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Newbie - Antenna Mast, Antennas, etc

Aug 27th 2021, 16:55

KY4RWW

Joined: Aug 27th 2021, 16:13
Total Topics: 0
Total Posts: 0
Hello,

I'm new to the hobby, slowly building my first shack and need advice.

I currently have an old TV antenna on a 5' mast banded to my brick chimney. I've purchased a Diamond X30A, a Ultimax DXtreme 88' and a Channel Master Masterpiece 45 to replace the TV antenna.

1. Do I need to maintain a distance between the TV antenna and the HAM antennas?

2. If not, can all of these antennas be placed on the same mast? The Diamond above, the Ultimax below the TV antenna?

3. If it's ok to place all 3 antennas on the same mast, is top rail strong enough our should I consider using a heavier wall aluminum mast, something like a 1.50 to 2" diameter with .125 to .25" wall?

4. Is it stronger to ground mount the mast and affix it to the house in several places?

5. What is the maximum recommended unsupported mast length above the highest mount before it needs to be guyed?

6. Any issues with placing HAM radio antennas above a chimney?

Any advice would be greatly appreciated!

Thanks,

Rick
(KY4RWW)




Jan 31st, 20:42

KJ7WUZ

Joined: Mar 31st 2020, 15:11
Total Topics: 0
Total Posts: 0
I have tried vertically stacking a Comet CX-333 VHF/UHF and Comet CA-712EFC (GMRS) antennas on a mast following the suggestions of multiple documents. The documents seem to be geared toward folded dipole or dipole antennas, however. What I failed to consider is that my antennas are actually collinear antennas. The separation distance is different from the dipoles, in that the collinears are stacked 1/2 (or 1/4) waves and radiate along the entire 10ft length. With the antennas 10 ft center-center the GMRS radio below the VHF/UHF causes the VHF/UHF radio to open squelch when it transmits. I am trying the separation of 10 feet from end to end between them rather than center to center. The other consideration may be the creation of common mode current in the upper vertical antenna's coax shield by the lower antenna when it radiates (transmits). I will be trying ferrite common mode chokes around the upper antenna's coax at the antenna and just below the ground plane of the lower antenna. If this doesn't work the separate masts it is. I have not been able to find a low-pass filter commercially available with a sharp enough Q to filter the GMRS out of the UHF antenna system.

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