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R: Cross Boom



Hi Ken,

I aegree with you.

Suppose to have an ideal AC sincronous motor in condition to be supplyed
with AC at a frequency of 144 MHz and its shaft to rotate 144 million turns
for every second.

Now ideally mount mechanically a dipole for 144 MHz  at the end of the shaft
and connect the dipole electrically in parallel to the motor and both to a
144 MHz generator.

The dipole starts to rotate sincronously with the shaft of the motor 144
million turns for every second radiating with circular polarization.

Now the dipole can be seen as a solid propeller intercepting every thing is
introduced in it and into the radiated circularly polarized field.

In real life the above example is replaced by two crossed dipoles feed
with the same amount of power but 90 degrees out of phase so that
the resultant vector rotates 2 x pi x f  for every second producing CP
like the above propeller in the ideal example.

I cannot realize any condition to prevent that the rotating field will not
see a conductive material introduced in whatever position X or + or
any other place along the direction of CP radiation.

If the field experimentation demostrates that using a metallic boom X
is best than + there are for sure good reasons because between two bad
conditions one is the best.

Only ghost are able to cross metal  and the electromagnetic waves are
reflected.

73" de i8CVS Domenico


----- Original Message -----
From: kgshutt <kgshutt@cox.net>
To: i8cvs <domenico.i8cvs@tin.it>; Roy Welch <rdwelch@swbell.net>; hasan
schiers <schiers@netins.net>
Cc: AMSAT-BB <amsat-bb@AMSAT.Org>
Sent: Friday, March 07, 2003 7:35 PM
Subject: Re: [amsat-bb] Cross Boom


> Hello Everybody,
>
> Dom,  your comment is spot on.  I don't see how anyone can expect to
insert
> a conductive boom into the rotating electro magnetic field and expect it
not
> to have any effect on the radiated wave, regardless of x or + element
> orientation.
>
> 73 de Ken - K5GUU
>
> ----- Original Message -----
> From: "i8cvs" <domenico.i8cvs@tin.it>
> To: "Roy Welch" <rdwelch@swbell.net>; "hasan schiers" <schiers@netins.net>
> Cc: "AMSAT-BB" <amsat-bb@AMSAT.Org>
> Sent: Friday, March 07, 2003 12:19 AM
> Subject: R: [amsat-bb] Cross Boom
>
>
> > Hi All,
> >
> > Mounting a crossed yagi for CP in X or + configuration over a metallic
> > boom produces the same effect over the circularity.
> >
> > When two crossed dipoles are feed by the same amount of power but their
> > components are 90 degrees out of phase the resultant vectors of voltage
> > and current rotates by  2 x 360 x f  every second producing CP
> >
> > The rotor of a AC sincronous motor rotates by the same phisical
principle
> > of magnetic rotating field discovered by Galileo Ferraris.
> >
> > Try now to put your finger in to the squarrel cage of the motor in both
> > X or + position and see what happen to it !
> >
> > Your FINGER or your METALLIC boom are the same thing.
> >
> > 73" de i8CVS Domenico
> >
> > ----- Original Message -----
> > From: Roy Welch <rdwelch@swbell.net>
> > To: hasan schiers <schiers@netins.net>
> > Cc: <amsat-bb@AMSAT.Org>
> > Sent: Thursday, March 06, 2003 9:54 PM
> > Subject: Re: [amsat-bb] Cross Boom
> >
> >
> > >
> > > hasan schiers wrote:
> > > > I participated in the original discussion of this many months ago
and
> I
> > > > think that the article referred to is being "under quoted". It is
NOT
> > just
> > > > mounting the antenna in the "X" configuration. That is NOT what the
> > article
> > > > says. It also REQUIRES careful placement of the driven element
> distance
> > to
> > > > the cross boom. Doing the "X" alignment is a "necessary" but not
> > > > "sufficient" condition to get the results that the article claimed.
> > > >
> > > > Two conditions have to be met:
> > > >
> > > > 1. X configuration
> > >
> > > The article does say this.  Mounting the elements in a + configuration
> can
> > > "see as much as a 10db loss in gain and the circularity would be nil."
> > >
> > > > 2. Distance from the feed to the cross boom
> > >
> > > The article does say to avoid mounting the boom 1/2 or 1 full
wavelength
> > > from the driven element.
> > >
> > > As a third requirement the article says to "saw off any excess cross
> > boom."
> > >
> > > I think I said all three of these in my original reply.
> > >
> > > > Many people have testified anecdotally to the metal cross boom
> working.
> > The
> > > > work of the WA5 in the article made careful measurements. I wouldn't
> > > > hesitate to try it, but follow the instructions in the article
> > assiduously.
> > > > The half-baked representations I have seen discussed lately are
> unlikely
> > to
> > > > produce the "tenths of dB" performance hit described by the original
> > author.
> > >
> > > The author's test was done about 1993. I have used this configuration
> > since
> > > 1981 or 1982.  It has worked fine here and I have had reports of it
> > working
> > > fine for others.
> > >
> > > > My comments aren't to discourage the metal cross boom approach. The
> > article
> > > > convinced me. However, let's not forget the second requirement.
> > >
> > > I didn't omit the second requirement.
> > >
> > > > ...hasan, N0AN
> > >
> > > ----
> > > Sent via amsat-bb@amsat.org. Opinions expressed are those of the
author.
> > > Not an AMSAT member? Join now to support the amateur satellite
program!
> > > To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
> >
> >
> > ----
> > Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
> > Not an AMSAT member? Join now to support the amateur satellite program!
> > To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
> ----
> Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
> Not an AMSAT member? Join now to support the amateur satellite program!
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