[Antennas] Dipole Height

Thu Sep 17 13:25:52 EDT 2015

I think Ray is spot on with his reply. Save the good stuff for UHF where 
the lower loss will really mater.
If you look at the 1/2 db loss at 7 MHz for a 100 foot run of RG8...and 
translate that into S units...its about
1/12th of an S unit. At 500 MHz it’s the difference between heating the 
cable and getting some energy to the antenna.
Of course if you'd like to trade the hardline for some nice new RG-213....
Connectors for it are a bit expensive. Well worth it at UHF and up.
73,
Lyn
wa4geh
-----Original Message----- 
From: Ray, W4BYG
Sent: Thursday, September 17, 2015 11:26 AM
To: JK
Cc: antennas at mailman.qth.net
Subject: Re: [Antennas] Dipole Height
In my opinion, using the 1 5/8" coax in place of LMR-400 or RG-213 does
not make any practical sense. It would be excessive overkill which
would make the installation far more complex than it needs to be and not
cause any noticeable improvement in 40 meter performance.
The cost of the connectors and trouble installing them, plus the
tremendous weight difference are real negatives to the larger cable. If
your dipole is center fed, you would have to use a much heavier antenna
wire to sustain the weight. Your end support hardware would have to be
much heavier and costlier.
Again, the difference in losses experienced in daily operation between
the two would be hardly noticeable at 40 meters. You would not realize
it on receive and the DX station would not realize it either.
Save your 1 5/8" coax for a VHF-UHF application where it would make a
significant difference. It's a nice gift. Use it where it offers a
real advantage, or trade it for something else you need.
Enjoy,
Ray, W4BYG
On 9/17/2015 11:05 AM, JK wrote:
> Someone gave me 150 feet of Heliax AVA7-50 1-5/8" coax. I think that will 
> be lower loss than LMR-400 or RG-213.
>>> Jay NE2Q
>>> On Thu, Sep 17, 2015 at 10:42 AM, Ray, W4BYG wrote:
>>> I don't think I agree with this suggestion.
>>>> At 40 meters typical RG-8 cables losses are much less for 90' to 100' of 
>> cable, than the significant gain in low angel of radiation that would 
>> occur with the higher installation. RG-8 cable loss at 7.2 MHz for 100' 
>> at a VSWR of 1:5 to 1 are about 1/2 db. See:
>>>> http://www.kc7hxc.us/links/radio/Coax%20Calc/Coax%20Calculator.html
>>>> With antenna height of 7' AGL most of your energy is NVIS and going 
>> straight up and down warming the clouds and worms. At 90', most of your 
>> energy is going out on the horizon at good angles where it should be, for 
>> DX contacts.
>>>> Big difference!
>>>> 73,
>> Ray, W4BYG
>>>>>> On 9/17/2015 10:05 AM, David Robbins wrote:
>>> once you factor in the extra loss for the feedline needed to get it up 
>>> that high the improvement will be negligible.
>>>>>>>>> Sep 17, 2015 09:34:15 AM, jkolin at optonline.net wrote:
>>>>>>>>> Hey Ray,
>>>>>>>>> Will my 40 meter dipole work better for DX at 90 feet above ground
>>> instead of 7 feet above?
>>>>>>>>> Jay...NE2Q
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