Fire Ground Power Levels?

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joes243
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Fire Ground Power Levels?

Post by joes243 »

A question for the experts...

My fire department uses a uhf simplex frequency for fire ground communications. The communications on this frequency doesn't have go any further then the scene. We have repeaters in the trucks if we need to communicate with dispatch. A 45-watt mobile is used as the fire ground radio at the command post. We are using HT1250/750 portables on high power right now. Does anyone see an issue changing to low-power? Mainly I am looking to prolong battery life. The biggest building we have in our area is a 5 story hospital. I was reading that FDNY uses 2-watts on their fire ground frequencies, so I figured we should have no issue (of course we would test before we make the change system wide). Is the HT1250 on low power one or two watts?

Thanks for any help!
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Bill_G
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Re: Fire Ground Power Levels?

Post by Bill_G »

You radios have programmable option buttons. One of those options is to toggle between high and low power. You should demonstrate the feature, and practice with it at drill to see if low power meets your needs. I suspect you will lose some coverage in the deepest bowels of a concrete building trying to talk to a pumper at the curb. But, even high power might not make it under those circumstances. Tunnel levels and interstitial can be difficult in any situation. If most of your responses are to standard commercial and residential construction, and you are only tryong to cover a sq block, low power will serve you well. How much of a battery power savings you'll enjoy will have to be determined.
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maxkelley_kc2spy
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Re: Fire Ground Power Levels?

Post by maxkelley_kc2spy »

I would say don't mess with it. If there comes a time when you need that extra dB or whatever it is that high power gives you, in case of some weird circumstance within a building that seems to be really RF-absorbent, that signal's intelligibility can be the difference between life and death. I know that UHF portables within a local school, even running 4 watts, sometimes can't talk to each other if they're in particular parts of the building, etc. In your situation, I say forsake the battery lives for the sake of saving human lives!

Also, are you talking about battery life as in per charge, or looking at long-term battery life? And how long does it take you to put out fires that you need to swap batteries during an operation? ;)

My two cents.
Max Kelley KC2SPY
http://www.maxkelley.com
MT2000 VHF & UHF A7, Visar UHF, ASII UHF, Maratrac UHF, Astro Spectra UHF, MCS2KIII 900, XTS2.5K-Q
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kb9suy
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Re: Fire Ground Power Levels?

Post by kb9suy »

I wouldn't be comfortable running my portables below maximum power. There are too many variables on the fire ground that could inhibit transmission and reception. Truthfully that's why your fire personal should be maintaining there radios to make sure they are charged and ready to go. There have been line of duty deaths where I.C. has missed radio traffic due to being overwhelmed. Does your dispatch monitor the fire ground channel? They should! cutting power might take the option of dispatch monitoring the channel out of the equation. Just food for thought.
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Bill_G
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Re: Fire Ground Power Levels?

Post by Bill_G »

3db in a static test on the bench or between two fixed stations can mean the difference between the squelch opening or closing. In real life where signal fluctuations walking between rooms can be 10 to 20db, where having it on your hip versus a chest pack can mean 10db depending on your gear and body mass, and where all the receiving units are within a several hundred feet of each other with an overall rssi of -90db, 3db becomes inconsequential unless everybody comes to a stop, and adjusts their portables for best reception. 3db disappears in the myriad other reasons why a signal fails to propagate. 3db will move him from no communications to noisy, poor, nearly unusable communications that breaks up with the slightest change in environmental conditions. That's why I suggested he try it out. He has to have a reason why he is concerned about his battery life. OTOH, he should do some research into how many more minutes or hours he would gain by reducing power. He may be surprised by the answer. It depends on his battery types, and the condition of his equipment.

This endeth the sermon. amen.
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kb9suy
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Re: Fire Ground Power Levels?

Post by kb9suy »

Good point but your missing my whole point. Field testing will never account for real life situations. Most fire scenes never run past more then 2 hours. There is always a exception. Your not transmitting for long periods of times. Most fire ground transmissions are a few seconds at the most. If your batteries are dieing from transmission usage with-in a hour, 1 your talking way to much for fire ground operations 2 your batteries most likely need to be replaced. I run a VHF xts5000 model 3 for my fire ground portable. I have operated at 6 multiple alarm fires in the last month running on the same battery with lots of transmit time and haven't ran it dead. I am running my portable at 5 watts. It's better to lean on the side of caution having the best power available on your portable then lowering it. If God forbid something happens and you loose a fireman cause he got trapped in a room where he couldn't call out for help cause his radio would get out and that extra couple of watts would of been enough for him to call out for help. Your gonna have to answer that question why his equipment failed to perform. Stay on the safe side and leave it alone. Just my opinion. Give your fireman the best chance of survival. It's easier to replace batteries then a Firefighter.
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Bill_G
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Re: Fire Ground Power Levels?

Post by Bill_G »

I understood your point and totally agree with you. I'm glad you made it again emphasizing time versus personnel safety. If you are an urban agency and the majority of your responses are 2 to 3 hours on scene, it is better to lean towards safety because you will save nothing on the battery life. If he had said he was rural working field and forest fires, or aiding with SAR missions where responses can last for days, then battery life becomes part of the equation. However, because of the distances and terrain involved, and all the reasons stated already, everything should be at high power effectively turning battery life into a logistical issue. A well stocked command will have chargers and batts on hand to stay ahead of that as they rotate crews. Battery life is a purchasing decision, and not one you want to make in the field.
joes243
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Re: Fire Ground Power Levels?

Post by joes243 »

Thanks for your opinion guys. Those are the answered I thought I would get. Our dispatch center does NOT monitor the fire ground channels. It’s kind of stupid because the “evacuation” tones go out over a channel that nobody in the structure is monitoring. I did set up our radios to set out an MDC group call to make all the radios beep for evacuations. The problem is the officer in command either won’t have time to or remember how to do it. As far as battery life, our issue is that each fire fighter is issued a radio. The radio (95% of them anyway) are kept on the gear racks with the gear. When the guys come back from a call, they don’t check the batteries and it doesn’t get charged. The next call after about 15 min on scene and a couple transmissions batteries start to go dead. We have no chargers/batteries on the scene (I am working on that). So I thought reducing the power might give the batteries a little more time before they die.

Thanks again!
tvsjr
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Re: Fire Ground Power Levels?

Post by tvsjr »

OK, let's put some numbers to this.

For this analysis, let's use 10/10/80 (10% TX, 10% RX, 80% Standby) as a metric. Moto typically uses 5/5/90 but we'll stay closer to the real world. To understand these numbers, think of it this way - you would need to spend 6 minutes of every hour in constant transmit. That's either an incident commander or a rookie with lets-talk-on-the-radio-itis.

I don't have a Waris service manual handy, but let's look at an XTS5000, since I have that manual here. From the XTS5000 Basic Service Manual, for a VHF model, typical current drain is:
2100mA - transmit
240mA - receive @ rated audio
80mA - standby

We'll assume we're using a standard 1500mAh Waris NiMH pack on the radio.

In an hour, at maximum output, we'll consume:
2100*.1 + 240*.1 + 80*.8 = 298mAh
Or, 5.03 hours.

Dropping to 2.5 watts (using the previous 3dB decrease), let's assume we'll see the input current cut in half. That's being very generous... the drop is likely to be 25% or less.
1050*.1 + 240*.1 + 80*.8 = 193mAh
Or, 7.77 hours.

So, using some pretty aggressive/specious numbers, you pick up 2.74 hours (2h 44m) by dropping the power 3dB. Using more reasonable figures (5/5/90, 75% of max input for 2.5W out) you can figure on less than half of that.
1575*.05+240*.05+80*.9 = 162.75mAh or 9.2 hours.

So, now for some questions:
How many incidents do you have that last longer than 5 hours?
When are firefighters demobilized for significant rehab, feeding, and medical evaluation? Hint - the answer should be less than 5 hours.
For most incidents, if they exceed 4 hours, the chance of them exceeding 8 hours is fairly high. Do you have spare batteries and chargers on a mobile platform to allow swapping at the scene? When is this performed - during the rehab we just discussed? If so, any of these situations gets you across 4 hours, which should be the deadline for an extended rehab period.

The next question - what's the key reason you're asking this question? Do you have radios exhausting their batteries on scene? Or is this a solution in search of a problem?

If you indeed have radios dying on scene, you may have other issues. Have you considered:
The battery charging and maintenance regimen?
When were these batteries purchased?
Moto or aftermarket?
Impres? If not, when were they analyzed and conditioned last?
When are they charged - by a volunteer at home or by on-duty personnel at the station?
Are radios being left on all the time by on-duty personnel to monitor dispatch/response/etc.?
Are the radios drawing excessive current? PA failure?

Finally - if, $DEITY forbid, a department member is killed or injured in the line of duty, and the NIOSH report cites a communications failure that might possibly in the mind of a lawyer somewhere be linked to the reduction in transmit power, do you have the backing of the department and the governmental body? If they come looking for someone to crucify (read: sue into oblivion), do you want to be on the list?

FDNY has lots of smart people and lots of money to study things and back them up. They also have in-building systems in many of their large facilities. You probably don't. "FDNY does it!" isn't a valid answer if someone asks why you turned the power down (to use another example, and with absolutely no disrespect intended: FDNY suffers more LoD injuries and deaths than any other department around the world, oftentimes due to their aggressive firefighting tactics (whether or not that style is justified is another discussion entirely). If you started fighting fire like they do, and taking the losses they do, what would your command staff, city management, and community say? Again, "FDNY does it!" ain't gonna fly...)

Consider other solutions:
Chargers and spare batteries in a mobile platform (command post?)
Spare battery for each issued radio... enact SOPs and train the members to put their spare battery on their assigned apparatus so they'll have it... the spare should be swapped for the battery on the radio at the end of shift and the battery from the radio placed in the charger, to ensure both packs get cycled. This has some up-front cost, but negligible long-term cost, since the batteries will (optimally) be cycled at half the rate and thus should last twice as long before needing replacement.
Vehicle chargers (not my favorite)

And, I hope you have some plan for communications in that 5-story hospital besides "hope it works" - because it won't... but that's a soapbox for another time!
joes243
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Re: Fire Ground Power Levels?

Post by joes243 »

Thanks for the detailed answer tvsjr! I was thinking of this prior to learning that FDNY uses low power. The reason I asked here is to see what other departments do, not just because FDNY does it. Like I said in the original post, everything would be tested prior to making the switch. After reading the replies I got here, I am no longer considering dropping the power.

We do have plans and continually test our communications at the hospital.
xxx2fan
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Re: Fire Ground Power Levels?

Post by xxx2fan »

As a Chief Officer in a Vol.Fire Dept.

Do not change off of HIGH power. Instead you may want to look into changing your batteries to
Motorola HT1250 7.5V 1800mAH Li-ION Replacement Two Way Radio Battery

"Motorola HT1250 7.5V 1800mAH Li-ION Replacement Two Way Radio Battery by Titan. Fits And Replaces: HNN9008, HNN9008_R, GP1280, GP140, GP320, GP328, GP338, GP340, GP360, GP380, GP640, GP680, HT1225, HT1250, HT1550, HT750, MTX8250, MTX8250LS, MTX850, MTX85"
Last edited by xxx2fan on Wed Aug 18, 2010 5:19 pm, edited 1 time in total.
jbella
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Re: Fire Ground Power Levels?

Post by jbella »

joes243 wrote:As far as battery life, our issue is that each fire fighter is issued a radio. The radio (95% of them anyway) are kept on the gear racks with the gear. When the guys come back from a call, they don’t check the batteries and it doesn’t get charged. The next call after about 15 min on scene and a couple transmissions batteries start to go dead. We have no chargers/batteries on the scene (I am working on that). So I thought reducing the power might give the batteries a little more time before they die.

As with most fireground radio problems this is a training issue. Firefighters (and I am one with 20+ years on the job) need to be trained and drilled on radio systems and operating procedure. It doesn't have to be too technical, it just has to make sense and be applicable.

I would not under any circumstances go to low power.

I would work on chargers for the radios and put a policy in place that the firefighters or someone at the station be responsible for upkeep of the batteries and radios, making sure they are charged. A link is missing in the chain where a radio can be just put back on the shelf and left to die until the next call .
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escomm
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Re: Fire Ground Power Levels?

Post by escomm »

xxx2fan wrote: We have switched to all Li-ion batteries and Impress Charger<gang> we also use our normal charger and just run the batteries through the impress charger every other month.
You gain no benefits by putting a non-Impres battery in an Impres charger. It's basically charging the batteries the same as any other rapid charger.
Tishers
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Re: Fire Ground Power Levels?

Post by Tishers »

If you have large structures like hospitals, hotels, commercial buildings, etc... You may have some pull in your fire codes to have those buildings retrofitted with radiax (leaky coax cable) running through the emergency stairwells or elevator shafts.

When IC pulls up to the scene your commo person would stretch out a coax cable and jack into the building with a connection between the fireground radio and the radiax.

Most certainly you would have great signals in the stairwells and extending quite a bit onto each floor.

This is a one-time expense. It is not powered, there is no radio left at the building and it can be used for nearly any frequency. The biggest threat is from some yahoo who cuts into black cables to steal the copper.

This is an antenna system frequently seen in subway tunnels.

For about $30K in materials they could have equipped all three stairwells in each of the WTC buildings.
Ms. Tisha Hayes
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Bill_G
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Re: Fire Ground Power Levels?

Post by Bill_G »

Many city's are adopting requirements for building owners to ensure public safety communications indoors with semi-annual review. That sometimes requires no corrective action, sometimes requires a whole building BDA installation, and sometimes requires a BDA only in the subterranean parking levels. The investment in a BDA often has a secondary benefit of enhancing cellular coverage making the decision more attractive. With the increased volume in sales, manufacturers are responding with more innovative, lower cost solutions. We haven't quite reached "smoke detector" sized spot fill products yet, but I anticipate something like that coming. However, we have reached the stage of multiple fubar generators installed by unqualified individuals causing system interference. They make life interesting.

None of the systems we have installed have a tap that an IC could plug into to utilize the building distributed antenna system. It's an interesting concept. I'd like to see some standards on where and how to deploy it.
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kb9suy
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Re: Fire Ground Power Levels?

Post by kb9suy »

That's a interesting idea I would have never thought of. No need for a bda just radiax from top to bottom and "fire department Connection" on the outside of the building just like your sprinkler and stand pipe connection. That's a cheap and easy concept I never would of thought of. It would work too.
resqguy911
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Re: Fire Ground Power Levels?

Post by resqguy911 »

http://www.npstc.org/inBuilding.jsp
We are in process of acquiring models of these http://www.modtech-corp.com/?page=sipsbda800 to enhance coverage in certain buildings. You can have a distributed antenna system brought out to an FDC or Knox type box, and bring your own BDA to the scene if necessary. Our test implementations went very well.
"TDMA = digital and same great taste, half the bits"
Tishers
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Re: Fire Ground Power Levels?

Post by Tishers »

I have used the BDA approach and a "passive antenna" setup to provide cellular coverage in the tunnels under a sewage treatment plant. There are about 3 miles of tunnels under the plant (LARGE plant, major metropolitan area) and 10-12 stairways that descend down to around 30 feet below grade. It is a much worse environment than a parking garage and a place that sometimes has a Class 1, Div 2 explosive atmosphere (methane). The un-powered nature of the system means that it remains in FM compliance. These are passive antenna sites with a high gain directional antenna above ground, pointed at the nearest cellular tower. Down below it is a matching directional antenna pointing down a long tunnel or leaky coax.

What is cool is that cellular coverage is 2-3 bars underground, Nextel radios work and the police/fire trunking system operates as well. It was an issue with worker safety and the other alternative was to go with several powered BDA solutions, one for each different system or to put explosion-proof telephones every few hundred feet.

For a building needing both conventional cellular BDA and an optional firegrounds connection at street level you could mount a directional yagi antenna pointed at the nearest cellular tower(s) on the top of the stairwell. Attach it to radiax down the stairwell and then have the terminating end at a jack at street level. During non-fire operations the yagi antenna at the top and the radiax will passively enhance cellular/ portable coverage in the building. During an incident the command post can jack in at street level and the radiax becomes an antenna up through the building, the yagi on the rooftop would also serve as a mismatched antenna to the command post radio but the SWR problems will be minor as there is quite a bit of dB/ft losses for the radiax to get up to the antenna.

BDA cellular services, command post radio and potentially even simplex portables could make use of the system at the same time.
Ms. Tisha Hayes
Principal Consultant, Wireless and Telecom (EE)
Energy and Utilities Practice
also AA4HA
Winger2002
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Re: Fire Ground Power Levels?

Post by Winger2002 »

joes243 wrote:Thanks for your opinion guys. Those are the answered I thought I would get. Our dispatch center does NOT monitor the fire ground channels. It’s kind of stupid because the “evacuation” tones go out over a channel that nobody in the structure is monitoring. I did set up our radios to set out an MDC group call to make all the radios beep for evacuations. The problem is the officer in command either won’t have time to or remember how to do it.

Might be a good idea to look into a few xts's for officers, they can send out their own evac tone (standard hi lo hi lo...) if programed for it by holding ptt then pressing the emergency button once, really a simple little feature that adds alot of functionality.
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kb9suy
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Re: Fire Ground Power Levels?

Post by kb9suy »

Illinois Mabas has adopted 1500.0hz as our evacuation tone for fire ground operations. I programmed our mobile cdm radios for one button press to get to the tone then hit the ptt. I carry the xts and also use the evacuation tone function it comes in very handy.
Squad5
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Re: Fire Ground Power Levels?

Post by Squad5 »

I don't know about you guys but I carry 2 sometimes 3 spare batteries in my turnout gear for my 5k portable.
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