MRA Antenna
 

Has anyone taken a look at this antenna? I heard the designer on 75 last
night working a CT0, he says his is 18 foot in diameter. His buddy was
running a 6 foot version and 200 watts and worked the DX as well. He claims
that it is a "minium reactance antenna" thus the name.

http://www.smeter.net/wb4ene/mra-antenna.php

I am only guessing, but there isn't a backpack/portable version of that
antenna available, is there?
And, I just looked at my car, where would I mount that?
Or, is that the kids playhouse, and it obscures the view of the antenna?
grin

Regards,
John

--
I would like to point out, I do appreciate the "Been there--done that!"
posts. Indeed, now your observations, comments and discourse should be
filled with wisdom--I am listening!!!
"Fred W4JLE" wrote in message
...
Has anyone taken a look at this antenna? I heard the designer on 75 last
night working a CT0, he says his is 18 foot in diameter. His buddy was
running a 6 foot version and 200 watts and worked the DX as well. He
claims
that it is a "minium reactance antenna" thus the name.

http://www.smeter.net/wb4ene/mra-antenna.php

Fred,
I seem to recall a simular antenna made by 'MFJ' or 'Hygain',
maybe? No idea how 'well' it worked.
'Doc

On Mon, 11 Apr 2005 21:02:01 -0400, "Fred W4JLE"
wrote:
He claims that it is a "minium reactance antenna" thus the name.
http://www.smeter.net/wb4ene/mra-antenna.php

Hi Fred,

A simple glance at the SWR chart reveals it is in fact a Maximally
Reactive Antenna - at least the initials are preserved.

73's
Richard Clark, KB7QHC

On Wed, 13 Apr 2005 13:35:42 GMT, 'Doc wrote:

Fred,
I seem to recall a simular antenna made by 'MFJ' or 'Hygain',
maybe? No idea how 'well' it worked.
'Doc

I'm having a hard time seeing the "minimal reactance" part of this
design. Looking at the plot of S11 it looks pretty much like any
other antenna with a single resonance.

It has "minimal" reactance at resonance and is highly reactive
elsewhere.

"Richard Clark" wrote in message
...
On Mon, 11 Apr 2005 21:02:01 -0400, "Fred W4JLE"
wrote:
He claims that it is a "minium reactance antenna" thus the name.
http://www.smeter.net/wb4ene/mra-antenna.php

Hi Fred,

A simple glance at the SWR chart reveals it is in fact a Maximally
Reactive Antenna - at least the initials are preserved.

73's
Richard Clark, KB7QHC

A conventional monopole, resonant at about 7 MHz, would completely circle
the Smith Chart for almost two complete revolutions from 1.8 to 30 MHz. I
suppose that is what is meant by "MRA". Apart from that it would be
interesting to know the precise structure details to attempt a NEC model.
It looks suspiciously like the CFA class of antennas.

Frank

Thanks for the reply Richard...

He and his cohart were in the DX window on 75 working a CT0, his buddy had a
6 foot version and both got good reports. The large (18 foot) was running
1500 watts. The smaller one was running 200 watts. As to band conditions, I
later worked an EA with a 5/9+ running 100 watts to a G5RV. I was hoping
one of the EZNEC Gurus would take a look and give us the skinny.


When I looked at the photo, I had deja vu of a CFA.




"Richard Clark" wrote in message
...
On Mon, 11 Apr 2005 21:02:01 -0400, "Fred W4JLE"
wrote:
He claims that it is a "minium reactance antenna" thus the name.
http://www.smeter.net/wb4ene/mra-antenna.php

Hi Fred,

A simple glance at the SWR chart reveals it is in fact a Maximally
Reactive Antenna - at least the initials are preserved.

73's
Richard Clark, KB7QHC

I could probably park my truck out in front of his
house, and do the same thing with my mobile
antenna...My mobile often outperforms my 35-40
ft high dipoles to DX on the lower bands....
To me, it seems to be a very ugly version of a
short top loaded monopole. Nothing more, or
less really....1500 w? He *should* be working dx,
or something is kuput....I work DX mobile with 100w
no problemo. That the "MRA junior" is only 200w doesn't
mean too much to me. He's still twice what I run...
If I were to run a MRA, I would at least install a hot tub
or spa in the middle...Add cup holders...Seats around
the outer section...etc...Shrubbery around the outside to
keep the old lady happy....Hell, with a used JATO engine,
you could probably take a trip in that thing...
I bet it would show on radar, until you ran into the underbelly
of that passing 737-700 that happened to be flying over the
house at the same time...:( Ouch....Can we spell headache?
MK

I'm having a hard time seeing the "minimal reactance" part of this
design. Looking at the plot of S11 it looks pretty much like any
other antenna with a single resonance.

It has "minimal" reactance at resonance and is highly reactive
elsewhere.

It looks to me as if this is a member of the "Super C" antenna...
short, relatively low radiation resistance, and a lot of top-loading
capacitance.

There's an article or two in one of the early ARRL Antenna Compendium
collections (#1 or #2) which analyzes the "Super C" approach, compared
to a short vertical with a more traditional capacity hat made of
straight wires. The analysis seemed to add up to "Probably not worth
the trouble and money", as a similar efficiency can be achieved more
easily and less expensively with the traditional approach. There's a
*lot* of metal in the MRA, and at the price of aluminum this month I
doubt it's a project I'd start.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Dave Platt wrote:

I'm having a hard time seeing the "minimal reactance" part of this
design. Looking at the plot of S11 it looks pretty much like any
other antenna with a single resonance.

It has "minimal" reactance at resonance and is highly reactive
elsewhere.


It looks to me as if this is a member of the "Super C" antenna...
short, relatively low radiation resistance, and a lot of top-loading
capacitance.

There's an article or two in one of the early ARRL Antenna Compendium
collections (#1 or #2) which analyzes the "Super C" approach, compared
to a short vertical with a more traditional capacity hat made of
straight wires. The analysis seemed to add up to "Probably not worth
the trouble and money", as a similar efficiency can be achieved more
easily and less expensively with the traditional approach. There's a
*lot* of metal in the MRA, and at the price of aluminum this month I
doubt it's a project I'd start.

Yea, but put in on a rotator and add some horses and it could double as
a merry-go-round. :-)

ac6xg