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nvrpunk
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Joined: 17 Jan 2009
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I am in Iraq and bought the Maxx2007+ Kit. I am limited in height for broadcasting. It's extremely flat here and not many building etc. What distance should I expect at what heights? Ideally, I might be able to get it about 15 meters up. How far will it broadcast at that height and how long is the cable in the kit?
Sat Jan 17, 2009 12:13 am View user's profile Send private message
gfg
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Joined: 05 Oct 2008
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Radio waves tend to keep going till one of three things happen:


1) They hit the radio horizon;

in your case 1.415 x sqr ( 15 x 3.281 ) x 1.609 = 15.97207088 Km
Lets call it 16 Km. If you want to play around the formula for Excel is: =(1.415*(SQRT(15*3.281)))*1.609
It's from Wikipedia: http://en.wikipedia.org/wiki/Radio_horizon
This website seems to have some java that does the work for you: http://www.vwlowen.co.uk/java/horizon.htm


2) They hit some very solid object;

Some building materials just attenuate the signal (reduce its strength),
but a hill, mountain, large rock / stone formation etc. Tends to stop radio waves completely.



3) They run out of energy;

http://en.wikipedia.org/wiki/Free-space_path_loss
The formula is: Loss dB = 32.44 + 20 log (dist in km) + 20 log (freq in MHz)
Assuming 100 Mhz at 16 km which would be about the perimeter of your coverage with a 15m mast.
You're looking at a path loss of 96.52239965 dB, Excel formula: =32.44+(20*LOG(16))+(20*LOG(100))

I believe the unit your are looking at has a 15W transmitter power, I'm not sure the antenna you
intend to use, but assuming the antenna gain & cable losses cancel each other out you're looking at a
transmit power of 42 dBm, Excel formula: =10*LOG(15*1000)

42 - 96.5 = -54.5 dBm or if we add 107 to convert to dBuV = 52.5 dBuV

Thats under the official Analog Service Contour of most countries, but still well within the receive capabilities of most modern radio's.
Modern FM receivers, especially car receivers have stunning sensitivity.

For your curiosity, using a 15m mast your official coverage area (I.E. 60 dBuV or above) would by 6.5 Km radius, but as above you
should have no problems right out to your Radio Horizon at 16 Km.

If you wanted to get a detailed idea of coverage you could try:

http://www.qsl.net/kd2bd/splat.html
This tool is good, but requires moderate setting up.

http://lrcov.crc.ca/cov.php?lang=en
This is an online prediction tool

Hope this helps,


GFG
Sun Jan 18, 2009 1:40 pm View user's profile Send private message
pcs
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Joined: 18 Jan 2002
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Location: Radio Land

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Great answer, thanks for posting this!

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Mon Jan 19, 2009 1:25 am View user's profile Send private message Visit poster's website
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