, some have duplexers & combiners to get enough isolation.