It’s been a few years since I had a permanent base set up. Been running a 5/8 stick 12 feet off the ground in my yard for a couple of years since relocating. As soon as we get in Spring here in New Hampshire, I want to get this 5/8 stick up on the roof. The mounts are already in place on the chimney. Trying to decide mast height from the mount. The top of the chimney mount bracket that will hold the mast sits about 26 feet off the ground. Using the bottom of the 5/8 stick as the reference point, how high is the minimum I should try to get that point from the ground? I'm sure the concept of the higher the better holds here, but at 26 feet as the reference point I'm limited because I'm not going to add guy-wires. So the mast is all I have to work with here and I also concerned with wind load on the mounts. I think they are strong but I do sit up on a good high open spot here and we get heavy winds. The higher the mast off the top of the bracket increases the leverage on the mounts and I want to minimize the risks of over stressing this. Thanks
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Ideal Minimum Antenna Height
- Thread starter Mark Scannura
- Start date
Hi, Mark.
According to this, 10' is the max. I personally wouldn't feel safe that high with your winds if you are not going to guy it.
https://support.channelmaster.com/hc/en-us/articles/200383775-Installing-a-Chimney-Mount-CM3080-
According to this, 10' is the max. I personally wouldn't feel safe that high with your winds if you are not going to guy it.
https://support.channelmaster.com/hc/en-us/articles/200383775-Installing-a-Chimney-Mount-CM3080-
Hi Riverman
Thanks for that link.
I have 3 of those type brace mounts as opposed to 2. So there is some additional support with the 3rd brace. That said, 3 feet of a 10 foot mast would be sunk into the 3 braces leaving about 6 to 7 feet above the top brace. So this gets the bottom of the antenna at about 32 feet above ground.So I think the question becomes is 32 feet a good height or should I try for higher for optimum performance?
Mark
Thanks for that link.
I have 3 of those type brace mounts as opposed to 2. So there is some additional support with the 3rd brace. That said, 3 feet of a 10 foot mast would be sunk into the 3 braces leaving about 6 to 7 feet above the top brace. So this gets the bottom of the antenna at about 32 feet above ground.So I think the question becomes is 32 feet a good height or should I try for higher for optimum performance?
Mark
Thirty two feet should be more then adequate to see an improvement, if you want to go higher then you need to look into a different support system. The old adage is "higher is better" but you have to factor in cost and wind loading.
A few feet one way or the other won't matter. Theory says something magic happens at one fullnwavelenght and it does. It just isn't noticeable. Also that reference to above ground is actually talking about RF ground which may actually be several feet below the surface depending on your soil.
If the antenna is vertical then higher is better for local talking.
for DX 1/2 wl agl will work so minimum height is determined by what type of operating you prefer to do.
If local rag chew a light weight high as you can install vertical is great for Omni directional coverage.
If DX is your goal a simple 1/2 wl dipole installed 1/2 wl agl will work great, It is not a beam no gain but do not let that fool you,
for DX 1/2 wl agl will work so minimum height is determined by what type of operating you prefer to do.
If local rag chew a light weight high as you can install vertical is great for Omni directional coverage.
If DX is your goal a simple 1/2 wl dipole installed 1/2 wl agl will work great, It is not a beam no gain but do not let that fool you,
Captain KW has the best answer. The best MINIMUM antenna height is one wavelength above rf ground. In the case of cb freqs, this works out to 36 feet to the base of the antenna. I have always had good success both local and dx using the 36' height. When I was in Socal, I had an antron 99 w/ ground plane kit mounted on a steel tube fastened to our chimney. It was at 36' and had no guy wires. Never had a problem. I always assume that rf ground and the surface of the soil is the same. Rf ground will never be above the surface, and if it is below so much the better. BTW ... I don't know if this is fact or not, but in my experience, if the antenna is one wavelength above ground, your neighbors won't experience as much (or any) RFI. If anyone knows that this is a fact (or not), let me know.
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I use an A-99 on a galvanized 30' push pole , my Sirio 27-4 is about 35' to the beam I'd like to go higher but I have no problems and really don't want to guy wire the beam . I get a lot of wind and so far my beam with no complaints . JMO
http://www.dx-antennas.com/Height versus take off angle.htm
http://www.hamuniverse.com/wb4yjtdipolepatterns.html
Notice the dipole patterns and even more so notice the nulls in the lobes.
then look at the pattern at 1/2 wl agl.
No nulls and good low angle of radiation. Hard to beat a 1/2 wl dipole at 1/2 wl agl
for all around antenna rag chew and dx.
http://www.hamuniverse.com/wb4yjtdipolepatterns.html
Notice the dipole patterns and even more so notice the nulls in the lobes.
then look at the pattern at 1/2 wl agl.
No nulls and good low angle of radiation. Hard to beat a 1/2 wl dipole at 1/2 wl agl
for all around antenna rag chew and dx.
I have always preached to not worry about where the lobes are but rather worry about where the nulls are as the nulls are MUCH further down than the lobes are up in gain.
I realize the tread is old. Where I live I have had the best luck putting my antennas in the tree tops. 80-110 ' off the ground. I live in the forest so I have really good luck getting out with the antenna poking out in the tree tops.
I have a A99 32" off the ground with out a ground plain kit and it works great. It tunes 10,15,12 and 20Mtr. Using the internet tuner on my kenwood. It also has a great match on 11Mtr. Without a tuner.