Mounting a hex beam on top of a high urban building

Question

I am moving into a new apartment in the city soon which is on the 24th and last floor of an apartment building. I will have access to the roof of the building also.

I'm still trying to understand antenna theory fully.

I am very tempted to buy one of those 6-band hex beams and install it there. The question is, will such a height from the ground have a negative or positive impact for me? I plan to operate from 20 to 10 meters.

The fact that this is a balanced antenna, do I have to worry about a ground or distance from the ground?

The location in the city where the apartment building is already at over 1000ft above sea level. My guess is that this along with the building height, I should be able to send out one hell of a signal locally, but what about for DX'ing? I am interested to hear your thoughts. Thanks in advance.

Answer 1

As already mentioned by @Andrew's answer; as a general rule: the higher the better.

Another very important rule is: any antenna is better than no antenna. So a hex-beam on top of a 24 floor building is better than none !

Lightning was mentioned, which is something you need to give serious thought. Try to find out who is the facilities engineer, and have a chat with him. Make sure you keep to the electrical code, and incorporate lighting ground in your antenna design/placement.

Another one is: wind speeds and force. At that height you want to make sure your antenna, and its individual components do not come loose due to wind. Anker it, secure it, lock it.

Answer 2

The general rule of thumb is that for antennas the higher the better.

The height above ground in this case is an absolute advantage.

Your ability to put an antenna on top of a very high building is enviable to say the least.

Height above ground affects the angle of radiation, which is the vertical angle compared to ground of maximum radiation for an antenna.

You don't need to worry about DX, normally for a beam antenna the angle of radiation goes down as you increase the height, so higher means better DX.

I would still try and get the antenna mounted as high above the top of the building as is possible, for example a 3 meter mast minimum would be best, but regardless of what you do the antenna will work very well at that height.

That would be an awesome location to set up a VHF/UHF station or mess around with repeaters!

The only other thing to mention is that you would need to consider lightning protection which is another whole subject, though I would imagine the building already has this.

Can I come and move in with you ?? : )