[Antennaware] Trap design

[n7wbjohn .]

I found the article here, http://www.iz5cml.it/forum/trap.pdf

if it doesn't work, I got a copy I can send  you.

73 de John N7WB

On Thu, May 30, 2019 at 8:31 AM n7wbjohn . <n7wbjohn at gmail.com> wrote:

> I found the article here, http://www.iz5cml.it/forum/trap.pdf
>
> if it doesn't work, I got a copy I can send  you.
>
> 73 de John N7WB
>
> On Thu, May 30, 2019 at 4:19 AM Don Webster via Antennaware <
> antennaware at contesting.com> wrote:
>
>>
>> David,
>>
>> Yardley Beers, W0JF wrote an article in the August 1987 issue of Ham
>> Radio about a "new approach to designing trap antennas". It dealt with the
>> design frequency of the traps being about  midway between the two bands.
>>
>> I built a 3 element yagi for 12 and 17 meters using his approach and it
>> works very well. You have to adjust the length of the elements to
>> compensate for effects of the traps.
>>
>> Don
>> K9MUF
>>
>> -----Original Message-----
>> From: David Gould <dave at g3ueg.co.uk>
>> To: antennaware <antennaware at contesting.com>
>> Sent: Wed, 29 May 2019 9:35
>> Subject: [Antennaware] Trap design
>>
>> Yes, I know traps are a compromise and some people don't like them, but
>> my feeling is that it is often the design and construction that are the
>> main problems.
>>
>> I plan to build one for 15m (for a 15m/20m elevated vertical) using a
>> heavy duty doorknob capacitor and small diameter copper tube for the
>> inductor, which should optimise the construction issue.
>>
>> Question 1)  What should the design frequency be?  I vaguely remember
>> reading somewhere that the design freq should **NOT** be the middle of
>> the higher freq band (eg 21.225 in this case) but on some other freq
>> somewhere between 21MHz and 14MHz.  I have done several Google searches
>> and cannot find any references, in particular I would like to know the
>> reasoning behind doing this, and  how using such a mid-freq affects the
>> length of the two parts of the antenna?
>>
>> Question 2)  Are there likely to be any issues measuring the resonant
>> freq of a trap using a RigExpert AA-54 analyser, or is there a better
>> way?    Again I vaguely remember reading that a dip oscillator is the
>> best way, but I don't have access to one.
>>
>> 73,
>>
>> Dave, G3UEG / K1MDX
>>
>>
>>
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>