1. Home
  2. ⏚ Electrical Engineering
  3. "Shorted Turn" Phenomena ?

"Shorted Turn" Phenomena ?

Hello:

Have a receiving only simple long wire antenna strung out my window for my short-wave radio. Will be stringing up a new one, with different supports, etc.

Got to wondering about this:

If the antenna wire is fastened using, e.g., metal supports, metal pulleys or rings, that completely go 360 deg. around the wire (but are spaced from it essentially by the wire insulation thickness, is there any effect from the "shorted-turn" phenomena ?

Or, does the shorted turn problem only arise for a varying magnetic flux field, and would not be applicable in this case ?

(Again, this is a receiving only application, but I guess you could argue that there is an actual E and H field in this receiving antenna)

Thanks, Bob

Reply to
Robert11
Loading thread data ...

yes a current is only induced in the shorted turn when there is a varying flux. it is after all the secondary of a theoretical transformer with the antenna being the primary. the amoung of flux in your receiving antenna is so small that the loss is buried way below the thermal noise. if you were using a transmitter you would not want any shorted turn around the antenna.

-bob

Reply to
bob mcree

in electronics everything affects everything the question is how much? in this case not much.

first, its not a shorted turn if the wire is insulated... it just a turn or loop. it adds inductance, in this case making the antenna seem just a bit longer electrically.

second, the longwire should be fastened to an insulator (like a ceramic egg) not a pulley or metal support.

safety note: some form of lightning arrester mounted outside the house and well grounded is recommended.

Reply to
TimPerry

Practically, if the distance between the conductors is small compared to the wavelength of interest, the parallel conductors will act as, well, parallel conductors. If the spacing between the conductors is greater than, say, 1/10 wavelength then your "shorted turn" will start to have a noticeable effect.

Reply to
BFoelsch

On Sun, 22 Jan 2006 13:22:52 -0500, "Robert11" Gave us:

A radio wave IS a variable flux field.

A radio antenna IS a transformer primary.

Reply to
Roy L. Fuchs

On Sun, 22 Jan 2006 15:22:36 -0500, "BFoelsch" Gave us:

This is why and how a beam antenna works to make reception directional.

Learn to refrain from top posting in Usenet.

Reply to
Roy L. Fuchs

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.