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How you tell antennas range it picks up

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How do you find out about how far an antennas range will go to receive freqs.

I'm trying to find a antenna that will go about 150 miles, but don't know what to look for to see if it will reach.

Thanks.
 

ka3jjz

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#2
It depends on several factors; the frequency, the height above any obstacles your antenna is, the type of antenna, any amplification, the general environment (urban, rural), the height and power of the transmitting antenna and the scanner's own sensitivity, just to name a few. There was a formula you can use to estimate this, but I don't remember what it is off the top of my head. That's a good one for the wiki....

Anyway, you'll need to be a bit more specific about those factors above just to get even a half educated guess. My uneducated guess would be a beam of some kind, but expecting 150 miles in hilly terrain, on UHF frequencies or better is pushing it. Even in relatively flat terrain, I would expect no more than half that on UHF or better, and even that might be a stretch.

You might do better finding an online scanner provider for the area in question, frankly

73 Mike

[edit] If your sig indicates your area of interest, I believe Albuquerque uses ProVoice, which is unmonitorable on any scanner
 
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thewenk

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wa8pyr

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#5
Croaker90 said:
How do you find out about how far an antennas range will go to receive freqs.

I'm trying to find a antenna that will go about 150 miles, but don't know what to look for to see if it will reach.
You don't mention which band you're trying to monitor, but in any case, the antenna isn't the only determining factor in your reception distance. Frequency band, antenna height, transmitter power and terrain all play a part.

1. Frequency band: basically, the higher the frequency the shorter the distance. VHF and UHF are line-of-sight, which means that if the transmitter is below the horizon for your antenna, you're probably not going to hear it.

2. Antenna height: The higher the antenna, the farther away you'll hear stuff.

3. Transmitter power: the less power the transmitter is putting out, the less chance you're going to hear anything.

4. Terrain: You're not going to hear anything from a transmitter on the other side of that 1500 foot mountain. Buildings also have an effect...

All of these things interact with one another to determine reception distance.

If you're into math, try this formula:

DA1 = 1.415 times the square root of H1
DA2 = 1.415 times the square root of H2

DA1 - distance to the radio horizon from your antenna
DA2 - distance to the radio horizon from the transmitter antenna
H1 - height of your antenna in feet
H2 - height of the transmitter antenna in feet

Now add DA1 and DA2 to get D1 (the approximate reception distance). This will give you the theoretical maximum line-of-sight distance between your antenna and the transmitter antenna.

Remember that D1 is purely an approximation. 1, 3 and 4 are all going to affect your true reception distance. A general rule of thumb is to assume an effective maximum of 20 to 25 miles for scanner reception, with an antenna 30 feet up. Your mileage may vary, but 150 miles is pretty much not going to happen unless your antenna is really, really, really, really high in relation to the transmitter.
 
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#6
Ok, thanks guys.

Yea I was reading the reviews on the website of the antenna, and some people said they heard from 100 to 150 miles away with it, so I decided to ask you guys, as I belive you guys instead of them.

It was probably RadioShack personall posting the reviews. :p

Thanks for the help guys.

Yea Albuquerque is Encrypted.

I heard the only thing you can pick up is Dispatch telling officers calls to respond to. Not sure if true, but if it is, I wonder if its digital.
 
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#7
What antenna do you have, Croaker? I have the RS 20-176 and it does get pretty far out in my experience. It doesn't go out 150 miles, but 70 or 80 miles is possible, on 150 Mhz anyway. On 400 or 800 MHz, it may only go out 20 or 30 miles.

Hearing signals from 150 miles away would be pretty cool, but that's probably not possible for most people. You would have to have the antenna quite high in the sky on a tower, and the frequency you're listening to would have to output a pretty strong signal. And since the majority of police, EMS, and other stations only broadcast to cover their local territory, I'd say the chances of anyone hearing 150 miles away is pretty low.
 

nd5y

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#8
It depends on your location. Out west where most of the repeaters and base stations are on mountain tops you can easily hear stuff over 100 miles away.
 
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