Topband: Topband Digest, Vol 237, Issue 4
Mamuka Kordzakhia
mamuka4l2m at yahoo.com
Mon Sep 19 15:45:25 EDT 2022
3) These frequencies and now are loaded by illegal stations from Caucasus or other former Soviet region's stations
On Monday, September 19, 2022, 08:00:49 PM GMT+4, topband-request at contesting.com <topband-request at contesting.com> wrote:
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Today's Topics:
1. Misbehaving verticals (Dennis Ashworth)
2. Tuning Christman Phasing (Kenny Silverman)
3. Non-amateur stations in Europe on 1860 and 1900 kHz
(John Kaufmann)
4. Re: Misbehaving verticals (update) (Dennis Ashworth)
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Message: 1
Date: Sun, 18 Sep 2022 20:03:50 -0500
From: Dennis Ashworth <dennis at ashworth.org>
To: topband at contesting.com
Cc: Terry Conboy <n6ry at arrl.net>
Subject: Topband: Misbehaving verticals
Message-ID:
<CAEn-CUrM2x9vm7Jd_5Hf+z+WOF71FoK4yxw+aJvNNSGVfjOU3Q at mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"
I have 4 identical short verticals (part of a broadside array) where EZNEC
predicts a 12.5 ohm feed-point impedance. That seems reasonable, but my
actual measurements indicate 25 ohms at resonance.
My first thought was something lossy in the ground system. The ground
system consists of 32 copper wires, .3 wavelength long, laying on the
ground. The ground connections are via a 3/8? copper tubing ring; all
radials are soldered. Additionally, the FCC tables used for ground
conductivity assumptions on MF frequencies shows the area to exhibit
between 15 and 30 millimhos (or millisiemens) per meter ? quite good. I
just don?t believe I have 10 ohms of ground loss.
The radiator(s) are built of 3? aluminum tubing, 1/8 wavelength tall, top
loaded with two top hat wires sloping away at about 45 degrees (180 degrees
apart). Top hat lengths adjusted for resonance.
How do I know the 25 ohms is real? An SWR bridge at the base indicates a
2:1 SWR. Two MFJ analyzers read 25 ohms.
As mentioned above, there are 4 identical verticals/ground systems. I
measured each vertical impedance and found consistent results. Measurements
were made with the other 3 verticals floating. No other antennas, power
lines, fences are in the near-field. There are no RF sources nearby that
could affect the MFJ readings.
I am wracking my brains on this issue. The ground system should be fine as
configured. Somewhere I'm burning up half my power in this unknown source
of loss.
Ideas?
Thanks
Dennis, K7FL
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Message: 2
Date: Sun, 18 Sep 2022 23:30:47 -0400
From: Kenny Silverman <kenny.k2kw at gmail.com>
To: topband <topband at contesting.com>
Subject: Topband: Tuning Christman Phasing
Message-ID: <7B06CFF4-85C1-46F2-9869-08A4CAAE721D at gmail.com>
Content-Type: text/plain; charset=utf-8
?I?m planning a 2ele 160m array using the Christman phasing method. Each vertical will be about 80-90? tall hung from trees, each using 2 sloping top-loading wires. I assume the elements won?t be exactly 90 degrees apart, but I could slope 1 element so the bases are 90 degrees apart.
Are there any tips or guidelines on how to tune the array? For example:
- adjust each vertical wire to the same/similar height? (Impacts impedance and bandwidth of each element)
-if the elements aren?t spaced exactly 90 degrees apart do the phasing lines need to be adjusted? (I wouldn?t have a clue how to adjust so the voltages are the same with changed lengths)
- Tune each vertical with the other out of the system?
- lay enough radials so each vertical has a similar impedance? (I?m planning on 60 x 100? radials for each element, but can add more to balance the impedance)
- tune each vertical to the same desired center freq? (1.840 for example)
- impedance match each vertical to 50 ohms (using hairpin coil or toroidal transformation)?
- use a 1:2 toroidal transformation at the phase line junction?
-Other?
Thanks, Kenny K2KW
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Message: 3
Date: Mon, 19 Sep 2022 10:14:37 -0400
From: "John Kaufmann" <john.kaufmann at verizon.net>
To: "'topband'" <topband at contesting.com>
Subject: Topband: Non-amateur stations in Europe on 1860 and 1900 kHz
Message-ID: <021e01d8cc32$27cd59b0$77680d10$@verizon.net>
Content-Type: text/plain; charset="us-ascii"
Some evenings I hear noise-like transmissions, approximately 3 kHz wide,
around 1860 and 1900 kHz that appear to be originating in Europe. I presume
they are not amateur signals. On European SDR's they are quite loud and
operating continuously every day. I find they are actually useful as
propagation indicators into Europe. They are usually audible when there are
no European amateur signals (CW) to be heard.
Do any of you folks in Europe know what these transmissions are?
Transmitter location? Transmitter power? Antenna?
73, John W1FV
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Message: 4
Date: Mon, 19 Sep 2022 10:32:59 -0500
From: Dennis Ashworth <dennis at ashworth.org>
To: topband at contesting.com
Subject: Re: Topband: Misbehaving verticals (update)
Message-ID:
<CAEn-CUreh+VTn3uWnbt0zS1xK1fAko2tgT1tTJh+5Fg31SCtGQ at mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"
Thanks for all who responded. I?ve taken the liberty of sharing my response
to Hank, K7HP who touched on many of the potential issues posted by others:
My comments are inserted below:
On Mon, Sep 19, 2022 at 2:03 AM hp <pfizenmayer at q.com> wrote:
>
> I wonder how much coupling between the top loading wires ??I guess you
> have looked at base
> resistance too with one or all of the others tied to the radials to see
> how much change 0
> or if you could drop a couple of the top loading wires down next to the
> vertical so it would
> not be resonant . I am wondering about them looking like a parasitic
> element.
>
Interesting point. I believe the only thing I did to isolate the remaining
elements when testing a specific element was to open them at the base
(disconnect the ground system). I like your idea of dropping the top
loading wires. It certainly doesn?t hurt and may provide an important clue
if the impedance changes.
>
> You did not say what the element spacings were - if you have an EZNEC
> model for all 4 or just made
> a model of a couple you could play with seeing what the effect is.
>
The rectangle measures 144?x58? (the array is for 80m).
I?m sure how the Topband list handles attachments, but I can share the
EZNEC model for the array off line if interested.
>
> Reason I am thinking about the coupling is I have been doing some
> modeling of the effect of my 80M INV VEE on a two element 80M active vert
> phased RX array spaced as far away as I can get it in my yard and the
> coupling is incredible -the two el array is crap until I get the 80M inv
> vee effective "open" impedance at INV VEE feedpoint to at LEAST 500 ohms .
>
The site is >120 acres of flat, arid land. Although there are many antennas
on the property, there are none within what I?d consider the near field.
The closest is a multiple element 160M vertical array, probably 3
wavelengths distant.
>
> Also I assume that you know about the issues with radials and "ground"
> with radials in EZNEC unless you go to the EZNEC4 with the license or you
> can raise them an inch or so above ground and be fairly OK. Unless you
> raise the radials a tad in your model .
>
Yes. Here?s a helpful note from Terry, N6RY who modeled some of the ground
options/variables. Good work, and indicates to me that ground assumptions
made in the model above are probably close:
*?I modeled a single element from ?your? array with 32 x 80 foot radials.
I used #12 for all conductors (including the mast) to get rid of errors in
NEC2 from mixing conductor diameters.Here are the variations of gain and
Z. ?Sandy" soil is 0.002 S/m, diel constant 10. ?Pastoral? is much better
at 0.01 S/m, diel const 14 (perhaps more likely for Beryl).Free space 0.68
dBi, 6.83 ohms ? (and with zero loss conductors, the average gain is
-0.03 dB, which indicates the model is fairly decent).Radials 6? high,
Sandy -0.58 dBi, 12.44 ohmsRadials 1? high, Sandy -0.26 dBi, 11.02
ohmsRadials 4? high, Sandy -0.26 dBi, 10.48 ohmsRadials 6? high,
Pastoral 1.02 dBi, 12.05 ohmsRadials 1? high, Pastoral 1.09 dBi, 11.81
ohmsRadials 4? high, Pastoral 1.10 dBi, 11.52 ohmsSo at least from the
NEC2 perspective, there?s nothing even close to 25 ohms and your mystery
continues.?*
I think what I?ll try next is to be absolutely certain the other elements
in the array are detuned electrically from the vertical under test. Stan
Stockton (call?) suggested adding additional radials to see if the
impedance drops. This probably makes sense too, once I?m sure the
decoupling mentioned above is complete.
Thanks all for the input!
Dennis, K7FL
Las Vegas
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