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Author Topic: Antennas in the wind  (Read 11623 times)

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KF7SZX

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Antennas in the wind
« on: March 02, 2012, 10:20:52 AM »
So I just stepped outside and it's getting windy around these parts and I was thinking...

How much does wind effect an antenna's signal? 
I've noticed that on some windy nights the local repeater has some noise and wondering if it's actually the wind or the Cloud cover?

but, I have never noticed any difference with my mobile antenna whether I'm at a stop light or flying down the freeway at 80mph. I have a 42" antenna so there is some swaying for sur.

Just wondering.
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KF7SZX, Eric

idial1911

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Re: Antennas in the wind
« Reply #1 on: March 02, 2012, 10:43:02 AM »
That all depends on if it blows down your tower ;)
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KF7SZX

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Re: Antennas in the wind
« Reply #2 on: March 02, 2012, 11:00:04 AM »
It'd be a long time before I get a tower, sadly.

Side note: what would one do to boost a signal going through a longer length of coax?  I set up a paint pole with my mobile antenna on top but I couldn't even extend the pole to its longest because I only have 12 or 15 ft of coax from my mag mount. Would be looking into amplifier territory?
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KF7SZX, Eric

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Re: Antennas in the wind
« Reply #3 on: March 03, 2012, 03:18:08 PM »
What radio are you running?   You can get a Diamond X50 that has high gain and run low low coax
http://www.hamradio.com/detail.cfm?pid=H0-000022
http://www.rfparts.com/diamond/x50a.html

You can tie some 550 cord around the top and haul it up in a tree. 

The issue with the mag mount coax or RG8X is that at the UHF/VHF freqs, you suffer higher losses per foot than you do a the HF levels. (ie 7.340 mHz vs 440 mHz).

I have posted coax types and cable loss somewhere on this site. 
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BTPost

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Re: Antennas in the wind
« Reply #4 on: March 03, 2012, 04:05:48 PM »
The tradeoff here is, Antennas Hight VS Coax Cable Attenuation.... You gain range by moving your antenna higher in the air, away from obstructions, and you lose Range due to attenuation in the Coax Cable. Google some Coax Cable OEMs like Beldon and Andrew, and get an idea of what each type of coax has as an attenuation figure at the Frequency you intend to use. With that as a starting point you can calculate how much coax of that type you can use before the attenuation overcomes the gain you receive by height of the antenna above Ground. I like top use the "Poor Mans Heliax" (Beldon 9913) for all my 50-450 Mhz coax runs, over 75 feet. I haven't purchased any in a decade but it used to cost about $.50/Foot.  For things higher than 450 Mhz and longer than 35ft, I go to 1/2" Heliax for power levels under 1 Kw, and then build flexible Jumpers for each end of the those runs, out of 9913. Just Say'en.... YMMV.....
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Bruce in alaska AL7AQ
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