I didn't see that reference. It is a good one. Exactly the information
I was trying to convey, with more detail.
When you have something as complicated as what N6RK was building, it may
justify trying to do switching like this, but as you can see from the
reference you gave, it is not easy. When you try to apply this to a
dual band dipole, I don't think it is worth the effort. Why not just do
something simple like adding a trap. OK, so a trap narrows the
bandwidth, but this shouldn't be a problem on 30 and 40 meters.
Jerry, K4SAV
VR2BrettGraham wrote:
>K4SAV commented on switching in & out some top loading on an
>HF2V or switching the linear loading in & out of a shorty-forty
>element with a relay to work 30:
>
>
>
>>That might work.
>>
>>The other idea about RF detection, used to trigger a latching relay has
>>some merit if the relay is used at the right location.
>>
>>If you use the relay to disconnect the end segment of an antenna, on one
>>band it will end up at a high impedance point of the antenna. You will
>>have thousands of volts of RF across the relay contacts. It will
>>require a huge relay with very good isolation. Not something you would
>>like to hang in the middle of an antenna wire. (Assuming you could even
>>find a latching relay like this.)
>>
>>If you use the relay to short out a coil or loading stub, at a point
>>that is not at the end of the antenna, you might be able to make it
>>work, although, this sure seems like a hard way to make a dual band dipole.
>>
>>
>
>Interesting - what I recall from before was a thread on switching a top
>hat in & out - which understandably has its challenges - did get
>mention from N6RK of band switching his vertical:
>
>http://lists.contesting.com/archives//html/Towertalk/2001-07/msg00292.html
>
>I would expect rigging some sort of series trap to get around the linear
>loading in order to make a 40m dipole work on 30 to be more
>troublesome than shorting the linear loading out - especially if the dipole
>without the loading isn't close enough by itself.
>
>Even if the dipole were made of wire, two bands from one antenna on a
>single untuned & reasonably flat feeder into a self-resonant dipole would
>need to pretty difficult if, for example, space is an issue & performance is
>desired (at least from my experience with long doublets in the past).
>
>73, VR2BrettGraham
>
>_______________________________________________
>
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>Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
>questions and ask for Sherman, W2FLA.
>
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>
>
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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