the theoretical distance to the radio horizon for an antenna

[Sully]

OK.... I put a new Shakespeare Phase111 antenna on today 8)
So I looked this up to get how far out I should get in a perfect situation
I have a total height of boat and antenna of about 18 feet so I should get out about 25 miles
Just thought Id pass the formula along :roll:

I am not a scientist i just play one on Classic Parker :shock:


The space wave signal path is the so-called "line-of-sight" path between the transmit and receive antennas. The curvature of the Earth is the primary limiting factor for the maximum distance a space wave propagated signal can travel.

If you are into math, the approximate distance (in miles) to the radio horizon can be calculated by multiplying the square root of the antenna height (in feet) by 1.415 times. For example, the theoretical distance to the radio horizon for an antenna 1,000 feet above the ground is just under 45 miles.




The distance, D1, to the radio horizon for the transmitter is 1.415 times the square root of h1 (feet). The theoretical maximum line-of-sight distance between two elevated points, presumably the transmitter (h1) and the receiver (h2), is the sum of the two distances to the radio horizon (D1 + D2).

All this, of course, assumes that the Earth is a perfectly smooth sphere, and that no signal disturbances or enhancements occur along the path between the transmit and receive points. As we know, the Earth is not a perfect sphere, and the space through which the radio signal travels is not perfect either.

 

[Megabyte]

No problem with the distance calculations for theoretical distance...
But when factoring in the output power of the radio combined with atmospheric conditions, my guess is those two could be a greater limiting factor than distance.

But... I'm no radio expert.

 

[Sully]

I here your point
I put a couple of waypoints on my chart plotter for seatow auto repeater service
Green Harbor marshfield mass ch26
E boston channel 28
When I go out this year I will call out to there fix spot and see just how far I can get on a given day
Would be good to know if i can reach Green harbor from Stellwagon bank about 19-24 mls out depending on position
Looking forward to finding out how good this new Shakespare Phase 111 antenna is :shock:

 

[jeffnick]

I stopped at the TowBoatUS station in Ft Lauderdale. They say they receive calls from boats in Bimini - 55 miles away, go get them and tow them back.

 

[macomber]

I had to reach SeaTow in Green Harbor from Stellwagen a few years ago and had to go through the CG. We were also in pea soup fog which could have been a factor.

 

[Sully]

I would like to hear more reports about how far their VHF reached
And there Antenna height and radio and conditions at the time
I will update when I get back out also
I find it interesting to see how everyone else dos real time

 

[jimbo]

VHF radios generally have a range of about 20-25nm. A phenomenon called ducting can occur where the signal is trapped in layers of the atmosphere sometimes in foggy conditions. When this happens VHF signals can travel over 100nm I Have perrsonally witnessed this.

 

[wflgator]

Having worked in the land mobile radio world now for more years than I care to mention.....radio range or coverage is a function of several factors: transmitting and receiving antenna heights and gains, coaxial cable losses, as well as transmitter power output and receiver sensitivity. In the maritime environment obviously most of the antenna heights are relatively low so this is your limiting factor though atmospheric conditions and noise can often be a significant factor as well. Biggest issues I used to see, years ago, when I dabbled with marine radios, was poor ground/power connections and poor antenna connectors (bad crimps or soldering). Both of these will limit your range significantly as well as the radio and antenna will not be performing at their optimum levels.