[TowerTalk] Ladder Line Fed Dipole Issue

[Tony]

Mike:

I expected the outcome you describe to some extent. Unfortunately, my 
antenna tuner has limited range so I'll need to modify the feed line 
length to bring the SWR down and hopefully retain the antennas 
multi-band capabilities.

Thanks,

Tony




On 10/25/2018 1:56 PM, Mike Fahmie via TowerTalk wrote:
> Your transmission line, being an odd multiple of ¼ wavelength, will transform your nominal 70Ω antenna to about 1300Ω so your observed SWR seems to be what I would expect.  If the line were an even multiple, then 70Ω would be presented at the radio end with a 1.4:1 SWR into your 50Ω system.
> -Mike-WA6ZTY
>
>        From: Tony <dxdx at optonline.net>
>   To: TowerTalk at contesting.com
>   Sent: Thursday, October 25, 2018 10:14 AM
>   Subject: [TowerTalk] Ladder Line Fed Dipole Issue
>     
> All:
>
> I have an 80 meter dipole fed with 300 ohm ladder line that needed to be
> moved to a different location. The antenna is 110 feet long and the
> ladder line is attached to a DX Engineering 1:1 tuner balun with a short
> 10 foot run of coax. The length of the ladder line is cut to an odd
> multiple of the 80 meter wavelength.
>
> The SWR on 80 meters was very high so I trimmed the ladder line a few
> inches which lowered it from 25:1 to 18:1. I continued to trim a few
> more inches and noticed no change: changing the coax length had no effect.
>
> My question is: is it normal to expect an SWR to be that high on 80
> meters with this setup? Should I continue trimming the feed line to find
> a length that presents a more reasonable SWR or look for other issues
> with the antenna system? The ladder line does not touch the ground, it's
> not folded onto itself and it's not near any metal object.
>
> Tony
>
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