RX/TX distance

[PlugYer]

Question? I have a 5 watt handheld that I talk to a friend with as the crow flies approx 5 miles away a drive to his house is 7.6 miles . My question is about how far should I TX/RX if I put a 60” GMRS antenna on a 20ft pole ? Other than the trees and houses that is the only obstacle in the line of sight. No hills or large buildings. Note: we both have same radio and have the Nagoya 771 17” antenna

 

[tomk62]

I think this might help you: Line of Sight Calculator - everythingRF

 

[vagrant]

Use this LOS calculator instead. Also, find out if one location is higher than the other ASL (above sea level). It may not seem like it, but there could be be a twenty foot difference.

Line Of Sight Calculator

calculators, engineering calculators....

www.calculatoredge.com

 

[nd5y]

Hight above sea level is totally meaningless for RF propagation. What is important is height above average terrain (HAAT), the terrain in the path between two stations, and the curvature of the earth if the path is more than a few miles.

 

[nd5y]

Some online line of sight calculators are useless. Like this one.

 

[tomk62]

Some online line of sight calculators are useless. Like this one.

Is that because there's something wrong with the calculation, or it's just too far a distance to be practical?

 

[vagrant]

If point A is 20‘ higher than point B five miles away it is not meaningless. Stay focused on the OP’s question and details. Terrain between is important as well and the OP notes that point.

 

[nd5y]

Is that because there's something wrong with the calculation, or it's just too far a distance to be practical?

The calculator only uses ground elevation above sea level and assumes the earth is flat. It doesn't know transmit power, receive sensitivity, path loss, total system gain at each end and noise floor at each end.

 

[tomk62]

The calculator only uses ground elevation above sea level and assumes the earth is flat. It doesn't know transmit power, receive sensitivity, path loss, total system gain at each end and noise floor at each end.

Thank you! So is there a better calculator to use?

 

[mmckenna]

I'm not sure there is one calculator that will cover everything.

You need to establish if the RF path is there. Line of sight isn't the only thing that plays in here, as RF, even at UHF frequencies, can exceed line of sight. Google Earth has a ruler function that can be useful for short range tests like this.

You also need to figure in free space losses, know the performance of the radios, antennas and feedlines at each end:

Friis Transmission Equation Calculator

www.everythingrf.com

Or, just set up your radios and try.

 

[nd5y]

RadioMobile is good.

Radio Mobile WEB Site

www.ve2dbe.com

There is an older Windows version and an online version (that I have never used) that requires an account. It has a steep learing curve. You need to know a lot about RF or you won't get useful maps or path plots out of it.

 

[GadgetGeek]

Or, just set up your radios and try.

+1

 

[PlugYer]

Thanks for responding. I’m going to put up my antenna next week and try it. My friend can’t do an install because of his HOA .

 

[mmckenna]

My friend can’t do an install because of his HOA .

There are a number of creative ways around that if they decide to give it a try. Range really, really depends on a good antenna as high up as you can safely get it.