W9BHI
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« on: April 21, 2016, 02:26:59 PM » |
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Hello all,
Could anybody out here model an end fed long wire antenna for 160 meters?
I would like to find out what L and C that I would need to build an antenna tuner for it.
If someone can do this, I can give you the measurements and configuration of the antenna.
Thanks,
Don W9BHI
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Steve - K4HX
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« Reply #1 on: April 21, 2016, 04:46:57 PM » |
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I need the dimension and geometry.
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WD8BIL
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« Reply #2 on: April 21, 2016, 04:53:24 PM » |
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It 160 meters long!  |
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W9BHI
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« Reply #3 on: April 21, 2016, 05:19:45 PM » |
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Steve,
It will be fed 30 feet up at the peak of the roof and will span horizontally 200 feet to a 30 foot tall utility pole and then make a 90 degree bend straight down 25 feet to an insulator that is connected to a ground rod.
I may put in two 200 foot long ground radials.
Is this enough info?
Thanks,
Don W9BHI
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MikeKE0ZUinkcmo
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« Reply #4 on: April 21, 2016, 10:30:28 PM » |
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It 160 meters long! Grin Seems to me I remember somewhere long ago, that a "long wire" was taken to mean a wire antenna at least 2-1/2 wave lengths long at the frequency of interest.  |
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KA0HCP
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« Reply #5 on: April 22, 2016, 03:03:45 AM » |
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Traditional Long Wire = Greater than one wavelength.
***What is proposed ground/radial/"counterpoise" type and length?? This is a large factor in the impedance (L/C) factors.
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New callsign KA0HCP, ex-KB4QAA. Relocated to Kansas in April 2019.
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Steve - K4HX
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« Reply #6 on: April 22, 2016, 07:29:06 AM » |
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So the far end is grounded?
With the far end grounded the impedance numbers are as follows.
f (MHz) Z (Ohms)
1.8 383.73 - j9274.8
1.9 753.29 - j8095.9
2.0 1922.4 - j6591.1
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W9BHI
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« Reply #7 on: April 22, 2016, 08:13:59 AM » |
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Steve,
There is an insulator between the end of the antenna and the ground rod.
The ground radials will be 200 feet each parralleling the the antenna on the ground.
Don
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Steve - K4HX
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« Reply #8 on: April 22, 2016, 10:09:51 AM » |
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With the far end not grounded (floating 5 feet above ground) the impedance numbers are as follows.
f (MHz) Z (Ohms)
1.8 279.12 - j9519.7
1.9 486.58 - j8508.8
2.0 1009.3 - j7286.3
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Steve - K4HX
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« Reply #9 on: April 22, 2016, 10:37:05 AM » |
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If you placed an appropriate coil at the feed point to cancel the capacitive reactance at 1.9 MHz and fed it through a 9:1 UNUN, you'd get an SWR curve something like the one shown below.
Looks like the 2:1 points are at 1.870 and 1.940 MHz. I reality, it may be a little better than this since the coil I used had almost no loss. A resistance of the coil would broaden the bandwidth some (at the expense of efficiency).
If the coax run is not long and/or low loss coax is used, I see no reason why you couldn't use the the system at 3:1 or even 4:1 (at least from a coax loss standpoint). Not sure how the UNUN would react (no pun intended) with the large amounts of reactance as you move away from 1.9 MHz.
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WD8BIL
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« Reply #10 on: April 22, 2016, 02:43:26 PM » |
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Good stuff Steve. What does the 3D rad pattern look like?
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W9BHI
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« Reply #11 on: April 22, 2016, 04:13:38 PM » |
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Steve,
I want to build a dedicated 160 meter tuner for this longwire antenna.
what L and C combinations would I need?
I could use a roller inductor from a BC transmitter and possibly a vacuum capacitor.
I will be running full legal limit.
Thanks,
Don W 9BHI
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DMOD
AC0OB - A Place where Thermionic Emitters Rule!
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« Reply #12 on: April 22, 2016, 09:10:09 PM » |
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Hello all,
Could anybody out here model an end fed long wire antenna for 160 meters?
I would like to find out what L and C that I would need to build an antenna tuner for it.
If someone can do this, I can give you the measurements and configuration of the antenna.
Thanks,
Don W9BHI
Why not turn into an Inverted-L. The dedicated tuner could then be a SeriesL-ShuntC-SeriesL "T" tuner. Phil - AC0OB |
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Charlie Eppes: Dad would be so happy if we married a doctor. Don Eppes: Yeah, well, Dad would be happy if I married someone with a pulse. NUMB3RS  |
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Steve - K4HX
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« Reply #13 on: April 22, 2016, 10:14:58 PM » |
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An inverted-L that long would only need a cap for a tuner, same as your proposed setup. And a 9:1 balun.
Or you go with a tank circuit and tap down on the coil.
The pattern is mostly high angle are almost omni-directional. If it were me, I would add a 25' section on the other end and feed the thing in the center (make it a dipole). No tuner required.
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W9BHI
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« Reply #14 on: April 25, 2016, 12:36:51 PM » |
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How about if I have the feed near the ground next to the house, go up 30 feet to the peak of the roof, and go out 200 feet to the top of the utility pole.
Does that seem like it would work better?
(I guess that would make it an inverted L)
Thanks,
Don W9BHI
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Steve - K4HX
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« Reply #15 on: April 25, 2016, 08:05:15 PM » |
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It will still be a high angle radiator. Given that, center fed as a dipole is easier and more efficient.
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flintstone mop
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« Reply #16 on: April 28, 2016, 12:10:33 PM » |
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It will still be a high angle radiator. Given that, center fed as a dipole is easier and more efficient.
what is the magic number??? 1/2 wavelength high from the ground to become directional?? 80 meters gets a little easier and 40 is sweet. We're all in the same basket, when it comes to antennas and 160 Meters............cloud warmers. high angle radiators. Can't fight the science |
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Fred KC4MOP
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W3RSW
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« Reply #17 on: April 29, 2016, 10:28:19 AM » |
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Well there are some plusses, like being able to work the local guys without
the roar of distant, constant lightning storms.
Still, winter's are magic on top band.
Haven't worked it much in years since moving south in '95.
-miss it and listen occasionally.
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RICK *W3RSW*
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Fred k2dx
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« Reply #18 on: April 29, 2016, 11:29:24 AM » |
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It's very easy to feed without anything complicated, modeling isn't needed.
At your end feedpoint connect a parallel tuned circuit to ground. Resonate with a variable cap, preferably a vacuum cap. Tap the coil for a 50 ohm point, it will be close to the bottom (ground end). Alternatively you can link couple a few turns to the big coil.
There isn't a need to overthink it or closely measure it. It isn't rocket science. Look in any older ARRL handbook for an end fed random wire to get some ideas. What you are doing sounds like an end fed half wave (approximately). I would not waste time with any newer handbooks.
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