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Old 18-Nov-2015, 3:20 PM   #1
JimMcGowanPMCM
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2 Antenna's, 1 Mast, Not Combined

I would like to mount 2 Low band VHF TV antennas on the same mast about 160 degrees directional difference. I need to monitor two TV stations. One in NY and one in PA. I will NOT be combining the signals. They will have separate coax runs and feed separate TVs.

The question is do I need to be concerned how far apart I mount the antennas. Is several inches ok, or do I need a specific minimum distance.

They will be identical antennas on the same pipe.

Thanks
Jim
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Old 18-Nov-2015, 3:46 PM   #2
MikeBear
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Two low band VHF antenna's should be mounted about 5 FEET apart minimum, if they are on the same mast. If not, they will affect each other in some way depending on your circumstances.

Last edited by MikeBear; 18-Nov-2015 at 3:48 PM.
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Old 18-Nov-2015, 3:47 PM   #3
rabbit73
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The general rule is 1/2 wave for the lowest frequency:
http://www.tonercable.com/pdf/antenna.pdf
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Old 18-Nov-2015, 4:34 PM   #4
Stereocraig
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That, is a lot of wind load for a single mast, so plan accordingly.
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Old 18-Nov-2015, 4:58 PM   #5
ADTech
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Tower Guy, IMHO, probably has the most experience with low-VHF, perhaps he'll chime in.
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Old 19-Nov-2015, 1:31 AM   #6
Tower Guy
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Let's see; 1/2 wavelength on channel 6 is 5.8 feet. On channel 2 that's 8.6'. That's a bare minimum for modest interaction between the antennas. The real question is can you live with some coupling between the antennas? With strong signals, LOS paths, and minimum reflections you can get by with closer antennas. You'd be best off separating the antennas horizontally and positioned so that they do not aim at each other.
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Old 19-Nov-2015, 6:43 PM   #7
JimMcGowanPMCM
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Wind Load is not a concern because this is a temporary setup and if it gets windy I will just take it down but weight is a concern. I am using a pneumatic 30' Clark Mast and its limited to 20 lbs. Each antenna is 6.5 lbs. The bad news for me is I need to get Channel 2 and Channel 3 so per Tower Guy that's 8.5 feet separation. To go horizontal Clark has a 1 meter T-bar.

http://www.clarkmasts.com/mast-acces...-mast-adpater/

This bar would get the antennas only 1 Meter apart and one antenna would only be 8" above the other. Its about 160 degrees direction difference but a mere 1 meter horizontal and 8" vertical separation doesn't sound like it will prevent issues. If I only care about one Channel on each antenna would a notch filter or other device allow closer mounting?

Thank you for the advice.
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Old 19-Nov-2015, 7:24 PM   #8
ADTech
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Do your antennas have their mast clamps at the rear of their boom(s) or at the center of mass or pressure?
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Old 20-Nov-2015, 12:30 AM   #9
Tower Guy
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Go with your original plan for vertical stacking. Try 5' anyway, it might work OK.

Few low band antennas have rear mount options.
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Old 20-Nov-2015, 2:00 AM   #10
ADTech
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Yeah, I wouldn't expect them to, but we have no idea what he's using. If they did have rear mounting capability, most of each antenna would not be over each other and the distance requirements could be substantially relaxed without affecting reception very much.
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Old 20-Nov-2015, 3:49 AM   #11
JimMcGowanPMCM
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Quote:
Originally Posted by ADTech View Post
Do your antennas have their mast clamps at the rear of their boom(s) or at the center of mass or pressure?
Center of Mass, but its nothing more then holes drilled in the aluminum. I could drill a second set of mounting holes near the back of the antenna. I would have to get the balance close on both antennas to keep from stressing the mast but that may be ok with the T-Bar. The antennas are very light, only 4.5 lbs each. At 160 degrees I could probably keep the overlap to a single element.

Last edited by JimMcGowanPMCM; 20-Nov-2015 at 4:06 AM.
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Old 20-Nov-2015, 3:52 AM   #12
JimMcGowanPMCM
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They are both Channel Master Yagi 5-2-6's

http://www.solidsignal.com/pview.asp?p=y5-2-6

One antenna on the mast at a time I have received a good signal at 52 Miles.
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Old 20-Nov-2015, 4:05 AM   #13
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Those antennas were made by AntennaCraft. Handle them with care because AntennaCraft is no longer on the scene and there are no replacements.
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Old 20-Nov-2015, 4:08 AM   #14
JimMcGowanPMCM
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Which method should I try? 5' spacing on the same mast or moving the mounting brackets back and getting a T-Bar?
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