K2 ATU and 43-ft Vertical

[Edward R Cole]

I am using a top-loaded 43 foot vertical (43x130-foot inverted-L) on
495.6 KHz (600 meters).  The antenna Z = 0.81 - j681.5 from EzNEC.  I
built an air coil from #12 thhn copper wire (ordinary solid conductor
electrical housewire) roughly 10-in diam by 10-inch long 39 turns and
tapped it about 3/4 for a match.  A tap at 2-1/2 turns matches
50-ohms coax to the xmtr which is a converted 100w NDB (aviation
non-directional beacon).
Details at:  http://www.kl7uw.com/600m.htm

The base loading coil is nearly identical in design to the toroidal
coil of AD5X, linked below.  I do intend to find 160 & 80m tap
locations for the antenna.

One thing I wanted to share was that I am using 2-foot chicken wire
as ground radials lying on the ground.  They are obviously short on
600m (1/4 Wave = 496 feet).  Two radial are 50-foot long and one is
70-foot long.  I am using the shield of my 1-5/8 inch Heliax hardline
coax as the fourth radial (it is 120-foot long and has ground rod at each end).

With a modified MFJ-269B, I get a measured Z = 20 + j0; the 50-ohm
tap sees Z = 63 + j15 for SWR=1.3  antenna efficiency is 4%
(ERP=4.15w for 100w xmtr output).  With this I have been heard in BC
over 1300-miles away (not in the prime DX season).

73, Ed - KL7UW
------------------------------

Message: 15
Date: Sat, 5 Jun 2010 18:26:41 -0500
From: "Bob Naumann" <[hidden email]>
Subject: Re: [Elecraft] K2 ATU and 43-ft Vertical
To: <[hidden email]>
Message-ID: <017001cb0506$8e203850$aa60a8f0$@COM>
Content-Type: text/plain;       charset="us-ascii"

As Don mentioned, the 2-part article in QST was written by AD5X and can also
be seen here:

http://www.ad5x.com/images/Articles/Match160.pdf

I  built one of these "matching networks" (it's not a tuner) for my 43'
vertical and it works very well on 160, 80 and up. The AD5X matching network
is a very clever design and makes tuning of this short radiator quite easy
as it offsets the huge capacitive reactance of these antennas and even
allows control of the relays right over your feedline. Very slick.

I have a Zero Five vertical and it is made very well, has been up about 3
years and still looks brand new. The only difference is that with the AD5X
matcher I can tune it on 160 and 80 now!

The feedline makes a huge difference primarily due to the loss that will
impact your performance with poor SWR. If you have a lossy feedline (like
RG8X like I used at first) the antenna will appear to match pretty easily.
If you switch (like I did to 1/2" hardline, with its much lower loss) you'll
see the impact of all of that capacitive reactance in making tuning of the
43' antenna very difficult especially on 160 and 80. In fact, I could not
match it at all on 160.

73,

Bob W5OV



73, Ed - KL7UW, WD2XSH/45
======================================
BP40IQ   500 KHz - 10-GHz   www.kl7uw.com
EME: 144-600w, 432-100w, 1296-60w, 3400-fall 2010
DUBUS Magazine USA Rep [hidden email]
======================================

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[W8JI]

> The base loading coil is nearly identical in design to the
> toroidal
> coil of AD5X, linked below.  I do intend to find 160 & 80m
> tap
> locations for the antenna.

I hope you have serious top loading.

I have a video of a base loading coil throwing a two inch
long arc when running 500 watts on 160 meters into a 43-foot
vertical that is mounted over a good ground system. It
looked like the Northern Lights from Macon.    :-)

73 Tom

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[Alan Bloom]

I happened to be down at Harbor Freight yesterday and noticed they have
20-foot telescoping aluminum flag poles on sale for $55.  That should
make a good vertical on 40-10 meters (almost 5/8 wave on 10) with maybe
a little bit of top-loading needed on 40.  It even comes with an
American flag.  :=)

Al N1AL


On Sun, 2010-06-06 at 20:06 -0400, Tom W8JI wrote:

> > The base loading coil is nearly identical in design to the
> > toroidal
> > coil of AD5X, linked below.  I do intend to find 160 & 80m
> > tap
> > locations for the antenna.
>
> I hope you have serious top loading.
>
> I have a video of a base loading coil throwing a two inch
> long arc when running 500 watts on 160 meters into a 43-foot
> vertical that is mounted over a good ground system. It
> looked like the Northern Lights from Macon.    :-)
>
> 73 Tom

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[Phil Salas]

"The base loading coil is nearly identical in design to the toroidal
coil of AD5X, linked below.  I do intend to find 160 & 80m tap
locations for the antenna."

FYI - The maximum power I've run with my 43-foot vertical and matching
system is 1200 watts with no problems experienced for several months.  But
then one humid morning the unit did arc from the output connection across
the electrical box to a nearby ground point (you could see a nice carbon
trace across the box).  The SWR jumped suddenly and the amplifier (ALS-1300)
tripped out like it should.  I replaced the output screw with a ceramic
feedthru and haven't had the problem since.  As Tom W8JI stated, the
voltages can be extremely high especially if you are running high power.  If
you run an amplifier, I'd recommend using a ceramic feedthru output, and
keep the output port several inches away from any ground connections.

Phil - AD5X

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