Antenna height

[nfsus]

I have a crank up pole that let's me get pretty close to 50ft in the air if I had it mounted firmly, but I dont. Anyway, on this pole I've mounted an original Shakespeare two piece big stick I rescued.

Ok heres the test. Over my ground, how much change will I see according to height? The antenna is only able to be adjusted by trimming so that's not an option. I started by raising the antenna to a height of 21ft to the base of the antenna then I raised it measured it and raised it higher. Heres the results without adjust the antenna, only the height.

26.940 was used for all three levels as it had the lowest starting numbers

21ft
1.26 swr
3.29 j
159.89 phase

28 ft
1.25 swr
2.49 j
163 phase

36 ft
1.24 swr
3.56 j
156 phase

 

[nfsus]

Just for a non scientific test, theres some florida skip rolling into arkansas. I have a better signal on the half wave at a lower height than the .64 at 10 more feet in the air. Height is not always might

 

[sp5it]

Make choke balun right under feed point, insulate antenna from pole, measure again.

 

[nfsus]

What size how many turns

 

[nfsus]

Wait, which antenna should get the choke?

 

[Ed Cole]

The question is not only higher or lower being better. Its about the take off angle and radiated pattern at certain heights. And the radiated pattern also changes with the actual wavelength of the antenna. 1/4 wave, 5/8 wave, and so on. Without the availability of an rf modeling program, simple trial and error will find your "sweet spot" depending on what you're trying to do. Generally, "Big Sticks" and "A-99's" and the like need to be at least 35 ft. to be reasonably effective. And some common sense. If your house has a metal roof, you're going to want to be at least 12 feet above it in order to prevent interference to your radiated pattern, or SWR interference. Also, take into consideration that your antenna has no ground plane radials, which also affects your take off angle. If you reference "antennas 101", you should remember that slightly downward sloping radicals can help lower your take off angle. So "no radial" antennas generally need to be at least 1/4 wavelength above the ground to achieve a decent take off angle for working DX. The radials on an aluminum ground plane antenna provide the reflection necessary at lower heights, whereas a "stick" antenna just doesn't have it. But, all individual situations vary....depending on surroundings, obstacles, earth conductivity and so on. But the 1/4 wavelength rule of thumb is good to follow for a stick antenna in any case.

 

[loosecannon]

both antennas should have the common mode chokes.
right at the feedpoint.

if you don't want to build and install the choke coil, you can just buy a kit like this:
https://www.ebay.com/itm/203312252024?hash=item2f565ac478:g:HX8AAOSwAixgqoaK

this is for 1/2" coax, but they make kits for 1/4" coax as well.

one note about isolating your antenna from it's metal mast.

if you do this, you MUST make sure you have a lightning arrestor mounted to a ground rod right before the coax enters the house.

The reason for this is because that mast is dissipating any charges that might get built up on your antenna.

with the antenna isolated from the mast (which does indeed improve it's performance)
the only route those charges have to take is your coax shield and they will absolutely arc across to the center pin and anything else that is connected to that coax.
LC