[Lf] [Fwd: LF: Loop Amperage ~~~~~~]

[Andre Kesteloot]

"Ashlock,William" wrote:

> Hi 136-ers,
>
> >Everyone in EU is screaming to the ARRL and the FCC to permit you folks to
> use 1W erp. I have
> >calculated the amperage to your loop to achieve this 1W erp and the figures
> >frighten me. You said your loop was suspended amongst trees and I would say
> >with this high amperage I will be able to see your smoke signals  before I
> >hear you signal. Let us have your calculated antenna amperage to see if my
> >figures compare?
>
> Well let's see...... I presently have ~1w input into the loop and the
> current is ~1.5A. If I go to an input of 100w the current will be sq rt 100
> x 1.5 = 15A. From a 'wasted power' standpoint the loop is a big 100w wire
> wound resistor covering 50'x 50' = 2500 sq ft. Don't see a problem here.
> Could even be a good perch for the birds in the winter?
>
> The present ERP with a 1w input is about 1mw (according to the radiation
> resistance formula that I like the best). I would therefore have to run 1KW
> to produce a 1w ERP and a current of sq rt 1000 = 31.6 X 1.5A = 47.4A .
> Well, yes, that frightens me too.  BUT..... If I utilize my 450ft wide back
> woods the situation improves. The radiation resistance goes up to the square
> of the loop area gain to 81X. The ERP for 1w of input is now 81mw. To reach
> a 1w ERP the current multiplier will need to be only 1/.081 = 12.3 X 1.5 =
> 18.5A. The actual input power for this loop will depend on the conductor
> used. I calculate the total Rac (including soil loss) would have to be 2.92
> ohms minimum for an input power of 1KW, and 18.5A, and this would be
> equivalent to a 2.92/9 = .325 ohm Rac with a 50'x50' loop. (So my 4 x #12
> Litz conductor or a 1/2" Cu pipe would be required...... not cheep!) So, it
> appears that all I am doing, when power limited like this, is to spread out
> the 1KW power loss over a larger portion of the back woods! But at least
> it's doable.
>
> Comments, please.
>
> Bill A
>
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