Originally Posted by Simon B
Not a clue but a clue can be gained, will look into this, I believe stable antenna height is more of a factor than power. Not that any of this will do any good when you are out there!
Popular misconception that power effects range. With VHF it does not make a blind bit of difference. It does not matter how strong a signal you send out, if the top of your antenna is line of sight with the top of the receivers antenna then the signal will get there. All that higher power does is make your signal drown out everyone elses.
If of course we were talkng about MF then an increase in power would increase range but with VHF and HF not so.
I have always worked on the formulae being 2.12 sq route height, however it does not make much difference so lets call it 2.2 etc.
Jon The formulae works for either sort of aerial. The difference is effectivly the angles that the signal leaves the antenna from. I can explain easily by diagram so will show you when I next see you if you are still interested.
Now to put the formuae into practice. If I have an antenna height of 16m and a CG has an antenna height of 100m- how far apart could we communicate?
Well sq route of 16 is 4, times by 2.2 equals 8.8. My radio horizon is therfore 8.8 miles. Sq route of 100 is 10, multiply this by 2.2 and the CG has a radio horixon of 22 miles. OUr range from/to each other is therfore the sum of the two=30 miles. I expect that if you have a look at the rising/dipping distance table in the almanack it will give you much the same result.
In reality of course the CG generally has a higher mast than that and most RIBS dont have a 16m A frame.
Now there are of course various conditions that can increase or decrease this range. Sea State, atmospheric pressure, temperature differences, sun spot activity to name but a few. Yacht sof Gibralter have been known to pick up Dover Coastaguard but when it happens it does not happen for long.