building shielded from repeater...very poor reception

eboe · Post by **eboe** » Wed May 19, 2004 5:20 pm

we have our repeater antenna on the roof of the courthouse. we have several channels, but only channel 1 is repeated from this location. we have approximately 30 buildings throughout the city that need to access this repeater. most of the radios in the buildings are portables, but a few have mobiles used as base stations. the repeater antenna is mounted on the eastern edge of the courthouse roof. there is one building in particular towards the west that has horrible reception. apparently the signal is being shielded by the building it's mounted on.

what's the best/easiest/cheapest way to solve this problem? changing frequencies on any of the portables is not an option. they all need to be able to work from any building. neither is moving the antenna on the courthouse. is there any type of simulcast system that won't break the piggy-bank? or is there some other way i don't know about?

thanks

thebigphish · Post by **thebigphish** » Wed May 19, 2004 6:12 pm

What frequency are you using? whgat kind of portables? what kind of antenna? feedline? system setup? are the mobiles having the same issues as the portables? (a nicely aimed directional ant will help that) HAAT....just tell us a little more....we can figure it out....

RKG · Post by **RKG** » Thu May 20, 2004 7:30 am

If I get this right, you have a repeater antenna mounted at one edge of the roof of a building and not elevated very far (if at all) above the roof, resulting in a near-field interference shadow in the direction that is (a) toward the other side of the building and (b) most likely depressed from the roof level.

The solution is to raise the antenna. Probably as little as 20-40 feet will solve the problem.

eboe · Post by **eboe** » Thu May 20, 2004 11:25 am

we're in the uhf ~450Mhz. the portables are mostly ht's and ex's, waris stuff. the mobiles are cdm's. the building that's having the problem doesn't have a mobile as a base station, just portables. vehicle mounted mobiles that are in the area have much better reception.

i can't find the literature on the repeater antenna and since i'm new at this, i'm not exactly sure what it is, but it's some sort of omni-directional dipole.

the roofline of the building is akin to a tower, pointed in the center. all the antennas are mounted around a railing several feet below the peak. moving the antenna is not an option as this is the space we are given. i'm not sure about raising it either, but i can find out. ...i doubt it though.

wa2zdy · Post by **wa2zdy** » Thu May 20, 2004 1:07 pm

Are you talking about the county courthouse downtown? If so, as tall as that building is, you should have coverage anywhere in the city. If you're talking some other building, let me know.

If worst comes to worst, I could take a peek at it for you one day when I visit my sister-in-law (off Magie Ave.) If nothing is variable though, you may be stuck.

Be in touch if I can help.

spareparts · Post by **spareparts** » Thu May 20, 2004 1:26 pm

eboe wrote:we're in the uhf ~450Mhz. the portables are mostly ht's and ex's, waris stuff. the mobiles are cdm's. the building that's having the problem doesn't have a mobile as a base station, just portables. vehicle mounted mobiles that are in the area have much better reception.

i can't find the literature on the repeater antenna and since i'm new at this, i'm not exactly sure what it is, but it's some sort of omni-directional dipole.

the roofline of the building is akin to a tower, pointed in the center. all the antennas are mounted around a railing several feet below the peak. moving the antenna is not an option as this is the space we are given. i'm not sure about raising it either, but i can find out. ...i doubt it though.

Eboe - Is that short for Elizabeth Board of Education? Anyway, I'm pretty sure your TX frequency is 466.8500.

Lat/Long of the Union County Courthouse is 40.662141 / 74.215238

To describe the County Courthouse, think Empire State Building shape, with the antenna's mounted on the observation deck with the view of the horizon obstructed by the building itself.

eboe · Post by **eboe** » Thu May 20, 2004 2:04 pm

yup, i'm with the board of ed. the building is plenty tall enough, tower room is located on the 17th floor, but like spareparts says, the antennas are not quite at the tippy top. the 466 is one of our frequencies, but not the one on the courthouse. the courthouse repeater is on a 451/456 split.

what i'd really like is some sort of low-cost simulcast system that would use a secondary site (or two) somewhere in the city to fill in the gaps. unfortunately i know virtually nothing about simulcast or what it involves. the only thing i know about simulcast is that it uses gps pulses to keep all the stations in sync and these stations have to be linked up somehow like with a T1 line or something. not sure if there are different methods, but that's about all i know. if i could just learn a little more about how these systems work, perhaps i could suggest it as a solution to the problem. unless there's another way to get the coverage we need.

btw - we have several repeaters on several different frequencies located around the city. none of them give 100% coverage. even our new "emergency" channel is plagued by dead-spots. there is no more room available on the courthouse for another antenna, so we're lucky we got the spot we have now.

spareparts · Post by **spareparts** » Fri May 21, 2004 3:07 am

eboe wrote:what i'd really like is some sort of low-cost simulcast system that would use a secondary site (or two) somewhere in the city to fill in the gaps. unfortunately i know virtually nothing about simulcast or what it involves. the only thing i know about simulcast is that it uses gps pulses to keep all the stations in sync and these stations have to be linked up somehow like with a T1 line or something. not sure if there are different methods, but that's about all i know. if i could just learn a little more about how these systems work, perhaps i could suggest it as a solution to the problem. unless there's another way to get the coverage we need.

btw - we have several repeaters on several different frequencies located around the city. none of them give 100% coverage. even our new "emergency" channel is plagued by dead-spots. there is no more room available on the courthouse for another antenna, so we're lucky we got the spot we have now.

Are the dead spots inside buildings or in the open? Some of the closer buildings are steel frame / steel deck roof. That's goning to be problem as the roof is in the line of sight.

BTW, the BOE has access to the fiber municipal ring. If you did go simulcast, You could use IP to tie the remote sites back to the primary site. Latency is real low, and is fairly consistant.

eboe · Post by **eboe** » Fri May 21, 2004 3:17 am

the dead spots are 'mostly' in the buildings with a few exceptions. almost all of the buildings have trouble with reception down in the boiler rooms and such, but that's expected. it's just a few buildings that have trouble on the main levels. yeah, there's alot of metal in the rooflines with i-beams and corrugated panels, etc. outside is usually much better, but there are a few dead spots outside too. it's as if the immediate area is very weak and being in the building just puts you over the edge.

nmfire10 · Post by **nmfire10** » Fri May 21, 2004 4:11 am

I don't know much about simulcasting either. But maybe this could work...

Put a transmitter inside the troubled building. Make it low power enough to not be heard outside where the main one does fine. The building might provide enough isolation that GPS sync will not be needed. You can't hear the main transmitter anyway so there would be nothing to cause heterodyning.

eboe · Post by **eboe** » Fri May 21, 2004 11:20 am

i'm not sure that would work too good, matt. reception is pretty good for simplex communications from inside to outside. you'd definately get some heterodyning if you were outside the building in the immediate area. it's just that they can't get (or get at) the repeater very well from there. sometimes they can get through with just a little static, but mostly it's all garbled like someone is stepping on their transmission.

spareparts, tell me more about the fiber municipal ring. maybe i'm dumb, but i never heard of it.

wa2zdy · Post by **wa2zdy** » Fri May 21, 2004 4:24 pm

Satellite receivers might help?

And yes, I'm familiar with the city and courthouse, I wasn't thinking HTs inside the buildings. That's a tough nut to crack in most cases. You may be asking too much from the system. I dunno.

Jim202 · Post by **Jim202** » Tue Aug 03, 2004 8:20 am

Have you looked at putting a remote receiver into the building that the portables have trouble getting out of?

Jim

building shielded from repeater...very poor reception

building shielded from repeater...very poor reception

Poor receiver coverage