Even better solution - put variable capacitor at the base of antenna to
shorten it electrically for 30m band, and add a relay to shorten
capacitor when antenna is used on 40m band! After you find the right
value for capacitor, you may replace variable one with block one (it can
even be made of proper length of coax cable).
73 Mirko, S57AD
n8de@thepoint.net pravi:
> Forget the trap idea.
>
> Put a 1/4-wavelength of 75-ohm coax between your 50-ohm feedline and
> the feedpoint. The antenna will work on both bands if you use a tuner
> at the rig.
>
> Don't ask me why, but I've worked almost 200 countries on 30m with a
> good signal using the above antenna.
> Don
> N8DE
>
>
> Quoting Ron W8RJL <youngron@verizon.net>:
>
>
>> Rick, you are correct, I was in a rush and had my thinking backwards.
>>
>>> From the feed point to the trap should be 1/4 wave for 30 meter ~23 feet
>>>
>> depending on conductor diameter.
>> The trap should be resonant at about 10 MHZ. It is better to error on the
>> low side.
>> On 40 meters the 23 foot section plus the inductance of the trap plus what
>> is above the trap resonates on 40 meter.
>> Feed impedance depends on many factors including the numbers of radials.
>> 73, Ron W8RJL
>>
>>
>> ----- Original Message -----
>> From: "Richard (Rick) Karlquist" <richard@karlquist.com>
>> To: "Tower and HF antenna construction topics." <towertalk@contesting.com>
>> Sent: Monday, April 19, 2010 1:52 AM
>> Subject: Re: [TowerTalk] 1/4 wave vertical question
>>
>>
>>
>>> Ron W8RJL wrote:
>>>
>>>>> From the bottom of the vertical to the bottom of the 40 meter trap will
>>>>> be
>>>>>
>>>> about 32 feet depending on the diameter of the vertical. The larger the
>>>>
>>> The trap should be a 30 meter trap located about 24 feet up.
>>>
>>> Rick N6RK
>>> _______________________________________________
>>>
>>>
>>>
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>>>
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>>
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>
>
>
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