Re: Topband: Impedance of inv l?
For comparison sake... my inverted L measure 19 ohms over a K2AV FCP. Increasing the vertical wire height gained another several ohms... ended up with an R value of 26 ohms at resonance (no reactive component.) Pete _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Impedance of inv l?
_ A. E. BUZZ JEHLE POB 2277 BANDERA TX 78003-2277 USA 1 830 796 4196 CELL 1 713 725 5914 On Nov 22, 2018, at 18:03, Stan Stockton wrote: Frank and all, I thought I would share a little real world experience I had today. I have a T, loaded vertical that is only something like 57 feet tall at the moment. The R should probably be in the neighborhood of 10. It is located about 30 feet from the water. I had about 40 radials and they ranged from about 30 feet (ones going straight toward the water or sometimes in the water) and perhaps 75 feet long. I would say the average length is about 60 feet or so. I added 8 more radials yesterday wanting to get the R down to something I liked better. I made a ring out of some 3/8 copper tubing, scraped, soldered, generally made better connections than what I originally had. I moved the R by 1 ohm down from 22 to 21. :-) Today, despite the fact that "my property" is about 100 feet wide, I first added 6 radials that are well in excess of 100 feet long each - probably 115-125 feet long. The R dropped from 21 to 14. WOW. Then I added 4 more long radials. The R dropped from 14 to 13. I am stopping there. I think I would likely have to add another six going on the neighbors yard to drop it by another 1 ohm. I think I probably just picked up 3/4 dB - maybe that's enough to work the EP6 that I have called for a couple hours. In my particular case, I am not sure I could have reduced the 22 to 13 if I had added another 30 radials x 70 feet long each. The longer ones did the trick in a big way. 73, Happy Thanksgiving and see you this weekend. Stan, ZF9CW On Sun, Nov 18, 2018 at 8:31 PM wrote: > > Hi Jamie, > > > I use my AA-54 frequently in exactly the manner you're using your > AA-23, I've never had any reason to be suspicious of any of its > readings. I'm lucky to have no AM broadcast stations within ten > miles. > > > Your AA-230 is telling you that at least half of your power is being > lost to ground resistance and need to at least double the number of > radials to significantly reduce your resistive losses. > > > The 2000 feet of wire in your radial system likely would have produced > much better results with twice as many radials of half the radial length > you used. Quarter wavelength radials aren't cost effective until many > more than 60 radials are used. > > > www.w0btu.com/Optimum_number_of_ground_radials_vs_radial_length.html > > > 73 > Frank > W3LPL > > > > > - Original Message ----- > > From: "Jamie WW3S" > To: "Topband" > Sent: Sunday, November 18, 2018 10:33:13 PM > Subject: Re: Topband: Impedance of inv l? > > several have asked how I am measuring the impedance.I'm using an > AA-230, > and am all the ALL PARAMS setting.the 230 defaults to a series model, > is > that what I want, don’t see how to change it to parallel. I think the > symbol > for impedance is |Z|, correct? > > -Original Message- > From: F Z_Bruce > Sent: Sunday, November 18, 2018 3:20 PM > To: wes_n...@triconet.org ; Topband > Subject: Re: Topband: Impedance of inv l? > > > The far end is high impedance voltage, and has minimum horizontal > current radiation. The inverted L is a good trade off signal vs > available height. Not an expensive antenna to build. > > 73 > Bruce-k1fz > > On Sun, 18 Nov 2018 12:31:38 -0700, Wes Stewart wrote: > > That also drives up the current in the horizontal wire with attendant > increased > horizontal radiation. > > I chose for a couple of reason to do the opposite; shorten the wire to > make > the > feedpoint capacitive and use a shunt inductor to get a 50-ohm match. > This > really doesn't improve the 2:1 VSWR, that I consider acceptable, however. > > Wes N7WS > > On 11/18/2018 8:55 AM, F Z_Bruce wrote: > > That sounds about right. As you put a good ground system under it, > that > value will come down, and the efficiency will come up. > > > > Many add extra antenna wire that pushes the current up the wire, this > also raises the impedance, hopefully to near 50 ohms with the right > length. > > A capacitor (variable, then fixed) in series at the feed point can > cancel the added inductance. > > > > 73 > > Bruce-k1fz > > https://www.qsl.net/k1fz/beverage_antenna.html > > > > > > On Sun, 18 Nov 2018 10:41:36 -0500, WW3S wrote: > > > > What should the Z be for a 1/4 wave inv l, with the radials attached > to > a radial plate? Mine seems to be 60 ohms or so > > > > Sent from my iPad > > _ > > Searchable Archives: http://www.contesting.com
Re: Topband: Impedance of inv l?
Frank and all, I thought I would share a little real world experience I had today. I have a T, loaded vertical that is only something like 57 feet tall at the moment. The R should probably be in the neighborhood of 10. It is located about 30 feet from the water. I had about 40 radials and they ranged from about 30 feet (ones going straight toward the water or sometimes in the water) and perhaps 75 feet long. I would say the average length is about 60 feet or so. I added 8 more radials yesterday wanting to get the R down to something I liked better. I made a ring out of some 3/8 copper tubing, scraped, soldered, generally made better connections than what I originally had. I moved the R by 1 ohm down from 22 to 21. :-) Today, despite the fact that "my property" is about 100 feet wide, I first added 6 radials that are well in excess of 100 feet long each - probably 115-125 feet long. The R dropped from 21 to 14. WOW. Then I added 4 more long radials. The R dropped from 14 to 13. I am stopping there. I think I would likely have to add another six going on the neighbors yard to drop it by another 1 ohm. I think I probably just picked up 3/4 dB - maybe that's enough to work the EP6 that I have called for a couple hours. In my particular case, I am not sure I could have reduced the 22 to 13 if I had added another 30 radials x 70 feet long each. The longer ones did the trick in a big way. 73, Happy Thanksgiving and see you this weekend. Stan, ZF9CW On Sun, Nov 18, 2018 at 8:31 PM wrote: > > Hi Jamie, > > > I use my AA-54 frequently in exactly the manner you're using your > AA-23, I've never had any reason to be suspicious of any of its > readings. I'm lucky to have no AM broadcast stations within ten > miles. > > > Your AA-230 is telling you that at least half of your power is being > lost to ground resistance and need to at least double the number of > radials to significantly reduce your resistive losses. > > > The 2000 feet of wire in your radial system likely would have produced > much better results with twice as many radials of half the radial length > you used. Quarter wavelength radials aren't cost effective until many > more than 60 radials are used. > > > www.w0btu.com/Optimum_number_of_ground_radials_vs_radial_length.html > > > 73 > Frank > W3LPL > > > > > - Original Message ----- > > From: "Jamie WW3S" > To: "Topband" > Sent: Sunday, November 18, 2018 10:33:13 PM > Subject: Re: Topband: Impedance of inv l? > > several have asked how I am measuring the impedance.I'm using an > AA-230, > and am all the ALL PARAMS setting.the 230 defaults to a series model, > is > that what I want, don’t see how to change it to parallel. I think the > symbol > for impedance is |Z|, correct? > > -Original Message- > From: F Z_Bruce > Sent: Sunday, November 18, 2018 3:20 PM > To: wes_n...@triconet.org ; Topband > Subject: Re: Topband: Impedance of inv l? > > > The far end is high impedance voltage, and has minimum horizontal > current radiation. The inverted L is a good trade off signal vs > available height. Not an expensive antenna to build. > > 73 > Bruce-k1fz > > On Sun, 18 Nov 2018 12:31:38 -0700, Wes Stewart wrote: > > That also drives up the current in the horizontal wire with attendant > increased > horizontal radiation. > > I chose for a couple of reason to do the opposite; shorten the wire to > make > the > feedpoint capacitive and use a shunt inductor to get a 50-ohm match. > This > really doesn't improve the 2:1 VSWR, that I consider acceptable, however. > > Wes N7WS > > On 11/18/2018 8:55 AM, F Z_Bruce wrote: > > That sounds about right. As you put a good ground system under it, > that > value will come down, and the efficiency will come up. > > > > Many add extra antenna wire that pushes the current up the wire, this > also raises the impedance, hopefully to near 50 ohms with the right > length. > > A capacitor (variable, then fixed) in series at the feed point can > cancel the added inductance. > > > > 73 > > Bruce-k1fz > > https://www.qsl.net/k1fz/beverage_antenna.html > > > > > > On Sun, 18 Nov 2018 10:41:36 -0500, WW3S wrote: > > > > What should the Z be for a 1/4 wave inv l, with the radials attached > to > a radial plate? Mine seems to be 60 ohms or so > > > > Sent from my iPad > > _ > > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector > > > > _ > > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector > > > >
Re: Topband: Impedance of inv l?
Hi Jamie, I forgot to mention that nearby conductive objects, especially nearby towers can significantly affect the base impedance of a vertical. Nearby on 160 meters is about 200 feet... 73 Frank W3LPL - Original Message - From: donov...@starpower.net To: "Topband" Sent: Monday, November 19, 2018 1:31:27 AM Subject: Re: Topband: Impedance of inv l? Hi Jamie, I use my AA-54 frequently in exactly the manner you're using your AA-23, I've never had any reason to be suspicious of any of its readings. I'm lucky to have no AM broadcast stations within ten miles. Your AA-230 is telling you that at least half of your power is being lost to ground resistance and need to at least double the number of radials to significantly reduce your resistive losses. The 2000 feet of wire in your radial system likely would have produced much better results with twice as many radials of half the radial length you used. Quarter wavelength radials aren't cost effective until many more than 60 radials are used. www.w0btu.com/Optimum_number_of_ground_radials_vs_radial_length.html 73 Frank W3LPL - Original Message - From: "Jamie WW3S" To: "Topband" Sent: Sunday, November 18, 2018 10:33:13 PM Subject: Re: Topband: Impedance of inv l? several have asked how I am measuring the impedance.I'm using an AA-230, and am all the ALL PARAMS setting.the 230 defaults to a series model, is that what I want, don’t see how to change it to parallel. I think the symbol for impedance is |Z|, correct? -Original Message- From: F Z_Bruce Sent: Sunday, November 18, 2018 3:20 PM To: wes_n...@triconet.org ; Topband Subject: Re: Topband: Impedance of inv l? The far end is high impedance voltage, and has minimum horizontal current radiation. The inverted L is a good trade off signal vs available height. Not an expensive antenna to build. 73 Bruce-k1fz On Sun, 18 Nov 2018 12:31:38 -0700, Wes Stewart wrote: That also drives up the current in the horizontal wire with attendant increased horizontal radiation. I chose for a couple of reason to do the opposite; shorten the wire to make the feedpoint capacitive and use a shunt inductor to get a 50-ohm match. This really doesn't improve the 2:1 VSWR, that I consider acceptable, however. Wes N7WS On 11/18/2018 8:55 AM, F Z_Bruce wrote: > That sounds about right. As you put a good ground system under it, that value will come down, and the efficiency will come up. > > Many add extra antenna wire that pushes the current up the wire, this also raises the impedance, hopefully to near 50 ohms with the right length. > A capacitor (variable, then fixed) in series at the feed point can cancel the added inductance. > > 73 > Bruce-k1fz > https://www.qsl.net/k1fz/beverage_antenna.html > > > On Sun, 18 Nov 2018 10:41:36 -0500, WW3S wrote: > > What should the Z be for a 1/4 wave inv l, with the radials attached to a radial plate? Mine seems to be 60 ohms or so > > Sent from my iPad > _ > Searchable Archives: http://www.contesting.com/_topband - Topband Reflector > > _ > Searchable Archives: http://www.contesting.com/_topband - Topband Reflector > _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector --- This email has been checked for viruses by AVG. https://www.avg.com _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Topband: Impedance of inv l?
Correct Rob, Things are sometimes the reverse of what they initially seem to be. When I was a very young kid I watched workers put in telephone poles, then put wire lines on them. I knew the poles supported the wires. Later another kid said the wires hold up the poles. I disagreed, but he got me wondering. About a year later a fast driven car hit a pole and knocked out about 6 feet of pole at the bottom, and the pole was suspended by the wires. This got me wondering for some time. Its well known the current does most of the radiating. Voltage/impedance at the top of a vertical can be minimized by going to a fat antenna to maximize current radiation. But the vertical needs something to work against. Salt water is great, but otherwise most DXers go for an efficient radial field. Lower restive loss to the radials, the less power loss occurs. A matching network can change this low resistance (impedance) to that of your coax. 73 Bruce-K1FZ https://www.qsl.net/k1fz/beverage_antenna.html On Mon, 19 Nov 2018 09:58:31 -0600, Rob Atkinson wrote: My inv. L is 50 feet up and 70 horizontal. Wire is #14 bare 7 strand hard drawn. 3 feet out from mast. 101 radials, two ground rods and aluminum siding on garage strapped in to ground sys. on around 1840 Z is 11 R and ~ 20 ohms X. A typical inverted L with a good ground system should be down around 15 ohms at feedpoint from my experience and rapidly change above and below the minimum reactance point. High resistance flat antennas have an inadequate ground system. Rob K5UJ _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Impedance of inv l?
My inv. L is 50 feet up and 70 horizontal. Wire is #14 bare 7 strand hard drawn. 3 feet out from mast. 101 radials, two ground rods and aluminum siding on garage strapped in to ground sys. on around 1840 Z is 11 R and ~ 20 ohms X. A typical inverted L with a good ground system should be down around 15 ohms at feedpoint from my experience and rapidly change above and below the minimum reactance point. High resistance flat antennas have an inadequate ground system. Rob K5UJ _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Impedance of inv l?
I am not sure where you are getting your information that cutting the losses in your 160 vertical from 60 - 37 Ohms will have no difference in performance - technically or noticeably but its not correct. Reducing ground losses is THE ISSUE on 160M. Calling a 1.2:1 SWR great and not realizing what is being traded to get there, it really lacking of the right solution. A 160M antenna should have the lowest possible losses for the site and then the resulting SWR matched or tolerated. Not the other way around. 73 Ed N1UR "Date: Sun, 18 Nov 2018 11:41:12 -0500 From: To: , , "Topband" Subject: Re: Topband: Impedance of inv l? Message-ID: Content-Type: text/plain;charset="UTF-8" Theoretical impedance for a perfect 1/4 wave ground plane is 37 ohms. 60 ohms is great; 1.2:1 VSWR ? leave it alone, you will never notice any difference if you try to improve it. It will change with rain, snow, etc anyhow..73 Jay ny2ny" _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Impedance of inv l?
Yes, the "far end" has minimal radiation; it's the wire getting there that does. Doubt me, model it. Wes On 11/18/2018 1:20 PM, F Z_Bruce wrote: The far end is high impedance voltage, and has minimum horizontal current radiation. The inverted L is a good trade off signal vs available height. Not an expensive antenna to build. 73 Bruce-k1fz _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Impedance of inv l?
Hi All, Frank is correct. We originally designed the Battle Creek Special to use 16 radials 1/4 wavelength long on 160 (about 135 ft each) and then found that 32 radials 1/8 wavelength long (about 70 ft each) were much better for 160, 80 and 40 meter radiation. With 50 feet of mast and an 80 meter trap on top and the top loading wire, the feed point impedance on 160 is about 25 ohms, of which almost half is ground losses as determined by a DXpedition on a Pacific island that found a 13 ohm feed point on a beach over salt water. GL, 73, George, K8GG > > Hi Jamie, > > > I use my AA-54 frequently in exactly the manner you're using your > AA-23, I've never had any reason to be suspicious of any of its > readings. I'm lucky to have no AM broadcast stations within ten > miles. > > > Your AA-230 is telling you that at least half of your power is being > lost to ground resistance and need to at least double the number of > radials to significantly reduce your resistive losses. > > > The 2000 feet of wire in your radial system likely would have produced > much better results with twice as many radials of half the radial length > you used. Quarter wavelength radials aren't cost effective until many > more than 60 radials are used. > > > www.w0btu.com/Optimum_number_of_ground_radials_vs_radial_length.html > > > 73 > Frank > W3LPL > > > > > - Original Message - > > From: "Jamie WW3S" > To: "Topband" > Sent: Sunday, November 18, 2018 10:33:13 PM > Subject: Re: Topband: Impedance of inv l? > > several have asked how I am measuring the impedance.I'm using an > AA-230, > and am all the ALL PARAMS setting.the 230 defaults to a series model, > is > that what I want, donât see how to change it to parallel. I think the > symbol > for impedance is |Z|, correct? > > -Original Message- > From: F Z_Bruce > Sent: Sunday, November 18, 2018 3:20 PM > To: wes_n...@triconet.org ; Topband > Subject: Re: Topband: Impedance of inv l? > > > The far end is high impedance voltage, and has minimum horizontal > current radiation. The inverted L is a good trade off signal vs > available height. Not an expensive antenna to build. > > 73 > Bruce-k1fz > > On Sun, 18 Nov 2018 12:31:38 -0700, Wes Stewart wrote: > > That also drives up the current in the horizontal wire with attendant > increased > horizontal radiation. > > I chose for a couple of reason to do the opposite; shorten the wire to > make > the > feedpoint capacitive and use a shunt inductor to get a 50-ohm match. > This > really doesn't improve the 2:1 VSWR, that I consider acceptable, however. > > Wes N7WS > > On 11/18/2018 8:55 AM, F Z_Bruce wrote: > > That sounds about right. As you put a good ground system under it, > that > value will come down, and the efficiency will come up. > > > > Many add extra antenna wire that pushes the current up the wire, this > also raises the impedance, hopefully to near 50 ohms with the right > length. > > A capacitor (variable, then fixed) in series at the feed point can > cancel the added inductance. > > > > 73 > > Bruce-k1fz > > https://www.qsl.net/k1fz/beverage_antenna.html > > > > > > On Sun, 18 Nov 2018 10:41:36 -0500, WW3S wrote: > > > > What should the Z be for a 1/4 wave inv l, with the radials attached > to > a radial plate? Mine seems to be 60 ohms or so > > > > Sent from my iPad > > _ > > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector > > > > _ > > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector > > > > _ > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector > > _ > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector > > --- > This email has been checked for viruses by AVG. > https://www.avg.com > > _ > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector > > _ > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector > _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Impedance of inv l?
Hi Jamie, I use my AA-54 frequently in exactly the manner you're using your AA-23, I've never had any reason to be suspicious of any of its readings. I'm lucky to have no AM broadcast stations within ten miles. Your AA-230 is telling you that at least half of your power is being lost to ground resistance and need to at least double the number of radials to significantly reduce your resistive losses. The 2000 feet of wire in your radial system likely would have produced much better results with twice as many radials of half the radial length you used. Quarter wavelength radials aren't cost effective until many more than 60 radials are used. www.w0btu.com/Optimum_number_of_ground_radials_vs_radial_length.html 73 Frank W3LPL - Original Message - From: "Jamie WW3S" To: "Topband" Sent: Sunday, November 18, 2018 10:33:13 PM Subject: Re: Topband: Impedance of inv l? several have asked how I am measuring the impedance.I'm using an AA-230, and am all the ALL PARAMS setting.the 230 defaults to a series model, is that what I want, don’t see how to change it to parallel. I think the symbol for impedance is |Z|, correct? -Original Message- From: F Z_Bruce Sent: Sunday, November 18, 2018 3:20 PM To: wes_n...@triconet.org ; Topband Subject: Re: Topband: Impedance of inv l? The far end is high impedance voltage, and has minimum horizontal current radiation. The inverted L is a good trade off signal vs available height. Not an expensive antenna to build. 73 Bruce-k1fz On Sun, 18 Nov 2018 12:31:38 -0700, Wes Stewart wrote: That also drives up the current in the horizontal wire with attendant increased horizontal radiation. I chose for a couple of reason to do the opposite; shorten the wire to make the feedpoint capacitive and use a shunt inductor to get a 50-ohm match. This really doesn't improve the 2:1 VSWR, that I consider acceptable, however. Wes N7WS On 11/18/2018 8:55 AM, F Z_Bruce wrote: > That sounds about right. As you put a good ground system under it, that value will come down, and the efficiency will come up. > > Many add extra antenna wire that pushes the current up the wire, this also raises the impedance, hopefully to near 50 ohms with the right length. > A capacitor (variable, then fixed) in series at the feed point can cancel the added inductance. > > 73 > Bruce-k1fz > https://www.qsl.net/k1fz/beverage_antenna.html > > > On Sun, 18 Nov 2018 10:41:36 -0500, WW3S wrote: > > What should the Z be for a 1/4 wave inv l, with the radials attached to a radial plate? Mine seems to be 60 ohms or so > > Sent from my iPad > _ > Searchable Archives: http://www.contesting.com/_topband - Topband Reflector > > _ > Searchable Archives: http://www.contesting.com/_topband - Topband Reflector > _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector --- This email has been checked for viruses by AVG. https://www.avg.com _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Impedance of inv l?
Yes it does. I made my inverted-L a little longer to raise the Z and the point of max current, based on a post here years ago by K3LR. I also used two elevated radials. Jay can do that or use K9AV FCP. www.w0btu.com/160_meters.html (scroll down) lists.contesting.com/_topband/2007-11/msg00248.html www.w0btu.com/Optimum_number_of_ground_radials_vs_radial_length.html 73, Mike www.w0btu.com On Sun, Nov 18, 2018, 11:17 AM Wes Stewart wrote: > That is not great. It implies excessive ground loss. > > On 11/18/2018 9:41 AM, jayb1...@optonline.net wrote: > > Theoretical impedance for a perfect 1/4 wave ground plane is 37 ohms. 60 > > ohms is great; 1.2:1 VSWR – leave it alone, you will never notice any > > difference if you try to improve it. It will change with rain, snow, etc > > anyhow..73 Jay ny2ny > > _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Impedance of inv l?
several have asked how I am measuring the impedance.I'm using an AA-230, and am all the ALL PARAMS setting.the 230 defaults to a series model, is that what I want, don’t see how to change it to parallel. I think the symbol for impedance is |Z|, correct? -Original Message- From: F Z_Bruce Sent: Sunday, November 18, 2018 3:20 PM To: wes_n...@triconet.org ; Topband Subject: Re: Topband: Impedance of inv l? The far end is high impedance voltage, and has minimum horizontal current radiation. The inverted L is a good trade off signal vs available height. Not an expensive antenna to build. 73 Bruce-k1fz On Sun, 18 Nov 2018 12:31:38 -0700, Wes Stewart wrote: That also drives up the current in the horizontal wire with attendant increased horizontal radiation. I chose for a couple of reason to do the opposite; shorten the wire to make the feedpoint capacitive and use a shunt inductor to get a 50-ohm match. This really doesn't improve the 2:1 VSWR, that I consider acceptable, however. Wes N7WS On 11/18/2018 8:55 AM, F Z_Bruce wrote: > That sounds about right. As you put a good ground system under it, that value will come down, and the efficiency will come up. > > Many add extra antenna wire that pushes the current up the wire, this also raises the impedance, hopefully to near 50 ohms with the right length. > A capacitor (variable, then fixed) in series at the feed point can cancel the added inductance. > > 73 > Bruce-k1fz > https://www.qsl.net/k1fz/beverage_antenna.html > > > On Sun, 18 Nov 2018 10:41:36 -0500, WW3S wrote: > > What should the Z be for a 1/4 wave inv l, with the radials attached to a radial plate? Mine seems to be 60 ohms or so > > Sent from my iPad > _ > Searchable Archives: http://www.contesting.com/_topband - Topband Reflector > > _ > Searchable Archives: http://www.contesting.com/_topband - Topband Reflector > _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector --- This email has been checked for viruses by AVG. https://www.avg.com _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Impedance of inv l?
The far end is high impedance voltage, and has minimum horizontal current radiation. The inverted L is a good trade off signal vs available height. Not an expensive antenna to build. 73 Bruce-k1fz On Sun, 18 Nov 2018 12:31:38 -0700, Wes Stewart wrote: That also drives up the current in the horizontal wire with attendant increased horizontal radiation. I chose for a couple of reason to do the opposite; shorten the wire to make the feedpoint capacitive and use a shunt inductor to get a 50-ohm match. This really doesn't improve the 2:1 VSWR, that I consider acceptable, however. Wes N7WS On 11/18/2018 8:55 AM, F Z_Bruce wrote: > That sounds about right. As you put a good ground system under it, that value will come down, and the efficiency will come up. > > Many add extra antenna wire that pushes the current up the wire, this also raises the impedance, hopefully to near 50 ohms with the right length. > A capacitor (variable, then fixed) in series at the feed point can cancel the added inductance. > > 73 > Bruce-k1fz > https://www.qsl.net/k1fz/beverage_antenna.html > > > On Sun, 18 Nov 2018 10:41:36 -0500, WW3S wrote: > > What should the Z be for a 1/4 wave inv l, with the radials attached to a radial plate? Mine seems to be 60 ohms or so > > Sent from my iPad > _ > Searchable Archives: http://www.contesting.com/_topband - Topband Reflector > > _ > Searchable Archives: http://www.contesting.com/_topband - Topband Reflector > _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Impedance of inv l?
That also drives up the current in the horizontal wire with attendant increased horizontal radiation. I chose for a couple of reason to do the opposite; shorten the wire to make the feedpoint capacitive and use a shunt inductor to get a 50-ohm match. This really doesn't improve the 2:1 VSWR, that I consider acceptable, however. Wes N7WS On 11/18/2018 8:55 AM, F Z_Bruce wrote: That sounds about right. As you put a good ground system under it, that value will come down, and the efficiency will come up. Many add extra antenna wire that pushes the current up the wire, this also raises the impedance, hopefully to near 50 ohms with the right length. A capacitor (variable, then fixed) in series at the feed point can cancel the added inductance. 73 Bruce-k1fz https://www.qsl.net/k1fz/beverage_antenna.html On Sun, 18 Nov 2018 10:41:36 -0500, WW3S wrote: What should the Z be for a 1/4 wave inv l, with the radials attached to a radial plate? Mine seems to be 60 ohms or so Sent from my iPad _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Impedance of inv l?
That is not great. It implies excessive ground loss. On 11/18/2018 9:41 AM, jayb1...@optonline.net wrote: Theoretical impedance for a perfect 1/4 wave ground plane is 37 ohms. 60 ohms is great; 1.2:1 VSWR – leave it alone, you will never notice any difference if you try to improve it. It will change with rain, snow, etc anyhow..73 Jay ny2ny _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Impedance of inv l?
To the first order, the feedpoint Z (at resonance) will depend on the height of the vertical portion, which affects the radiation resistance. and the resistive loss of the ground connection which appears in series with it. A full height (1/4 wavelength) vertical over perfect (zero ohm) ground will be about 35 ohm. A shortened vertical, toploaded (the "L" portion) will be lower than this, again over perfect ground. Sixty ohm seems way too high and since you have a respectable, but not outstanding radial system, suggests to me measurement error. How are you measuring this? My inverted L, 55 feet vertical, the rest horizontal measures ~24 ohm at resonance, with a very marginal (work in progress) radial field of twenty, 55' long insulated radials on the ground. I've used three different instruments, all vector analyzers, to confirm this. (DG8SQQ, FA-VA5 and AA-55) I have a 50KW BC station on 1550 kHz that measures -3 dBm on this antenna. Only a vector analyzer, used with care, will handle this. Wes N7WS On 11/18/2018 9:48 AM, Jamie WW3S wrote: well, I THOUGHT I had a good ground.16 radials I think, 1/4 long.so I thought I'd see around 30-35 ohms impedance.not sure what to think now.I was going to get either a balun and unun at the feed point, was going be someone else's statement that there inv l was around 22 ohms, glad I measured mine before I ordered one - Original Message - From: "F Z_Bruce" To: w...@zoominternet.net, "Topband" Sent: Sunday, November 18, 2018 10:55:47 AM Subject: Re: Topband: Impedance of inv l? That sounds about right. As you put a good ground system under it, that value will come down, and the efficiency will come up. Many add extra antenna wire that pushes the current up the wire, this also raises the impedance, hopefully to near 50 ohms with the right length. A capacitor (variable, then fixed) in series at the feed point can cancel the added inductance. 73 Bruce-k1fz https://www.qsl.net/k1fz/beverage_antenna.html On Sun, 18 Nov 2018 10:41:36 -0500, WW3S wrote: What should the Z be for a 1/4 wave inv l, with the radials attached to a radial plate? Mine seems to be 60 ohms or so Sent from my iPad _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Impedance of inv l?
well, I THOUGHT I had a good ground.16 radials I think, 1/4 long.so I thought I'd see around 30-35 ohms impedance.not sure what to think now.I was going to get either a balun and unun at the feed point, was going be someone else's statement that there inv l was around 22 ohms, glad I measured mine before I ordered one - Original Message - From: "F Z_Bruce" To: w...@zoominternet.net, "Topband" Sent: Sunday, November 18, 2018 10:55:47 AM Subject: Re: Topband: Impedance of inv l? That sounds about right. As you put a good ground system under it, that value will come down, and the efficiency will come up. Many add extra antenna wire that pushes the current up the wire, this also raises the impedance, hopefully to near 50 ohms with the right length. A capacitor (variable, then fixed) in series at the feed point can cancel the added inductance. 73 Bruce-k1fz https://www.qsl.net/k1fz/beverage_antenna.html On Sun, 18 Nov 2018 10:41:36 -0500, WW3S wrote: What should the Z be for a 1/4 wave inv l, with the radials attached to a radial plate? Mine seems to be 60 ohms or so Sent from my iPad _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Impedance of inv l?
Theoretical impedance for a perfect 1/4 wave ground plane is 37 ohms. 60 ohms is great; 1.2:1 VSWR – leave it alone, you will never notice any difference if you try to improve it. It will change with rain, snow, etc anyhow..73 Jay ny2ny _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Impedance of inv l?
That sounds about right. As you put a good ground system under it, that value will come down, and the efficiency will come up. Many add extra antenna wire that pushes the current up the wire, this also raises the impedance, hopefully to near 50 ohms with the right length. A capacitor (variable, then fixed) in series at the feed point can cancel the added inductance. 73 Bruce-k1fz https://www.qsl.net/k1fz/beverage_antenna.html On Sun, 18 Nov 2018 10:41:36 -0500, WW3S wrote: What should the Z be for a 1/4 wave inv l, with the radials attached to a radial plate? Mine seems to be 60 ohms or so Sent from my iPad _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Topband: Impedance of inv l?
What should the Z be for a 1/4 wave inv l, with the radials attached to a radial plate? Mine seems to be 60 ohms or so Sent from my iPad _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
