[Lowfer] Re:Top Hat qustion

Mon Oct 13 05:38:52 EDT 2008

Hi Andy, my work suggests that the top hat has two bonuses to a straight
vetical, one it increases the radiation resistance (and the "effective
height"), and two it can increase the antenna capacitance which in some
cases reduces the ground loss.

The first effect is limited to the case whether the farthest extent of the
thop hat wires are about equal to the height. At this state the effective
height is about 95% of the true vertical height (top wires horizontal.)
Futher extention or "filling in" does not increase the height ....I hade 450
feet length of top wire on my vertical, and measured the difference interms
of the open circuit voltage induced by a known field strength local
(groundwave) signal.

Increasing the top wires further than a length equal to the height will
incease the antenna capacity provided there is a spacing of about 2 feet
between the wires you will gain about 2pF per foot. This extra capacity
leads to reduced ground loss and a smaller loading coil so less coil loss,
which has a major effect on increasing the ERP for a given input power. One
snag is that the top should be over "open ground" and not lossy foliage or
buildings. An elevated ground plane can compensate for a lot of this as Bill
showed on his experiments.

One problem is that if the tophat is short rather a lot of the extra
capacity is to the vertical element iteslf rather than to ground and I guess
this is not so effective.

The theory says that the top hat doesnt radiate because its currents are
canelled out due to the proximity of the ground in terms of a wavelength.
this is seen in practice in measurements, though the ground resistance means
that the cancellation is not exact it is "near enough".

See http://www.alan.melia.btinternet.co.uk/spiraltop.htm  for some
measurements on a "short" antenna. It was unfortunately destroyed before we
could do field strength measurements with it, but the effects of the bow-tie
top can be seen in the bridge measurements of the ground loss. Also
http://www.alan.melia.btinternet.co.uk/umbarial.htm for a bigger version.

Best wishes
Alan G3NYK

----- Original Message -----
From: <lowfer-request at mailman.qth.net>
To: <lowfer at mailman.qth.net>
Sent: Monday, October 13, 2008 9:01 AM
Subject: Lowfer Digest, Vol 44, Issue 8

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> Today's Topics:
>
>    1. Beacon status - EAR (J. B. Weazle McCreath)
>    2. A Tophat Question (Andy - KU4XR)
>    3. Beacon List? (Joe)
>    4. Re: Beacon List? (Andy - KU4XR)
>    5. XES 137.779 (John Andrews)
>    6. Re: XES 137.779 (Andy - KU4XR)
>    7. WD2XES 137 KHz DFCW (Andy - KU4XR)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sun, 12 Oct 2008 18:50:55 +0100
> From: "J. B. Weazle McCreath" <weazle at hurontel.on.ca>
> Subject: [Lowfer] Beacon status - EAR
> To: "Discussion of the Lowfer (US, European, &amp; UK) and MedFer
> bands" <lowfer at mailman.qth.net>
> Message-ID: <000001c92c93$18b1f420$0b01a8c0 at weazle>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Hello Lowfers,
>
> Now that the vegitation in the immediate vacinity of my final/antenna
> tuner has discarded its leaves for another year, I re-tweaked the old
> variometer for max output.  According to my RF ammeter, beacon
> "EAR" on or about 188.830 kHz. is back at its baseline current.
> It transmits in QRSS30 mode 24/7 for all listeners/lookers.
>
> 73, J.B., VE3EAR - VE3WZL
> Solar and wind powered
> Lowfer " EAR"  188.830
> EN93dr
>
> http://www.hurontel.on.ca/~weazle
>
>
>
>
> ------------------------------
>
> Message: 2
> Date: Sun, 12 Oct 2008 18:14:28 -0700 (PDT)
> From: Andy - KU4XR <ku4xr at yahoo.com>
> Subject: [Lowfer] A Tophat Question
> To: lowfer at mailman.qth.net
> Message-ID: <650206.77486.qm at web63607.mail.re1.yahoo.com>
> Content-Type: text/plain; charset=us-ascii
>
> Greetings all:
>
> I am currently using a straight 40 foot " T " style tophat for my LOWfer
beacon.I would like to try another style, but it needs to be as short as
possible, and as lightweight as possible, so I can lift it into the air
> by myself, so PVC pipe will be the material. I have calculated the lengths
of different formations, and the one that will fit on a 10 foot stick of PVC
is the " BOWTIE " style such as the Butternut, Butterfly beam.
> By taking the 20 foot leg ( each side ), and shaping it into an " M "
pattern with each section 5 feet long, it will take up about 7 feet of
> pipe. That will leave 3 feet to use as a mounting pipe. My thoughts were
to make 2 bowties on the same pipe in an " X " pattern. This will be like
turning the bowtie on its end ( 2 triangles standing tip to tip ). After
saying all of this, my question now is; does the same rule apply for a
physically shortened tophat in reference to its overall capacitance, as to
the overall efficiency of a physically shortened antenna ?? I also keep
reading statements that say the tophat dosen't actually radiate any RF, it
just electrically pulls the RF current to the top of the antenna, so would
the tophats heigth above ground affect antenna radiation ??
> By the way; not to get into a debate with anyone, but I'm not so sure as
to the electrical accuracy of the " dosen't radiate any " RF " statement in
regards to the tophat. Suffice it to say however, that at such low
frequencies, and short lengths; It May Not ! just something that raises my
eyebrow when I read it. Thanks for any comments;
>
> 73,  Andy  " XR "
>
>
>
>
>
> ------------------------------
>
> Message: 3
> Date: Sun, 12 Oct 2008 20:46:30 -0500
> From: Joe <nss at mwt.net>
> Subject: [Lowfer] Beacon List?
> To: lowfer at mailman.qth.net
> Message-ID: <48F2A876.5000405 at mwt.net>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Hello All,
>
> New here to this deep freq land.
>
> I was wondering if a web page someplace that has a list of beacons out
> there that i can try to listen to?
>
> Joe WB9SBD  EN43xo
>
>
> ------------------------------
>
> Message: 4
> Date: Sun, 12 Oct 2008 18:52:00 -0700 (PDT)
> From: Andy - KU4XR <ku4xr at yahoo.com>
> Subject: Re: [Lowfer] Beacon List?
> To: "Discussion of the Lowfer (US, European, &  UK) and MedFer bands"
> <lowfer at mailman.qth.net>
> Message-ID: <157481.16452.qm at web63606.mail.re1.yahoo.com>
> Content-Type: text/plain; charset=us-ascii
>
> Welcome Joe:  try this link:
>
> http://www.lwca.org/sitepage/part15/index.htm
>
> Hope it helps, and good luck listening.
>
> 73, Andy  " XR "
>
>
> --- On Sun, 10/12/08, Joe <nss at mwt.net> wrote:
>
> > From: Joe <nss at mwt.net>
> > Subject: [Lowfer] Beacon List?
> > To: lowfer at mailman.qth.net
> > Date: Sunday, October 12, 2008, 9:46 PM
> > Hello All,
> >
> > New here to this deep freq land.
> >
> > I was wondering if a web page someplace that has a list of
> > beacons out
> > there that i can try to listen to?
> >
> > Joe WB9SBD  EN43xo
> > _______________________________________________
> > >From the Lowfer mailing list
> > Send messages to: Lowfer at mailman.qth.net
> > To sub/unsub visit:
> > http://mailman.qth.net/mailman/listinfo/lowfer
>
>
>
>
>
> ------------------------------
>
> Message: 5
> Date: Sun, 12 Oct 2008 22:12:58 -0400
> From: John Andrews <w1tag at w1tag.com>
> Subject: [Lowfer] XES 137.779
> To: "Discussion of the Lowfer (US, European, &amp; UK) and MedFer
> bands" <lowfer at mailman.qth.net>
> Message-ID: <48F2AEAA.1090002 at w1tag.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> WD2XES is on 137.779 kHz with 500 watts output. DFCW90 (use Argo 30 sec
> or similar screen) until 0600 UTC. Presently showing on the F1AFJ and
> CT1DRP grabbers.
>
> John Andrews, W1TAG/WD2XES
>
>
> ------------------------------
>
> Message: 6
> Date: Sun, 12 Oct 2008 19:53:01 -0700 (PDT)
> From: Andy - KU4XR <ku4xr at yahoo.com>
> Subject: Re: [Lowfer] XES 137.779
> To: "Discussion of the Lowfer (US, European, &  UK) and MedFer bands"
> <lowfer at mailman.qth.net>
> Message-ID: <72914.99138.qm at web63603.mail.re1.yahoo.com>
> Content-Type: text/plain; charset=us-ascii
>
> So you're the mysterious signal that popped up tonite. I,ve been trying
> for an hour to determine the mode and callsign. Lots of noise here tonite,
and my reception lacks alot this low, but seeing you in there.
>
>
>
>
>
>
>
> ------------------------------
>
> Message: 7
> Date: Sun, 12 Oct 2008 22:33:57 -0700 (PDT)
> From: Andy - KU4XR <ku4xr at yahoo.com>
> Subject: [Lowfer] WD2XES 137 KHz DFCW
> To: lowfer at mailman.qth.net
> Message-ID: <935431.24087.qm at web63604.mail.re1.yahoo.com>
> Content-Type: text/plain; charset=us-ascii
>
> Greetings all:
>
> It was a pleasure to be able to copy a signal on 2200 meters again.
> Thank you John for the DFCW signal on Sun. night. This was the first
> DFCW signal I have copied and captured to date. You can view it at:
> http://webpages.charter.net/ku4xr   , open the 2200 mtr folder, then
> the WD2XES folder, and you can pull up the jpeg there. 73 to all !!
>
> Andy - KU4XR - EM75xr - Friendsville, TN.
>   LOWfer Beacon " XR " @ 184.322 KHz
>
>
>
>
>
>
> ------------------------------
>
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> End of Lowfer Digest, Vol 44, Issue 8
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