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Re: AW: Problems with Wimo 70cm Helix



Am Donnerstag, 8. August 2002 00:09 schrieb Paul Kupper:
> Hi Luc
>
> I use this antenna since longtime. Jus after reading your Mail, I, went to
> control my SWR and found that the SWR is rising from 1.2 to 7 measured with
> the build in meter of a Icom IC475.
>
> After connecting the Daiwa NS-4663PA SWR meter in the shack, the readings
> were as bad with the rig's SWR meter, but the Daiwa showed following
> readings:
>
> 430.0 1.1
> 431.0 1.2
> 432.0 1.25
> 433.0 1.28
> 434.0 1.2
> 435.0 1.1
> 436.0 1.2
> 437.0 1.3
> 438.0 1.45
> 439.0 1.45
> 440.0 1.3
>
> Not too bad I would say, even when we include the line damping of 3dB, the
> worst true SWR at the antenna is 2.

>
> That is the first part of my story. Once a while, I've measured even with
> my Daiwa, a real bad SWR. Together with other works at the antennas, I
> downed the 70 cm Crossyagi and found water in the matching housing of the
> feeder Loopdipol. After a short investigation I concluded, that the water
> is entering trough the fastening screw. Wimo made a hole in the tube of the
> Loop and water entered this hole went trough the tube into the housing. As
> I move my antennas in Azimuth and Elevation, the pick up of water is
> pronounced. In the housing is some sort of foam to hold the parts together.
> This foam acted as sponge for the water.

Hmm... are we speaking of the same antenna? Its the helix, not the cross yagi 
I have problems with. But what I now did, is tuning the koax so that at least 
the Transmitter does not drop its output power level. I will try to reach 
someone at Wimo, so that they can help me. But they are currently at 
vacation.

>
> I've let the Loop dry out really well. Then I sealed all the possible holes
> with silicone. I even tried to fill the inner parts of the tube with
> silicone. When i consider the moist weather in Switzerland I've succeeded
> with my efforts, when I may trust the Daiwa.
>

I do only have this MFJ SWR analizer, but even do not know if I can trust him 
at 70cm. Everything above 30MHz is newland for me ;)

> Hope this helps and hope that the weather in LX land is better than ours..

Hmm... sunny during the day, and rain during the night - not really bad I 
would say.

Thanks, Luc

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