LiveATC Discussion Forums

Air Traffic Monitoring => Listener Forum => Topic started by: kolkol on June 27, 2005, 06:40:38 AM

Title: VHF Range?
Post by: kolkol on June 27, 2005, 06:40:38 AM

Hello,

Is VHF based soley on line of sight? I bought a scanner a while back, and didn't pick up a thing from my house. I'm about 10-15nm north of the airport, but behind trees, and tall buildings in between. I'm about 40nm from the ACC, with no buildings inbetween but trees. My question is, would a good scanner be able to pick up ATC chatter. My radio works fine here (obviously) so I figured a scanner would too. Was the scanner crap or am I out of luck? THanks

Title: VHF Range?
Post by: dave on June 27, 2005, 08:12:10 AM

You need an outside antenna.

Check out this thread for some more info:

http://www.liveatc.net/forum/viewtopic.php?t=520

Also, you can search in this forum for 'antenna' and find a lot of information that will help you.

Dave

Title: VHS Range
Post by: Shaun on July 21, 2005, 08:29:08 AM

FYI (hope this helps)

DIRECT WAVES   (VHF UHF SHF EHF)

Frequencies in the VHF, UHF, SHF and EHF bands are DIRECT WAVES.  Due to their high frequencies they pass through the ionosphere and escape into space. They do not bend with the surface of the earth thus their range is limited to 'line of sight'.  The distance of the horizon is calculated by 1.25 Ö H where H is the height of the observer in feet.  There is a slight improvement in range due to atmospheric refraction and the range of VHF in nautical miles is calculated by :-

Range in nms     =   1.25 √ Transmitter height in feet    +   1.25 √ Receiver height in feet


Ground waves follow the curvature of the Earth's surface (diffraction).

Direct wave      Range Line of Sight
Frequencies      118 to 136 Mhz    720 Channels    25 Khz apart

Transmission      A3E Amplitude Modulated   Vertically Polarised


Shaun