In Building Repeater

[GMC]

Hello,

I'm try to fix a dead spot in a building, it is a basement level. I priced out a system from TxRx and they want $11,000 for there bydirectional amp, I was hoping there might be a cheaper system or way to do it. The system that were trying to communicate with is a UHF repeated system. The only place we are seeing a problem is in the basement of this one building.

Thanks in advance
Gary

[nmfire10]

You could do this WITHOUT the bidirectional amplifier. I'm not saying it will work, but it is an option depending on a lot of varables.

1/4 wave a antenna in the basement
Coax to the outside
Yagi pointed at the repeater outside
$250 maybe?

Now, even with the BDA, I don't know what could possibly cost $11,000.00.

[MSS-Dave]

Well.......

Need to have lots more info before saying a passive repeater would work. They will provided you have enough signal at each end of the coax run in the building. TX/RX Systems UHF high gain (70-80 dB of gain) does run around 11K+. The filtering is what drives that price. It's also narrowband, meaning you pass a nominal 2 MHz or less on each side. I had one special made to pass 461.1 to 464.825 with the coresponding uplink frequencies at 85 dB of gain. Cost around 22K or so but worked like a champ. You might want to check Kaval to see what they cost for the same thing.

Are you trying to pass 1 channel or a certain bandwidth? Give us a little more info so we can try to help more.

Dave

[Dan562]

Hello Gary,

I would need to know how many floors to the building including the basement?

Is this building a hospital?

Does it contain a RF Paging System with Radiax cable?

Does the current base station/repeater penetrate into the basement in these poor coverage areas?

Meaning, can the Handheld Portables always hear the Tx but can't be heard by the repeater's receiver?

How much Tx RF power output?

What is the Gain of the repeater's antenna?

Did TxRx Quote you Andrews Radiax Slotted Coaxial Feedline Cable with the BDA?

I think what is happening is the UHF Antenna on the penthouse roof is shadowing signals or creating an "umbrella effect" directly underneath it.

Dan

[rickbuckner]

Transmitter in the basement and radiax to the roof does it every time.

[GMC]

that won't work because the repeater location and the building with the problem are not the same.....

Gary

[wavetar]

You could do this WITHOUT the bidirectional amplifier. I'm not saying it will work, but it is an option depending on a lot of varables.

1/4 wave a antenna in the basement
Coax to the outside
Yagi pointed at the repeater outside
$250 maybe?

Now, even with the BDA, I don't know what could possibly cost $11,000.00.

Well, since I recently a gave quote for a similar passive system, I can say it costs a hell of a lot more unless you're getting your best ham buddy to do it for a case of beer.

In our case, 125ft of 7/8ths Heliax, a high-gain antenna outside & omni inside came in at just under 3 grand, and we're not gouging anybody. You have to take into account the time taken to run a large cable within a fully finished building, and the minimum amount of time you're gonna need some sort of manlift if it's a steeply inclined roof (as in our case). Factor in the fact most shops will require two people present for at least the portion where one of them is working at heights, and the costs soon add up!

Add in another $8000 for a Kaval or TX/RX bidirectional system, and you easily get the $11,000 quote.

Todd

[Dan562]

Hello Gary,

Time to consider a Receiver Voting System to add on to your present UHF Repeater.

http://www.jps.com/index.asp?node=93

Reference the SNV-12 Voting Comparator specifications. Since you didn't provide any information on the UHF repeater I'd be guessing what is sitting in the mechanical room penthouse. I suppose I would recommend using a CDM Series UHF Mobile as a Satelitte Receiver in the basement of the other building. Installed a 1/4 wave whip with a ground plane with the mobile radio.

Install the SNV-12 Voting Comparator co-located in the mechanical penthouse with UHF repeater, interface the repeater's recovered audio into the first Input voter module. Have a Telco pair installed between the CDM Mobile and the second Input voter module which will allow the system to vote the best signal level, feed that output to the UHF repeater and if there's console it will be fed down to the dispatcher's office.

You'll need to contact Raytheon JPS Communications for a Price and Delivery on the SNV-12 and refer to the /\/\ Price pages for a CDM UHF Mobile. I think you'll find this combination of equipment much more reasonable that the TxRx Product that was quoted.

Dan

[GMC]

Hello......

Have not had time to respond.

What I have is a university campus with 23 buildings, none of which is higher than 4 stories and most have 1 basement level. The repeater is in a mechanical room and the antenna is on top of that buildings penthouse and with the mast puts it about 6 stories in the air. The system does not have a base connected to it, it is a stand alone repeater and everone is using a portable with the execption of the office which has a mobile with powers supply and antenna on there roof. We have one building which has very spotty coverage in the basement level and that is what I'm trying to clear up. I think I'm going to try NM suggestion and since I'm the one who gets to install it that will cut the cost. Let you know what happens.

Thanks for the input

Gary

[nmfire10]

Who says you need to put the external antenna on the roof? Go out the basement to ground level and put it on a pole or on the side of the building with a bracket. You don't need to go to the roof. This can significantly reduce the length of expensive coax and the complexity of the install.

Please note, I am not saying that this will work for every scenario. I'm simply pointing out that you don't always need the most expensive and elaborate system when something really simple will do the job quite nicely.

[GMC]

Hello again.....

NM I was actually going to try that. We have a room with a fire pump and there is a grate for fresh air for the engine on the pump that will give me access to the side of the building facing the building with the repeater.

Gary

[rickbuckner]

YEp, I agree ......
Consider your radiation pattern and put your radios there.
RIck

[N4DES]

You could also look into using an antenna with downtilt being this seems like a campus system. There are antennas with 3 and 6 degree downtilt available from db Products and I'm sure if you sent them your operational requirements they would be glad to tell you if it would fix your problems.

[bondipowell]

Hello, I am also working on a similiar system problem. It is odd that you have 23 buildings with basement levels and only one basement issue, or reported issue. It may be a RF unfriendly environment (motors, generators, pumps, steel wall, etc )in the one basement which could be overcome with the external yagi, leaky coaxial, hybrid couplers, inside antenna(s), etc. Other issues include whether it is a talk-out, talk-in or both type problem.

If you need a BDA the least expensive I have found is from Andrew (now CommScope). The Andrew WIG TFAN50-14 is 400-512MHz with 10dB gain, 120 VAC. The next would be Empower RF Systems, Inc. at $6000 for 20dB gain. Other manuf. are TX/RX, CommProd and EMR.

It would be wise to measure your free space signal from the repeater outside the building at the donor antenna location (near ground level) and measure the free space signal inside the basement. Also, your portable specifications for receiver sensitivity to see what the minimum power required is.

Nick

[rickbuckner]

Gary,
I've been successful with a two of R/shack high gain TV amplifiers ($79.00+ models) one driving the other with a tuned filter in between them and a yagi outside looking at the closest site and a mag mount inside, bringing the desired signal inside. I mounted them on a piece of plywood in the ceiling. Produces a few miliwatts, but may be enough.
Then, if you need it, a duplicate 5mhz away going the other direction.
Sounds home brew wierd, but it worked for me.

Good luck !
Rick