Like a police officer’s handheld radio is able to transmit to another unit let’s say 10 miles away, and he’s able to do that with ease. How is this possible? How come handheld radios that we have access to can’t do that? I know this probably sounds dumb to most of ya’ll but
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Handheld radios you have access to can absolutely do that. My little $50 baofeng radio can easily reach a repeater over 10 miles away.
Their radios are connected to repeaters.
A repeater is a radio that receives a signal and transmits it again with a lot more power and usually is high in the air (on top of buildings or radio towers) so it has better line of sight to a large area. The small radio only has to be heard by the repeater everything in a large area will hear the repeater.
More important then the power level is the height of the repeaters antenna. The higher the antenna is the more area can receive it.
Cell phone towers are repeaters and operate in a similar manner. They are more complicated and can do more but the basic concept is similar.
Are you taking about compared to FRS walk-in talkies? First FRS is limited to 2 watts and their built in antenna which are often not good. Police will radios will have a good antenna and probably 5-10 watts of power. Also in many cases they will actually be being picked up by a repeater which is at a high altitude to improve the chances of line of sight. The repeater receives the signal and then retransmits it at 100-200 watts from its high location. So the other officer 10 miles away with a hand held didn’t need to directly receive the signal they get the booster repeater signal.
First responders typically have whole radio networks built out that cover the whole territory they’re assigned to. It’s much like wifi, with a series of antennas and amplifiers and other equipment to ensure there’s adequate coverage to allow relatively low powered handsets to operate.
Most of the handheld radios you can buy without a license is limited to a power output of 10mW. This is almost nothing which means the signal can not go far until it is too low power to be picked up above the background noise. The size of the device is limited by the frequency and not power at these low power ranges. A cell phone however is a licensed radio managed by the network operator and can therefore transmit up to 2W on similar bands. So a cell phone can contact a cell tower miles away without much issues and can even go through light coverage such as a forest or wooden houses. This is mostly because it have 200 times more power then the radio which essentially gives it somewhere around 5 to 14 times the range.
Most handheld police radios are 5W with vehicle mounted models being 10-20W. So that is an order of magnitude more again. It is first at these powers that the physical size start becoming a problem as the batteries struggle delivering enough power. This is why larger models that can be connected to a permanent power supply can transmit at higher powers then handheld devices. In addition many police radios have relay stations, similar to cell towers. So two officers who want to talk to each other over the radio do not have to be in range of each other as long as they are in range of one of the relay towers.
The disadvantage of these high power radios is that you can not have many people using the same frequency at once. If there are different police activities happening even several tens of miles from each other they have to switch channels to not disrupt each other. This limits how much activity you can have in a certain area. For this reason, and to conserve battery life it is a common practice to turn down the power of these radios when not needed. So you can turn down the power to 1W or even 500mW when conducting local operations within a mile and then turn it up if you are further away from the people you are working with. Similarly the police will switch away from the channels that have repeaters when not needed.
The FCC reserves several frequency bands for various government agencies.
In radio, there is generally a tradeoff between higher and lower frequencies.
Higher frequencies are good at going through stuff (walls, roofs, trees, etc). Lower frequencies tend to bounce off of things.
It gets particularly interesting because even high frequencies (at least the ones we use in radio) aren’t good at going through really huge things (like the earth). Low frequencies are so good at bouncing off stuff that they can bounce off the ionsphere.
Practically that means that high frequencies tend to get you a very clear signal with limited range at high power usage. Lower frequencies get you a noisy signal but over huge ranges at low power usage(people have bounced radio calls to the other side of the earth).
Police typically operate at short ranges so they use the higher frequencies. The power usage only matters when you’re transmitting so they’ll send those to “repeaters”. Those are basically radios that listen on one frequency and forward the signal to an other frequency that they pump a lot of power into. You can repeat that process to increase the range or even have segments that go over wires. That’s how you can listen in on police scanners in other cities over the interent.
Lots of talk about repeaters and power, but it’s also very likely (in the UK definitely so) that the radios they use actually use the mobile (cell) phone network so when they use the radio it’s like making an instant phone call.
Edit: ignore me, I’m wrong
The handheld radioshack style radios you are used to operate on rules defined by the FRS (Family Radio System) and GMRS (General Mobile Radio Service).
These are rules that allow manufacturers to produce low-cost general use radios for the public.
They are very under powered (usually 1/2 a watt) and the frequencies they can operate on are open so that anyone can use them without a license (in Canada, in the US I think you need to register them).
But the frequency bands they operate on are very congested and prone to interference from things like Microwaves.
The Police use Radio bands that are licensed and reserved specifically for them
The transmit power is much much higher giving them a clearer signal and much longer range.
They also have networks of repeaters and boosters all throughout the metro area so that they can get a clean signal wherever they are. Radio repeaters can act like cellphone towers where they can receive a radio signal and transmit it to dispatch over the internet.
Fleetnet radios used in industry like trucking, power companies, etc are very similar
AFAIK, there are 3 main kind of radios. Handheld (typical police radio), a mobile station (typical a radio hooked up in a car with a mini antenna) and a base station (the big station with big antennas) Each produce different varying amounts of powers, obviously the bigger the antenna the more powerful the signal.
But radio is actually measured via frequencies. The higher the frequency, the shorter the distance however can usually travel through and over objects such as buildings but just not as far. However, lower frequencies can travel much further but basically cannot go through anything. So typically lower frequencies are really only used by submarines and planes (additionally fun fact: there is a specific depth in the ocean and altitude in the sky that can let frequencies travel incredibly far. Which was usually the reason military subs chilled at this depth)
When higher frequencies face distance issues, they use repeaters, or Tangoes as they’re actually called. They basically record the message and resend it. Now, typically the police will have their own tangoes that is specifically used by their frequencies and can be illegal to listen or broadcast using these. I know this because a friend of mine taped an antenna to his garden trampoline and it interfered with emergency service radios. Awkward visit that.
But I’ve seen police recently use their squad cars as repeaters. Something to just give a bit more juice to their handheld radios.
Police carry around a big heavy radio that weighs 3-6 times what a small phone or radio weighs. They use that weight to get a more powerful signal, like a phone vs a Bluetooth speaker. They also use lower frequencies, which carry farther for the same power, like a boom box vs a water bottle size speaker. To get even farther they network those radios together like a Sonos, so you can hear from everywhere.
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