Tim
Thanks for bringing up the use of the XG3. Recently acquired one and was
wondering how I could do some near field measurements.
Any other particulars I should be aware of regarding pattern testing with this
unit?
Regards,
Mark, K1RX
> On Oct 3, 2019, at 10:33 AM, Tim Duffy <k3lr@k3lr.com> wrote:
>
> Hi John,
>
> It's easy to see pattern issues with using a Elecraft XG3 generator
> https://www.dxengineering.com/parts/ect-xg3
> to excite the antenna under test. Then use another antenna (almost any
> horizontal antenna will work) 1000 feet away for the RX and then turn the
> XG3 antenna. The pattern distortion was identified with the NEC model and
> confirmed with the XG3 test.
> If the VSWR varies as you rotate the antenna, that is a good indicator of
> probable Preform interaction.
>
> 73
> Tim K3LR
>
> -----Original Message-----
> From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of
> john@kk9a.com
> Sent: Thursday, October 3, 2019 9:37 AM
> To: towertalk@contesting.com
> Subject: Re: [TowerTalk] EHS leads for Phillystran
>
> I am not sure how you know that the pattern was distorted but I think
> this is a good practice Tim. My top homebrew 15m beam has a higher SWR
> than the lower two - 1.4:1 vs 1.1:1. Just below the top antenna is a
> Rohn 65 massive star guy bracket with six Phillystran Big Grips
> directly attached. Perhaps insulating the guy would help.
>
> John KK9A
>
>
> Tim Duffy k3lr at k3lr.com
>
> I had a problem with just Preforms attaching to the tower legs connection -
> which caused distortion in the pattern of close mounted Yagi's. That is,
> Yagi's that were mounted only a few feet above a guy connection point. The
> VSWR of the affected Yagi would change with rotation and the effect of three
> Preforms connected to the tower was confirmed with modeling. The solution
> was to use a bent pin shackle and an insulator right at the tower
> connection. You can see it in this view of the middle four element 40 meter
> OWA Yagi stack at K3LR:
> http://www.k3lr.com/2016/ring.jpg
>
> Using insulators at the tower connection completely solved the pattern
> distortion and VSWR changes with rotation.
>
> 73
> Tim K3LR
>
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