[TowerTalk] Voltage at ends of yogi parasitic elements?

[Jeff AC0C]

There is literally no benefit to do the switching at the ends.  But there 
are a lot of reliability issues so why take the hard road when there is no 
performance increment - and at the same time the headaches with that 
solution are going to be ongoing.  The HV switch is going to have mass and 
is going to be an ice accumulation point if you have weather.  I would bet 
you good money that if you go with an end-switched solution in a couple of 
years you are going to be in the "what was I thinking?" camp...

My antennas were run in KW level RTTY and I never had a relay issue with a 
the phasing control stuff done in the center - the voltage there is low and 
the currents high but that's a much easier fix than trying to put a HV 
switch out on the ends of an antenna.

Good luck!

73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie

-----Original Message----- 
From: Kelly Taylor
Sent: Tuesday, October 18, 2016 1:24 AM
To: john at kk9a.com
Cc: towertalk at contesting.com
Subject: Re: [TowerTalk] Voltage at ends of yogi parasitic elements?

I should add that it doesn’t change needing a robust switching mechanism to 
handle the voltage, but at least resolves the issue of conductors to switch 
a relay being in the vicinity of the antenna.

73, kelly, ve4xt

> On Oct 17, 2016, at 12:10 PM, Kelly Taylor <ve4xt at mymts.net> wrote:
>
> 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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