Originally Posted by Hal
Is the backstay antenna just popular because it is convenient and relatively easy or are there others that would give a better pattern with a little more effort.
Well you could put a yagi and rotator on the top of the mast
if yer really keen
Other than that there is very little to know for a small sail boat as the possibilites are very limited.
First thing is that all the rigging
which is likely grounded is mostly within 1/2 wavelength of any antenna and so will have a big affect on the antenna's radiation pattern no matter where the antenna is located. I propose that effect cannot be reliably modeled so the influence of the rig is best forgotten about as just being part of life. A vertical whip at the transom places the anteena furtherest away from the rigging
but I would venture that the gains are not worth considering.
The best antenna (assuming only verticals will fit which is the case for small sail boats) is a 1/2 or 5/8 wavelength height vertical for the frequency of interest, either bottom fed or centre fed - bottom fed being by far the easiest, is frequency independant (centre fed can be frequency independant too if open wire feeders are used but open wire feeders are impractical on a sail boat) and probably the only seaworthy
BUT this antenna may not be optimum on higher frequencies where it becomes longer than around 5/8 to 3/4 wavelength due to low angle radiation being lost
from the pattern (lower frequencies are fine, low angle radiation is not lost
even if the antenna is very short for the frequency of interest - only efficiency is lost). Whether this vertical antenna is the back stay, a whip or a piece of wire on a halyard
makes no difference whatsoever - they are all just bits of metal stuck up in the air. So one just wants a bit of metal up in the air that never exceeds around 5/8 to 3/4 wavelength in length for the frequencies of interest.
That is all very easy and why people try to complicate it I have no idea. I just use a bottom fed wire on a halyard
to the upper spreaders, bottom just clear of the shrouds and the run of it clear of boom and sails
. Despite being right close to the rig it works far better than any vertical I have had on land (my boat is metal though) - before the boat was built I experimented with verticals close in to my metal antenna tower simulating a yacht rig and that satisfied me that the arrangement would be ok to specify for the boat.
Then there is grounding - a topic which I have my own views on but avoid getting involved in on forums
due to the emotive but not necessarily very scientific views many have on the subject.