Received-SPF: neutral (gmail.com: 193.82.116.20 is neither permitted nor denied by best guess record for domain of owner-rsgb_lf_group@blacksheep.org)
Message-Id: <6.1.0.6.2.20060419171908.02a17870@127.0.0.1>
Date: Wed, 19 Apr 2006 17:33:27 +0200
To: rsgb_lf_group@blacksheep.org
From: Dick Rollema <dickrollema@casema.nl>
In-Reply-To: <5.1.0.14.0.20060419162451.02431a98@u0019445.kuleuven.be>
References: <6.1.0.6.2.20060419144651.02a19240@127.0.0.1>
 <5.1.0.14.0.20060419162451.02431a98@u0019445.kuleuven.be>
Mime-Version: 1.0
Subject: Re: LF: Top load coil at ground level?
Content-Type: multipart/alternative;
	boundary="=====================_12670540==.ALT"
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org
Status: O

--=====================_12670540==.ALT
Content-Type: text/plain; charset="us-ascii"; format=flowed

Rik, ON 7YD wrote

At 16:29 19-4-06, you wrote:
>Hi Dick,
>
>I guess you are right with
>"The stub functions as a transmission line to transfer the inductive 
>reactance of the coil to the top of the radiator."
>
>But I am afraid that for any reasonable antenna height (< 50..100m) the 
>stub is that short (in wavelengths) that it will hardly transfer any reactance.

To check  this I took as a stub 50ft of 600 ohm open line. At one end I 
connected a coil of 2mH, a typical value I think for a top load coil. Its 
reactance at 136kHz is 1700 ohm.
Using a transmission line program by ARRL I find that at the other end of 
the line a reactance of 1978 ohm appears, which looks like a coil of 2.32mH.
So it seems to work.

>What is the result when you model both quarter wave 80m antennas (+/- 20 m 
>height) for 2200m ?

The antennas and the distance between the legs of the stub (20cm) are so 
small in wavelengths that the program does not work.

73, Dick, PA0SE


>At 14:54 19/04/2006 +0200, you wrote:
>>To All from PA0SE,
>>
>>By chance I came across an interesting article in the Dutch weekly (!) 
>>magazine Radio Expres of 11 January 1934. It referred to an article in 
>>the Proceedings of the IRE of December 1933 by Nickle, Dome and Brown on 
>>a procedure to increase of the feed point impedance of a vertical antenna 
>>by means of top loading. A normal way is to use a series resonant circuit 
>>as in fig.1, consisting of a capacitive hat and a coil. The coil is in a 
>>awkward position for tuning. The alternative by Nickle, Dome and Brown is 
>>to use a short circuited stub slightly shorter than an quarter wave that 
>>at its top end produces the proper inductive reactance for series 
>>resonance with the capacitive hat. Indicated in fig. 2a. The system is 
>>tuned by moving the short circuit at the bottom up or down. The left leg 
>>of the stub is doubling as the radiator. An easier way of tuning is to 
>>make the stub too short and lengthening it with a coil(b) or a stub that 
>>is too long and shortening it by a capacitor (c). I modelled a quarter 
>>wave vertical for 80 m according to (c) using Antenna Optimizer by Brian 
>>Beezley, K6STI. When in resonance the feed point impedance was raised 
>>from 36 ohm without top load to 4925 ohm! The radiation diagram was 
>>identical to the one for the unloaded vertical within a few tenths of a dB.
>>
>>It occurred to me that the system could perhaps also be used for a 136kHz 
>>vertical. Using system (b) in fig.2 the loading coil between top of the 
>>radiator and topload could be at ground level. The stub functions as a 
>>transmission line to transfer the inductive reactance of the coil to the 
>>top of the radiator. Of course a second coil could be inserted between 
>>bottom of the stub and ground for matching and feeding of the antenna.
>>
>>What do you think?
>>
>>73, Dick, PA0SE
>>
>>

--=====================_12670540==.ALT
Content-Type: text/html; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable

<html>
<body>
<font size=3D3><b>Rik, ON 7YD wrote<br><br>
</b>At 16:29 19-4-06, you wrote:<br>
<blockquote type=3Dcite class=3Dcite cite=3D"">Hi Dick,<br><br>
I guess you are right with <br>
&quot;</font><font face=3D"Courier New, Courier" size=3D3>The stub functions
as a transmission line to transfer the inductive reactance of the coil to
the top of the radiator.</font>&quot;<br><br>
But I am afraid that for any reasonable antenna height (&lt; 50..100m)
the stub is that short (in wavelengths) that it will hardly transfer any
reactance.</blockquote><br>
<b>To check&nbsp; this I took as a stub 50ft of 600 ohm open line. At one
end I connected a coil of 2mH, a typical value I think for a top load
coil. Its reactance at 136kHz is 1700 ohm.<br>
Using a transmission line program by ARRL I find that at the other end of
the line a reactance of 1978 ohm appears, which looks like a coil of
2.32mH.<br>
So it seems to work.<br><br>
</b><blockquote type=3Dcite class=3Dcite cite=3D""><font size=3D3>What is th=
e
result when you model both quarter wave 80m antennas (+/- 20 m height)
for 2200m ? </font></blockquote><b><br>
The antennas and the distance between the legs of the stub (20cm) are so
small in wavelengths that the program does not work.<br><br>
73, Dick, PA0SE<br><br>
<br>
</b><blockquote type=3Dcite class=3Dcite cite=3D""><font size=3D3>At 14:54
19/04/2006 +0200, you wrote:<br>
<blockquote type=3Dcite class=3Dcite cite=3D"">To All from PA0SE,<br><br>
</font><font face=3D"Courier New, Courier" size=3D3>By chance I came across
an interesting article in the Dutch weekly (!) magazine <i>Radio Expres
</i>of 11 January 1934. It referred to an article in the <i>Proceedings
of the IRE</i> of December 1933 by Nickle, Dome and Brown on a procedure
to increase of the feed point impedance of a vertical antenna by means of
top loading. A normal way is to use a series resonant circuit as in
fig.1, consisting of a capacitive hat and a coil. The coil is in a
awkward position for tuning. The alternative by Nickle, Dome and Brown is
to use a short circuited stub slightly shorter than an quarter wave that
at its top end produces the proper inductive reactance for series
resonance with the capacitive hat. Indicated in fig. 2a. The system is
tuned by moving the short circuit at the bottom up or down. The left leg
of the stub is doubling as the radiator. An easier way of tuning is to
make the stub too short and lengthening it with a coil(b) or a stub that
is too long and shortening it by a capacitor (c). I modelled a quarter
wave vertical for 80 m according to (c) using Antenna Optimizer by Brian
Beezley, K6STI. When in resonance the feed point impedance was raised
from 36 ohm without top load to 4925 ohm! The radiation diagram was
identical to the one for the unloaded vertical within a few tenths of a
dB.<br><br>
It occurred to me that the system could perhaps also be used for a 136kHz
vertical. Using system (b) in fig.2 the loading coil between top of the
radiator and topload could be at ground level. The stub functions as a
transmission line to transfer the inductive reactance of the coil to the
top of the radiator. Of course a second coil could be inserted between
bottom of the stub and ground for matching and feeding of the
antenna.<br><br>
What do you think?<br><br>
73, Dick, PA0SE <br><br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <br>
</font></blockquote></blockquote></body>
</html>

--=====================_12670540==.ALT--