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Old 09-14-2017, 11:58 PM
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Default Hospital communications issue

Hello all, I really didn't know where to put this so please excuse me if I put it in the wrong place. I work as a telecommunicator at our local hospital and we double as the comm center for the Hospital Police. The building is a seven story steel and masonry building and we have repeaters on the roof. It is a single antenna system with duplexers. We use motorola handhelds and a mobile in a base configuration set up in the comm room. We operate on the 400 mhz business band. One of the major problems we have is spotty service in certain areas of the hospital, mainly on the lower floors near the er and around radiology. I have seen small desktop repeaters and I was wondering if placing one in the spotty area with a properly polarized interior antennae would help. I don't know enough about repeaters to know how far apart they have to be without causing problems. Any help would be greatly appreciated
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Old 09-15-2017, 12:34 AM
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Default Repeater coverage

I was a sales manager for a company that had a repeater installed in the Arkansas Mental Health offices just west of the Capital. I made a service call since our office in Little Rock had been closed and I found repeater coverage spotty in the building. The actual repeater was installed in a elevator shaft on the tallest part of the building but even uhf does not penetrate everything. Moved the repeater to a building next to the main building that was lower in height but would transmit through the glass windows of the taller building while providing good coverage on the small in height building. The taller building was narrower in width then it was taller in height so rf would go through the glass fine and cover all parts of the taller building. Perhaps where you are located there is a shorter in height building that the repeater can be placed. The same holds true for a clubs Hospital support comms. We have a uhf repeater a short distance from the hospital that faces the hospital and we transmit through the glass facing the hospital. Height supports Hospital to Hospital comms but intrahospital comms, suffer sometimes. Since you are uhf, do your ht's have a simplex frequency available. Can you work around the hospital ht to ht without the repeater? Then is there ta building hear by that you can transmit ht simplex to hospital ht simplex. Basically through the glass from outside the building, This might give you a rough idea. The repeater we had at Arkansas Mental Health was a Motorola GS300,believe running 15 watts.
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Old 09-15-2017, 1:24 AM
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Thank you for the reply. Unfortunately moving the repeater is not an option and we don't have a simplex frequency. We have four frequency pairs that are used by plant ops, PD and other dept's. I have always believed that we should have a simplex freq for a time when the repeater may go down but the powers that be didn't see a need for it.
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Old 09-15-2017, 5:07 AM
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The proper way to address the situation would be a full distributed antenna system within the building. It isn't at all cheap.

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Old 09-15-2017, 6:41 AM
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A lower gain antenna may work better than a higher gain antenna the DB420 or the Station Master @ 6DB and 10DB may not work as good for you as a 3DB antenna. Just a thought as this has worked in the past.
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Old 09-15-2017, 8:33 AM
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Nothing really new here.

Hospital's have been building these areas as rf faraday cages for many many years.

Since you really did not tells us much about you system other than it's one of the couple dozen or so the Motorola makes, it is hard to help.

But look at leaky coax, bda, and maybe multi-site or voting for coverage to start with. If you need more than just the radio system then a fiber based multi band DAS.

Good luck.
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Old 09-15-2017, 9:11 AM
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Common problem in high story hospital buildings. I solved this for one hospital, which originally had a 1/4 wave ground plane mounted upside down on a small tower on the roof. I replaced it with a 10dB gain Yagi pointed straight down into the building and it worked fine. This is only usable if the repeater is only intended to work within the building and surrounding parking lots, etc. Its also the cheapest solution if it works.

I've been in various hospitals that had leaky line run everywhere and that does get expensive. Another simple system I've seen work is placing a high power divider at the repeater and running coax to a lower floor with another low gain omni antenna. You would have to experiment to find the floor and location that will enhance coverage for the entire building. The drawback is the cost of hardline running down many floors and the installation cost.
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Old 09-15-2017, 9:27 AM
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Just remember that any potential solution pointing RF into the building or similar needs to be evaluated for EME exposure.

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Old 09-15-2017, 9:58 AM
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Quote:
Originally Posted by firedog359 View Post
Thank you for the reply. Unfortunately moving the repeater is not an option and we don't have a simplex frequency. We have four frequency pairs that are used by plant ops, PD and other dept's. I have always believed that we should have a simplex freq for a time when the repeater may go down but the powers that be didn't see a need for it.
A couple of things….

As for the coverage issues:
Can the repeater here you? Can you hear the repeater? Differentiating between the type of coverage deficiency will tell you something and point to the type of solution you might need.

What kind of coverage are you trying to get out of the system? Is it interior of the hospital only? Interior of the hospital and immediate surrounding areas? Or is it a wider coverage system?

Did the system ever work satisfactorily? Did it change with new construction on the building? Has it deteriorated over time?


As for the simplex frequencies if the repeater fails, this likely isn't a licensing issue, it's a radio programming issue. If the repeater fails, you can go into talk around mode and use it in simplex. No additional licensing needed. Whoever set up your radios/designed the system/oversaw the project should have figured this in as part of the design. Having talk around capability to allow communications if the repeater fails is/should be common practice. This could easily be fixed by adding a button for talk around, or preferably, setting up a separate channel.

Sounds like the antenna system was originally designed for a wider area coverage. As PRC said, the upside down 1/4 wave or Yagi pointed downwards would likely be a cheap/easy solution. I've seen this same solution done for UHF radio coverage for the interior of ships. Upside down quarter wave ground plane antenna mounted near the top. They still provide pretty decent coverage locally around the antenna.

Leaky coax systems can work, but there's a lot of design that needs to go into it. I've never installed in a hospital, so there's probably a lot of funny code things I'm not aware of, but I can tell you that it would probably require plenum grade cable. Running down elevator shafts might trigger some code things you'd have to address. If it's an "emergency responder" type system as in used by fire, the BDA systems usually have to be hardened. Coax has to be in conduit, battery backup, fire/water rated enclosures, etc. None of those systems are cheap.

The antenna change is probably the right approach.

Either that, or start looking at WiFi based radio systems, either for your operations or for facilities. Most hospitals have pretty good WiFi networks that can be leveraged for these sorts of internal systems. For non-critial applications, it can be a cheaper solution. Also, IT tends to get better funding than the radio guys, so sometimes it's an easier way to approach it.
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Old 09-15-2017, 2:09 PM
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I have dealt with this dozens of times. As noted above, this is the order in which I run solutions:

1-Move from a high gain to a low or 0dB gain antenna on top of the building.
2-Investigate a power divider (50/50 or 70/30 are typical for my applications) run from repeater room to 1st floor (if there is a basement) or 2nd floor (if there is no basement). This inside antenna would be near center of poor coverage area.
3-If MOTOTRBO, look at adding a IPSC site if conventional or CAP+ voting site if trunking (this assumes you can hear the repeater on the roof and are not able to get back).
4-DAS (a real engineered solution, not some pile of crap a shop throws in).

Good luck, this problem requires real skill that many shops/organizations do not have any longer AND cost real dollars that many facilities do not want to allocate. TT
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Old 09-15-2017, 7:30 PM
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This is a common problem with two way companies that use the wrong antennas on repeaters

The repeater antenna on the roof is sending most of its signal to the horizon instead of downward through the building

I've done many high rise building and hospital repeater installations and have used UNITY gain antennas with great results but many hospital roofs use steel or foil in their roofing so no signal will make it through the roof regardless of what antenna you use

And higher isn't always better

Instead of roof mounting repeater antennas, you will likely get far better building coverage by moving the repeater to a lower roof on an adjacent building

Hospitals have large windows and hallways that run from end to end
so the repeater signals would penetrate far better from an antenna on the side of the building vs ANY type of antenna on the roof
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Old 09-15-2017, 8:52 PM
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the fix does not have to be a DAS. Switching to a digital system that allows multiple receivers, and multiple transmitters may be cheaper. This can be done with a few different brands, but the Icom NXDN does it very well and has a proven history of coverage in hospitals.
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Old 09-15-2017, 9:43 PM
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Radiology departments are usually much better shielded to RF than anything else short of nuclear power plants. They are very problematic for overall coverage. Accept the high probability that you won't be able to solve THAT particular problem with a minimal investment.

As for the rest, centrally locating the repeater or at least its antennas, and using unity gain antennas, is a solid first step in the right direction.

A DAS may be required in some cases, depending on the layout and desired coverage areas of the building(s) in question, and a good DAS is not cheap. It's also a bit of an engineering specialty, something a typical radio shop will not be able to properly design and engineer. You bring in a specialist, such as the engineering staff of EMR. This will involve detailed site propagation analysis studies, access to hospital blueprints, and a fair amount of time and money. But a well engineered DAS or BDA system can get the job done when a conventional installation just won't do it.

I know of a hospital that had a very good full coverage repeater system that achieved its coverage goals
by installing the repeater system not in the hospital itself, but in a nearby building that had a clear line of sight to the hospital. The repeater used fairly low gain yagi antennas on both TX and RX, pointed at the hospital, and the beam coverage angle of the antennas matched nicely to the profile of the hospital.
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Old 09-15-2017, 9:55 PM
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We've use 2 way splitters to indoor and outdoor antennas on hospital paging systems with great success.
Like the others pointed out, a simple dipole does wonders.

We installed a new paging system in the Minneapolis VA a few years ago, they have a DAS for VHF and UHF.
2 weeks ago I noticed an intent to award a DAS contract to GE to 'extend police radio coverage'. The VA PD took out their UHF repeater and went on the state's 800 trunking system.

That building has 38 acres of roof so you can imagine how poor 800 MHz coverage is. Now we taxpayers are shelling out over half a million to cure a problem that didn't exist before. It looks like the RFP started out for the GE telemetry system to cover poor coverage and expanded from their, the only spec I saw was for a 600 MHz xmtr.
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Old 09-16-2017, 8:12 AM
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Default Digital upgrade is the likely answer

Quote:
Originally Posted by gesucks View Post
the fix does not have to be a DAS. Switching to a digital system that allows multiple receivers, and multiple transmitters may be cheaper. This can be done with a few different brands, but the Icom NXDN does it very well and has a proven history of coverage in hospitals.
Winner, winner. As someone who has been involved in these types of systems before, the best way to line it up is to do budgetary quotes between a full digital upgrade using networked digital repeaters (think MotoTrbo IP Site Connect) vs. the cost of an antenna based solution.

Obviously if wide area coverage isn't the main objective, then a Yagi pointing downwards is the quick, easy, and cheap solution that makes you look like an RF hero. But if they truly want to have wide area coverage PLUS complete indoor coverage, your solutions will get pretty expensive pretty quickly. Someone else also touched on the realities of running lengths of plenum cable and the costs of leaky coax... Lots of sunken costs just to try to flog the old system along.

Networked digital systems are 10 times more simple to deploy than running splitters and leaky coax all over the place in an existing building that's fully staffed. They also seem to be easier to "sell" to the people in control of funding - just an observation. If you can't get it paid for, it really doesn't matter which solution is the right one.
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Old 09-16-2017, 9:16 AM
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I hate to keep bringing it up but this is something that needs to be competently engineered, not just darts thrown at a wall. There are many considerations, the least of them is not EME. Throwing a yagi pointing down in a skylight or similar sounds great until you realize that you are easily pushing 500watts ERP directly into an uncontrolled area. Throwing a splitter (or directional coupler) in for a second in building antenna sounds easy until the noise floor at one antenna renders the other deaf. The bottom line is that this needs competent engineering from a qualified firm. The fact that it is a healthcare facility only amplifies the matter. If management needs motivation, advise them to look at joint commission standards and they can quickly be lead to the benefit.

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Old 09-16-2017, 10:21 AM
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With 50W into a 10dBd antenna yes you have 500W ERP but at 460MHz its below the uncontrolled environment level at about 25ft above the roof. At a more realistic 20w into the same antenna your legal at about 15.5ft above the roof. 10W into the antenna would be safe at about 11ft. Change to a 7dBd Yagi and 10W is safe at 8ft above the roof and so on.

Most hospitals have some kind of small tower or antenna mounting structure that may be high enough and simply placing a Yagi pointed down at a safe height is a dirt cheap way to test the results. Anything else is a lot of $$ and my never get off the ground.
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I hate to keep bringing it up but this is something that needs to be competently engineered, not just darts thrown at a wall. There are many considerations, the least of them is not EME. Throwing a yagi pointing down in a skylight or similar sounds great until you realize that you are easily pushing 500watts ERP directly into an uncontrolled area. Throwing a splitter (or directional coupler) in for a second in building antenna sounds easy until the noise floor at one antenna renders the other deaf. The bottom line is that this needs competent engineering from a qualified firm. The fact that it is a healthcare facility only amplifies the matter. If management needs motivation, advise them to look at joint commission standards and they can quickly be lead to the benefit.

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Old 09-16-2017, 12:56 PM
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We've use 2 way splitters to indoor and outdoor antennas on hospital paging systems with great success.
You can't just put a splitter on an antenna that's connecting to a transmitter. You do know that, right?

Try that trick and you'll be experiencing PA failures before the week is out.
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Old 09-16-2017, 3:51 PM
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Why not? I do it all the time with high power splitters from Antenna Specialists, KLM and others. They combine two 50 ohm antenna systems onto one coax and giving the repeater a 50 ohm match and two antennas to cover different areas or combined for more gain.
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Originally Posted by ElroyJetson View Post
You can't just put a splitter on an antenna that's connecting to a transmitter. You do know that, right?

Try that trick and you'll be experiencing PA failures before the week is out.
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Old 09-16-2017, 5:43 PM
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As long as the transmitter sees a 50 ohm load, it'll be OK. But a simple T splitter with an antenna on each port of it will present a 25 ohm load to the transmitter. The splitter must have a matching network, and most importantly, the matching network has to have the required power handling capacity.
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