[TowerTalk] Voltage at ends of yogi parasitic elements?

[Kelly Taylor]

John’s old idea seems like the perfect application of something in QST a while back: a pneumatic relay.

A puff of air up a non-conducting piece of tubing would trigger the switch: I can’t recall if it was latching or not.

73, kelly, ve4xt



> On Oct 17, 2016, at 11:44 AM, john at kk9a.com wrote:
> 
> That is a good question.  Years ago I thought of building an 80m vertical
> with a relay on top to make it a 160m inverted L at my P40A home but I did
> not know if even a vacuum relay would hold up and I knew that there would
> be RF issues with the control wires running down the vertical. I had never
> seen it done and did not want something likely to fail. If you are just
> changing band segments most manufactures are using switchable loading
> coils at the feed point.
> 
> GL
> John KK9A
> 
> 
> To:	towertalk at contesting.com
> Subject:	[TowerTalk] Voltage at ends of yogi parasitic elements?
> From:	Rob Katz <rob.katz at thelegacycenter.com>
> Date:	Sun, 16 Oct 2016 23:09:11 -0400
> 
> 
> I’m playing with some wire yagis, and I’d like to put relays at the ends
> of the
> parasitic wires to switch the director to a reflector (and vice versa). 
> If I’m
> driving the antennas with a full 1.5 KW, what would be the maximum voltage
> that
> I can expect at the ends of the PARASITIC elements?  Even a rough estimate
> would be useful, I just need to get a sense of what kind of a relay I would
> need to use.
> 
> 73,
>   Rob  K4OV
> 
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