Good enough for the government is good enough for me! @MileHighCitizen
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I can work out the advanced physics of radio waves but can't figure out how to use a forum.
Bottom line there's no easy answer on antenna selection, if you want max performance never buy an antenna just on looks, pretty antennas are usually poor performers, and if you try to hide an good performing ugly antenna, it might perform worst than the pretty antenna,
Below is the long winded version, based on over 42 years working for a major telecommunications company, where before cell phone obsoleted the 2-way radios in the field vehicles, one of my other assigned duties was designing, maintaining and installing the repeaters used for the fleet vehicles and sometimes the radios in the fleet vehicles. During my time with the company have installed and maintained just about every type of transmission lines, antennas and transmitter systems known to mankind, along with some design work of these systems
As to antennas and their range it's all about quality design, placement and good installation. Yes the science of antenna design is important, but in real world practice the actual design and proper installation is more art form than actual science.
The standard reference antenna is referred to an Isotropic antenna and when you look at antenna specs when they spec the antenna gain that spec is referenced against the Isotropic antenna. The Isotropic antenna transmission field would be seen as a perfect sphere. For a standard 1/4 wave whip antenna placed in the open air without a ground plane and held up in space the field would appear to be a sphere with holes at either end of the antenna rod, just think of the pictures you have seen of the earth's magnetic field, much like an perfect apple.
What vehicle antenna designers try to accomplish in their design is to focus the RF energy from the transmitter into a circular horizontal plane for transmission instead of the sphere, much like what a the Fresnel lenses of a tower beacon does with it's light source. Now if you were to add a reflector to the light source and rotate it you would have a light house. Light waves and radio wave behave in the same manner with their differences based strictly on their respected wavelengths.
As to the ground plane, think of it as taking the energy from bottom half of the transmission sphere of the Isotropic reference antenna and then reflect it back up into the top half of the sphere, we now in theory have twice the energy in the upper half of the sphere. In practice the ground plane should be at least a 1/4 wavelength of the transmission freq. With that said some antenna designs do not need a ground plane to meet their rated spec.
Now if you mount the antenna close to the roof A-pillar, on a bumper or even to the side of a fender it will or can cause the antenna transmission field to become directional.
For transmission range height is your friend.
Ideally for our bronco's they would all have metal roofs and the antenna would be mounted on the roof exactly in the center of the roof. Can't be done, no metal roof and all of the roofs are removable.
Don't automatically rule out antennas with coils, if they are properly designed they can help antenna performance in the proper situation. You will even see antenna's much longer that a 1/4 wavelength, these typically have a insulated tube over the main rod or might have a coil twisted approx midway in the rod and their purpose is to focus the transmission energy into a horizontal plane instead of the sphere shape field.
For those that don't know, why is the 1/4 wavelength used as the standard antenna length, think of a sine wave, at the 1/4 wavelength time period it's at max amplitude, therefore max transmission power, now if the antenna is shorter or longer the antenna's transmission output power is lower. That unused power doesn't simply disappear, it get reflected back down the antenna feed-line into the transmitter output and that reflected power can damage the transmitter output. Now the antenna doesn't actually have to be actually 1/4 wavelength in length, thru design and art form the designer can make the antenna appear to be 1/4 wavelength to the transmitter.
To calculate wavelength, wavelength = Vp / freq
Vp = velocity of propagation which is a measure of how fast a signal travels over time
Vp in space = 300,000,00 meters per second
Vp in a vacuum = 299,792,458 meters per second
Vp in free air = 299,702,547
The two GMRS band are approx. 462 and 467 Mhz
1/4 wave @ 462 = 6.38 in
1/4 wave @ 467 = 6.31 in
Link to a wavelength calculator https://www.omnicalculator.com/physics/wavelength
When looking at antenna gain spec's, they will be usually referenced dbi, meaning it's referenced to the Isotropic antenna mentioned earlier. The db scale is logarithmic, so if an antenna has a 3 dbi gain, this means it has double the ERP (effective radiated power), therefore if your transmitter puts out 50 watts, an antenna with a 3 db gain will have a ERP of 100 watts as compared to the isotropic antenna's 50 watt ERP, likewise if the antenna has an 6 dbi gain you will have a 200 watt ERP.
the dbi spec of the antenna is meaningless unless you look at the antenna manufacturer radiated power pattern graph for both the vertical and horizontal pattern. They might be claiming a 6 dbi gain, but when you look at the radiated power pattern graphs it might all be focused vertically up into space and the horizontal pattern might show a minus 6 dbi gain. Remember all that an antenna's dbi gain means they focused the antennas power gain in some direction, while doing that they removed power from another direction, the sum of the total power output in all directions doesn't change
-9 dbi gain 1/8 the ERP, radio 50 watts out = 6.25 watts ERP
-6 dbi gain 1/4 the ERP, radio 50 watts out = 12.5 watts ERP
-3 dbi, half the ERP, radio 50 watts out = 25 watts ERP
0 dbi, no gain, radio 50 watts out = 50 watts ERP
+3 dbi twice the ERP, radio 50 watts out = 100 watts ERP
+6 dbi four times the ERP, radio 50 watts out = 200 watts ERP
+9 dbi eight times the ERP, radio 50 watts out = 400 watts ERP
You also have to account for the loss for the coax feed-line between the radio and the antenna, the standard feed line used is RG-58 vehicle antennas, for an example we'll use 25 feet, at 462 Mhz RG-58 loses approx. 3 db of power, so with the radio output at 50 watts, feed-line loss of 3 db we'll have 25 watts at the antenna, then with a 3 dbi antenna we would have a 50 watts ERP. Golden rule here is keep the feed line as short as possible.
Feed line calculator https://www.timesmicrowave.com/Calculator?Product=RG-58&RunLength=25&Frequency=462
Now you have your radio and antenna installed, the antenna needs to be tuned to insure a low VSWR. Basically this is to insure you have max power radiated at the antenna and very low reflected power back towards the transmitter. Just do a search on VSWR (Voltage Standing Wave ratio
Below is the long winded version, based on over 42 years working for a major telecommunications company, where before cell phone obsoleted the 2-way radios in the field vehicles, one of my other assigned duties was designing, maintaining and installing the repeaters used for the fleet vehicles and sometimes the radios in the fleet vehicles. During my time with the company have installed and maintained just about every type of transmission lines, antennas and transmitter systems known to mankind, along with some design work of these systems
As to antennas and their range it's all about quality design, placement and good installation. Yes the science of antenna design is important, but in real world practice the actual design and proper installation is more art form than actual science.
The standard reference antenna is referred to an Isotropic antenna and when you look at antenna specs when they spec the antenna gain that spec is referenced against the Isotropic antenna. The Isotropic antenna transmission field would be seen as a perfect sphere. For a standard 1/4 wave whip antenna placed in the open air without a ground plane and held up in space the field would appear to be a sphere with holes at either end of the antenna rod, just think of the pictures you have seen of the earth's magnetic field, much like an perfect apple.
What vehicle antenna designers try to accomplish in their design is to focus the RF energy from the transmitter into a circular horizontal plane for transmission instead of the sphere, much like what a the Fresnel lenses of a tower beacon does with it's light source. Now if you were to add a reflector to the light source and rotate it you would have a light house. Light waves and radio wave behave in the same manner with their differences based strictly on their respected wavelengths.
As to the ground plane, think of it as taking the energy from bottom half of the transmission sphere of the Isotropic reference antenna and then reflect it back up into the top half of the sphere, we now in theory have twice the energy in the upper half of the sphere. In practice the ground plane should be at least a 1/4 wavelength of the transmission freq. With that said some antenna designs do not need a ground plane to meet their rated spec.
Now if you mount the antenna close to the roof A-pillar, on a bumper or even to the side of a fender it will or can cause the antenna transmission field to become directional.
For transmission range height is your friend.
Ideally for our bronco's they would all have metal roofs and the antenna would be mounted on the roof exactly in the center of the roof. Can't be done, no metal roof and all of the roofs are removable.
Don't automatically rule out antennas with coils, if they are properly designed they can help antenna performance in the proper situation. You will even see antenna's much longer that a 1/4 wavelength, these typically have a insulated tube over the main rod or might have a coil twisted approx midway in the rod and their purpose is to focus the transmission energy into a horizontal plane instead of the sphere shape field.
For those that don't know, why is the 1/4 wavelength used as the standard antenna length, think of a sine wave, at the 1/4 wavelength time period it's at max amplitude, therefore max transmission power, now if the antenna is shorter or longer the antenna's transmission output power is lower. That unused power doesn't simply disappear, it get reflected back down the antenna feed-line into the transmitter output and that reflected power can damage the transmitter output. Now the antenna doesn't actually have to be actually 1/4 wavelength in length, thru design and art form the designer can make the antenna appear to be 1/4 wavelength to the transmitter.
To calculate wavelength, wavelength = Vp / freq
Vp = velocity of propagation which is a measure of how fast a signal travels over time
Vp in space = 300,000,00 meters per second
Vp in a vacuum = 299,792,458 meters per second
Vp in free air = 299,702,547
The two GMRS band are approx. 462 and 467 Mhz
1/4 wave @ 462 = 6.38 in
1/4 wave @ 467 = 6.31 in
Link to a wavelength calculator https://www.omnicalculator.com/physics/wavelength
When looking at antenna gain spec's, they will be usually referenced dbi, meaning it's referenced to the Isotropic antenna mentioned earlier. The db scale is logarithmic, so if an antenna has a 3 dbi gain, this means it has double the ERP (effective radiated power), therefore if your transmitter puts out 50 watts, an antenna with a 3 db gain will have a ERP of 100 watts as compared to the isotropic antenna's 50 watt ERP, likewise if the antenna has an 6 dbi gain you will have a 200 watt ERP.
the dbi spec of the antenna is meaningless unless you look at the antenna manufacturer radiated power pattern graph for both the vertical and horizontal pattern. They might be claiming a 6 dbi gain, but when you look at the radiated power pattern graphs it might all be focused vertically up into space and the horizontal pattern might show a minus 6 dbi gain. Remember all that an antenna's dbi gain means they focused the antennas power gain in some direction, while doing that they removed power from another direction, the sum of the total power output in all directions doesn't change
-9 dbi gain 1/8 the ERP, radio 50 watts out = 6.25 watts ERP
-6 dbi gain 1/4 the ERP, radio 50 watts out = 12.5 watts ERP
-3 dbi, half the ERP, radio 50 watts out = 25 watts ERP
0 dbi, no gain, radio 50 watts out = 50 watts ERP
+3 dbi twice the ERP, radio 50 watts out = 100 watts ERP
+6 dbi four times the ERP, radio 50 watts out = 200 watts ERP
+9 dbi eight times the ERP, radio 50 watts out = 400 watts ERP
You also have to account for the loss for the coax feed-line between the radio and the antenna, the standard feed line used is RG-58 vehicle antennas, for an example we'll use 25 feet, at 462 Mhz RG-58 loses approx. 3 db of power, so with the radio output at 50 watts, feed-line loss of 3 db we'll have 25 watts at the antenna, then with a 3 dbi antenna we would have a 50 watts ERP. Golden rule here is keep the feed line as short as possible.
Feed line calculator https://www.timesmicrowave.com/Calculator?Product=RG-58&RunLength=25&Frequency=462
Now you have your radio and antenna installed, the antenna needs to be tuned to insure a low VSWR. Basically this is to insure you have max power radiated at the antenna and very low reflected power back towards the transmitter. Just do a search on VSWR (Voltage Standing Wave ratio
- First Name
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- Black Diamond
Anyone figure out where in the rear of the Bronco to mount the antenna? I’m looking for ideas…preferably by or with the tire carrier…?
Are there actually AM radio stations still in existance?
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- First Name
- Eric
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- #21
The only time I tune into AM radio is if I'm stuck in the car and hockey playoffs are on... And only if it's my team! Lol
Not very often....
- First Name
- Eric
- Joined
- Jul 9, 2020
- Threads
- 195
- Messages
- 4,365
- Reaction score
- 6,873
- Location
- Ontario Canada
- Vehicle(s)
- 2 door Squatched
- Your Bronco Model
- Badlands
- Banned
- #22
I've heard people say, that if they drive into branches and wack their antenna, it'll knock it outta tune....?
What's up with this?
What's up with this?
Watch some of NotARubicon YouTube reviews, the guy is a riot and a GMRS god.I wanted to buy this but didn't pull trigger and now looks sold out. Do you think this stubby is likely good when not separated by big mountains?
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