[Amps] corona on a quad

Fri Jul 13 01:22:34 PDT 2012

Hi Charles,

Yes, we have suffered problems in a quad, but I guess that it can not be called "Corona", just power issue.

I have designed a 4 elements quad for 27 MHz for a friend of mine who does "Key Down" competitions.
He is running +40 Kw from a 3CX20.000 and the antenna system needs special care to handle that power and trying to convert it in RF, not in flames. And it is not a easy task. In the Handbook is not that information.

After some test and re-design, finally this quad is performing very good, in fact, it is the champion (over yagis almost twice long).

The power issue is always happening in the quad´s corners, on driver and directors, burned!! 
Now is not burnng any more, after use Teflon corners over ceramic insulators (yes, with +40 Kw fibreglass is not isolating anymore).

Coax cable is Heliax 1 5/8, but needs special care as well. since it is not rated to that power.

You can see the setup in You Tube:  http://youtu.be/R8T_KingCSs

73, Máximo - EA1DDO

> From: k4vud at hotmail.com
> To: apolloeme at live.com; adrianjamesflynn at gmail.com
> Date: Fri, 13 Jul 2012 04:55:44 +0000
> CC: amps at contesting.com
> Subject: [Amps] corona on a quad
> 
> 
> My understanding is that corona discharge would be most off a single isolated point, like the tip of a vertical ant or the ends of a yagi elements.
> 
>  
> 
> I doubt the corners of a quad would act like that as much if at all.  Likely someone has some hard test data on this.
> 
>  
> 
> I also wonder if a corona charge is enlarged by the spread out and larger "area" of a quad loop.  That is, is there a maximum charge that can be induced on any one isolated object or is the charge larger solely because the structure is larger?
> 
> Inquiring minds want to know.
> 
> Charles Harpole
> k4vud at hotmail.com
> 
> 
> ----------------------------------------
> > From: apolloeme at live.com
> > To: adrianjamesflynn at gmail.com
> > Date: Thu, 12 Jul 2012 21:11:10 -0700
> > CC: amps at contesting.com
> > Subject: Re: [Amps] Antennae (?)
> >
> >
> > Here is the story:
> > http://lists.contesting.com/_towertalk/2002-11/msg00393.html
> >
> > Best Regards,
> > Pat Barthelow AA6EG
> > From: adrianjamesflynn at gmail.com
> > Date: Fri, 13 Jul 2012 00:01:14 -0400
> > Subject: Re: [Amps] Antennae (?)
> > To: apolloeme at live.com
> > CC: alex.k2bb at gmail.com; k8ri at rogerhalstead.com; amps at contesting.com
> >
> > I seem to remember that there was 4 times as much Corona Discharge on a Cubical Quad Antenna due to the 4 right angle turns.Adrian KF7DYU
> >
> >
> >
> > On Thu, Jul 12, 2012 at 11:37 PM, Patrick Barthelow <apolloeme at live.com> wrote:
> >
> >
> >
> >
> > I remember Corona Discharge, aggravated by thin air of High altitude, and QRO at HCJB in Quito Ecuador, literally burned, melted the antenna element tips, and led to the adoption of the Cubical Quad Antenna.
> >
> >
> >
> > Best Regards,
> >
> > Pat Barthelow, AA6EG
> >
> > > From: alex.k2bb at gmail.com
> >
> > > Date: Thu, 12 Jul 2012 23:28:58 -0400
> >
> > > To: k8ri at rogerhalstead.com
> >
> > > CC: amps at contesting.com
> >
> > > Subject: Re: [Amps] Antennae (?)
> >
> > >
> >
> > > Speaking of corona discharge...
> >
> > > I remember reading an article (back in radio technical university) regarding antennas detuning due to corona at the end of elements.
> >
> > > Soviet Union, military, kilowatts :)
> >
> > >
> >
> > > ... iPhone
> >
> > >
> >
> > > On Jul 12, 2012, at 19:23, "Roger (K8RI)" <k8ri at rogerhalstead.com> wrote:
> >
> > >
> >
> > > > On 7/12/2012 8:00 PM, Jerry Kaidor wrote:
> >
> > > >>> The most effective ball on the top of the vertical is the copper float
> >
> > > >>> from
> >
> > > >>> a toilet. Especially appropriate when using 8 sweep tubes in parallel.
> >
> > > >>
> >
> > > >> *** Or six 3-500Zs?
> >
> > > >
> >
> > > > Sounds kinda fragile. I'd go for the 3CW20,000A7 myself.
> >
> > > > And there is a real reason for the ball on top. The prevent, or minimize
> >
> > > > corona discharge at those higher powers, even the legal limit on a
> >
> > > > mobile whip.
> >
> > > >
> >
> > > > Running the legal limit on multi band, stub tuned verticals can get
> >
> > > > colorful. I burned the plastic caps off the ends on one. All they
> >
> > > > needed was a 1/2" or 3/4" aluminum ball in place of the cap.
> >
> > > >
> >
> > > > BTW what material would make a good core for the matching transformer to
> >
> > > > run from 160 through six?
> >
> > > >
> >
> > > > 73
> >
> > > >
> >
> > > > Roger (K8RI)
> >
> > > >
> >
> > > >
> >
> > > >>
> >
> > > >> - Jerry Kaidor
> >
> > > >>
> >
> > > >>
> >
> > > >>>
> >
> > > >>> 73, Colin K7FM
> >
> > > >>>
> >
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> >
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> >
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> >
> > > >>
> >
> > > >>
> >
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> >
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> >
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> >
> > > >
> >
> > > >
> >
> > > >
> >
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> >
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