[Lowfer] loop Rr

[Jay Rusgrove]

Dave

That agrees with my understanding and earlier discussion with Paul.

One question. If one were to construct a two turn loop, how would the spacing
between the turns affect the gain?

Jay Rusgrove, W1VD

Telegrapher9@aol.com wrote:

> Paul C,
>
> here's some info on single-turn, electrically short loops (<1/10 wavelength
> circumference). The radiation resistance for a loop in free space is found by
> this formula: Rr = (4 X 10E-6)(F^4)(A^2), F in MHz, area in square meters.
> For a loop over perfect GND the Rr doubles. Example: A square loop 1 meter on
> a side at 1 MHz has a radiation resistance of 4 micro-ohms. Place it over GND
> and it is 8 micro-ohms.
>
> So, for your question about reducing the area of a loop by a factor of 4. The
> reduction in radiation resistance is A^2 = (1/4)^2 = 1/16. Given equal
> current when the loop area is reduced by a factor of 4 the power radiated
> drops by a factor of 16. This is 12 dB. Another way to look at it is that the
> Electric Field (in the far field) is proportional to the area of the loop. In
> your case the area was reduced by a factor of 4 so the E-field is reduced by
> a factor of 4. This is 20LOG4 = 12 dB.
>
> A lowfer loop that is 50 feet on a side, and is placed over a ground plane,
> has a radiation resistance of 2.2 u ohms at 185 kHz.
>
>    Dave WX7G
>
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