Jump to content

Long Range GMRS


Guest Steven Ulrich
 Share

Recommended Posts

linking won't affect the range of a specific repeater; it's going to be dependent on the location, the machine itself, the antenna, and everything in the RF path from repeater to antenna.

across the link, it's pretty much wherever the repeater can be linked to, you can reach, as long as you're within RF range of the repeater you're accessing the network through.  if i were to travel down to socal (where one of the repeaters is linked in for the national nets, i could talk to a user in Brooklyn or New Jersey, or anywhere else that a repeater is linked into the network.

if you throw something like zello into the mix, you can, it's pretty much the sky's the limit. i've checked into repeaters in Bronx, Jersey, Utah, and Arizona that way, as there's not currently anything in my range that's linked for the nets.

Link to comment
Share on other sites

  • 3 weeks later...
Guest Repeater tower

If I was to build a repeater tower for GMRS I can go 99' up.
I can't go any higher because a local farmer has an airplane that is about 1 mile away as the crow flies.
Does anyone have any idea who would have the information for lighting the tower with the strobe LEDs?
Does anyone know if that 99' is with the antenna on the top or just the tower itself?

Next:
What is involved with installing a good strong community GMRS tower?
Besides having 2 radios and excellent grounding?

Link to comment
Share on other sites

The FAA has specifications for tower lighting and the maximum height does include the antenna if it extends above the tower structure. The best repeaters are commercial or public safety grade units purposely built as repeaters. These are not "just two radios connected together" but units built for constant transmit/receive use. Typical radios spend most of their life receiving and about 10 to 20% of their life transmitting. The transmitter is the part that draws the most power and generates the heat that causes failure. Repeaters on the other hand are built to spend 50 to 100% of the time transmitting. Your best bet for getting a good repeater system is from the used market. Check the usual sources like E-Bay, local two-way radio dealers and do an Internet search for used radio dealers.

Link to comment
Share on other sites

21 minutes ago, AdmiralCochrane said:

FAA (and I think EPA as well) restrictions come in at 200 feet.  Lots of 199 foot antennas in the ham world. 

Yes, 200 feet is a magic number. And it's not a huge deal to exceed 200 feet, depending on location, but you do need to have FAA approved obstruction lighting on it and it needs to be registered.  We deal with that at the site and it's just a hoop to jump through. 

But if you are considering going that high you need to contact the FAA / FCC before beginning construction.  They have to grant you permission to do it and they will need to do a location study to verify it's not too close to an airport or in a flight path. 

 

Link to comment
Share on other sites

The 200 foot measurement is supposed to include any antennas that extend above the tower. The regulation states the total height of the structure which, by definition, will include antennas as they are part of the "structure." There have been a few reports of tower owners being cited but they have only been after complaints have been filed. From the few I remember the complaint was filed by pilots that do ag spraying,

Link to comment
Share on other sites

5 hours ago, BoxCar said:

The 200 foot measurement is supposed to include any antennas that extend above the tower. The regulation states the total height of the structure which, by definition, will include antennas as they are part of the "structure." There have been a few reports of tower owners being cited but they have only been after complaints have been filed. From the few I remember the complaint was filed by pilots that do ag spraying,

Here is a question. I've noticed on some towers than none of the antennas extend above the top of the structure, all are mounted on side arms. Is that done to stay under the permitted height of the tower?

Link to comment
Share on other sites

13 minutes ago, Lscott said:

Here is a question. I've noticed on some towers than none of the antennas extend above the top of the structure, all are mounted on side arms. Is that done to stay under the permitted height of the tower?

My understanding is: It’s easier to mount an antenna to the side of the tower (picture the poor tower climber trying to wrestle the antenna into position while being strapped to the tower), lights can be mounted to the tower (but not many antennas), and the tower provides some measure of lightning protection for the antenna.

Link to comment
Share on other sites

35 minutes ago, Lscott said:

Here is a question. I've noticed on some towers than none of the antennas extend above the top of the structure, all are mounted on side arms. Is that done to stay under the permitted height of the tower?

Side mounting antennas is done for several reasons including those already stated. One of the more common reasons is to restrict the radiation pattern from the antenna. The tower is used to cancel a portion of the radiation pattern often to prevent interference to other stations on the same frequency. This often happens with public safety and commercial installations as another user just a few miles away can be on an adjacent channel and their application was approved for coordination with the non-interference requirement.

Link to comment
Share on other sites

22 minutes ago, Sshannon said:

My understanding is: It’s easier to mount an antenna to the side of the tower (picture the poor tower climber trying to wrestle the antenna into position while being strapped to the tower), lights can be mounted to the tower (but not many antennas), and the tower provides some measure of lightning protection for the antenna.

Not to mention there is only one 'top spot' and, not every user requires a full omnidirectional pattern.  However, many (commercial) tower sites have one massive antenna at the top spot and feed it through RX multi-couplers and transmitter combiners, for customers who want, need, and can afford the 'top spot'.

Side arms, in addition to the previously mentioned reasons, are a way to generate even more income to the site owner (more customers).

None of this necessarily has anything to do with range, although height rarely is a bad thing.  While coverage/range can be predicted, anything short of that is speculation (it depends).  Even coverage prediction tools have their limitations.

🙂
 

Link to comment
Share on other sites

Ok. The modified radiation pattern due to the tower acting as a passive reflector makes sense. Another group member here has done it on a multi bay vertical where the mast was the reflector. I modeled it using EZNEC and it does work. There was noticeably higher signal strength on the side opposite the mast. It wasn’t a huge difference however.

I get the extra revenue from more antennas mounted on the tower, and using it the shield one antenna from another, why you see a lot on side arms. I just thought it a bit odd nothing was mounted on the top spot on a number I’ve seen. 

Link to comment
Share on other sites

There are several reasons for side mounting.  First is increased gain based on height.  A taller antenna will talk farther.  But unlike GMRS and HAM commercial radio operators are limited by their license on how far their equipment can be talked on from the tower.  It's typically on the license as a radius in KM.  Legally you can't operate at a distance further than your license allows.  To limit that a properly designed system will only talk that far or only slightly more. 

Another reason for limiting coverage is system design.  If you have a DMR system that has multiple sites, you want to limit how far each site talks so the subscribers will vote the sites and switch to the better site as it approaches it.  If the system was installed by the old guard types that believe it needs to talk as far as possible, it will not work right.  We have such a system that the 100 watt repeaters are turned down to 20 watts.  Why 20, because they will not go any lower and it still talks farther than it can hear.  Antenna is 675 feet AGL.  Cable length is 780 feet and 7/8.  Cable loss is 6 dB.  Combiner output is 5 watts, and it's DB-420 antenna's.  It can be heard forty miles away in some directions but it will only hear for 30 miles and less in some directions.  Now that is as extreme as I have seen. But my crap talks and hears at 30 miles on a bad antenna with 6 watts forward and 3 watts reflected on the current antenna.  Antenna height is 110 for transmit and 240 for receive. 

Vertical Real Estate (commercial tower space rental) is calculated by the foot, and by the load.  The higher you are and the more you load the tower the more you pay.  A tower also has a limited amount of wind loading that it can take.  If you significantly exceed that rating bad stuff happens.  So it's also a juggling act with the renter to figure out how high they NEED to be for the coverage they want without needing to pay for unneeded height.  While we sit and discuss the cost of antenna and line, we typically don't consider the reoccurring cost of rent.  We look at a DB-420 and 300 feet of line costing 3 to 5K installed with a side mount arm and wring our hands at the idea of that expense ONCE.  When there is a 600 dollar difference PER MONTH for a higher or lower place on a tower, that 5K number seems mundane compared to the cost savings going lower on the tower if the coverage is adequate for the customers need. 

Link to comment
Share on other sites

1 hour ago, WRKC935 said:

There are several reasons for side mounting.  First is increased gain based on height.  A taller antenna will talk farther.  But unlike GMRS and HAM commercial radio operators are limited by their license on how far their equipment can be talked on from the tower.  It's typically on the license as a radius in KM.  Legally you can't operate at a distance further than your license allows.  To limit that a properly designed system will only talk that far or only slightly more. 

Another reason for limiting coverage is system design.  If you have a DMR system that has multiple sites, you want to limit how far each site talks so the subscribers will vote the sites and switch to the better site as it approaches it.  If the system was installed by the old guard types that believe it needs to talk as far as possible, it will not work right.  We have such a system that the 100 watt repeaters are turned down to 20 watts.  Why 20, because they will not go any lower and it still talks farther than it can hear.  Antenna is 675 feet AGL.  Cable length is 780 feet and 7/8.  Cable loss is 6 dB.  Combiner output is 5 watts, and it's DB-420 antenna's.  It can be heard forty miles away in some directions but it will only hear for 30 miles and less in some directions.  Now that is as extreme as I have seen. But my crap talks and hears at 30 miles on a bad antenna with 6 watts forward and 3 watts reflected on the current antenna.  Antenna height is 110 for transmit and 240 for receive. 

Vertical Real Estate (commercial tower space rental) is calculated by the foot, and by the load.  The higher you are and the more you load the tower the more you pay.  A tower also has a limited amount of wind loading that it can take.  If you significantly exceed that rating bad stuff happens.  So it's also a juggling act with the renter to figure out how high they NEED to be for the coverage they want without needing to pay for unneeded height.  While we sit and discuss the cost of antenna and line, we typically don't consider the reoccurring cost of rent.  We look at a DB-420 and 300 feet of line costing 3 to 5K installed with a side mount arm and wring our hands at the idea of that expense ONCE.  When there is a 600 dollar difference PER MONTH for a higher or lower place on a tower, that 5K number seems mundane compared to the cost savings going lower on the tower if the coverage is adequate for the customers need. 

Thanks. That was a very good detailed explanation. 
 

Tower rental costs isn’t something I see mentioned hardly at all on these forums. Hams get spoiled since a lot of them get freebie, or nearly so, space on buildings etc. Everyone else ends up having to pay. 

Link to comment
Share on other sites

14 hours ago, WRKC935 said:

There are several reasons for side mounting.  First is increased gain based on height.  A taller antenna will talk farther.  But unlike GMRS and HAM commercial radio operators are limited by their license on how far their equipment can be talked on from the tower.  It's typically on the license as a radius in KM.  Legally you can't operate at a distance further than your license allows.  To limit that a properly designed system will only talk that far or only slightly more. 

It isn't that your signal can't go beyond the limit on your license and connect to a unit outside the assigned radius as much as your use of that frequency is not "protected" from another user being coordinated in an adjacent area. Typically, the coordinators assign a 32 km (20 mile) protection area, but they also issue city, county and state-wide areas of operation. The different frequency coordinators have different periods in which they review and approve or object to another coordinator's application. Commercial B/ILT coordinators must file their objection within 24 hours while public safety coordinators have 5 days to review a proposed coordination. The difference in review times is due to the nature of the coordinations. B/ILT coordinators work on the premise that all frequencies are shared while the public safety coordinators assign exclusive use to a frequency.

Link to comment
Share on other sites

5 hours ago, BoxCar said:

It isn't that your signal can't go beyond the limit on your license and connect to a unit outside the assigned radius as much as your use of that frequency is not "protected" from another user being coordinated in an adjacent area. Typically, the coordinators assign a 32 km (20 mile) protection area, but they also issue city, county and state-wide areas of operation. The different frequency coordinators have different periods in which they review and approve or object to another coordinator's application. Commercial B/ILT coordinators must file their objection within 24 hours while public safety coordinators have 5 days to review a proposed coordination. The difference in review times is due to the nature of the coordinations. B/ILT coordinators work on the premise that all frequencies are shared while the public safety coordinators assign exclusive use to a frequency.

Yes, that is true.  I suppose I should have clarified that and said it was partly to minimize interference with co-channel users.  And what I was referring to were the typical FB2 licenses.  I also deal with FB6 and FB8 and we even have a few 'market frequencies" that are fully exclusive use in our market.  Problem with those is they were paging frequencies.  Of course the ERP on those was silly high, I believe 1KW output.  Oddly we have a couple on the mentioned tower site with the antennas at 700 feet.  Our co-channel owner in Indiana still uses the 'input' frequency as a link freq for paging and in the spring tends to get into our receivers pretty good. 

And please don't get me started with the coordinators.  We had 3 customers in a 10 mile radius with the same repeater pair and two of them were DMR licenses and of course just tore each other up.  Swear those guys at times use a spinning wheel like the "Price is Right" to choose what they are gonna grant someone with zero effort to do actual coordination.

Link to comment
Share on other sites

3 hours ago, WRKC935 said:

Yes, that is true.  I suppose I should have clarified that and said it was partly to minimize interference with co-channel users.  And what I was referring to were the typical FB2 licenses.  I also deal with FB6 and FB8 and we even have a few 'market frequencies" that are fully exclusive use in our market.  Problem with those is they were paging frequencies.  Of course the ERP on those was silly high, I believe 1KW output.  Oddly we have a couple on the mentioned tower site with the antennas at 700 feet.  Our co-channel owner in Indiana still uses the 'input' frequency as a link freq for paging and in the spring tends to get into our receivers pretty good. 

And please don't get me started with the coordinators.  We had 3 customers in a 10 mile radius with the same repeater pair and two of them were DMR licenses and of course just tore each other up.  Swear those guys at times use a spinning wheel like the "Price is Right" to choose what they are gonna grant someone with zero effort to do actual coordination.

I’m going to guess the coordinators use some software tools to estimate area coverage and signal levels to figure out potential interference to co-channel users. Are these publicly available, free to use, or expensive proprietary software?

Link to comment
Share on other sites

The coordinators use proprietary software that is available for license. The suite we used carried a $1500 a year license fee. The software was sophisticated enough that it could coordinate a trunked system using multiple sites and frequencies at the same time. Our advantage was we did the coordinations in house rather than farming them out to local, volunteer frequency advisors which often took months to complete. We processed over 95% of our applications within 3 days. 

Link to comment
Share on other sites

2 hours ago, BoxCar said:

The coordinators use proprietary software that is available for license. The suite we used carried a $1500 a year license fee. The software was sophisticated enough that it could coordinate a trunked system using multiple sites and frequencies at the same time. Our advantage was we did the coordinations in house rather than farming them out to local, volunteer frequency advisors which often took months to complete. We processed over 95% of our applications within 3 days. 

The yearly license fee doesn't sound too bad if you use it frequently. A 3 day turn around time is quick. What is the typical charge to get, lets say one frequency (or pair for a repeater), for business use? I've seen people mention anywhere from a few hundred bucks to thousands. Reason for asking is on these forums it's been suggested that anyone who wants a "private" frequency for communications get a business frequency. That ignores if you even qualify for one. If you do and the cost is reasonable the suggestion makes sense.

Link to comment
Share on other sites

The fees vary by coordinator. The best I can tell you is to go to the FCC website and look up the web address of all the coordinators for B/ILT and check their posted prices.

There is no restriction on who can hold a business license other than what the FCC requires for any applicant. Licenses under Part 90.20 are restricted to specific parties but 90.35 doesn't have those.

Link to comment
Share on other sites

Join the conversation

You are posting as a guest. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use and Guidelines.