need more signal

[rchamberlain1]

First post. Hope in the right place. We have a large 3 story brick building that has been added onto several times. Have a 30w UHF repeater on the roof with a small gain antenna. Need more signal on the bottom floor for the portables. The Kenwood HHs work better but not 100%. Only need to cover the building. Cannot penetrate the roof. More power would probably do it but was looking for a different solution. This is the simple description and i know a lot more info is needed.

 

[dryfb]

Reception or transmitting issues on the handhelds? Also what radio model are the handhelds, which antennas, and what power setting? If there's space on the second floor then maybe putting the repeater there could work. Someone much smarter than me can help with antenna and RF science lol.

 

[prcguy]

A vertical gain type antenna will put most of the signal out to the sides and will have a null below it. How large is the building footprint? If you only need to cover the building you might try something like a 3 element Yagi in the middle of the roof pointing straight down. I had a problem with a paging system in a 10 story building years ago and replaced the roof mounted vertical with a 10dBd Yagi pointed straight down and it saturated the building just fine all the way to the basement using small pagers with lousy internal antennas.

Edit: Today I might use a circular polarized panel antenna pointed straight down.

 

[AM909]

If the repeater is already at 30 watts, and using 5 watt handhelds, you're probably already imbalanced to where your handhelds will hear the repeater in places the repeater doesn't hear them. Since 5 watts is about the reasonable limit on the handhelds, you need better antenna coverage on the repeater, so you will affect both its receive and transmit. Can you draw a picture of the building outline and where the repeater antenna currently sits? What exactly is the antenna?

Moving the repeater to another nearby bulding may work (if allowed). As for the repeater antenna, less gain / wider vertical beamwidth, adding mechanical or electrical downtilt, and moving it to a corner of the building can all help.

 

[wtp]

can the antenna be put on another building and face yours ?
that way it could cover the whole building.
and there was a thing called passive repeater.
two antennas connected with cable in between, no radio.

 

[cavmedic]

and there was a thing called passive repeater.

This is on my list of things to actually try. Ya don't hear much about them much unless you work with some old timers who used to hang out with Marconi

 

[wtp]

i don't feel that old.....

 

[speedway_navigator]

This is on my list of things to actually try. Ya don't hear much about them much unless you work with some old timers who used to hang out with Marconi

Didn't know him but Tesla was on my paper route.

I used a passive repeater in a stadium once, might have been the Astro dome. NBA folks had office down a hall off the main walkway which the site survey folks failed to test in their trip there a month before.

Used a 5 element Yagi down the hall and an onmi, did not have another Yagi. It worked well enough in the hall and rooms for down link, up link only worked from the hall or a few feet into each room. My cousin put an omni in a hospital basement with a donor on the roof, pagers worked fine after that.

 

[wtp]

at a JC Penny store i almost got to try the passive thing.
i was 'helping' with security and they could not talk from the third floor to the basement reliably.
it would have cost them for the antennas and the cable, but a big wig said no.
so it was like your situation but with a 10 watt base and 2 watt handhelds.

 

[speedway_navigator]

Edit: Today I might use a circular polarized panel antenna pointed straight down.

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[RCBi-Dave]

We have a large 3 story brick building that has been added onto several times. Have a 30w UHF repeater on the roof with a small gain antenna. Need more signal on the bottom floor for the portables.

The actual "signal pattern" from the repeater “small gain antenna” is most important in trying to target your bottom floor coverage area located below the antenna.

Moving the repeater and antenna system to another location to paint the RF signal equally into the whole side of the building for all 3 floors is a good idea as someone had suggested.

Omnidirectional antennas with 6 to 12dB of gain; obtain their signal gains by flattening/squishing/focusing the signal pattern into the shape of a pancake aiming the majority of the RF signal pattern towards the horizon. They have zero signal directly above or below the antenna.

Omnidirectional antennas with <5dB of gain; obtain their signal gains by squeezing the signal pattern into the shape of a doughnut. They usually have very little signal directly above and much less below the antenna.

Omnidirectional antennas with very low <2dB or 0dB gain; will have a simple antenna pattern that resembles a ball with a good amount of signal available above the antenna and slightly less below the antenna.

I have had this same type of coverage problem frequently in cities that have buildings with 10 to 45+ floors in height and require radio repeater coverage in their first-floor interior office spaces. Most of the buildings use very rugged 0dB gain quarter wave ground plane antennas (Decibel Products/Commscope/Andrew DB-201) on their roof tops mounted on a mast along the outside parapet wall. Inverting the DB-201 antenna to be upside down and hang slightly over the edge of the wall using an ∩ shape antenna mast magically solves the communications coverage 99% of the time. It does look strange, but it does work. This modification does require special attention to weatherproofing the coax cable connections that are now inverted and have the coax cable follow the shape of the ∩ mast.

The DB-201 antenna when mounted normally will have a signal pattern that covers equally from the horizon to almost 80 degrees straight up. By inverting the antenna, the signal pattern then covers from the horizon to 80 degrees straight down.

Please attach photos and/or share more technical details of your actual repeater unit, repeater frequency used, roof top antenna system, coax transmission line, and of the building itself if possible.

This info will help everyone understand what you are trying to deal with.

Best Regards

 

[kayn1n32008]

Gain is your enemy. A gain antenna is pushing your power to the horizon, and also making your repeater deaf where you actually need to be heard from.

Try replacing the existing antenna with a single folded dipole.