[TowerTalk] MACAntenna

Wed May 20 08:50:21 PDT 2009

By putting two relays in series, don't you create a situation where there would be a voltage breakdown nearest the RF, and then a second voltage breakdown/arc at the second relay?

I guess I'm not seeing how two in series increases voltage handling, as to me it would seem that the relay with RF on one side is still the same size and as prone to arcing at a given voltage.

However, isn't voltage at a minimum at the end of a full-sized 1/4 wave radiator (half of a dipole) and current at a maximum?

Art

--- On Wed, 5/20/09, Pete Smith <n4zr at contesting.com> wrote:

From: Pete Smith <n4zr at contesting.com>
Subject: Re: [TowerTalk] MACAntenna
To: "bill rubin" <brubin2010 at gmail.com>
Cc: towertalk at contesting.com
Date: Wednesday, May 20, 2009, 10:19 AM

They say that they modified the design after the QST article to put 
two relays in series, thereby raising the voltage handling 
capacity.  They now claim 1500 watts RTTY key down on all bands.

It's not really loops, but rather ladder line segments where one line 
carries the control pulses and the other serves as the antenna.  The 
DC is separated out at the magic box in the center.  To their credit, 
they are very open about schematics and the like.

73, Pete N4ZR

  At 10:44 AM 5/20/2009, you wrote:
>The antenna I saw at dayton looks like ladder line loops for each
>element with relays along each element to close the loops for each
>band selected. This is done with a relay control box. Seems to be a
>good idea but there is always compromise.  Relay failures and parts
>with each board, control box and power output limitations.
>
>On 5/20/09, Arthur Trampler <atrampler at att.net> wrote:
> > duh me...
> >
> > --- On Wed, 5/20/09, Dubovsky, George
<George.Dubovsky at andrew.com> wrote:
> >
> > From: Dubovsky, George <George.Dubovsky at andrew.com>
> > Subject: RE: [TowerTalk] MACAntenna
> > To: "Arthur Trampler" <atrampler at att.net>, "Pete
Smith"
> > <n4zr at contesting.com>, towertalk at contesting.com, "Brian
Gieryk"
> > <ke6iyc at mac.com>
> > Date: Wednesday, May 20, 2009, 8:47 AM
> >
> > Probably a typo in your email, Art, but I presume you meant feet, 
> not inches
> > ;-)
> >
> > 73,
> >
> > geo - n4ua
> >
> > -----Original Message-----
> > From: towertalk-bounces at contesting.com
> > [mailto:towertalk-bounces at contesting.com] On Behalf Of Arthur
Trampler
> > Sent: Wednesday, May 20, 2009 9:43 AM
> > To: Pete Smith; towertalk at contesting.com; Brian Gieryk
> > Subject: Re: [TowerTalk] MACAntenna
> >
> > That's easy Brian.
> >
> > If the boom to mast is at the center of the boom, then one has
10.25" on
> > that side of the right triangle; 17.333 inches on the other side of
the
> > right
> > triange; and 20.13" turning radius.
> >
> > Art
> >
> > --- On Wed, 5/20/09, Brian Gieryk <ke6iyc at mac.com> wrote:
> >
> > From: Brian Gieryk <ke6iyc at mac.com>
> > Subject: Re: [TowerTalk] MACAntenna
> > To: "Pete Smith" <n4zr at contesting.com>,
> > towertalk at contesting.com
> > Date: Wednesday, May 20, 2009, 8:11 AM
> >
> > Perhaps a typo on their site, or an oversight, but how cane one have
a
> > turning radius (20 ft, 1 in.) LESS than the boom length (20 ft, 6
in.)?
> >
> > Brian
> > KE6IYC
> >
> > On May 20, 2009, at 4:41 AM, Pete Smith wrote:
> >
> >> This year at Dayton, there was a vendor (www.mactenna.net)
> >> demonstrating something called the SB20-10 Simple Beam.  The
basic
> >> principle was described in a QST article in September 2008,
applied
> >> to a wire dipole, and I remember at the time thinking
"You've
> > gotta
> >> be kidding."  Now, however, the inventor has incorporated
the idea
> > in
> >> a 3-element yagi, and unless he has cooked the books, the EZNEC
> >> models look pretty good.  On all 5 bands between 20 and 10
meters,
> >> the models show very similar pattern and gain numbers and
excellent
> >> SWR bandwidth, all without motors, moving parts (other than relay
> >> contacts), and at a decently low price.
> >>
> >> The manufacturer's web site is very forthcoming with
information,
> >> which tends to inspire confidence.  Still, I'd appreciate 
hearing
> >> what the gurus among us think.
> >>
> >> 73, Pete N4ZR
> >> New Articles Daily - the Contesting Compendium at
> > http://wiki.contesting.com
> >> The World Contest Station Database, updated daily at
> > www.conteststations.com
> >> The Reverse Beacon Network at http://reversebeacon.net
> >>
> >>
> >> _______________________________________________
> >>
> >>
> >>
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>
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