#234387 - 10/25/11 04:04 AM
Re: Most Reliable Communication Means, Emergency
[Re: firefly99]
|
Pooh-Bah
Registered: 04/01/10
Posts: 1629
Loc: Northern California
|
When your house loss power, land line phone and mobile handset not operational. During every power outage I've experienced, my land line phones and cable Internet phones have still worked. The cable Internet phones worked as long as I had a battery backup for the cable modem and VOIP device. I suspect if the power outage lasted for days, then the land line and cable would probably go out of service.
_________________________
If you're reading this, it's too late.
|
Top
|
|
|
|
#234397 - 10/25/11 05:37 AM
Re: Most Reliable Communication Means, Emergency
[Re: firefly99]
|
Veteran
Registered: 09/01/05
Posts: 1474
|
And don't forget to have a means of charging radio batteries, and/or a large stash of new alkalines.
I think CB's are a great idea. I use a Uniden/Little Wil combo for road trips.
|
Top
|
|
|
|
#234400 - 10/25/11 11:05 AM
Re: Most Reliable Communication Means, Emergency
[Re: ireckon]
|
Carpal Tunnel
Registered: 12/26/02
Posts: 2997
|
Test your CB/FMRS radios though. I found that in my neighborhood none of them will transmit past the next street over. May be due to all the interference which might not be there in a power outage from wifi or it may be the 2 to 2.5 story houses close toegther just blocking the signal I don't know. I ordered a bigger antanna for the handheld.
|
Top
|
|
|
|
#234509 - 10/26/11 03:49 PM
Re: Most Reliable Communication Means, Emergency
[Re: Eugene]
|
Journeyman
Registered: 05/28/06
Posts: 58
|
For CB radio, due to the way the radio wave propagate. There is a blind zone. Hence the CB may link up with another CB unit 50 miles away. But cannot link up those CB within a 2 miles radius.
Most FMRS radio are low wattage unit, operating on UHF frequency. The low wattage reduce the operating range of the radio unit. Being UHF device, requires line of sight to connect. So if there is any trees or tall building, it will not be able to link up another unit further down the street.
So look for a walkie talkie unit that has at least 5 watt of power and operates on VHF frequency. Such an unit would be more effective within 2 ~5 miles range.
|
Top
|
|
|
|
#234513 - 10/26/11 04:18 PM
Re: Most Reliable Communication Means, Emergency
[Re: ireckon]
|
Sheriff
Carpal Tunnel
Registered: 12/03/09
Posts: 3842
Loc: USA
|
The difference between VHF and UHF for range is pretty small, maybe 10% in the open using the same height, antenna gain, and wattage. Sometimes UHF has better penetration of buildings and trees.
All FRS and GMRS frequencies in the US are UHF. The FCC limits FRS output to 500 milliwatts, and radios must have fixed antennas to be type accepted. It's rare to get much more than a mile out of them, and less is common. GMRS can be significantly better due to higher wattage (1-5 commonly in handhelds, with a 50 W limit) and better antennas for many units.
While CB uses a much lower frequency, propagation can work locally if two stations have line of sight. Without line of sight, CB can propagate over the horizon by bouncing off the ionosphere, often producing a blind zone.
|
Top
|
|
|
|
#234517 - 10/26/11 04:30 PM
Re: Most Reliable Communication Means, Emergency
[Re: firefly99]
|
Carpal Tunnel
Registered: 12/26/02
Posts: 2997
|
For CB radio, due to the way the radio wave propagate. There is a blind zone. Hence the CB may link up with another CB unit 50 miles away. But cannot link up those CB within a 2 miles radius.
Most FMRS radio are low wattage unit, operating on UHF frequency. The low wattage reduce the operating range of the radio unit. Being UHF device, requires line of sight to connect. So if there is any trees or tall building, it will not be able to link up another unit further down the street.
So look for a walkie talkie unit that has at least 5 watt of power and operates on VHF frequency. Such an unit would be more effective within 2 ~5 miles range. odd thing though is I've been able to use the handheld before when down in the city, I hadn't tested it since we moved. I'm hoping the better antanna will get me out, investig in different radios and licensing for them is a little out of budget for the moment.
|
Top
|
|
|
|
#234552 - 10/26/11 11:44 PM
Re: Most Reliable Communication Means, Emergency
[Re: firefly99]
|
Veteran
Registered: 08/19/03
Posts: 1371
Loc: Queens, New York City
|
For CB radio, due to the way the radio wave propagate. There is a blind zone. Hence the CB may link up with another CB unit 50 miles away. But cannot link up those CB within a 2 miles radius.
Most FMRS radio are low wattage unit, operating on UHF frequency. The low wattage reduce the operating range of the radio unit. Being UHF device, requires line of sight to connect. So if there is any trees or tall building, it will not be able to link up another unit further down the street.
So look for a walkie talkie unit that has at least 5 watt of power and operates on VHF frequency. Such an unit would be more effective within 2 ~5 miles range. Actually, it depends on your antennas - You can optimize your antenna system (and antennas are a system) for longer range communications (skip) or for short range comms The issue you are talking about is often refered to as "the dreaded doughnut" - 2 Miles is usually NOT an issue, as you are within what is called 'ground wave' communications, then you have NOTHING just beyond that, and then you have signal again - so, in a doughnut pattern you have no comms The way around this is with what is called a "Near Vertical Incidence System" - basically, you mount your antenna horizontally (or use a horizontal dipole) LOW to the ground - on a 40m or 80m it's typically in the range of 4-6 ft off the ground, and it tends to raise the 'take off angle' of you signal to near vertical, where your signal reflects off the ionosphere, and bounces back down - the exact OPPOSITE of what you want for working distant contacts, but perfect for close (in Ham terms, this becomes a 0-200 or so mile antenna system) BTW, it is a BIG reason you actually WANT that nice 1/2 wave whip tied down like you see on Military vehicles - it's NOT only for clearance under things, but it actually makes the radio work BETTER in the doughnut - The military has thought about this
|
Top
|
|
|
|
#234589 - 10/27/11 04:06 PM
Re: Most Reliable Communication Means, Emergency
[Re: KG2V]
|
Journeyman
Registered: 05/28/06
Posts: 58
|
The issue you are talking about is often refered to as "the dreaded doughnut" - 2 Miles is usually NOT an issue, as you are within what is called 'ground wave' communications, then you have NOTHING just beyond that, and then you have signal again - so, in a doughnut pattern you have no comms "the dreaded doughnut" is a serious handicap in an emergency if you trying to contact another party that move beyond 2 miles into the black out zone. Actually, it depends on your antennas - You can optimize your antenna system (and antennas are a system) for longer range communications (skip) or for short range comms
The way around this is with what is called a "Near Vertical Incidence System" - basically, you mount your antenna horizontally (or use a horizontal dipole) LOW to the ground - on a 40m or 80m it's typically in the range of 4-6 ft off the ground, and it tends to raise the 'take off angle' of you signal to near vertical, where your signal reflects off the ionosphere, and bounces back down - the exact OPPOSITE of what you want for working distant contacts, but perfect for close (in Ham terms, this becomes a 0-200 or so mile antenna system)
BTW, it is a BIG reason you actually WANT that nice 1/2 wave whip tied down like you see on Military vehicles - it's NOT only for clearance under things, but it actually makes the radio work BETTER in the doughnut - The military has thought about this Agreed, there are various things you can do to get the communication link working, if you are a ham or professional radio operator. In an emergency, walkie talkie enable short range communication between neighbours. For most ordinary citizens, the walkie talkie is just another handset.
|
Top
|
|
|
|
#234593 - 10/27/11 05:09 PM
Re: Most Reliable Communication Means, Emergency
[Re: ireckon]
|
Pooh-Bah
Registered: 07/11/10
Posts: 1680
Loc: New Port Richey, Fla
|
KG2V... thanks for the explaination of the near vertical incidence... I get 1:1 SWR, and good ground plane off the roof of my Explorer with the 1/4 wave magnetic mount CB antenna.. it is however tied down with a tarp bungee to get it in the garage, which probably accounts for the pretty consistent 2 to 3 mile mobile comms I get with interstate truckers
for anyone invesitgating a home CB for your local comms...a telescoping mast, 1/2 wave Shakespear Big Stick antenna..usually doesn't upset the neighbors... and be sure to include a good ground rod,... a 12v regulated power supply and a car transceiver will see if it works for you...
|
Top
|
|
|
|
#234619 - 10/27/11 11:49 PM
Re: Most Reliable Communication Means, Emergency
[Re: ireckon]
|
Addict
Registered: 06/04/03
Posts: 450
|
If I may just amplify (sorry) on the donut issue (one of my fav hobbies BTW, eating them that is....no I'm not a Constable On Patrol), actually a great deal of the efficiency of a vertical "ground-plane" type of antenna is the "radiation resistance" factor. By efficiency, I mean the relative amount of transmitted signal radiated by the antenna, in other words, it's effective radio signal output.
Look at it this way. A vertical antenna a quarter wavelength long at the operating frequency, when one ground wire (called a radial) is attached to the shield (ground side) of the coaxial transmission line and laid on the round going away from the antenna, will provide approximately a 50 ohm load (actually more like 38 ohms or so), which is what most solid-state radio transmitters these days like to operate into. Now this will certainly radiate a signal. However, the radiation resistance of this arrangement is relatively high, certainly higher than if a whole bunch of radials (say 10 or so) are used, in which case the effective radiated signal from the 10 radial antenna will be substantially higher than the 1 radial antenna system. Not only that, but the one radial antenna will tend to be somewhat directional in the direction that the one radial is pointing. If 10 radials are laid out spoke-wise around the antenna, this will help make the antenna more omnidirectional. So, bottom line, if you're going to use a vertical antenna, try to use as many radials as comfortably possible arranged more or less equally around the antenna. This provides a similar ground "plane" to that which might be achieved by placing a short roof-mount antenna smack in the middle of the top of a big van.
Sorry, I was going to say that radiation resistance is pretty much directly dependent on the quality of the ground plane, being higher in the case of just one radial, and much closer to ideal with 10 or more wire radials or a flat metal rooftop all around the vertical antenna. So, in a nutshell, adding more radials within reason tends to bring down the radiation resistance and increases the effective radiated signal output from the vertical antenna.
Sorry if this has already been mentioned.
|
Top
|
|
|
|
|
|
|
|
|
|
1
|
2
|
3
|
4
|
5
|
6
|
7
|
8
|
9
|
10
|
11
|
12
|
13
|
14
|
15
|
16
|
17
|
18
|
19
|
20
|
21
|
22
|
23
|
24
|
25
|
26
|
27
|
28
|
29
|
30
|
|
0 registered (),
750
Guests and
22
Spiders online. |
Key:
Admin,
Global Mod,
Mod
|
|
|