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: Fwd: Re: Impedance of inv l?
One of the reason you make an INV-L a bit longer is to address the capacitance you need to tune out the inductive reactance. Capacitance and capacitive reactance is an inverse relationship. See attached graph. 73 Mark K3MSB On Sun, Nov 18, 2018 at 10:59 AM F Z_Bruce wrote: > > > > > Original Message > Subject: Re: Topband: Impedance of inv l? > Date: Sun, 18 Nov 2018 10:55:47 -0500 > From: F Z_Bruce > To: w...@zoominternet.net, Topband > > > > 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 inductive reactance. > 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 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
Topband: Fwd: Re: Impedance of inv l?
Original Message Subject: Re: Topband: Impedance of inv l? Date: Sun, 18 Nov 2018 10:55:47 -0500 From: F Z_Bruce To: w...@zoominternet.net, Topband 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 inductive reactance. 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 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
Re: Topband: ARRL DXCC - 160 Meters
At 08:47 17/11/2018 -0500, you wrote: (or overworked ARRL staff person at a hamfest). It was made at Friedrichshafen in 2008 and he was listed in the pdf file "DXCC Standings". In 2009 he was removed from the file. I have those files in my archive if needed. Paolo I4EWH _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
