UHF BDA for hospital

[emtprt]

I am writing a grant for a UHF BDA for our local hospital. 2 Shops have provided information and are working out prices.

The questions that I am unsure of are the use of radiating cable vs power dividers with antenna.
BDA vs Passive repeater system or distributive antenna system.

The project is primarily for the ER a(a 3/4 block lock) but may someday be extended to the basesment for Fire department use.

Any experiences with these devices please feel free to share with me

[Bill_G]

Passive system - discussed a bit here in another thread. Doesn't work. Forget it.

BDA is best if you have good isolation between inside antenna system and outside world. Otherwise, it's a fubar generator. Needs good engineering study.

Low power multicast may be more appropriate.

Radiax is okay for open spaces like a mall grand hallway, or a highway tunnel. Requires specialized mounting and lots of clearance from obstructions.

Heliax with distributed antennas is best for busy ceiling spaces with complex ductwork, conduits, plumbing, and structural steel. Allows you to mount the heliax where possible, and drop an antenna to clear area. Easier to install in buildings with multiple floors. Easier to plan losses and customize coverage.

[emtprt]

The radio system has a voting receiver 6 blocks from the hospital and receives portables fairly well from the hospital. Portable units in the hospital have spoty reception. There are 5 other services that each have there own UHF frequncy with various levels of radio coverage in the ER. The frequency range is 453.050-463.575. The services with the poorest coverage are on 453.050, 453.975 and 463.575. Both of the 453.xxx frequencies have good coverage from the upper floors and outside the building.

1 option discussed was ROIP with 2 low power Transmitters for the 2 453.xxx channels. This would allow user to stay on the same channel when at the hospital.

Another option discussed building 2 small repeaters RX 453.xxx TX on 465.xxx 2 watt channels that we are currently licensed for but users would have to change channels when arriving at the ER.

Multicasting from the closer receiver site (changing to transceiver) is out of our price range (GPS setup, new repeater cost...)

A BDA sounds like the best option but can it cover the range 453-463 or would the 453.xxx have run on a stand alone unit

[Bill_G]

BDA's are preferred when trying to pass multiple freqs within a band as long as the spread isn't too wide since there will be fixed splits for the uplink and downlink that essentially match the repeater splits. In your case two or more UHF BDA's would be required to serve both the 453 and 463 channels. However, because you have coverage, albeit fair to poor coverage, in both directions in the areas needing improvement, a BDA could easily become a fubar generator. It could create an area of interference around the hospital that has to be compensated for. That's why I recommend having an engineering firm review and design it.

Multicast is transmitting on two or more freqs at once. Not to be confused with simulcast - multiple transmissions on the same freq. It is a non-standard split unidirectional repeater (one direction at a time). For example, the normal wide area repeater output is 453.375, input 458.375. To serve the ER you install a unidirectional repeater made from two mobiles. One has the normal mobile split for repeater service (tx 458.375, rx 453.375) with its antenna on the roof. The other has a simplex channel (458.525) with its antenna indoors in the area needing service. Personnel change to the ER channel when on site. Transmissions on 458.525 are retransmitted at 458.375, sent to the repeater, and heard over the wide area system. Transmissions on the wide area are heard on 453.375, and retransmitted into the ER on 458.525.

One would have to be built for every channel needing service. It is the cheapest option for single channel systems, but gets expensive quickly as you attempt to serve many channels. With careful planning, they work well.

[emtprt]

I ment to say simulcast when discussing cost factors; sorry. We are planning to experiment this weekend. We will place a mobile radio and a yagi antenna pointed directly at the hospital from a tower which is 6 blocks away. We want to see if we are able to transmit in to the ER from the location. This would allow a dispactcher to select that tower if a unit is in the ED. Reception from the same tower seems to work fair using a 3.8 omni dipole antenna.

We are trying to get the most bang for the buck when we write the grant. The grant Max. is 10,000.00

[emtprt]

The need for a BDA was validated with our recents testing aiming a Yagi from a tower 0.5mile directly into the hospital. The XRAY department blocks radio signals through the ER to the tower.


I understand the basic BDA concept but have not been involved in the purchase or cost factors of a BDA install. I assume the following items need to be considered: BDA, Cable, antennas with hardware and labor.

I will be dealing with drop ceilings and a straight hallway 175-200' . The outdoor antenna can easily be mounted and aimed at our UHF base wwith a 60' run of cable.

If anyone has had experience with the purchase or intallation of a similar sytem i would like to know if will 10k cover the cost of this project?

[Bill_G]

I'll ask our in house BDA expert. We sell Tx/Rx and I'm inclined to say that $10K is not enough. There may be alternative product available. Dekolink makes reasonably priced 800M fill BDA's that I've used quite a bit to light up an inner squad room, or a basement hallway. But, I've never used their UHF product. Part of the problem is the UHF splits being only 5M apart, but the band being +10M wide. The uplink and downlink pass freqs usually limit the number of UHF channels you can successfully use.

http://www.axellwireless.com/?get=conte ... &id=127-22

[emtprt]

We had investigated a BDA system for a new school to cover VHF/UHF 25k, the recommended placing 2 low power repeaters in the building. One on 465Mhz in to cover the 453.xx dispatch and and second 159Mhz in for a 155.xxx dispatch frequency inplace of the BDA