David Gilbert wrote:
>
>Ian White GM3SEK wrote:
>> With one more capacitor, it probably wouldn't be difficult to make
>>the same network match on 40m as well, without switching. As a
>>starting-point, try doubling all the L and C values in this 40/20m
>>design:
>>
>> http://www.arrl.org/qst/2005/09/richardson.pdf
>>
>>
>
>That's a very cool idea, but I think he'd need a 65 foot vertical or so
>to make it work with double those values. The author himself suggests
>that it's pretty hard to come up with values that work at all if the
>antenna isn't on the long side for the lowest band, but I guess it
>might be feasible to accomplish that with top loading wires.
>
I was assuming he might follow your suggestion to do that.
On 80m it would be a top-loaded T, to be fed at low impedance against a
good ground. On 40m it would be what G3VA describes as an "inverted
ground-plane" with its current point and two radials at 32ft, and
high-impedance feed (though probably only several hundred ohms).
All three elements of the two-band matching network would need to be
adjusted, so the doubled values from the 40/20m reference would be a
good place to start from.
--
73 from Ian GM3SEK
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