In building coverage
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It has to do with WAVE LENGTH the high the frequency the shorter and tighter the wave length. Not to confuse you but that is why it takes several feet of concrete to block radio active material. 150mhz wave lenght = 6 meters 460mhz = .65 meters 800mhz = .375 meters 1900mhz = .157 meters.
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ScannerSK
Member
Just a few reasons that came to mind:
1.) Higher frequencies travel greater distances with less power (however are more dependent upon line of sight the higher the frequency).
2.) Cell phone towers are typically taller in elevation than handheld VHF receivers thereby increasing reception.
3.) The receivers used in towers are of the highest quality.
The same could probably be said of ham radio repeaters. I am able to reach the Colorado Springs ham repeater on 146.970 approximately 100 miles away with just a few watts here in Northern Colorado. The main reason for this is likely due to the repeaters high altitude on Pike's Peak.
Shawn
1.) Higher frequencies travel greater distances with less power (however are more dependent upon line of sight the higher the frequency).
2.) Cell phone towers are typically taller in elevation than handheld VHF receivers thereby increasing reception.
3.) The receivers used in towers are of the highest quality.
The same could probably be said of ham radio repeaters. I am able to reach the Colorado Springs ham repeater on 146.970 approximately 100 miles away with just a few watts here in Northern Colorado. The main reason for this is likely due to the repeaters high altitude on Pike's Peak.
Shawn
DickH
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Really? The last time I checked it was around 2 meters.
Yes typo 6 feet 2 meters good catch
mmckenna
I ♥ Ø
It's also not uncommon for a cell site to have antennas with close to 20dB of gain. Newer designs put the radio right at the antenna, so feed line losses are minimized. Even when the radios are at the base of the tower, they are often using 1 5/8" heliax.
Pretty easy to hear a 1/4 watt at 2 miles with a setup like that. Although some building construction is still problematic. Heavy reinforced concrete buildings with lots of HVAC ducts not to mention the "low-E" glass makes some of the newer buildings pretty RF resistant.
Pretty easy to hear a 1/4 watt at 2 miles with a setup like that. Although some building construction is still problematic. Heavy reinforced concrete buildings with lots of HVAC ducts not to mention the "low-E" glass makes some of the newer buildings pretty RF resistant.
Not enough info to solve the problem. How thick is the marble used in the building? What other materials are used in the space between the indoors / outdoors (walls)? What floor of the building are you on? Are you in the center of the building, or near a window? What is the thickness of the windows, and are they LEED-type with metallic thermal insulation designed to keep out solar heating (and block radio signals)? What antenna is used on the handheld? On the receiver at the tower? The point is there are so many variables that the answer is going to be such a wide range of results that you will not be happy to hear. The answer will be something like, "It depends (on all of the variables cited... and more) and ranges from a low distance of perhaps 1/4 mile to a high of 50 miles or more".
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A lot of factors need to be seen how tall is the building what is between the two sites how tall is the receiving site and still it would work better at 450mhz to 470mhz than 150mhz.
mmckenna
I ♥ Ø
Answer = Maybe.
Way too many variables involved, too many to list here.
One thing to look at is that VHF is, for the most part, line of site. Yes there are ways to bend it over the horizon, but let's stick with line of site for the moment.
Receiver sensitivity
Antenna gain
local noise floor
etc. etc. etc....
A 5 watt hand held would likely be able to reach to the "radio horizon" if things were perfect.
Building construction is a huge factor here, though.
They may have come to mind but they are incorrect. The higher you go in frequency the more free space loss you will incur, which is opposite of your statement. The receivers used in cell phone towers are not of any special quality that would increase range.
One of the things that allows cell phones to be used deep inside buildings has to do with wavelength and the shorter wavelengths at 800MHz/1900MHz will fit through windows and bounce off concrete walls to penetrate dense buildings better than VHF. You also get more gain per square foot of antenna at higher frequencies and cell tower antennas can have quite a bit of gain compared to a typical 2m antenna.
prcguy
One of the things that allows cell phones to be used deep inside buildings has to do with wavelength and the shorter wavelengths at 800MHz/1900MHz will fit through windows and bounce off concrete walls to penetrate dense buildings better than VHF. You also get more gain per square foot of antenna at higher frequencies and cell tower antennas can have quite a bit of gain compared to a typical 2m antenna.
prcguy
W8RMH
Feed Provider Since 2012
I'm no engineer but I would think that the "connection" between the cell phone and the tower may have something to do with it too.
nd5y
Member
It does. The cell phone's transmit power is adjusted almost continuously depending on conditions. They don't all put out 1/4 watt all the time. The maximum power depends on the type of cellular system (GSM, CDMA, etc.) and the band used.
In the basement of a downtown NYC building, we couldn't pick up a thing, including the 50,000 Watt "clear channel" broadcast radio stations, except with an antenna poked up to a street-level window.
Good masonry-over-steel construction, or simple reflective window glass, is enough to block everything including those cell phone signals, so the OP is under a misapprehension from the start. Any building that blocks a VHF signal probably also can block the microwave signals used by cell phones. A lot of offices actually employ cell phones boosters (aka picocells or femtocells) to give their staff cell phone reception in buildings like that. You may have seen the Verizon commercial where their guys are installing one of those above the drop ceiling tiles in an office--this is nothing new.
Different frequencies, different gain antennas, different radio penetration/shielding...all part of basic radio theory and once you become aware of which facts are relevant, or not, fairly easy to predict and understand.
Why my cell phone works in so many elevators with stainless steel wall paneling, does baffle me. (It shouldn't work inside a Faraday cage at all.) Why it gets no signal in the subway tunnels, is no surprise.
Good masonry-over-steel construction, or simple reflective window glass, is enough to block everything including those cell phone signals, so the OP is under a misapprehension from the start. Any building that blocks a VHF signal probably also can block the microwave signals used by cell phones. A lot of offices actually employ cell phones boosters (aka picocells or femtocells) to give their staff cell phone reception in buildings like that. You may have seen the Verizon commercial where their guys are installing one of those above the drop ceiling tiles in an office--this is nothing new.
Different frequencies, different gain antennas, different radio penetration/shielding...all part of basic radio theory and once you become aware of which facts are relevant, or not, fairly easy to predict and understand.
Why my cell phone works in so many elevators with stainless steel wall paneling, does baffle me. (It shouldn't work inside a Faraday cage at all.) Why it gets no signal in the subway tunnels, is no surprise.
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