Re: New antenna, new loggings


Has anyone seen a comparison between ferrite rod antenna and air core loops which gives the sizes which are about equal in signal strength? - FARMERIK

--- In ultralightdx@..., D1028Gary@... wrote:

Hi Tim,

Thanks for the reference to the PVC Loop article, also posted at
_ ( .
Dimensions and spacing for loops from 18" up to 9' (side sizes) are given in a
table, along with weights and cost. All of these loops have actually been
constructed, and tested.

In constructing any AM-DXing loop, it's important to remember that size
does matter. If you want better DX performance, build one of the bigger loops

73, Gary

In a message dated 3/21/2010 8:55:21 A.M. Pacific Daylight Time,
timchandler2001@... writes:

Don't forget Gary's article in this group's Files section, on PVC loop
_http://tinyurl.http://tiny_ (

This calculator may also prove useful although it does not apparently take
into account "distributed capacitance" when the windings are closer
together, but with .5 inch spacing you are probably not affected that much:

Tim C.

--- In _ultralightdx@ultralightdxult_ (mailto:ultralightdx@...)
, "farmerik" <farmerik@...> wrote:

Still thinking! The circumference of a 30 inch loop is quite similar to
the perimeter of a 2 foot square, does changing the shape make much

If my memory of High school geometry is correct, a round loop form could
be made from a strip of Masonite 8 feet long which would be close to 30
inches. Of course it would need 'spokes' or spreaders to KEEP it round. A 2
foot square loop should be easier to make, if it is just about as good.

It's Electronics 101, but I still don't have a clear understanding of
the difference of Impedance and Inductance. Do you happen to know of an
Impedance calculator for loops this big? What I am wondering is there
transmission line I could use to mount the loops in the attic, pointing in a few
different directions, and choose the one I want by connecting it to the radio
separately. I just have no idea if that is possible or impossible. - FARMERIK

--- In _ultralightdx@ultralightdxult_
(mailto:ultralightdx@...) , "farmerik" <farmerik@> wrote:

OK, now I am getting somewhere, at least in my mind. A 30 inch
diameter, with 1/2 inch spacing [I think I need that to prevent capacitance
between windings?] gets me to 258 uH with 15 turns and the wire I chose.
Now I need to think of a coil form that big. Sonotube? Made up from
long strips of Masonite? If I can't come up with a round form, would you
happen to know how to calculate for a square one?


--- In _ultralightdx@ultralightdxult_
(mailto:ultralightdx@...) , "jim_kr1s" <jkearman@> wrote:

--- In _ultralightdx@ultralightdxult_
(mailto:ultralightdx@...) , "farmerik" <farmerik@> wrote:
> Thanks for the additional explanation, it is clearer to me now.
> > > What sort of loop would I wind if I wanted to connect it
directly, and
not use a torrid [or other] transformer?

In that case, the inductance of the antenna has to resonate directly
with the varactor diode on the chip. Taking into account stray
capacitance in the connecting wires and the loop itself, design for
about 240 uH. This calculator should get you close.
> > <_http://electronbunkhttp://electronbhttp://electronbhttp://el_
( > It
gives more accurate results for large air-loop coils than the one
"Professor Coyle."
> > 73,

Jim, KR1S
_http://kr1s.http://kr1s._ (
<_http://kr1s.http://kr1s._ ( >
> >

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