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Safety First
Alan Applegate (K0BG)
on
April 7, 2004
View comments about this article!
Safety should be the highest priority item an amateur radio operator instills to his hobby. Most of us know better than to stick our hands inside a live HF power amplifier or climb a tower without a safety belt. However when it comes to mobile operation we seemingly forget the dangers involved. In a recent OpEd article (April 2004 issue of QST) I wrote the following words: It is distracting enough to talk on amateur radio and drive without adding further distraction caused by poor installation practices. It is up to us amateurs to set a safe operating environment level, as free of distraction as possible. This is the essence of this article.
I've been operating mobile for over 30 years with a great deal of that time traveling the highways and byways of the mountain west. I averaged over 40 hours each week behind the wheel and mitigated these hours operating the HF bands. I DXed, county hunted, rag chewed, and mostly listened. I wore out about a dozen cars, and not once did I temporarily mount a rig or antenna. Company cars and personal cars alike, I drilled holes and installed ballmounts, screwed down mounting brackets, and hid the wiring all in the name of safety.
I like the readers of this article to recall the part of their high school physics class which dealt with energy. More specifically, the formula for kinetic energy which is 1/2(m*v2), where m equals the mass and v equals the velocity. For example, a 2-pound object traveling 8.8 feet per second (10 mph) will have a kinetic energy of 77+ foot-pounds. Then there is the law of Conservation of Energy, which deals with the change of kinetic energy to potential energy and back again. Using the above 10 mph example, a 2 pound object laying on the top of your car has a potential energy of 77+ foot-pounds. If your car stopped instantly and we ignore any friction losses, all of the potential energy turns into kinetic energy. In any case, I wouldn't want to be hit on the head with the object!
I used the 2 pound example above for two reasons; this is about the weight of the average remote head (face plate), or that of a VHF mag mounted antenna. Let's assume we're merrily traveling down the highway at 60 mph. At this speed the potential energy of our example becomes 7,744 foot-pounds. All of this potential energy would not become kinetic energy in the event of crash because other factors must be considered. For example, the mag mount does have some adherence to the car body, there is friction, and there are deceleration components as well. But don't kid yourself! If you have a crash while driving 60 mph, that mag mount will dislodge itself and most likely will snap its coax cable allowing the antenna to become a missile with enough kinetic energy to maim and kill! This is true of a remote head as well when we trade magnetic lines of force for the tensile strength of Velcro.
As I inferred above, it is difficult if not impossible to determine the actual kinetic energy of any object without knowing all of the factors involved. In some crashes nearly all of the potential energy will become kinetic, and others just a fraction. The point here is, even 77 foot-pounds can kill.
There is another aspect of safety which most amateurs miss, and that is the distraction factor. Improperly positioned and/or mounted devices can cause an inordinate amount of distraction. Distraction can be described as the length of time your eyes are off the road and/or controls of the vehicle. At 60 mph (88 feet per second) the average vehicle needs 144 feet to come to a stop (102 feet for some sports cars to 208 feet for some loaded 8 passenger vans) and you have used over half of it due to distraction. You may not be paying attention, but our lawmakers are!
Early this year, the NHTSA (National Highway traffic Safety Administration) amended its rules to require reporting of the use of telematics in any vehicle involved in a crash (the word crash is now used in place of accident as crashes are seldom accidents). Telematics is their term for radios, FAX machines, computers, cell phones, etc. installed or in use in a vehicle. The most prevalent of these is of course is cell phones. This fact has spawned a rash of new laws against telematic use.
Go to this site
http://www.nhtsa.dot.gov/ncsl/Index.cfm and select 'Distracted Driving' from the right-hand popup, and push the button. While most of the listings cover cell phone use, a closer look at the individual laws just might make your blood boil. And the real spotlight is yet to come. The first annual telematic use report is about 9 to 12 months away, but preliminary data indicate an extraordinary high incidence of telematic use in crashes. Incidentally, amateur radio is one of the sub headings.
One of the easiest ways to avoid distraction is to properly mount your equipment in your vehicle. This means Velcro, bungie cords, rubber bands, and other temporary means are not only verboten, they're hazardous to driver and passengers alike. You can add mag mounts and many other temporary schemes to this list.
It is difficult to address every mobile mounting scenario as each piece of equipment and each type of vehicle is different. However, one can list a set of guide lines which should be considered regardless of the telematic or the vehicle in question. Just for brevity I'll use the words rig and car.
1). The rig should be located so it is clear of all the controls yet is easy to operate and view from the driver's seat. This is not always easy to accomplish. In my own car, I mounted the rig face plate along side of the center console just to the right of my right leg using a home brewed bracket made from DIY aluminum purchased from Home Depot. I can get to the rig controls easily and the mic can be stored in the lower dash cubby hole and out of the way when not in use.
Contrary to popular belief mounting a rig on top of the dash in plain sight is not such a good idea from a distraction standpoint or injury one to say nothing of the theft issues.
2). All brackets should be securely affixed to the various surfaces inside of the car. With proper planning the requisite mounting screws can either use existing attachment points or placed where they're not easily seen. On my previous car, I used two screws, which secured the AM/FM radio frame and center console together to secure a home brew bracket. In turn my IC-706 faceplate was bolted to that bracket.
3). Depending on the year, make, and model of car you own, one or more SRS units (supplemental restraint system commonly called air bags which they're not) will be installed. All rig controls, mounting brackets, mic and power cables should be clear of the SRS. In my OpEd article, I sited an instance where the rig faceplate was mounted atop the drivers SRS, smack dab in the center of the steering wheel. Imagine what sort of smack he'd get if the SRS went off?
4). All wiring should be properly sized, fused, and affixed to eliminate interference with in-car wiring and controls, and out of the way to avoid abrasion, shorts and tripping hazards. Avoid using splices and electrical tape. Never use existing circuits for power even though they appear adequate. In other words, always wire directly to the battery with proper fusing in both leads at the battery end.
The accessory sockets which are replacing cigarette lighter sockets these days are never wired adequately for use by rigs? -- No matter how they are fused! And don't do what was recently suggested in QST; modify a mini-fuse to tap power from the electrical system. If you want to have a real rude awakening, induce enough RF into the SRS circuitry to set it off while you're doing 65 mph down the interstate!
5). How many of you have used one of these phrases or ones like it. My wife won't let me drill a hole in our new car. It's a lease car. I'll get docked thousands when I trade it in. I can't speak for you, but I bought and paid for my car and the one my wife drives. If I decide to drill a hole, even in hers, I will.
I don't lease cars and unless you can write off the expense of a lease car to business, you shouldn't either especially if you drive over 20,000 miles a year.
I just recently traded my old (1998) car for a new one. I covered the holes in the trunk and quarter panel with rubber plugs I purchased from Radio Shack. Not one word was said about them. Car dealers are much more concerned with overall appearance and mileage. A neat and clean installation is of less concern than a trunk lid all scratched up from using a mag mount. Drill the hole and do it correctly.
6). Clean up your operating practices. Just about every modern rig out there has multiple memories and typically more than you'll ever use or at least remember. If you're like me, and the majority of hams out there, your favorite frequencies can easily be stored with room to spare. The Icom IC-706 is no exception. Whether it be a repeater or HF frequencies, modes, tones, filters, power out, and a variety of other parameters, they're as easy to change as pushing a button on the mic once they're stored in memory. For those parameters you can't store, familiarize yourself sufficiently with the various menus so you can change any of them while in motion without having to take your eyes off of the road.
7). Stick to your best operating mode. Operating CW while driving requires a good memory, good coordination, and above average dexterity. If you can't copy 20 wpm solid in your head, or remember the call and name of the guy you're tapping code with, don't try it! Using FM is much easier as everyone is "59", you usually know the guy you're talking to, and all of the controls are set and forget for the most part.
If you're a logging freak, buy a small voice recorder. The newer solid state ones will record several hours worth of data and they're cheap. I saw one recently at Wal-Mart for $29 which boasted 4 hours of recording in the low fidelity mode which is more than adequate for any mobile logging function.
8). If it is legal in your area, use a headset with just one earphone so you can still hear traffic noise, sirens, and the like. Make sure it's comfortable for long-term use, and that the mic is compatible with your rig. The Heil I used originally was too hot for the rig it was designed for, so I modified a Pacific Plantronics unit, which I like much better. Make sure the cords do not interfere with your driving.
If possible use VOX rather than PTT. The use of VOX requires a good noise canceling mic and few mobile mics fit this parameter. For several years I used a visor-mounted mic from a Motorola M500 cell phone with good success until it died. I'd like to find another some day. Perhaps this is one item Mr. Bob Heil can address.
9). Traffic conditions should dictate whether you operate, listen, or turn off the rig. No contact you've ever made or will make is worth risking a crash for and the consequences, which follow. If you decide that contact is more important, pull off the road on to a side street to finish your contact.
10). If you're one of those folks who wish to refute or rebuke what I've suggested because crashes caused by distraction only happen to the other guy, remember this; to the other guy, YOU'RE the other guy!
This article has expired. No more comments may be added.
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Safety First
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by WIRELESS on April 7, 2004
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I absolutely disagree with the premise of this post that using anything, cell phone, ham radio, shaving, putting on makeup, etc. can be a tolerable risk WHILE THE CAR IS MOVING AND YOU ARE DRIVING. Every day I drive behind people using cell phones, looking for something in the car, or ??? and these people are potential killers.
Some states are making strict laws that you can't do anything while driving except drive the car. It can't come too quickly for every other state.
If you want to make a contact via your radio, stop somewhere and take a break and make a contact. While driving, just drive and stay alive.
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RE: Safety First
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by LNXAUTHOR on April 7, 2004
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- some excellent points regarding mobile operation, and quite timely, as i'm contemplating an HF mobile install in the next month...
- thanks for making me think about magmounts, etc. and proper rig installation...
- i just wish there was a central repository of amateur radio mobile installs, sorted by car make, model... i know a lot of folks are pretty handy at these installs, but i fear i'm more inclined to go with a professional installation (perhaps the local contractor who handles municipal/police vehicle radio installs?)
- great article!
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RE: Safety First
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by KA4KOE on April 7, 2004
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I ran a 74 Nova off the road one time while operating 20m mobile in it way back when.
Fortunately it was the interstate will little traffic at the time.
I didn't repeat the exercise.
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RE: Safety First
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by K5DVW on April 7, 2004
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A 2-pound object traveling 8.8 feet per second gives 2.4 ft-lbs force, not 77 ft-lbs. For your 60 mph case, the force should be 240 ft-lbs, not 7 thousand! Mass should be listed in slugs, not lbs. A slug = 32.2 lbs.
To put it in perspective, most tire lug nuts are torqued on at around 100 ft-lbs. That's a lot of force, especially on the side of the highway when you have to change a flat!
I still wouldnt want a radio to hit me in the head when I came to a quick stop.
K5DVW
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RE: Safety First
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by KA4KOE on April 7, 2004
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DVW:
It wouldn't hit you in the head at first, unless it was behind you when you made that sudden stop. Maybe if the radio bounced off the windshield, if it didn't break that too.
However, an ole' KDK 2016 is not an insignificant piece of electronics, and those shiny knobs and toggle switches really hurt when they peel your scalp off.
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RE: Safety First
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by K5DVW on April 7, 2004
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KA4KOE > That's true, but I have a bad habit of accelerating instantly. I still have the word MOCI pressed into my forehead from last time.
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RE: Safety First
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by K0BG on April 7, 2004
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To LNXAUTHOR. Funny you should mention a mobile radio installation repository. I had been talking with Bill Fisher, W4AN (SK) before his untimely death this past Sunday about this very subject. It is still my intention to have a web site which will indeed include the aforementioned. Stay tuned.
Alan, KØBG
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Safety First
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by GM7CXM on April 7, 2004
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Good article as usual, Alan.
Personally I don't have a permanent setup, for two reasons.
First, anything on or in cars here lasts a very short time.
Second, I respect my own life, not to mention that of others. Driving an automatic transmission car in the mountains west is a different world from rush hour traffic in Valencia. Therefore when driving my rig is in it's bag and the antenna is in the trunk, all out of harm's way. I use my free hands to toot at all and sundry and avoid my fellow lunatic drivers.
Radio starts after parking up.
73 de Duncan EA5ON / GM7CXM
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Radios in moving vehicles
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by KB0JQO on April 7, 2004
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It's kind of funny how ham radio is targed as a distraction while driving, yet nothing is mentioned of the countless law enforcement, ems, and fire services that make extensive use of mobile comms.
Take for example law enforcement, today's modern cruiser has a small computer for doing dl lookups, handling dispatches, etc as well as at times a multitude of radio gear. These people are involved in high speed pursuits, hazardous driving, and everything else, all while using these different devices. I'd be more inclined to remove my radios when am/fm radios are removed from all cars and all mobile comms equpment is removed from police/fire/EMS.
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RE: Radios in moving vehicles
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by K8YOY on April 7, 2004
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My urban commute from the NE corner of the Metro Detroit area to the SW corner has been (for the past 25 years) without incident simply by applying the common sense approach that you speak of Alan! I pretty much agree with your assessment of mobile operation. I too try to make common sense prevail in all of my operating. Putting down the mike when condx. warrant is excellent advice. Keep up the columns Alan, as your multiple experiences in Amateur Radio are a source of information to the less experienced hams that are getting started in this fascination hobby. Thanks!
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RE: Radios in moving vehicles
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by K0BG on April 7, 2004
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Ryan Butler, KBØJQO, you've made a keen observation; todays police cars look like mobile computer labs. It is this very fact which caused the NHTSA to do a series of "Distraction" seminars in 2000/2001.
There are countless more examples we could make, and some would be worse and some better. However, in light of the renewed interest by the various governmental organizations, it behooves us to keep our noses clean, even if their's is not.
Alan, KØBG
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RE: Radios in moving vehicles
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by KA4KOE on April 7, 2004
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MOCI...thats ripe!!! Of course, the C would be reversed too!!!
Is it possible to accelerate instantaneously via the laws of physics, even with Transwarp drive? The delta t would equal zero? Where are we going with this?
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RE: Radios in moving vehicles
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by KJ7XJ on April 7, 2004
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I AM the other guy! I have my 2m mobile sitting on the seat, plugged into the spare lighter plug. with the coax running out a window to a mag mount on the roof. If you dont like the way I drive, stay off the sidewalks!!
Seriously, you make valid points! I have only run "temporary" mobile a few times, and I know the risks involved. Thank you for the reality check!
Eric
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Safety First
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by N1OU on April 7, 2004
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One of the best bumper stickers I ever saw read, "Would you drive any better with that cell phone up your butt?"
I'll be adding a VHF/UHF rig to my new car soon. It'll be well bolted in and I have no intention of using it unless I'm parked.
Thanks for a good article!
73
Gordon, N1OU
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Safety First
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by OBSERVER11 on April 7, 2004
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to all those that find that they MUST park before operating a radio - do you include the car stereo too? - I rememeber a quote from a Dirty Harry movie...
"A man must know his limitations". I am glad you have found yours.
For the rest of us, I for one, will continue to operate MIDCARS, ECARS, the MM/Net or just rag chew while DRIVING.
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RE: Safety First
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by K1CJS on April 7, 2004
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There are some good points made in this article, and a few not so good. As in the replies, how about the police/fire/EMS people? Yes, most of the time there are two people in these units, but the driver still has their attention diverted from actual driving by signaling units that aren't even radio/communication gear at all.
How about those Nextel units--you know, the push to talk radio phones. Those are twice as dangerous, you have to know where they are, and the signaling tone is more than likely to sound right when you need your attention on driving.
Also, tractor trailer drivers who drive a different unit every day usually don't permanently attach the radios they use to the rigs--the employers don't want holes in the trucks, or doesn't want the drivers taking time putting the radios in. Don't say CB radios aren't heavy, either--and quite a few of the drivers I work with have ham rigs (yes, they're licensed).
Alan, most of this is good advise, but in some instances it just isn't practical in today's world. My personal car has ham equipment and public service gear (emergency management) also, all bolted in and properly wired, but short of leaving the equipment out of my work vehicle there is just no way it can be bolted down in a different vehicle every day.
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RE: Safety First
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by W5HTW on April 7, 2004
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Not sure this would apply anywhere else but the vast majority of police officers I know do not use the computer while in motion. It is used to obtain license and vehicle registration info after a vehicle is pulled over, or to display a list of warrants, etc, that remains on the screen and can be read as time permits. Other devices, though, are used in motion, such as alarm signals and two way radios. One advantage the police usually has over the ham is he doesn't continually, or even frequently, change channels. He simply talks; his only requirement is to find the mike and press the PTT button. When he does change channels he does so by choosing "Channel 1" or "Channel 5" or whatever, usually from a maximum of 6 channels. He can count switch positions. This is distracting, but not as distracting as a ham trying to read the dial on his 706 and figure out what channel he is on, what mode he is using, what tone has has plugged in, and did he accidentally press the Split button.
Medical and fire vehicles typically use only one or two channels, and again drivers need not look away from the road to figure out how to work the radio. Also, in those vehicles there is almost always someone else in the front seat who can work the radio, computer and other devices.
Do police have crashes due to inattention? Yes, they certainly do, and last year we had an officer killed for exactly that reason. Well, that was one of the reasons. But the officer is generally less distracted that the guy eating his McDonald's breakfast and shaving, while using his cell phone, in the high speed lane of the freeway. Or the lady reading the morning paper and applying lipstick in the slow lane, doing only 43 mph in a 65 mph highway. If she'd drive at the speed limit, she'd arrive at work early enough to put on lipstick, have a cup of coffee and read the paper before she signs in.
Many states are enacting stricter "attention" rules. They don't just apply to cell phones, but to anything that can cause inattentive driving. While in the city most officers are too busy to just pull someone over for inattentive driving alone, (unless it is severe) if it is in combination with other factors they may cite the driver for that as well.
I operate HF mobile. I am likely to pick a frequency while I am stopped somewhere, then lock the dial to that frequency or net. Thereafter, like the police officer, all I have to do is press the PTT switch. If I have to tune the radio, I am going to find a way to pull over, as I have already experienced some close calls while using my cell phone and having my attention diverted, and I sure don't want ham radio to be the cause of me killing someone! Or myself!
All in all, a good article. We hams often tend to think we are exempt from the rules of nature as well as the rules of the road, as we think in the process of being granted a ham license we were also granted "Top Driver" status, or "Qualified Emergency High Speed Driver" status. It's automatic. We are, though, human, and we make mistakes, and some of them are fatal.
73
Ed
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Safety First
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by N0VUB on April 8, 2004
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Very good article Alan,
I operate HF mobile everyday to and from work. I have my radios bolted in solid (I'd really like to have them still in the vehicle when I get off work!) for safety. I had the misfortune of seeing the result of a head-on crash and the two-way radio that the one driver had sitting on his dash went right thru the windshield and thru the other cars windshield critically injuring a passenger, not a very pretty scene. I also have my TS-50 programed so that all the functions I would need to perform can be done safely. Everyone drive safely, sure don't want to be talking to someone all of a sudden they're not there only to find out they have been in an accident.
73
Mark
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RE: Safety First
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by W2IRT on April 8, 2004
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Damn! I guess I shouldn't tell you about when I was in my early 20s back in Toronto, driving a stick shift VW Rabbit, in city traffic, eating Kentucky Fried Chicken and handling formal traffic on an HF phone traffic net! Yes, I really did it all at once and lived to tell the tale!
I also made a living in those olden days as a news photographer with 9 scanners and three 2-ways in the car at one point (well, it was more porcupine than car, but you get the idea).
Yes, I was single back then. How did you guess??
I'm now in my 40s and I'm down to one dual-band mobile and occasionally a Motorola HT.
I know my own limitations as well, and conversations on and basic operations of my dual-band transceiver, even in NYC traffic, is not outside the scope of my abilities.
73,
Peter, W2IRT
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Safety First
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by WD4TC on April 8, 2004
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I totally disagree with you all, it really depends upon the drivers skill,my ex-wife could drive a car, use the cell phone and drink a beer(in heavy traffic) all at the same time, while I was rolling a Hooter.
It all boils down to the drivers skill.
But for safety sake , we always kept the cooler in the back seat.
Wish I could state some of the other thinks we did with the vehicle in motion, but there might be younger one looking on.
See you on the highway.
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RE: Safety First
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by KA4KOE on April 8, 2004
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TC:
Is a hooter a doobie? Maybe you should revise your call suffix to THC?
:P
P
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RE: Safety First
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by N2KMF on April 8, 2004
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Just to confirm or deny, a 2 pound object weighs 14,000 grains (7,000 grains in a pound)
ft/lbs = ( mass * fps * fps ) / 450400
(14,000 * 8.8 * 8.8 ) / 450400 = 2.4 ft/lbs
Yep. Wouldn't want to get hit with it, but there is actually less energy there than most BB guns. But hey, it could put your eye out, kid....
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RE: Safety First
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by N2KMF on April 8, 2004
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Just to extend, 60 MPH is 88 fps.
( 14,000 * 88 * 88 ) /450400 = 240 ft/lbs.
That'll leave a mark.
Oh, and I just noticed something. Ten miles per hour isn't 8.8 fps, it is 14.67 fps. Six miles per hour would be 8.8 mph.
( 14,000 * 14.67 * 14.67 ) / 450400 = 6.7 ft/lbs
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RE: Safety First
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by K5PU on April 8, 2004
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"It all boils down to the drivers skill."
Uh huh...
I find it absolutely astonishing just how complacent the vast majority of drivers are concerning controlling a multi-ton mass of metal containing gallons of flammable and corrosive liquids at speeds exceeding 60 MPH within spitting distance of other similar vehicles.
And to do so while applying makup, eating Kentucky Fried, entering data into laptops, whatever!
I know, it's completely commonplace. But next time you jump in that car stop and OBJECTIVELY THINK about what you are really REALLY doing. You are NOT just 'going to the store'.
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RE: Safety First
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by KA4KOE on April 8, 2004
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Two cars traveling at the same direction at 60 mph and 55 mph respectively will collide with a net velocity of 5 mph. Its the difference in speed vectors that matter. Thats why head ons are so devasting, because the velocities add up positively.
Here's restatement of a post in my article "Inertia is your Enemy" for what its worth....
Here are the formulas of impact, quoted from the Fourth Edition of Engineering Mechanics, Jensen and Chenoweth, which state that-
Direct Central Impact where
e = (v'2 -v'1) / (v1 - v2) or
e = relative velocity after impact / relative velocity before impact
whereby
e = coefficient of restitution, or the ability of the bodies in question to retain their original shape.
Note that this formula is also typically used in conjuction with the formula expressing the Law of Conservation of Linear Momentum.
Completely elastic bodies e = 1
Completely inelastic bodies e = 0
Quoted from Page 414
Any questions? Please raise your hands.
KA4KOE
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Safety First
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by VK6AV on April 8, 2004
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My company recently banned the use of cell phones in company cars. I have occassionally used a mobile rig on voice but stop using it as soon as traffic gets heavy. Safety has to be the only priority.
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RE: Safety First
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by K0BG on April 8, 2004
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Gee, somehow that 10 mph vs. 8.8 snuck in there. And for those who caught it, you're correct it would be 6 mph or 8.8 fps. 10 mph obviously would be 14.66 fps. I must have read that 10 times and still missed it. Sorry about that.
Alan, KØBG
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RE: Safety First
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by KD5UJX on April 8, 2004
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Glad to see that my install follows what you have stated here. Good piece. It's mostly common sense. BTW: DRILL THAT HOLE! What a bunch of wimps! The only time I would not drill a hole is in rental. It's safer and your signal will be better.
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RE: Safety First
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by KG4PZZ on April 8, 2004
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I can speak for EMS, Fire, and LE in my area. LE uses a combination of radio and computer comms. Computer comms are strictly for when not in motion. 100% stopped. I'm sure not all deputies follow that, but that's what it's supposed to be, unless there is a partner in the car.
Fire and EMS have a driver and passenger, period. If they don't, you'll often hear radio communications degrade. I'm not saying it's safe, but saying "Medic 4-2 en route" is a lot easier than carrying on a conversation on HF. Most talking isn't even done while responding -- you talk when you're leaving the station, when you're arriving at the call, when you're leaving the call, and when you're back at the station. That's much less talking than I hear on 2m repeaters in the area.
Fire/EMS/LE is no safer than ham radio, but you have to admit that the "in motion" duty cycle is MUCH lower.
Sirens change tones by tapping the regular horn button or a foot switch that either the driver or front-seat passenger can operate without ever losing concentration. All those lights have one "master switch". It's amazing how simple, yet complex, everything in an emergency vehicle can be.
Fred
K4PZZ
KB0JQO
"It's kind of funny how ham radio is targed as a distraction while driving, yet nothing is mentioned of the countless law enforcement, ems, and fire services that make extensive use of mobile comms.
Take for example law enforcement, today's modern cruiser has a small computer for doing dl lookups, handling dispatches, etc as well as at times a multitude of radio gear. These people are involved in high speed pursuits, hazardous driving, and everything else, all while using these different devices. I'd be more inclined to remove my radios when am/fm radios are removed from all cars and all mobile comms equpment is removed from police/fire/EMS."
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RE: Safety First
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by AE6IP on April 8, 2004
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Physics is fun.
"Instantaneous acceleration" isn't possible, in theory, or in practice, but it has nothing to do with delta V. Recall from high school physics that acceleration is defined in change in velocity divided by change in time, or A = dV / dT.
To approach 'instantaneous', dT would have to approach zero. dV approaching zero leads to a = 0, that is *no* acceleration, rather than instantaneous acceleration.
Now recall from freshman calculus what happens to limit of (x/y) as y approaches 0, and also, recall from physics F=MA (ignoring relativistic effects.)
In other words, instantaneous acceleration would require infinite force, even at non-relativistic velocities.
Also, calculations of the force of impact can not be based solely on the initial velocity and mass of the moving object. To calculate force of impact requires knowning the (de)acceleration involved in the impact. Since F = MA and A = dV/dT, knowing dV isn't enough, one would also need to know dT. (This is why walking into a wall hurts less than running into one.)
People who live in cold climates may have the amusing opportunity to see perfectly elastic collisions, by the way. I once saw a north bound car collide with an east bound car at an icy interesection, in a way that caused no visible damage to either car, but also caused them to swap directions.
Wish I'd had a video camera for that one.
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Safety First
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by KI4DLK on April 8, 2004
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K0BG iv seen a sun visor microphone for Ham Radios in the HRO catalog thats made by Pryme.
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RE: Safety First
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by K1CJS on April 8, 2004
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K4PZZ wrote:
"Sirens change tones by tapping the regular horn button or a foot switch that either the driver or front-seat passenger can operate without ever losing concentration. All those lights have one "master switch". It's amazing how simple, yet complex, everything in an emergency vehicle can be."
How right you are--in some instances. There are still departments that have their cruisers set up differently. Some don't have those "alternate" controls--and that one master switch also controls alley lights, warning flashers meant to be used when the vehicle is stopped, etc., etc.
My point is that even though the one switch theory may be true, the officer/emt/fireman still doesn't use just the one. And as to the one or two channels may go, you've obviously not seen some of the newer radio setups that have twelve or more channels on one radio for convenience sake of the officer/emt/fireman using a certain vehicle.
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RE: Safety First
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by KA4KOE on April 8, 2004
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I've got a question:
What happens when an irresistible force meets an immovable object?
Hint: Its a trick question.
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RE: Safety First
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by KG4PZZ on April 8, 2004
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First, I want to say that this is probably going to sound rude, but I don't mean it that way -- I'm just stating things in a friendly debate :-).
I must say -- any department that still doesn't have alternate siren controls is either in the dark ages, or has no concern for safety. I have a box of discarded sirens sitting in my room gathering dust (E-bay pulls the auctions, so they're collecting dust now). Vintage is about 1980, maybe a little later. They include a 6-wire wiring harness -- two for power, two for the speaker, and two for a tone switch. I had always thought of it as 'standard equipment', in a way a seatbelt is in any car made after 1967 or so. However, a department's choice as to whether or not to use it is also like a passenger's choice as to whether or not to wear their seatbelt, so I guess that is where the ultimate choice lies.
I found my way into ham radio via commercial radio, which is what I want to make a career out of. I've seen some insanely complex systems with shared channels, linked VHF/UHF/microwave, etc, and know how complicated it can be. In the end though, all an EMT/Firefighter/deputy should need is "channel 1, 2, etc...". Adding a scan button is, at times, a bit of a dangerous concept.
As for the "one or two channels" -- our department has 64 'frequencies', on an 800MHz EDACS trunked system. Fire/EMS have 16 , Sheriff has an additional 16, 16 conventional 'talk-around', and 16 for general services. Even still, a public service radio should be set up for the easiest possible use. Channel 1, 2, 3, 4 etc... It's as simple as turning a knob a certain number of clicks, which you can do without taking your eyes off the road. Switching from fire to sheriff or conventional is as simple as a toggle switch and a quick glance. Motorola, Ericcson, Kenwood, and now Vertex-Standard all have the right idea. Two knobs -- volume and channel. We call it "fireman-proof".
I feel there's no excuse for the distraction of a driver of an ambulance or firetruck by the radio. A police officer, well, that may be a different story, he's got a hard enough job without having to worry about a radio, also, but it comes with the job.
Fred
K4PZZ
K1CJS
"How right you are--in some instances. There are still departments that have their cruisers set up differently. Some don't have those "alternate" controls--and that one master switch also controls alley lights, warning flashers meant to be used when the vehicle is stopped, etc., etc.
My point is that even though the one switch theory may be true, the officer/emt/fireman still doesn't use just the one. And as to the one or two channels may go, you've obviously not seen some of the newer radio setups that have twelve or more channels on one radio for convenience sake of the officer/emt/fireman using a certain vehicle."
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RE: Safety First
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by K1CJS on April 9, 2004
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Fred:
Of course! I always try to keep things that way, but sometimes I slip and start running off. ;-)
I have been involved in installations for equipment in emergency/public service vehicles, and can say that what you have said is becoming the norm, but it isn't quite yet. Some of the smaller communities have had their equipment switched from one car to another, and some of that equipment is older than the people using it!
There shouldn't be a need for more than two or three channels in a vehicle, but the changeover to higher frequencies in some areas has some communities running two or three radios in some vehicles because of the budget constraints. Granted, those vehicles are for supervisor use, but imagine three or four different mikes for various equipment, let alone trying to operate that equipment!
The commo van for the EMA in our community now has five different radio setups to cover the frequencies that maybe needed--one for HF, one for VHF and two for UHF, and the VHF ham radio. A sixth radio, ham HF, is being contemplated. Add to that the lighting and PA mode controls (the siren has been permanently disabled) and you have a hard time just running the setup. Thank God the drivers position has only a remote head for the EMA main radio and the lighting system controls.
Not every community is in the twenty first century (as far as communications setups) yet. We can only pray that the various communities try to make the patrol and first responce vehicles as safe to operate as possible.
And as you said Fred, this is offered in friendly debate, not in an argumentative way. Cheers!
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RE: Safety First
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by KC0LBZ on April 11, 2004
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"One advantage the police usually has over the ham is he doesn't continually, or even frequently, change channels. He simply talks; his only requirement is to find the mike and press the PTT button. When he does change channels he does so by choosing "Channel 1" or "Channel 5" or whatever, usually from a maximum of 6 channels. He can count switch positions."
Which is how I operate mobile (2M). I don't have to look at the radio to pick up the mike, and I can feel the knob clicks as I change repeaters. At worst, a quick glance tells me which one I'm on.
SSB is more problematical because it requires a certain level of attention to locate and fine tune an SSB signal. So I don't do that while driving.
Channelized FM is much easier to deal with, and therefore requires less attention and is safer for mobile. Much less flexible, but I can do without the extra excitement on the road; I get enough from all the crazies. (I'm an excellent driver, but most everyone else seems to have skipped Drivers Ed. <wink>)
As for bolting the radios in solidly: Absolutely!
I've had my 2M and 10M rigs in a scratchbuilt console between the seats of my minivan for a while--but the console was *not* solidly bolted in. One emergency stop (deer + fender = $1200!) conviced me that was inadequate, and I'm adding a tie-down frame. The console ended up upended against the lower dash--and I never saw it move (my attention was on the deer that nearly became a hood ornament). Fortunately, the radios weren't damaged. (And FWIW, the deer did walk away, if slowly.)
- Sam KC0LBZ
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