Re: Topband: Lab style comparison results on 160m small lot antenna changes.
Guy, why must we continually test NEC against measurements? The work by N6LF has shown great correlation between simulation and the real world. Those of us who design electronic circuits (including EM) in the world of computer simulation have great faith in the various programs and NEC-4 (and possibly NEC-2) should give us an adequate A-B comparison. Dave WX7G ___ Stew Perry Topband Distance Challenge coming on December 29th.
Re: Topband: Lab style comparison results on 160m small lot antennachanges.
Tests to answer the question is the FCP better than counterpoise X can be answered by 28 MHz scale models. The question the FCP is better at 1.8 MHz by Y dB cannot be answered by 28 MHz scale models. What question do we really need answered? Dave WX7G On Dec 21, 2012 11:30 AM, Tom W8JI w...@w8ji.com wrote: - Original Message - From: Guy Olinger K2AV olin...@bellsouth.net To: TopBand List topband@contesting.com Sent: Thursday, December 20, 2012 7:25 PM Subject: Topband: Lab style comparison results on 160m small lot antennachanges. A prior poster, lamenting the nature of FCP success reports, wrote: Who has done that, with only a radial change, against an unchanged reference antenna that is in the far field of the antenna under test. [Where's the post with the details] ? Perfectly logical question. We all would like that answered with posts listing lab grade experiments. Because of antenna size, laboratory measurements are impossible on lower bands. For that reason we can't make lab-style comparisons. There is one thing, though, that we probably all agree on. If more than one thing that can affect results changes in an unknown way in any test or experiment, like the ionosphere or reworking an entire antenna system from less-than-good system to a new one, we really don't know what caused the change or if any one particular thing was responsible for the change. If we A-B against any unchanged reference, we at least know which was better than the reference and how much better. None of this requires a lab, precise equipment, is unreasonable, or is in the most remote way unfair. It just requires reasonable methods. 73 Tom __**_ Stew Perry Topband Distance Challenge coming on December 29th. ___ Stew Perry Topband Distance Challenge coming on December 29th.
Re: Topband: LoTW, Ground mounted 1/2 wave etc.
KM1H should be banned once again. Dave WX7G On Dec 19, 2012 9:59 AM, HAROLD SMITH JR w0ri...@sbcglobal.net wrote: Hello Raoul, Yes there are a few 160 meter gentlemen and gentlegirls still left. If you notice, the flaming remarks mostly are made by one person. Several years ago he was banned from this reflector. I do have to agree that it really gets disgusting. Thank god there is a delete key on every keyboard. Wishing You and Your family a VERY Merry Christms and Prosperous New Year. Price W0RI and trustee of W0CKC Club Station: St. Louis Lowbaders Club Like most of us I have been reading and trying to absorb the excellent technical information in this group, but really, personal attacks and comments should be avoided. Or is this simply normal, a reflection of what is happening on the bands too? I hope this comes to an end, I would hate to unsubscribe. Will the 160m gentlemen please stand up, if there are any left? Merry Christmas to all, and a Happy new Year! Raoul ZS1REC ___ It is undesirable to believe a proposition when there is no ground whatsoever for supposing it is true. - Bertrand Russell ___ It is undesirable to believe a proposition when there is no ground whatsoever for supposing it is true. - Bertrand Russell ___ It is undesirable to believe a proposition when there is no ground whatsoever for supposing it is true. - Bertrand Russell
Re: Topband: Ground mounted 1/2 wave
On Mon, Dec 17, 2012 at 8:41 PM, Carl k...@jeremy.mv.com wrote: Subject: Re: Topband: Ground mounted 1/2 wave ** All that means is that the elevation peak of the wave as seen in the typical 2D plot increases by .38dB and as expected. It does not say what happens from that peak down to zero elevation which is what 160M DXers care about. What is the FS at 5, 10 degrees when going from a ground rod to a full bore radial field over a wide range of ground conductivity? Carl KM1H Yes, it does say what happens from that peak down to zero elevation. It says that the signal increases by 0.38 dB. To test this I ran two EZNEC simulations. One is a 90 degree vertical over thirty 90 degree radials over medium ground. The antenna is driven with 1 kW and the E-field at one mile is recorded from a height of 10' to 1000'. A second 90 degree vertical over four 23 degree radials driven with 1 kW and the E-field at one mile is recorded from a heights of 10' to 1000'. *The difference in E-field AT ALL ELEVATIONS is 0.86 dB*. Dave WX7G __**_ It is undesirable to believe a proposition when there is no ground whatsoever for supposing it is true. #8212; Bertrand Russell ___ It is undesirable to believe a proposition when there is no ground whatsoever for supposing it is true. #8212; Bertrand Russell
Re: Topband: Ground mounted 1/2 wave
Where is the helicopter you insisted we need? On Dec 18, 2012 10:03 AM, Carl k...@jeremy.mv.com wrote: I guess I wasnt clear enough so lets start again. We both agree that the .38 db increase is at all elevation angles since the increase in efficiency at the feed doesnt change the pattern shape, just levels. OK ? Where the differences are is in the initial far field signal strengths from zero to lets say 20 degrees. With a perfect theoretical ground the levels are the same. If that held in reality then no matter what the ground losses are the BC stations would not be spending the big bucks in radial fields, even for 1/2 waves. The city lot ham would be readily competitive with the antenna farm operator or the little guy in a coastal salt water swamp. My point all along is that ground losses change the shape of the main lobe curve at low elevations and reduce signal levels there. Total power doesnt change but it is no longer all radiated, some is now dissipated in the lossy ground. Basic physics tell us you cant have both at the same time. BC stations arent allowed to do that since it is the ground wave they are required to radiate to their local audience, the sole reason of their existence except for the few clear channel flamethrowers. A good ground wave signal means a good amount of power in all of that main lobe which results in the nightime skywave BCB DXers crave. Hams want some of that low angle just above the ground wave to work DX and those that radiate a high percentage of the output fed into the antenna to cover all those angles win the gold. Other than saltwater there is no magic fix as some want you to believe. Many years ago there was a BC station in Lowell, MA that had a tower on a 4th story industrial building metal roof, that was the total ground. Im about 6 miles LOS from there and the selective fading was intense. Their ground wave was minimal but somewhere along the way the FCC allowed them to operate. I dont remember the details but there were several stories floating around about why they kept operating. It all went away during the urban renewal of Lowell, establishment of an Urban National Park, and a huge city investment in its future. I suppose hams can use a high end local BCB station to evaluate changes as they make them. Find a moderately strong steady station and monitor/chart its strength for several days of the same weather. Then by adding radials, rods, screens, perimeter wires, etc progress (or lack of) can be tracked. By doubling radials each time from 4 to 32 or even 64 and having them all precut and ready to unroll this can be done in a few hours especially with a helper. Next comes the screen. Carl KM1H - Original Message - From: DAVID CUTHBERT To: Carl Cc: Tom W8JI ; Donald Chester ; topband@contesting.com Sent: Tuesday, December 18, 2012 8:00 AM Subject: Re: Topband: Ground mounted 1/2 wave On Mon, Dec 17, 2012 at 8:41 PM, Carl k...@jeremy.mv.com wrote: Subject: Re: Topband: Ground mounted 1/2 wave ** All that means is that the elevation peak of the wave as seen in the typical 2D plot increases by .38dB and as expected. It does not say what happens from that peak down to zero elevation which is what 160M DXers care about. What is the FS at 5, 10 degrees when going from a ground rod to a full bore radial field over a wide range of ground conductivity? Carl KM1H Yes, it does say what happens from that peak down to zero elevation. It says that the signal increases by 0.38 dB. To test this I ran two EZNEC simulations. One is a 90 degree vertical over thirty 90 degree radials over medium ground. The antenna is driven with 1 kW and the E-field at one mile is recorded from a height of 10' to 1000'. A second 90 degree vertical over four 23 degree radials driven with 1 kW and the E-field at one mile is recorded from a heights of 10' to 1000'. The difference in E-field AT ALL ELEVATIONS is 0.86 dB. Dave WX7G __**_ It is undesirable to believe a proposition when there is no ground whatsoever for supposing it is true. #8212; Bertrand Russell No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1430 / Virus Database: 2637/5468 - Release Date: 12/18/12 ___ It is undesirable to believe a proposition when there is no ground whatsoever for supposing it is true. #8212; Bertrand Russell
Re: Topband: GAP Vertical Question
*Half wavelength vertical ground loss* Let's see if we can quantify the conduction losses of a 1.8 MHz half wavelength vertical connected to average earth via a ground rod. This paper by N6LF shows one skin depth at 1.8 MHz to be 6 meters. http://www.antennasbyn6lf.com/files/ground_skin_depth_and_wavelength.pdf Let's assume the current magnitude in the ground mirrors that of the antenna. Driving the antenna at the base such that the current at the antenna center is 1 amp, the ground current 40 meters away from the antenna is 1 amp. The 1 amp of ground current passes through a section of earth having an effective depth of of 6 meters. For a 1 meter radial length and 40 meters from the antenna the section has dimensions of 1 meter X 6 meters X 250 meters (250 meters is the circumference). Given a resistivity of 200 ohms/meter the resistance of this section is 200/(6 X 250) = 0.13 ohms. The loss in this section is 0.13 watts. Using NEC we see with the base current set to give 1 amp at the antenna center the power into the antenna is 100 watts. Closer to the base of the antenna the effective ground resistance increases due to the smaller circumference. Closer to the antenna the current decreases. Roughly Integrating the ground loss from the base to the 80 meters away gives a total ground loss of 4 watts. The no-radial ground loss is 5 watts and the antenna gain is reduced by 10LOG(100/96) = 0.2 dB from the full radial case. How about ground loss due to the induced E-field in the ground? I believe this is accounted for in the previous calculation. I ran a NEC simulation to explore this. The two cases were a 266' vertical fed against thirty 3' radials and thirty 133' radials. The radials are 0.05' above medium ground. The NEC Average Gain was compared for the two cases and showed a difference of 0.06 dB. Dave WX7G On Sun, Dec 16, 2012 at 6:42 PM, Donald Chester k4...@hotmail.com wrote: Then, why do broadcast stations that use vertical towers at approximately a half wavelength, purchase valuable real estate and spend thousands of dollars for the copper to install from 120 to 240 or more radials, each usually a half wave or more in length? See G. H. Brown: Ground Systems as a Factor in Antenna Efficiency, IRE Proceedings, June 1937 p. 753. Brown demonstrated that the distribution of earth currents and ground losses is such that the region of maximum current and loss occurs at a distance of about 0.35 wavelengths from the base of a ground mounted half wave vertical antenna, which was verified experimentally. There is zero loss at the base of the antenna itself, since there is no base current because the antenna a fed at a current node. An rf ammeter inserted in the ground lead, as well as one inserted in in the antenna lead attached to the insulated base of the radiator will read zero. The ground losses occur farther out from the base of the antenna. Low effective earth resistance provided by a good ground system is ABSOLUTELY NECESSARY for vertical antennas of ANY height if one expects good radiation efficiency. The claim that no ground system is needed for a half wave vertical is nothing more than a long-standing popular misconception. This topic prompted me to dig out and review an anecdote I recall reading in my decades-old copy of CQ magazine's Vertical Antenna Handbook, by USNR Capt. Paul H. Lee, K6TS (1974). He reported receiving mail from a ham who had made the discovery that he could tune and operate a half wave vertical without a ground system, feeding it by a parallel tuned tank circuit whose lower end is grounded. Since an rf ammeter in the ground lead showed no current, he could dispense with the ground system and its loss. He suggested to the Capt. that he should discover the new world of half verticals with no ground system. Quoting from the text (p. 84): The correspondent's claim... is true ONLY IF HE IS CONTENT TO THROW AWAY FROM 40 TO 80 PER CENT OF HIS RADIATED POWER IN THE FORM OF EARTH LOSSES. (the correspondent) stated, 'The ZL's call ME, when I use my half wave vertical!' This is not surprising, in view of the fact that the half wave's vertical pattern has a lower main lobe angle than a quarter wave would have... However, he would hit the ZL's even harder if he would put in a ground system. Of course, the half wave vertical is not dependent on a ground plane, however lossy or efficient, for the condition of RESONANCE, since it is resonant in itself because of its half wave length. However, IT IS DEPENDENT ON A GROUND PLANE FOR ITS EFFICIENCY OF RADIATION, as is any vertical antenna...' Don k4kyv Given that a half wave vertical has a base impedance of over 1000 ohms and a single ground rod in dirt is 100 ohms at most not a single radial is needed to obtain close to 100% radiation efficiency. Dave WX7G And this statement is based on what? Publications, measurements, modeling? I have built a number of
Re: Topband: GAP Vertical Question
Where is the 40-60% claimed ground loss? I get 4%. On Dec 17, 2012 6:12 AM, DAVID CUTHBERT telegraph...@gmail.com wrote: *Half wavelength vertical ground loss* Let's see if we can quantify the conduction losses of a 1.8 MHz half wavelength vertical connected to average earth via a ground rod. This paper by N6LF shows one skin depth at 1.8 MHz to be 6 meters. http://www.antennasbyn6lf.com/files/ground_skin_depth_and_wavelength.pdf Let's assume the current magnitude in the ground mirrors that of the antenna. Driving the antenna at the base such that the current at the antenna center is 1 amp, the ground current 40 meters away from the antenna is 1 amp. The 1 amp of ground current passes through a section of earth having an effective depth of of 6 meters. For a 1 meter radial length and 40 meters from the antenna the section has dimensions of 1 meter X 6 meters X 250 meters (250 meters is the circumference). Given a resistivity of 200 ohms/meter the resistance of this section is 200/(6 X 250) = 0.13 ohms. The loss in this section is 0.13 watts. Using NEC we see with the base current set to give 1 amp at the antenna center the power into the antenna is 100 watts. Closer to the base of the antenna the effective ground resistance increases due to the smaller circumference. Closer to the antenna the current decreases. Roughly Integrating the ground loss from the base to the 80 meters away gives a total ground loss of 4 watts. The no-radial ground loss is 5 watts and the antenna gain is reduced by 10LOG(100/96) = 0.2 dB from the full radial case. How about ground loss due to the induced E-field in the ground? I believe this is accounted for in the previous calculation. I ran a NEC simulation to explore this. The two cases were a 266' vertical fed against thirty 3' radials and thirty 133' radials. The radials are 0.05' above medium ground. The NEC Average Gain was compared for the two cases and showed a difference of 0.06 dB. Dave WX7G On Sun, Dec 16, 2012 at 6:42 PM, Donald Chester k4...@hotmail.com wrote: Then, why do broadcast stations that use vertical towers at approximately a half wavelength, purchase valuable real estate and spend thousands of dollars for the copper to install from 120 to 240 or more radials, each usually a half wave or more in length? See G. H. Brown: Ground Systems as a Factor in Antenna Efficiency, IRE Proceedings, June 1937 p. 753. Brown demonstrated that the distribution of earth currents and ground losses is such that the region of maximum current and loss occurs at a distance of about 0.35 wavelengths from the base of a ground mounted half wave vertical antenna, which was verified experimentally. There is zero loss at the base of the antenna itself, since there is no base current because the antenna a fed at a current node. An rf ammeter inserted in the ground lead, as well as one inserted in in the antenna lead attached to the insulated base of the radiator will read zero. The ground losses occur farther out from the base of the antenna. Low effective earth resistance provided by a good ground system is ABSOLUTELY NECESSARY for vertical antennas of ANY height if one expects good radiation efficiency. The claim that no ground system is needed for a half wave vertical is nothing more than a long-standing popular misconception. This topic prompted me to dig out and review an anecdote I recall reading in my decades-old copy of CQ magazine's Vertical Antenna Handbook, by USNR Capt. Paul H. Lee, K6TS (1974). He reported receiving mail from a ham who had made the discovery that he could tune and operate a half wave vertical without a ground system, feeding it by a parallel tuned tank circuit whose lower end is grounded. Since an rf ammeter in the ground lead showed no current, he could dispense with the ground system and its loss. He suggested to the Capt. that he should discover the new world of half verticals with no ground system. Quoting from the text (p. 84): The correspondent's claim... is true ONLY IF HE IS CONTENT TO THROW AWAY FROM 40 TO 80 PER CENT OF HIS RADIATED POWER IN THE FORM OF EARTH LOSSES. (the correspondent) stated, 'The ZL's call ME, when I use my half wave vertical!' This is not surprising, in view of the fact that the half wave's vertical pattern has a lower main lobe angle than a quarter wave would have... However, he would hit the ZL's even harder if he would put in a ground system. Of course, the half wave vertical is not dependent on a ground plane, however lossy or efficient, for the condition of RESONANCE, since it is resonant in itself because of its half wave length. However, IT IS DEPENDENT ON A GROUND PLANE FOR ITS EFFICIENCY OF RADIATION, as is any vertical antenna...' Don k4kyv Given that a half wave vertical has a base impedance of over 1000 ohms and a single ground rod in dirt is 100 ohms at most not a single radial is needed to obtain close
Re: Topband: Ground mounted 1/2 and 1/4 wave verticals (was GAP)
Carl. I quantified ground loss in the near field. Now it's your turn. Numbers please, not adjectives or hand waving. Dave WX7G On Dec 17, 2012 2:59 PM, ZR z...@jeremy.mv.com wrote: Because youre still stuck in neutral and are measuring/calculating nothing of interest. The loss is determined at various elevation angles at a sufficient distance by field strength. Get a helicopter. Carl KM1H - Original Message - From: DAVID CUTHBERT telegraph...@gmail.com To: Donald Chester k4...@hotmail.com Cc: topband@contesting.com Sent: Monday, December 17, 2012 1:53 PM Subject: Re: Topband: GAP Vertical Question Where is the 40-60% claimed ground loss? I get 4%. On Dec 17, 2012 6:12 AM, DAVID CUTHBERT telegraph...@gmail.com wrote: *Half wavelength vertical ground loss* Let's see if we can quantify the conduction losses of a 1.8 MHz half wavelength vertical connected to average earth via a ground rod. This paper by N6LF shows one skin depth at 1.8 MHz to be 6 meters. http://www.antennasbyn6lf.com/**files/ground_skin_depth_and_** wavelength.pdfhttp://www.antennasbyn6lf.com/files/ground_skin_depth_and_wavelength.pdf Let's assume the current magnitude in the ground mirrors that of the antenna. Driving the antenna at the base such that the current at the antenna center is 1 amp, the ground current 40 meters away from the antenna is 1 amp. The 1 amp of ground current passes through a section of earth having an effective depth of of 6 meters. For a 1 meter radial length and 40 meters from the antenna the section has dimensions of 1 meter X 6 meters X 250 meters (250 meters is the circumference). Given a resistivity of 200 ohms/meter the resistance of this section is 200/(6 X 250) = 0.13 ohms. The loss in this section is 0.13 watts. Using NEC we see with the base current set to give 1 amp at the antenna center the power into the antenna is 100 watts. Closer to the base of the antenna the effective ground resistance increases due to the smaller circumference. Closer to the antenna the current decreases. Roughly Integrating the ground loss from the base to the 80 meters away gives a total ground loss of 4 watts. The no-radial ground loss is 5 watts and the antenna gain is reduced by 10LOG(100/96) = 0.2 dB from the full radial case. How about ground loss due to the induced E-field in the ground? I believe this is accounted for in the previous calculation. I ran a NEC simulation to explore this. The two cases were a 266' vertical fed against thirty 3' radials and thirty 133' radials. The radials are 0.05' above medium ground. The NEC Average Gain was compared for the two cases and showed a difference of 0.06 dB. Dave WX7G On Sun, Dec 16, 2012 at 6:42 PM, Donald Chester k4...@hotmail.com wrote: Then, why do broadcast stations that use vertical towers at approximately a half wavelength, purchase valuable real estate and spend thousands of dollars for the copper to install from 120 to 240 or more radials, each usually a half wave or more in length? See G. H. Brown: Ground Systems as a Factor in Antenna Efficiency, IRE Proceedings, June 1937 p. 753. Brown demonstrated that the distribution of earth currents and ground losses is such that the region of maximum current and loss occurs at a distance of about 0.35 wavelengths from the base of a ground mounted half wave vertical antenna, which was verified experimentally. There is zero loss at the base of the antenna itself, since there is no base current because the antenna a fed at a current node. An rf ammeter inserted in the ground lead, as well as one inserted in in the antenna lead attached to the insulated base of the radiator will read zero. The ground losses occur farther out from the base of the antenna. Low effective earth resistance provided by a good ground system is ABSOLUTELY NECESSARY for vertical antennas of ANY height if one expects good radiation efficiency. The claim that no ground system is needed for a half wave vertical is nothing more than a long-standing popular misconception. This topic prompted me to dig out and review an anecdote I recall reading in my decades-old copy of CQ magazine's Vertical Antenna Handbook, by USNR Capt. Paul H. Lee, K6TS (1974). He reported receiving mail from a ham who had made the discovery that he could tune and operate a half wave vertical without a ground system, feeding it by a parallel tuned tank circuit whose lower end is grounded. Since an rf ammeter in the ground lead showed no current, he could dispense with the ground system and its loss. He suggested to the Capt. that he should discover the new world of half verticals with no ground system. Quoting from the text (p. 84): The correspondent's claim... is true ONLY IF HE IS CONTENT TO THROW AWAY FROM 40 TO 80 PER CENT OF HIS RADIATED POWER IN THE FORM OF EARTH LOSSES. (the correspondent) stated, 'The ZL's call ME, when I use my
Re: Topband: Ground mounted 1/2 and 1/4 wave verticals (was GAP)
Carl, What we do in the near-field to control ground loss affects the far-field signal equally at all elevations. Therefore there is no need to measure far-field field strength at more than one elevation. We have control of the near-field and anything we do in that region shows up as a change in input impedance. Dave WX7G On Dec 17, 2012 3:08 PM, DAVID CUTHBERT telegraph...@gmail.com wrote: Carl. I quantified ground loss in the near field. Now it's your turn. Numbers please, not adjectives or hand waving. Dave WX7G On Dec 17, 2012 2:59 PM, ZR z...@jeremy.mv.com wrote: Because youre still stuck in neutral and are measuring/calculating nothing of interest. The loss is determined at various elevation angles at a sufficient distance by field strength. Get a helicopter. Carl KM1H - Original Message - From: DAVID CUTHBERT telegraph...@gmail.com To: Donald Chester k4...@hotmail.com Cc: topband@contesting.com Sent: Monday, December 17, 2012 1:53 PM Subject: Re: Topband: GAP Vertical Question Where is the 40-60% claimed ground loss? I get 4%. On Dec 17, 2012 6:12 AM, DAVID CUTHBERT telegraph...@gmail.com wrote: *Half wavelength vertical ground loss* Let's see if we can quantify the conduction losses of a 1.8 MHz half wavelength vertical connected to average earth via a ground rod. This paper by N6LF shows one skin depth at 1.8 MHz to be 6 meters. http://www.antennasbyn6lf.com/**files/ground_skin_depth_and_** wavelength.pdfhttp://www.antennasbyn6lf.com/files/ground_skin_depth_and_wavelength.pdf Let's assume the current magnitude in the ground mirrors that of the antenna. Driving the antenna at the base such that the current at the antenna center is 1 amp, the ground current 40 meters away from the antenna is 1 amp. The 1 amp of ground current passes through a section of earth having an effective depth of of 6 meters. For a 1 meter radial length and 40 meters from the antenna the section has dimensions of 1 meter X 6 meters X 250 meters (250 meters is the circumference). Given a resistivity of 200 ohms/meter the resistance of this section is 200/(6 X 250) = 0.13 ohms. The loss in this section is 0.13 watts. Using NEC we see with the base current set to give 1 amp at the antenna center the power into the antenna is 100 watts. Closer to the base of the antenna the effective ground resistance increases due to the smaller circumference. Closer to the antenna the current decreases. Roughly Integrating the ground loss from the base to the 80 meters away gives a total ground loss of 4 watts. The no-radial ground loss is 5 watts and the antenna gain is reduced by 10LOG(100/96) = 0.2 dB from the full radial case. How about ground loss due to the induced E-field in the ground? I believe this is accounted for in the previous calculation. I ran a NEC simulation to explore this. The two cases were a 266' vertical fed against thirty 3' radials and thirty 133' radials. The radials are 0.05' above medium ground. The NEC Average Gain was compared for the two cases and showed a difference of 0.06 dB. Dave WX7G On Sun, Dec 16, 2012 at 6:42 PM, Donald Chester k4...@hotmail.com wrote: Then, why do broadcast stations that use vertical towers at approximately a half wavelength, purchase valuable real estate and spend thousands of dollars for the copper to install from 120 to 240 or more radials, each usually a half wave or more in length? See G. H. Brown: Ground Systems as a Factor in Antenna Efficiency, IRE Proceedings, June 1937 p. 753. Brown demonstrated that the distribution of earth currents and ground losses is such that the region of maximum current and loss occurs at a distance of about 0.35 wavelengths from the base of a ground mounted half wave vertical antenna, which was verified experimentally. There is zero loss at the base of the antenna itself, since there is no base current because the antenna a fed at a current node. An rf ammeter inserted in the ground lead, as well as one inserted in in the antenna lead attached to the insulated base of the radiator will read zero. The ground losses occur farther out from the base of the antenna. Low effective earth resistance provided by a good ground system is ABSOLUTELY NECESSARY for vertical antennas of ANY height if one expects good radiation efficiency. The claim that no ground system is needed for a half wave vertical is nothing more than a long-standing popular misconception. This topic prompted me to dig out and review an anecdote I recall reading in my decades-old copy of CQ magazine's Vertical Antenna Handbook, by USNR Capt. Paul H. Lee, K6TS (1974). He reported receiving mail from a ham who had made the discovery that he could tune and operate a half wave vertical without a ground system, feeding it by a parallel tuned tank circuit whose lower end is grounded. Since an rf ammeter in the ground lead showed no current
Re: Topband: Ground mounted 1/2 and 1/4 wave verticals (was GAP)
Carl, why would we need a helicopter when we have simulation software? How much ground loss, or if you prefer, what difference in field strength do you calculate for a half wavelength vertical with a gnd rod vs a full radial field? Dave WX7G On Dec 17, 2012 4:00 PM, Carl k...@jeremy.mv.com wrote: You did absolutely nothing useful that I remember reading so far. Get a helicopter and get real data. Or ask Richard Fry for his plots. Carl KM1H - Original Message - From: DAVID CUTHBERT telegraph...@gmail.com To: ZR z...@jeremy.mv.com Cc: Donald Chester k4...@hotmail.com; topband@contesting.com Sent: Monday, December 17, 2012 5:08 PM Subject: Re: Topband: Ground mounted 1/2 and 1/4 wave verticals (was GAP) Carl. I quantified ground loss in the near field. Now it's your turn. Numbers please, not adjectives or hand waving. Dave WX7G On Dec 17, 2012 2:59 PM, ZR z...@jeremy.mv.com wrote: Because youre still stuck in neutral and are measuring/calculating nothing of interest. The loss is determined at various elevation angles at a sufficient distance by field strength. Get a helicopter. Carl KM1H - Original Message - From: DAVID CUTHBERT telegraph...@gmail.com To: Donald Chester k4...@hotmail.com Cc: topband@contesting.com Sent: Monday, December 17, 2012 1:53 PM Subject: Re: Topband: GAP Vertical Question Where is the 40-60% claimed ground loss? I get 4%. On Dec 17, 2012 6:12 AM, DAVID CUTHBERT telegraph...@gmail.com wrote: *Half wavelength vertical ground loss* Let's see if we can quantify the conduction losses of a 1.8 MHz half wavelength vertical connected to average earth via a ground rod. This paper by N6LF shows one skin depth at 1.8 MHz to be 6 meters. http://www.antennasbyn6lf.com/files/ground_skin_depth_and_http://www.antennasbyn6lf.com/**files/ground_skin_depth_and_** wavelength.pdfhttp://www.**antennasbyn6lf.com/files/** ground_skin_depth_and_**wavelength.pdfhttp://www.antennasbyn6lf.com/files/ground_skin_depth_and_wavelength.pdf Let's assume the current magnitude in the ground mirrors that of the antenna. Driving the antenna at the base such that the current at the antenna center is 1 amp, the ground current 40 meters away from the antenna is 1 amp. The 1 amp of ground current passes through a section of earth having an effective depth of of 6 meters. For a 1 meter radial length and 40 meters from the antenna the section has dimensions of 1 meter X 6 meters X 250 meters (250 meters is the circumference). Given a resistivity of 200 ohms/meter the resistance of this section is 200/(6 X 250) = 0.13 ohms. The loss in this section is 0.13 watts. Using NEC we see with the base current set to give 1 amp at the antenna center the power into the antenna is 100 watts. Closer to the base of the antenna the effective ground resistance increases due to the smaller circumference. Closer to the antenna the current decreases. Roughly Integrating the ground loss from the base to the 80 meters away gives a total ground loss of 4 watts. The no-radial ground loss is 5 watts and the antenna gain is reduced by 10LOG(100/96) = 0.2 dB from the full radial case. How about ground loss due to the induced E-field in the ground? I believe this is accounted for in the previous calculation. I ran a NEC simulation to explore this. The two cases were a 266' vertical fed against thirty 3' radials and thirty 133' radials. The radials are 0.05' above medium ground. The NEC Average Gain was compared for the two cases and showed a difference of 0.06 dB. Dave WX7G On Sun, Dec 16, 2012 at 6:42 PM, Donald Chester k4...@hotmail.com wrote: Then, why do broadcast stations that use vertical towers at approximately a half wavelength, purchase valuable real estate and spend thousands of dollars for the copper to install from 120 to 240 or more radials, each usually a half wave or more in length? See G. H. Brown: Ground Systems as a Factor in Antenna Efficiency, IRE Proceedings, June 1937 p. 753. Brown demonstrated that the distribution of earth currents and ground losses is such that the region of maximum current and loss occurs at a distance of about 0.35 wavelengths from the base of a ground mounted half wave vertical antenna, which was verified experimentally. There is zero loss at the base of the antenna itself, since there is no base current because the antenna a fed at a current node. An rf ammeter inserted in the ground lead, as well as one inserted in in the antenna lead attached to the insulated base of the radiator will read zero. The ground losses occur farther out from the base of the antenna. Low effective earth resistance provided by a good ground system is ABSOLUTELY NECESSARY for vertical antennas of ANY height if one expects good radiation efficiency. The claim that no ground system is needed for a half wave vertical is nothing more than a long
Re: Topband: Ground mounted 1/2 and 1/4 wave verticals (was GAP)
Tim, I believe those are valid conclusions. Referencing *Vertical antenna ground system experiment #1*, by Rudy Severns: 1) Table 1 shows that going from 8 radials to 64 radials increases field strength by* 1.6 dB*. 2) Figure 4 shows the resistive part of the base impedance changing from 58 ohms to 43 ohms. 3) Using a radiation resistance of 36 ohms the radiation efficiency for 8 radials is 62% and for 64 radials it is 84%. The difference is *1.3 dB*. Rudy's other papers confirm the correlation between the resistive part of base impedance and field strength. Dave WX7G On Mon, Dec 17, 2012 at 4:21 PM, Shoppa, Tim tsho...@wmata.com wrote: Dave... would it be a fair extrapolation to take your last sentence, and draw the conclusion that if adding radials changes feed impedance, then there was actual ground loss in the near field? Or that if we add more radials and feed impedance change is not seen, then we are at a minimum for ground loss? The above statements certainly align with my gut feeling, but my gut feeling is different than a mathematical proof :-) Tim N3QE ___ It is undesirable to believe a proposition when there is no ground whatsoever for supposing it is true. #8212; Bertrand Russell
Re: Topband: Ground mounted 1/2 and 1/4 wave verticals (was GAP)
Tim, I ran some sims using a work-around I developed to allow NEC-2 to mimic NEC-4 ground loss results. This sim is for a 90 degree, 1.8 MHz vertical over Medium ground. I get correlation within 0.06 dB between base impedance derived loss, E-field strength at 1000', and NEC Average Gain. More work needs to be done to see if this method gives results for other radial and vertical lengths that overlay the N6LF results. Dave WX7G On Mon, Dec 17, 2012 at 5:42 PM, DAVID CUTHBERT telegraph...@gmail.comwrote: Tim, I believe those are valid conclusions. Referencing *Vertical antenna ground system experiment #1*, by Rudy Severns: 1) Table 1 shows that going from 8 radials to 64 radials increases field strength by* 1.6 dB*. 2) Figure 4 shows the resistive part of the base impedance changing from 58 ohms to 43 ohms. 3) Using a radiation resistance of 36 ohms the radiation efficiency for 8 radials is 62% and for 64 radials it is 84%. The difference is *1.3 dB*. Rudy's other papers confirm the correlation between the resistive part of base impedance and field strength. Dave WX7G On Mon, Dec 17, 2012 at 4:21 PM, Shoppa, Tim tsho...@wmata.com wrote: Dave... would it be a fair extrapolation to take your last sentence, and draw the conclusion that if adding radials changes feed impedance, then there was actual ground loss in the near field? Or that if we add more radials and feed impedance change is not seen, then we are at a minimum for ground loss? The above statements certainly align with my gut feeling, but my gut feeling is different than a mathematical proof :-) Tim N3QE ___ It is undesirable to believe a proposition when there is no ground whatsoever for supposing it is true. #8212; Bertrand Russell
Re: Topband: Fw: raised radials
The 10 dB, or was it 20 dB, claim could be a case of belief preservation as described in section 3.5 of the paper *Teaching Critical Thinking: Lessons for Cognitive Science*, by Tim van Gelder http://frank.itlab.us/forgetting/teaching_critical_thinking.pdf Dave WX7G ___ Topband reflector - topband@contesting.com
Re: Topband: Optimal radial wire type and gauge?
Tom, I think you are extrapolating one case with a particular radial length to all vertical antenna ground systems. The N6LF radial papers detail his NEC-4 simulations and measurements of vertical antennas and radial systems. If I read his papers correctly base impedance does track field strength measurements. http://www.antennasbyn6lf.com/ Dave WX7G On Sat, Dec 15, 2012 at 5:10 PM, Tom W8JI w...@w8ji.com wrote: There is no magic about 120 radials, and long before 120 radials are reached the increase in field strength pretty much stops. At my house around 30 radials or so, about 1/4 wave long, go flat on efficiency increase on 160 meters. I could have a million radials and it would be insignificantly different than 30 radials when they are 1/4 wave long here. I found this by measuring field strength, and I also found feed resistance change did NOT necessarily track the field strength changes. Good luck on using base impedance to determine effiency changes! In a 40 meter test, for example, one ground system provided 35-40 ohms of feed resistance and another different system that provided almost 60 ohms of feedpoint resistance had equal field strength. I think N6RK and others have measured the same. 73 Tom - Original Message - From: DAVID CUTHBERT telegraph...@gmail.com To: Rick Kiessig kies...@gmail.com Cc: topband@contesting.com Sent: Saturday, December 15, 2012 10:49 AM Subject: Re: Topband: Optimal radial wire type and gauge? Read the N6LF radial papers and you will see that 1/8 wavelength radials are about as good as one can do. I use #14 stranded copper THHN wire because it is easy to work with. But how good can we get? For a 30' base loaded vertical I have 90 radials having an average length of 18 ft. The ground loss is 5 ohms, which is less than the loading coil loss. If I were to install 120 quarter wavelength radials I would gain 2 dB. Dave WX7G __**_ Topband reflector - topband@contesting.com ___ Topband reflector - topband@contesting.com
Re: Topband: raised radials
That is quite an improvement. I had to have dropped the base impedance from 400 ohms to 40 ohms for it to do that. Dave WX7G On Fri, Dec 14, 2012 at 1:12 PM, Carl k...@jeremy.mv.com wrote: A ground screen mesh extending out at least 25' from the base would reduces losses considerably since just 10-20 radials has little effect. At a prior QTH, going from 100 radials of 60-130' to spokes of 4' x 50' rabbit wire mesh on top of them made the difference between also ran and pileup busting on 160. Id call that at least 10dB in anybodys book. My soil was like beach sand altho 20 miles from the ocean; likely leftover from the iceage roll back. - Original Message - From: David Michael Gaytko // WD4KPD wd4...@suddenlink.net To: topband@contesting.com Sent: Friday, December 14, 2012 2:04 PM Subject: Topband: raised radials the more i read, it seems raised radials are a fairly easy way to raise the effeciancy of a short vertical. i have a hy-gain 18ht with base loading. can i use these raised radials with this antenna, and if so how to do it. it is impossible to raise the whole antenna to get the base off the ground. david/wd4kpd -- God's law is set in stone..everything else is negotiable. __**_ Topband reflector - topband@contesting.com - No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1430 / Virus Database: 2634/5459 - Release Date: 12/14/12 __**_ Topband reflector - topband@contesting.com ___ Topband reflector - topband@contesting.com
Re: Topband: Optimal radial wire type and gauge?
Read the N6LF radial papers and you will see that 1/8 wavelength radials are about as good as one can do. I use #14 stranded copper THHN wire because it is easy to work with. But how good can we get? For a 30' base loaded vertical I have 90 radials having an average length of 18 ft. The ground loss is 5 ohms, which is less than the loading coil loss. If I were to install 120 quarter wavelength radials I would gain 2 dB. Dave WX7G ___ Topband reflector - topband@contesting.com
Re: Topband: Fw: GAP VERTICAL QUESTION
Mike that QTH looks alot like the Great Salt Lake of Utah where I have operated a few 160 meter 'tests running a balloon vertical. Dave WX7G On Fri, Dec 14, 2012 at 9:52 AM, Michael Tope w...@dellroy.com wrote: On 12/13/2012 3:14 PM, Tom W8JI wrote: Somehow they thought moving the feedpoint eliminated the need for radials with an electrically short antenna, when the real mechanism was a 1/2 wave vertical was converted to a 1/4 wave groundplane 1/4 wave above ground and it only got a tiny bit weaker. The groundplane still had 8 radials, but they were hundreds of feet in the air. There was some more stuff about offsetting the feedpoint in that handout, but nothing that remotely applied to a fractional wavelength vertical just sitting on the dirt with a few radials laying directly on the lawn. They got rid of lossy traps and loading coils by using even lossier coax and some folded wires for a loading system. This is all why, as frequency increases and the current and voltage moves up the antenna, the GAP on most bands isn't terribly bad. This also why it is a real dog of an antenna on 160 and 80, where it is very short electrically, has no ground system, has an exceptionally poor loading method, and where it folds the radiator back and forth which suppresses radiation resistance. This is why a ten foot mobile antenna can tie it or beat it on 160, and why it is reasonably on par with anything else on most bands above 80 meters. 73 Tom I got hold of a brand new voyager about 7 years ago. The first thing I did was throw away all that yellow coax stuffed inside the bottom half. The fiberglass GAP for the elevated feed point makes a nice insulator for a center loading coil. Then I added some top hat wires with dimensions per WX7G's recommendation and fed the antenna from the bottom as a standard ground mounted vertical with a bunch of radials. For 80 meters, I put a short yard arm at the top with a pulley and hung a wire in parallel with the aluminum radiator. For only being 45ft tall this antenna has worked surprisingly well. I've since lengthened it to 56ft and added an additional parallel wire for 40 meters. I use an Ameritron RCS-4 remote switch at the base to select between 160 or 80/40 (the 80 and 40 meter vertical wires are tied together). I use a 50 to 12.5 ohms Unun on the 160 side to raise the feedpoint Z up to 50 ohms. With all these modifications done in haste before various contests it aint pretty to look at, but it does seem to hold its own against folks with shunt-fed towers and inverted-Ls (at least the ones who don't use overly active antenna tuners :-) ). Here are some pictures of it when I took a trip to one of the dry lake beds north of here: http://www.dellroy.com/W4EF's-**Ham-Radio-Page/CQ160/2006.htmhttp://www.dellroy.com/W4EF's-Ham-Radio-Page/CQ160/2006.htm 73, Mike W4EF... __**_ Topband reflector - topband@contesting.com ___ Topband reflector - topband@contesting.com
Re: Topband: GAP Vertical Question
Don, a 36 helium balloon filled to 32 is enough to lift 130' of #26 wire in no wind. It doesn't take much wind to blow it horizontal. A half wave vertical suffers more as it is blown down so I think it's best to fly 130' at the most. Flying the balloon from a 40' or taller mast would allow the 130' vertical to become an inverted-L as the wind picks up. Mounted 100' out from the shore at the Salt Lake the ground loss is virtually zero. The water depth is 6 at that point. In the ARRL 160 meter 'test this year the balloon blew into a sharp bush and perished. That may be the last balloon I fly at the lake and a 50' base loaded vertical will take its place. Given that a half wave vertical has a base impedance of over 1000 ohms and a single ground rod in dirt is 100 ohms at most not a single radial is needed to obtain close to 100% radiation efficiency. Dave WX7G ___ Topband reflector - topband@contesting.com
Re: Topband: Fw: GAP VERTICAL QUESTION
20 dB implies that the ground system loss is 10X the inverted-L radiation resistance. This would result in an input resistance of 250 ohms and a minimum VSWR if 5:1. I don't think that is what the real deal will deliver, do you? Dave WX7G On Dec 12, 2012 12:54 PM, Guy Olinger K2AV olin...@bellsouth.net wrote: With the following caveat: The very sparse and short buried radial systems he is showing are FAR more lossy in practice than shown in his gain tables. Four twenty foot buried radials beneath a 1/4 wave L on 160, could place you down 20 dB. You really can't do that as your 160 meter counter poise and expect decent results. You can end feed the same wire on 80/40/30 meters (full wave worth of wire in the L on 80m) with four buried 20 foot radials and it will be an excellent antenna. This is due to the high Z feed at the ground with current max AWAY from the feed point. A quarter wave L on 160 MUST deal with the counterpoise loss issues, one way or another. 73, Guy On Wed, Dec 12, 2012 at 2:07 PM, Ashton Lee ashton.r@hotmail.com wrote: This wonderful article written by L.B.Cebic W4RNL sure can make you a believer in a simple wire inverted L. It is the last antenna discussed. http://www.users.on.net/~bcr/files/backyard%20wire%20antennaes.pdf A $3 wire pulled up into a tree will beat just about any commercial antenna… because it is longer. So on low bands it has increased band width and efficiency, and on higher bands it has gain. Yes, I know , some of that high band gain is horizontally polarized, but that's not all bad. Just get the vertical portion 33 feet or so and you'll be happy as Larry. The article shows that an extensive radial field may not be necessary. And a wire is a lot less visible than a big hunk of aluminum. Without trees, just top load a 43 foot (or possibly even shorter) vertical. The top loading could be a T just as easily as an L. People can argue that one all day. On Dec 12, 2012, at 11:30 AM, k6xt k...@arrl.net wrote: My first antenna, still in use, on moving to CO is a GAP Titan, advertised to load up 80 thru 10 including WARC bands. The Titan is a bit shorter than Voyager, 28 feet or something like it. The advertising is correct, it loads up 180 thru 10. But wait. Is it effective on all those bands? No. On 80 its a dummy load. On 40 it works extremely well after I added a one foot extension to the bottom wire that encircles the antenna. In some cases it is the equal of my shorty HyGain 40 at 70 ft - which probably says more about the HyGain than the GAP. For the rest its better on the traditional bands than the WARC bands. It worked a lot of DX for me for the couple years it was my only antenna. Carrying my experience to the few feet taller Voyager, and from what I've been told by Voyager users, the ant will meet its spec which is to load up on the low bands. Expectation wise I'd expect it to be like the Titan. It loads up but is otherwise a dummy load. Maybe with a batch of radials it could be made to work as well as any other extremely short vertical or GP. Not to say there's anything wrong with GAP. My brother had up an R7 which he rated about like the GAP on bands both cover. Those multiband halfwave short verticals work but you get what you pay for. 73 Art K6XT~~ Success is going from failure to failure without a loss of enthusiasm. ARRL, GMCC, CW OPS, NAQCC ARRL TA On 12/12/2012 10:00 AM, topband-requ...@contesting.com wrote: With the prospect of downsizing and moving into senior housing in the future I am starting to look at vertical antennas that will allow me to continue this wonderful hobby.? I have heard some good things about the GAP series of antennas but the company says they do not need radials on most of them and that worries me.? Over the years I have become very skeptical about claims and the other BS put out by most companies ( maybe it is a function of age I dunno) so I wonder if these antennas really work.? The two antennas that I am interested are the Voyager DX for 160/80/40? and the Eagle DX for the rest of the bands. So my question is does anyone have actual experience with these antennas (especially the voyager) as compared to other antennas for a specific frequency.? Now guys .. I know you cant really compare a 6 element beam to a vertical of this kind but I am talking about a comparison that is realistic.. like how does it hear, tune, match get out compared to something like another vertical or a dipole up some reasonable distance. I sure hope this has not opend another can of worms.. some how I seem to do that .. private emails are ok..especially it the topic gets out of hand and we get a large volume of comments (Tree please dont shoot me before Christmas my wife will miss me.)
Re: Topband: Fw: GAP VERTICAL QUESTION
Correction, 100X the loss. The deal difference between a single ground rod and a BC station ground will be about 6 dB. Dave WX7G On Dec 12, 2012 1:13 PM, DAVID CUTHBERT telegraph...@gmail.com wrote: 20 dB implies that the ground system loss is 10X the inverted-L radiation resistance. This would result in an input resistance of 250 ohms and a minimum VSWR if 5:1. I don't think that is what the real deal will deliver, do you? Dave WX7G On Dec 12, 2012 12:54 PM, Guy Olinger K2AV olin...@bellsouth.net wrote: With the following caveat: The very sparse and short buried radial systems he is showing are FAR more lossy in practice than shown in his gain tables. Four twenty foot buried radials beneath a 1/4 wave L on 160, could place you down 20 dB. You really can't do that as your 160 meter counter poise and expect decent results. You can end feed the same wire on 80/40/30 meters (full wave worth of wire in the L on 80m) with four buried 20 foot radials and it will be an excellent antenna. This is due to the high Z feed at the ground with current max AWAY from the feed point. A quarter wave L on 160 MUST deal with the counterpoise loss issues, one way or another. 73, Guy On Wed, Dec 12, 2012 at 2:07 PM, Ashton Lee ashton.r@hotmail.com wrote: This wonderful article written by L.B.Cebic W4RNL sure can make you a believer in a simple wire inverted L. It is the last antenna discussed. http://www.users.on.net/~bcr/files/backyard%20wire%20antennaes.pdf A $3 wire pulled up into a tree will beat just about any commercial antenna… because it is longer. So on low bands it has increased band width and efficiency, and on higher bands it has gain. Yes, I know , some of that high band gain is horizontally polarized, but that's not all bad. Just get the vertical portion 33 feet or so and you'll be happy as Larry. The article shows that an extensive radial field may not be necessary. And a wire is a lot less visible than a big hunk of aluminum. Without trees, just top load a 43 foot (or possibly even shorter) vertical. The top loading could be a T just as easily as an L. People can argue that one all day. On Dec 12, 2012, at 11:30 AM, k6xt k...@arrl.net wrote: My first antenna, still in use, on moving to CO is a GAP Titan, advertised to load up 80 thru 10 including WARC bands. The Titan is a bit shorter than Voyager, 28 feet or something like it. The advertising is correct, it loads up 180 thru 10. But wait. Is it effective on all those bands? No. On 80 its a dummy load. On 40 it works extremely well after I added a one foot extension to the bottom wire that encircles the antenna. In some cases it is the equal of my shorty HyGain 40 at 70 ft - which probably says more about the HyGain than the GAP. For the rest its better on the traditional bands than the WARC bands. It worked a lot of DX for me for the couple years it was my only antenna. Carrying my experience to the few feet taller Voyager, and from what I've been told by Voyager users, the ant will meet its spec which is to load up on the low bands. Expectation wise I'd expect it to be like the Titan. It loads up but is otherwise a dummy load. Maybe with a batch of radials it could be made to work as well as any other extremely short vertical or GP. Not to say there's anything wrong with GAP. My brother had up an R7 which he rated about like the GAP on bands both cover. Those multiband halfwave short verticals work but you get what you pay for. 73 Art K6XT~~ Success is going from failure to failure without a loss of enthusiasm. ARRL, GMCC, CW OPS, NAQCC ARRL TA On 12/12/2012 10:00 AM, topband-requ...@contesting.com wrote: With the prospect of downsizing and moving into senior housing in the future I am starting to look at vertical antennas that will allow me to continue this wonderful hobby.? I have heard some good things about the GAP series of antennas but the company says they do not need radials on most of them and that worries me.? Over the years I have become very skeptical about claims and the other BS put out by most companies ( maybe it is a function of age I dunno) so I wonder if these antennas really work.? The two antennas that I am interested are the Voyager DX for 160/80/40? and the Eagle DX for the rest of the bands. So my question is does anyone have actual experience with these antennas (especially the voyager) as compared to other antennas for a specific frequency.? Now guys .. I know you cant really compare a 6 element beam to a vertical of this kind but I am talking about a comparison that is realistic.. like how does it hear, tune, match get out compared to something like another vertical or a dipole up some reasonable distance. I sure hope this has not opend another can of worms.. some how I seem to do
Re: Topband: Fw: GAP VERTICAL QUESTION
Guy, you make it sound like magic. See the IEEE paper RADIATION EFFICIENCY AND INPUT IMPEDANCE OF MONOPOLE ELEMENTS WITH RADIAL-WIRE GROUND PLANES IN PROXIMITY TO EARTH Dave WX7G On Dec 12, 2012 3:13 PM, Guy Olinger K2AV olin...@bellsouth.net wrote: Not all loss is visible as series resistance in the counterpoise system, which is the tack you are taking. Note that a dummy load is 50 ohms, and does not radiate worth a hoot. It takes modeling to identify some situations. One of my favorites in NEC4 results in a max gain of -18 dBi or so. This is compared to a commercial BC 1/4 wave of plus 1.2 dBi in the same ground. The reason for the extreme loss is completely counter-intuitive. We have a lot of mental simplification devices for thinking about antennas. In the end you need something to add up all the induced currents, all the losses On Wed, Dec 12, 2012 at 3:13 PM, DAVID CUTHBERT telegraph...@gmail.comwrote: 20 dB implies that the ground system loss is 10X the inverted-L radiation resistance. This would result in an input resistance of 250 ohms and a minimum VSWR if 5:1. I don't think that is what the real deal will deliver, do you? Dave WX7G On Dec 12, 2012 12:54 PM, Guy Olinger K2AV olin...@bellsouth.net wrote: With the following caveat: The very sparse and short buried radial systems he is showing are FAR more lossy in practice than shown in his gain tables. Four twenty foot buried radials beneath a 1/4 wave L on 160, could place you down 20 dB. You really can't do that as your 160 meter counter poise and expect decent results. You can end feed the same wire on 80/40/30 meters (full wave worth of wire in the L on 80m) with four buried 20 foot radials and it will be an excellent antenna. This is due to the high Z feed at the ground with current max AWAY from the feed point. A quarter wave L on 160 MUST deal with the counterpoise loss issues, one way or another. 73, Guy On Wed, Dec 12, 2012 at 2:07 PM, Ashton Lee ashton.r@hotmail.com wrote: This wonderful article written by L.B.Cebic W4RNL sure can make you a believer in a simple wire inverted L. It is the last antenna discussed. http://www.users.on.net/~bcr/files/backyard%20wire%20antennaes.pdf A $3 wire pulled up into a tree will beat just about any commercial antenna… because it is longer. So on low bands it has increased band width and efficiency, and on higher bands it has gain. Yes, I know , some of that high band gain is horizontally polarized, but that's not all bad. Just get the vertical portion 33 feet or so and you'll be happy as Larry. The article shows that an extensive radial field may not be necessary. And a wire is a lot less visible than a big hunk of aluminum. Without trees, just top load a 43 foot (or possibly even shorter) vertical. The top loading could be a T just as easily as an L. People can argue that one all day. On Dec 12, 2012, at 11:30 AM, k6xt k...@arrl.net wrote: My first antenna, still in use, on moving to CO is a GAP Titan, advertised to load up 80 thru 10 including WARC bands. The Titan is a bit shorter than Voyager, 28 feet or something like it. The advertising is correct, it loads up 180 thru 10. But wait. Is it effective on all those bands? No. On 80 its a dummy load. On 40 it works extremely well after I added a one foot extension to the bottom wire that encircles the antenna. In some cases it is the equal of my shorty HyGain 40 at 70 ft - which probably says more about the HyGain than the GAP. For the rest its better on the traditional bands than the WARC bands. It worked a lot of DX for me for the couple years it was my only antenna. Carrying my experience to the few feet taller Voyager, and from what I've been told by Voyager users, the ant will meet its spec which is to load up on the low bands. Expectation wise I'd expect it to be like the Titan. It loads up but is otherwise a dummy load. Maybe with a batch of radials it could be made to work as well as any other extremely short vertical or GP. Not to say there's anything wrong with GAP. My brother had up an R7 which he rated about like the GAP on bands both cover. Those multiband halfwave short verticals work but you get what you pay for. 73 Art K6XT~~ Success is going from failure to failure without a loss of enthusiasm. ARRL, GMCC, CW OPS, NAQCC ARRL TA On 12/12/2012 10:00 AM, topband-requ...@contesting.com wrote: With the prospect of downsizing and moving into senior housing in the future I am starting to look at vertical antennas that will allow me to continue this wonderful hobby.? I have heard some good things about the GAP series of antennas but the company says they do not need radials on most of them and that worries me.? Over the years I
Re: Topband: Fw: GAP VERTICAL QUESTION
Guy, here is where I believe your mysterious extra loss in NEC is coming from. You are reading the average gain loss. NEC calculates that by integrating the power at infinity and dividing by the power into the antenna. This accounts for the far-far field ground losses that vertically polarized radiation encounters. But, this is not how we report the radiation efficiency of a vertical. That is defined as the radiated energy in the far field (but not too far) divided by the power into the antenna. Dave WX7G On Wed, Dec 12, 2012 at 4:34 PM, Guy Olinger K2AV olin...@bellsouth.netwrote: [I may have sent an incomplete version of something on this topic. Apologies] 6 dB would be someone's calculation based on currents. The sometimes abysmal performance of a ground rod based vertical system cannot be explained by 6 dB. Cutting my amp from 1500w to 375watts just doesn't get bad enough. Not close. Part of the problem is that we figure all the current in the vertical is free and clear to useful radiation and is not affected by the RF appearance of the ground. You can model a near perfect commercial grade radial field, with a radial system apparent series resistance of a few tenths of an ohm, and NEC4 will still come back with an overall loss of 3 to 4 dB. There is no book-keeping of that loss in the 34 ohm vertical radiator in series with the near zero resistance of the radials, as people typically talk about it. If I run my EZNEC Pro NEC4 3D all points azimuth and elevation run for a gold standard commercial installation, 120 1/4 wave buried radials in average ground, at the bottom of the main window I will get a rather typical 3.9 dB overall loss. IF we have to understand loss as only book-kept in the feed resistance numbers, one would have to APPORTION the 34 ohms resistance to account for the loss. That would be 47 percent in the pattern and 53 percent lost somewhere, by some means, 16 ohms apportioned out to the pattern with 18 ohms of loss somewhere, but not in the radials and not in the vertical wire. Great radials. Top of the line radials. BUT there is still some mechanism draining off 53 percent of the power. The math in NEC 4 is doing and sensing something that explains loss not book-kept in our all-loss-is-shown-in-the-feed Z mental picture. Where's the loss, loss that does not change the feed Z as it comes and goes. How does it work? Can this non-Z-changing loss increase without the commercial radials and a wire fed right at the ground? One could picture my installing a really good antenna at a place looking at a fairly distant horizon. However, I could have trucks and bulldozers built a 1000 foot high dirt wall encircling my place a mile away, and my feed Z would not change. The wall would just soak up RF that otherwise would be out doing wonderful things at low angles. How much additional does unshielded dirt underneath a naked vertical soak up in terms of dB that does not alter the feed Z? Persons unnamed in 1995 recommended two 1/4 wave radials on the ground. I remember that K4CIA from the other side of town, running QRP on his well constructed 160 vertical could often beat me out running 100 watts. What I had was like running QRP on a good antenna. We don't know everything. And there are a lot of people that have awful results with hack job radials. We need to quit recommending hack jobs until we know exactly why they do or do not work, and can explain a FAR greater percentage of the anecdotal material than we can now, and can explain how in some scenarios how we can get results that ARE plainly down 20. If we're not careful, at some point we can be blowing off the essential majority story because we just don't want to listen. 73, Guy On Wed, Dec 12, 2012 at 3:17 PM, DAVID CUTHBERT telegraph...@gmail.comwrote: Correction, 100X the loss. The deal difference between a single ground rod and a BC station ground will be about 6 dB. Dave WX7G On Dec 12, 2012 1:13 PM, DAVID CUTHBERT telegraph...@gmail.com wrote: 20 dB implies that the ground system loss is 10X the inverted-L radiation resistance. This would result in an input resistance of 250 ohms and a minimum VSWR if 5:1. I don't think that is what the real deal will deliver, do you? Dave WX7G On Dec 12, 2012 12:54 PM, Guy Olinger K2AV olin...@bellsouth.net wrote: With the following caveat: The very sparse and short buried radial systems he is showing are FAR more lossy in practice than shown in his gain tables. Four twenty foot buried radials beneath a 1/4 wave L on 160, could place you down 20 dB. You really can't do that as your 160 meter counter poise and expect decent results. You can end feed the same wire on 80/40/30 meters (full wave worth of wire in the L on 80m) with four buried 20 foot radials and it will be an excellent antenna. This is due to the high Z feed at the ground with current
Re: Topband: Shunt fed towers and common mode chokes
Google G3TXQ COMMON-MODE Dave WX7 G On Dec 6, 2012 1:40 PM, Steve London n2ica...@gmail.com wrote: My 160 meter shunt fed tower project is essentially done. However, I have an issue with the 80 meter antennas hung off that tower. In a nutshell, the current baluns (ferrite beads) feeding these antennas don't have enough common mode impedance on 160 meters. They heat up, and the SWR of the shunt fed tower changes as they heat up. After some reading, I think what I need are some RG8X toroid baluns, wound on #31 ferrite material. If they are going to replace the existing bead baluns, then they will need to be placed at the feedline/antenna junction. However, if I want to completely isolate the 160 shunt fed tower from the 80 meter feedlines, shouldn't I place the new baluns as close to the tower-mounted antenna switch as possible, and leave the bead baluns in place at the end of the feedline to choke off the 80 meter common mode energy ? To add more complications for adding the RG8X toroid balun, my 80 meter antennas are switchable 2 element wire beams, with each element fed with 18' of RG-8. That dimension is critical, as it provides the proper amount of capacitive reactance at the feedpoint to make the element a director. Comments ? 73, Steve, N2IC __**_ Topband reflector - topband@contesting.com ___ Topband reflector - topband@contesting.com
Re: Topband: DX window
A way to bring back the DX Window is to not work US stations who call CQ in the window. Boycott them if you will. Dave WX7G ___ Topband reflector - topband@contesting.com
Re: Topband: QRP/Poor antenna stations ARRL160
Carl, Tree and all the rest I find it fascinating how just about any piece of random metal and low power will yield top band contacts. For the Stew Perry I propose an award for *lamest antenna* or something to that effect. I'll sponsor the plaque if some such award becomes part of the Stew. Dave WX7G ___ Topband reflector - topband@contesting.com
Re: Topband: November 30-December 2 -- ARRL 160 Meter Contest
To me each of the three 160 meter contests has its unique charm. In the ARRL 'test I compete against others in my US state or region. Yes it is a different game in the Western U.S. And I very much look forward to seeing my call in the QST article and summary. The Stew Perry 'test tends to level the playing field. The 15 hour operating limit is easier on the mind and body. *I would LOVE to see the results posted within a couple of months of the 'test. * The CQ 'test is great for getting on and just working lots of stations. The reporting is not by US state and that takes some of the fun out of it. Dave WX7G ___ Topband reflector - topband@contesting.com
Re: Topband: Detuning shunt fed towers
A UHF connector won't flash over at 1500 watts if the VSWR is low. Dave WX7G On Nov 29, 2012 9:04 AM, John Harden, D.M.D. jh...@bellsouth.net wrote: I have a 100 ft 45G, shunt fed tower with stacked monobanders for 80 -10 meters. This includes a 24 ft mast with 12 feet out the tower top. I do not even worry about detuning it. The shunt (4 wire) cage only goes up to 30 feet due to monobanders down to about 35 feet. It requires a 2000 pfd vacuum variable in series and a 1000 pfd vacuum variable to ground (Omega match) to resonate the system. The series capacitor is motor driven by a 1 RPM, 12 VDC motor. The SWR remains flat over the band measured at the match and in the shack. I have right at 40 radials on ground. At this point the curve becomes asymptotic.. With an Amphenol Type HN connector there is never any flashover. SO-239's did not cut it. Type N is even worse. My Hi-Z 4-8 PRO RX antenna is over 100 feet away and there appears to be little interaction. If you do the math there should be interaction but there is so little real interaction that I simply disregard it The guys at Hi-Z will tell you there is very little difference between the 4-8 PRO and the 8 el array that is in a 200 ft diameter circle. They have both up. The decrease in beam width between the two is inconsequential to me I can now hear about anything that is on compared to others in my area, and can work it quickly if I can hear it. The Hi-Z array is that good The waters of the sea have parted for me on top band. 73, John, W4NU K4JAG (1959 to 1998) __**_ Topband reflector - topband@contesting.com ___ Topband reflector - topband@contesting.com
Re: Topband: Inverted L SWR Jumps ???
W8JI solved another problem and saved someone much time and frustration. I'd like to thank Tom for the great help and knowledge he has imparted in me and many, many others over the years. In my expert opinion as an engineer he is one of just a very small number of super engineers I know. Dave WX7G On Nov 28, 2012 11:57 AM, Jim Brown j...@audiosystemsgroup.com wrote: On 11/28/2012 10:14 AM, Ashton Lee wrote: I rebuilt the antenna from new wire, built a two insulator termination at the end of the horizontal section where the high voltage is, One thing I observed here several years ago with a dipole with an end touching tree branches is arcing to the branch, accompanied by scorching of the wire insulation (white THHN). Also, a common mode choke whose choking impedance is too low can overheat if the common mode voltage is high enough. That voltage depends on the degree of imbalance, which, as Tom observes, is highly dependent on the antenna system, INCLUDING the feedline and the radial system (and/or counterpoise). Tom's analysis of Guy's folded counterpoise design showed it to have significant imbalance, which fried common mode chokes, but was at least partially corrected by the stray Z of an isolation transformer. Overheating in a common mode choke wound on a lossy ferrite core shows up in the wire itself (the coax shield) and can melt the dielectric, allowing it to either short, arc, or change spacing. I've done some experiments purposely intended to observe what happens when the choking Z is inadequate. 73, Jim K9YC __**_ Topband reflector - topband@contesting.com ___ Topband reflector - topband@contesting.com
Re: Topband: Short radials?
Tom, with this ground system and 90 degee monopoles I measure 5 ohms ground loss on 7 to 28 MHz. With the 30' vertical I measure about 10 ohms on 1.8 and 3.5 MHz. The 7 MHz measurement agrees with the N6LF papers (90 deg monopole and 1/8 wavelength radials). I have no evidence that would lead me to doubt the measurements of the other bands. 160 meters measurenent: 15 ohm base R 2 ohm radiation resistance 5 ohm cool loss 8 ohm ground loss (rounded to 10) This is the accepted procedure for measuring base referred ground loss, is it not? Dave WX7G On Sep 27, 2012 7:54 PM, Tom W8JI w...@w8ji.com wrote: I am presently using a 30' base loaded vertical. The ground system consists of 90 radials from 12 to 25 feet. The base referred ground loss is 10 ohms. The problem is we really can't measure ground loss at the base. Let me give an example A 40 meter vertical here, 1/4 wave tall of fixed length. Four elevated radials had less than 40 ohms feed resistance. About a dozen buried radials had around 60 ohms base resistance. Field strength was identical despite the resistance difference with the same length resonant radiator. Others have measured the same type of thing, and it is easy to duplicate results like this. 73 Tom ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Short radials?
The maximum base-referred ground loss number my system has is bounded at 0 and 15 ohms given a base R measurement of 15 ohms. N6LF found that for a 90 deg monopole the method of summing resistances can result in under estimating ground loss due to the radiation resistance being less than 36 ohms. If we apply this reasoning to my short monopole having (an assumed?) radiation resistance of 2 ohms the maximum ground loss error due to this is 2 ohms. Dave WX7G On Sep 27, 2012 8:18 PM, DAVID CUTHBERT telegraph...@gmail.com wrote: Tom, with this ground system and 90 degee monopoles I measure 5 ohms ground loss on 7 to 28 MHz. With the 30' vertical I measure about 10 ohms on 1.8 and 3.5 MHz. The 7 MHz measurement agrees with the N6LF papers (90 deg monopole and 1/8 wavelength radials). I have no evidence that would lead me to doubt the measurements of the other bands. 160 meters measurenent: 15 ohm base R 2 ohm radiation resistance 5 ohm cool loss 8 ohm ground loss (rounded to 10) This is the accepted procedure for measuring base referred ground loss, is it not? Dave WX7G On Sep 27, 2012 7:54 PM, Tom W8JI w...@w8ji.com wrote: I am presently using a 30' base loaded vertical. The ground system consists of 90 radials from 12 to 25 feet. The base referred ground loss is 10 ohms. The problem is we really can't measure ground loss at the base. Let me give an example A 40 meter vertical here, 1/4 wave tall of fixed length. Four elevated radials had less than 40 ohms feed resistance. About a dozen buried radials had around 60 ohms base resistance. Field strength was identical despite the resistance difference with the same length resonant radiator. Others have measured the same type of thing, and it is easy to duplicate results like this. 73 Tom ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: RX epiphany?
Bob and Bob, so it is! I thought it was just below the equator. Dave On Thu, Sep 13, 2012 at 7:55 PM, Bob Kupps n...@yahoo.com wrote: Hey Dave! (he was my first QSO as a novice 43 years ago) I am located at 20 degrees N. Actually my choice is between a 160m Xmit 4 square and concentric 80/160m 8 circle RX arrays. From: DAVID CUTHBERT telegraph...@gmail.com To: donov...@starpower.net Cc: Bob Kupps n...@yahoo.com; topband topband@contesting.com Sent: Friday, September 14, 2012 8:44 AM Subject: Re: Topband: RX epiphany? Bob, with US and European stations operating top band during the winter only you will only work them during your summer. So, you will always be subject to higher noise at your end of the path. Dave On Thu, Sep 13, 2012 at 7:12 PM, donov...@starpower.net wrote: Bob, If you have a choice of one or the other the choice is easy: the transmit 4-square as an excellent transmit array as well as an excellent receive array. Good luck! 73 Frank W3LPL Original message Date: Thu, 13 Sep 2012 16:56:45 -0700 (PDT) From: Bob Kupps n...@yahoo.com Subject: Re: Topband: RX epiphany? Cc: topband topband@contesting.com Hi thanks to all for the replies. Sorry I wasn't clear my QTH is northern Thailand. The point I was trying to make is that even though it is a noisy part of the season it is apparently less noisy at the European latitudes. Unfortunately I don't have enough land to put up a 160m Xmit 4 square and an RX array, it will have to be one or the other Bob-- Just curious -- How is your reception around sunrise, when most of the thunderstorms in the Americas are in daylight, and therefore their QRN probably isn't reaching you? Art, KB3FJO ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: electrical wavelength
Run the numbers and for RG-6 we see that sq root of L/C is good above a couple hundred kHz. Dave WX7G On Sep 10, 2012 2:37 PM, Jim Brown j...@audiosystemsgroup.com wrote: On 9/10/2012 10:44 AM, Tom W8JI wrote: I firmly do not believe that is true. Velocity factor in cable is the square root of the inverse of dielectric constant. Tom, Respectfully, I suggest that you go back to your college textbook on the fundamentals of Transmission Lines. The equations for Zo, velociity of propagation, and attenuation are COMPLEX -- that is, they contain real and imaginary components. The formula you cite is the result of simplification to remove those complex elements. It's good at VHF and is close for HF, but becomes increasing erroneous as you go down in frequency. Likewise, Zo is only sqrt (L/C) at VHF. The more complete equation is sqrt [ (R+J omega L) /( G + J omega C) ] At VHF, the equation SIMPLIFIES to sqrt (L/C) At low audio frequencies, and up to VHF, G is insignificant (leakage) so the complete practical equation is sqrt [(R+ j omega L) / j omega C] Note that this results in Zo being complex, and a proper measurement will confirm that this is true. There are MANY references to complex Zo in the ham literature. Frank Witt published some work about this, now available in one of the ARRL Anthologies. N6BV's TLW software, published in the ARRL Handbook, uses complex impedance data for its transmission line calculations, although it ignores the variability of Vf. At low audio frequencies, Zo is much, much larger than the VHF value, and Vf is much, much slower than the VHF value. Both properties begin a rapid transition to their VHF values and go though at least half of it within the audio spectrum, approaching the VHF values asymptotically. By 2 MHz, both are within a few percent of the VHF value. All of this was WELL KNOWN more than a century ago, and Oliver Heavyside did a lot of work on applications to equalize lines. While it is often assumed in modern times that equalization of telephone circuits was done only for the amplitude response, equalization is equally important for the TIME response. To get your head around that, consider speech where the highs arrive much sooner than the lows. Here's a simple test you can do with any 50 ohm signal source you can read to an accuracy of at least 0.1 percent and a decent voltmeter across the source Cut a quarter wave open stub for the lowest frequency you can observe and measure the first resonance to as many digits as you can, then repeat for the third, fifth, seventh, and ninth resonances. If you can hit the precise null and read enough digits, you can plot the variation in Vf. Or do the same with any vector analyzer, carefully reading the frequencies of each null. 73, Jim K9YC __**_ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Radials over a stone wall
I can run a NEC simulation tomorrow to see how much radials up and over affect things. Dave WX7G On Aug 10, 2012 10:16 AM, Herb Schoenbohm he...@vitelcom.net wrote: On 8/10/2012 11:17 AM, N2TK, Tony wrote: I shunt feed my tower for topband. I use variable vacuum caps and a vacuum relay at the base to switch between the low end and the high end of the band. It seems to work okay. I have 100' buried radials spaced 10' at the ends from o degrees going clockwise through about 220 degrees. I have a 4' high stone wall that runs about 20/200 degrees that is about 35' at its closest point to the tower. So the radials are progressively shorter on the West side of the tower. I am making an assumption that going up over the wall will distort any benefits of extending the radials on the West side? Is that a true assumption. I can't really have the radials go from the tower base up at an angle to clear the stone wall and continue on. If I am to extend them the radials would have to go on the ground to the wall then up and over and back down to the ground. Tony, A long masonry drill used in the cable TV industry (which has a hole on the pointed end to attach the wire and pull it through the wall, is your best option in my view. Herb Schoenbohm, KV4FZ ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Radials over a stone wall
Simulation will tell the tale but in the mean time we have two things caused by the up-and-over that we can mull over: 1) There is cancellation of the magnetic fields by the up-and-over wires thereby minimizing any additional inductance to the normal radial return current. 2) current is induced in the vertical wires by the antenna magnetic field. This induced current is opposite to the normal radial return current. Dave WX7G On Aug 10, 2012 10:26 AM, Bill Wichers bi...@waveform.net wrote: I would expect an up and over to clear the wall would result in a choke-like effect on the radial and would, at best, reduce the radial's effectiveness. It should be easy to just drill some small (maybe 1/4?) holes through the wall in a few places to pass the radials through. With a decent hammer drill and a carbide bit a small hole like that is pretty quick and easy to complete -- even in concrete or stone. Then just use a piece of coathanger wire as a wire fishing tool to run the radials through the hole. I use a wire pulling tool called a creep-zit to pull radials under fallen trees and logs in the woods. It works great. I basically just take one of the 6 foot long fiberglass rods (each of which is a little over 1/8 diameter), tape the radial to one end, and then I can push it under fallen debris easily. With a little practice you can even get around hidden obstructions in the ground this way. -Bill I shunt feed my tower for topband. I use variable vacuum caps and a vacuum relay at the base to switch between the low end and the high end of the band. It seems to work okay. I have 100' buried radials spaced 10' at the ends from o degrees going clockwise through about 220 degrees. I have a 4' high stone wall that runs about 20/200 degrees that is about 35' at its closest point to the tower. So the radials are progressively shorter on the West side of the tower. I am making an assumption that going up over the wall will distort any benefits of extending the radials on the West side? Is that a true assumption. I can't really have the radials go from the tower base up at an angle to clear the stone wall and continue on. If I am to extend them the radials would have to go on the ground to the wall then up and over and back down to the ground. 73, N2TK, Tony ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: FCP model
For a short vertical I prefer ground radials over an elevated counterpoise because the counterpoise height reduces the monopole length. Dave WX7G On Aug 1, 2012 9:32 AM, Tom W8JI w...@w8ji.com wrote: I think a more relevant question should be is there a better or simpler elavated radial arrangement that can fit into the 66 foot linear space that will radiate more effectively than the FCP design? I'd be willing to extend that distance to 100 feet since many surburban lots can support a 100 foot run. Most people cannot erect elevated 2 or 4 quarter wavelength full length radials. From what I have seen, within limits of what we could really notice, there are dozens of ways to accomplish the same thing. All have about the same result. There is no universal solution that makes every 50 foot backyard look the same, let alone look like 50 acres of flat rich soil. The key is always more about not doing something wrong, and doing what fits and lasts. Whoever said 2-4 elevated radials always works? Many times fifteen or twenty 50-foot radials on the ground are the same or better. 73 Tom ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: U think you've got interference
No, the military is not using tubes except for the occasional TWT high power amplifier. When specified for EMP military gear will take it. Dave WX7G On Jul 31, 2012 2:23 PM, jcjacob...@q.com wrote: Darl got zapped by an EMP from the Air Force testing range Darl: Sounds like a good case for tube type, boat anchors.. No menus, no microprocessors, no solid state. After all, the military keeps going back to it from what I've heard. Sand storms in the Middle East causing static buildup and taking out the front ends of the latest and greatest microprocessor gear. (Sorry, I couldn't resist!! ) Time for a Faraday cage around the radio room? Good luck you just may need lots of it. 73 K9WN Jake ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: elevated counterpoise and lightning
Bob, do you have ground rods for lightning? The stub should be ok for static discharge but not for near or direct strikes. Dave WX7G On Jul 29, 2012 7:04 PM, Bob Kupps n...@yahoo.com wrote: Hi in this thread I mentioned using a 1/4 wave shorted stub at the feed points of our 4 square for static drain. Since we want to farm the paddy land we will use a non-resonant counterpoise of 48 radials connected to a perimeter wire about 1.5m above the flooded ground. The only galvanic connection to earth would be back through the RG6 feed line to the center control box. So would adding an RF choke to the earth ground at the element base be a good idea in this case? Does anyone have any experience with the behavior of elevated radials in a lightning strike? 73 Bob HS0ZIA ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Spark Gaps..
Bob, that an excellent idea! Dave WX7G On Jul 28, 2012 6:06 PM, Robert Briggs vk...@bigpond.com wrote: Has anyone thought about using two trailer towing balls set up for a spark gap? I use this on a 90 foot insulated mast in a very lightning prone environmentTo date (25) years, with many direct hits, I have sustained no damage...Mast is located 20 feet from my lounge room.. 73..Bob..VK3ZL.. ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Fw: Choke Construction Info Needed
I agree with Tom and Bob that the big, heavy choke is not needed. Even it offers too much inductance to be an effective lightning path. A spark gap is the thing to use across the choke or shorted 90 degree feedline. It should have a weather cover and be set close but not too close. See ROSS ENGINEERING for a picture of a spark gap. I've use 1/4 carriage bolts for spark gaps at 1 kA. I would use a larger one for protection against a direct lightning strike. Only 1% of strikes reach 100 kA but I think that's a good current to design to. http://www.rossengineeringcorp.com/hv_spark_gap.htm Dave WX7G On Thu, Jul 26, 2012 at 7:53 PM, Bob Kupps n...@yahoo.com wrote: Hi Phil I'm no expert but plan to use a quarter wave shorted stub of RG6 at the feed point of my verticals for static drain and harmonic reduction, along with a spark gap in the event of a close strike. 73 Bob - Forwarded Message - From: Phil Clements philcleme...@centurylink.net To: topband@contesting.com Sent: Friday, July 27, 2012 2:03 AM Subject: Topband: Choke Construction Info Needed I need to construct a heavy-duty choke to be installed from the feed point of my 160 meter vertical to ground, for static drain and for lightning protection. How large does the wire, form, and inductance need to be? Thanks in advance for your expertize! (((73))) Phil, K5PC ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Spark gaps
Yes a direct hit should vaporize a spark plug. For a 100 kA hit two 1 diameter rounded steel balls may survive. Note that Ross Engineering uses carbon balls on their spark gaps. At 50 kA/us every inch of wire will have a voltage drop of 500 to 1000 volts, so very short wires are in order. Wide copper straps having a length-to-width ratio of 5:1 are good. Dave WX7G On Jul 27, 2012 8:09 AM, Tom W8JI w...@w8ji.com wrote: Has anyone looked at, or looked for, cheap electric fence gaps?? My system copper pipes near tower legs work great for me on rigid towers, I can bend them so they spring away from the tower and then slide an inner pipe in or out to set gap distance. I'm thinking of gaps for wire antennas. Maybe something is good from some other application that is a good bit better than a spark plug. ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Lightning protection
A low impedance tower ground is important. Google TOWER FOOTING RESISTANCE for an IEEE ppt. on this. I would aim for a couple of ohms. That means several long rods. Dave WX7G On Jul 27, 2012 9:06 AM, HAROLD SMITH JR w0ri...@sbcglobal.net wrote: About 20 years ago I decided to do something about lightning protection. My tower is 80 feet of Rohn 45G, with a 5el Telrex monoband 20 meter yagi at 82 feet. Hygain 153BAS at 90 feet and Hygain 103BAS at 100 feet. I have a homemade antenna switch box near the top. I shunt feed the tower with an Omega Match for 160. The shunt rod is 1/2inch EMT conduit. I use vacuum variables in the Omega match. At 65 feet I have a Diamond X200 for 2meter/440mhz. all cables come to the base and go underground to a steel box at the entry to the house. The HF antennas are fed with RG-17 and go through an ICE 308 15kw coax arrestor. The X200 is fed with RG213 through a PolyPhaser arrestor. The control wires all go through PolyPhaser arrestors. I made LC to UHF adapters. My tower is the tallest thing for several miles. The tower is guyed with 6700lb Phillystrand. So far so good. Price W0RI near St. Louis, MO ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Spark gaps
Google carbon ball gap lightning. Dave On Jul 27, 2012 9:33 AM, Mike Waters mikew...@gmail.com wrote: I don't think carbon balls are suitable for lightning protection. Think of the voltage drop that would appear across each ball during a direct hit. I think they would vaporize. At http://www.rossengineeringcorp.com/hv_spark_gap.htm lightning is not one of the applications mentioned for their carbon balls. 73, Mike www.w0btu.com On Fri, Jul 27, 2012 at 9:35 AM, DAVID CUTHBERT telegraph...@gmail.com wrote: Note that Ross Engineering uses carbon balls on their spark gaps. ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Spark gaps
www.rossengineeringcorp.com/toroids_spheres_coronary_nuts.htm Ross recommends carbon for lightning. Dave WX7G On Jul 27, 2012 9:33 AM, Mike Waters mikew...@gmail.com wrote: I don't think carbon balls are suitable for lightning protection. Think of the voltage drop that would appear across each ball during a direct hit. I think they would vaporize. At http://www.rossengineeringcorp.com/hv_spark_gap.htm lightning is not one of the applications mentioned for their carbon balls. 73, Mike www.w0btu.com On Fri, Jul 27, 2012 at 9:35 AM, DAVID CUTHBERT telegraph...@gmail.com wrote: Note that Ross Engineering uses carbon balls on their spark gaps. ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Spark gaps
www.rossengineeringcorp.com/toroids_spheres_corona_nuts.htm On Jul 27, 2012 9:43 AM, DAVID CUTHBERT telegraph...@gmail.com wrote: www.rossengineeringcorp.com/toroids_spheres_coronary_nuts.htm Ross recommends carbon for lightning. Dave WX7G On Jul 27, 2012 9:33 AM, Mike Waters mikew...@gmail.com wrote: I don't think carbon balls are suitable for lightning protection. Think of the voltage drop that would appear across each ball during a direct hit. I think they would vaporize. At http://www.rossengineeringcorp.com/hv_spark_gap.htm lightning is not one of the applications mentioned for their carbon balls. 73, Mike www.w0btu.com On Fri, Jul 27, 2012 at 9:35 AM, DAVID CUTHBERT telegraph...@gmail.com wrote: Note that Ross Engineering uses carbon balls on their spark gaps. ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Spark gaps
Mike, here it is. The resistivity of amorphous carbon is 35 u ohm meters (That's a 1 meter cube) A 1 cube has a resistivity of 1.4 m ohms, a one inch sphere about 3 m ohms. 100 kA for 20 us dumps 600 J into it. The density of carbon is 2.3 g/cm cubed The 1 inch sphere has a mass of 20 grams The specific heat capacity of carbon is 700 J/kg k The observe heats 43 deg C Dave WX7G On Jul 27, 2012 2:18 PM, Mike Waters mikew...@gmail.com wrote: Man, I don't know, Dave. How long have they been selling those carbon balls for that purpose? I don't have the figures in front of me, but carbon has a significant amount of resistance. (Maybe that's the secret: the current gets limited as a result. :-) It would be interesting to calculate the resistance of a carbon sphere sometime (how big are those?). Then we could roughly estimate the voltage drop across it and so come up with a ballpark figure of the instantaneous power dissipated in those balls. At that point, someone with way too much time on their hands could estimate the temperature rise based on the specific heat of carbon. :-) 73, Mike www.w0btu.com On Fri, Jul 27, 2012 at 2:42 PM, DAVID CUTHBERT telegraph...@gmail.com wrote: www.rossengineeringcorp.com/toroids_spheres_corona_nuts.htm On Jul 27, 2012 9:43 AM, DAVID CUTHBERT telegraph...@gmail.com wrote: http://www.rossengineeringcorp.com/toroids_spheres_coronary_nuts.htm Ross recommends carbon for lightning. On Jul 27, 2012 9:33 AM, Mike Waters mikew...@gmail.com wrote: I don't think carbon balls are suitable for lightning protection. Think of the voltage drop that would appear across each ball during a direct hit. I think they would vaporize. ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Spark gaps
I do make (all too frequent) mistakes so check away. Carbon is 2000 times more resistive than copper. Being more resistive the carbon skin depth at lightning frequencies is much deeper than copper or steel (note the steel is magnetically saturated). Dave On Jul 27, 2012 3:26 PM, Mike Waters mikew...@gmail.com wrote: Thanks, Dave. That's amazing, and I won't argue anymore, even though I didn't (and probably won't) check your figures. I would have thought that the carbon sphere would have a MUCH greater resistance than .003 ohms. 73, Mike www.w0btu.com On Fri, Jul 27, 2012 at 3:42 PM, DAVID CUTHBERT telegraph...@gmail.comwrote: A ... one inch sphere about 3 m ohms. ... The observe heats 43 deg C ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Choke Construction Info Needed
20 uH should be sufficient at the base of a 1/4 wave length vertical. #4 copper wire is used to connect towers to ground for direct strikes. Such an inductor can be close-wound with insulated #4 wire, diameter 8, 8 turns. It should survive intact except for the insulation. Dave WX7G On Jul 26, 2012 2:02 PM, ZR z...@jeremy.mv.com wrote: It all depends upon how much survivability you want, nothing will survive a direct hit. Any 1.5 to 2.5 mH choke will suffice, just look at the safety choke in a commercial amp for the smallest choice. The big ones are often found in scrapped BCB transmitters and tuning units as well as show up at hamfests and on Fleabay as old military gear had various candidates. Carl KM1H - Original Message - From: Phil Clements philcleme...@centurylink.net To: topband@contesting.com Sent: Thursday, July 26, 2012 3:03 PM Subject: Topband: Choke Construction Info Needed I need to construct a heavy-duty choke to be installed from the feed point of my 160 meter vertical to ground, for static drain and for lightning protection. How large does the wire, form, and inductance need to be? Thanks in advance for your expertize! (((73))) Phil, K5PC ___ UR RST IS ... ... ..9 QSB QSB - hw? BK - No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1424 / Virus Database: 2437/5155 - Release Date: 07/25/12 ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Choke Construction Info Needed
30 watts is correct for 1500 watts in a 50 ohm system and a coil Q of 226. The power loss is 0.1 dB and the coil temp rise is around 20 deg C. WX7G On Jul 26, 2012 3:20 PM, ZR z...@jeremy.mv.com wrote: ** That is only 226 Ohms at 1.8MHz and at 1500W will be dissipating about 30W in a 50 Ohm system but Phil didnt say how he is feeding his tower which is resonant well below 160M. Yes it will work as well as survive a lot of energy at 35-50 Ohms compared to a larger inductance 1A choke. Carl KM1H - Original Message - *From:* DAVID CUTHBERT telegraph...@gmail.com *To:* ZR z...@jeremy.mv.com *Cc:* philcleme...@centurylink.net ; topband@contesting.com *Sent:* Thursday, July 26, 2012 4:35 PM *Subject:* Re: Topband: Choke Construction Info Needed 20 uH should be sufficient at the base of a 1/4 wave length vertical. #4 copper wire is used to connect towers to ground for direct strikes. Such an inductor can be close-wound with insulated #4 wire, diameter 8, 8 turns. It should survive intact except for the insulation. Dave WX7G On Jul 26, 2012 2:02 PM, ZR z...@jeremy.mv.com wrote: It all depends upon how much survivability you want, nothing will survive a direct hit. Any 1.5 to 2.5 mH choke will suffice, just look at the safety choke in a commercial amp for the smallest choice. The big ones are often found in scrapped BCB transmitters and tuning units as well as show up at hamfests and on Fleabay as old military gear had various candidates. Carl KM1H - Original Message - From: Phil Clements philcleme...@centurylink.net To: topband@contesting.com Sent: Thursday, July 26, 2012 3:03 PM Subject: Topband: Choke Construction Info Needed I need to construct a heavy-duty choke to be installed from the feed point of my 160 meter vertical to ground, for static drain and for lightning protection. How large does the wire, form, and inductance need to be? Thanks in advance for your expertize! (((73))) Phil, K5PC ___ UR RST IS ... ... ..9 QSB QSB - hw? BK - No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1424 / Virus Database: 2437/5155 - Release Date: 07/25/12 ___ UR RST IS ... ... ..9 QSB QSB - hw? BK -- No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1424 / Virus Database: 2437/5155 - Release Date: 07/25/12 ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Choke Construction Info Needed
My mistake. Now then, for lighting we don't really want much inductance between the antenna and ground. For a 100 kA strike rising in 2 us 1 MV is developed across 20 uH. Instead we want a sturdy spark gap of 1/32 inch connected directly from the feedpoint to the ground system. WX7G On Jul 26, 2012 4:23 PM, Tom W8JI w...@w8ji.com wrote: 30 watts is correct for 1500 watts in a 50 ohm system and a coil Q of 226. The power loss is 0.1 dB and the coil temp rise is around 20 deg C. No, it isn't. 1500 watts is 273 volts into 50 ohms. If Q is 226, and reactance 226 ohms, Rp is 51,077 ohms. 273 volts is 1.46 watts heat. To get 30 watts of heat with 226 ohms reactance, Q would have down near unity. No one makes a coil that bad. ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Cable shields
Tom, I don't doubt that you performed the cable TI measurement correctly but I have seen folks take data that is actually the TI of the test fixture and not the cables under test. What TI impedance did you measure? Dave WX7G On Jul 11, 2012 2:37 PM, Tom W8JI w...@w8ji.com wrote: The statement CATV coaxial cables or cables with foil/drain shields do not have good shielding, because of transfer impedance and high resistance, was made a while ago here on this reflector. I think the statement was those shields are not good at MF or HF. This past weekend, I modified a test fixture to test sample cables for common mode. I compared two samples. One was an 8-foot long sample of two-year-old CommScope F6 dual-shield, and the other was a heavy copper braid RG6/U solid dielectric that was inside. The F6 was pulled out from a cut cable a week ago, one bonded foil overlaid with aluminum braid. The cables were within a dB or two of each other. http://www.w8ji.com/coaxial_cable_leakage.htm 73 Tom ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Reducing Noise in the Shack
The W7NQN line filter is a differential-mode filter. You need a filter that is designed for common-mode filtering. Dave WX7G On Jun 21, 2012 10:32 AM, Wayne Willenberg wewill...@gmail.com wrote: As I mentioned in a post a few days ago, I am at the very beginning of being able to operate on 160 and 80M’s. (To date, I have only operated on 10, 15 and 20M.) I have been doing a lot of reading, primarily ON4UN’s “Low-Band DXing.” My rig (FT-dx5000) is located on a desk. Immediately under the desk is my computer, and just above the rig is a shelf on which sits 2 flat-screen monitors. One of the points made in “Low-Band DXing” is the necessity of reducing noise in the shack. The author states at page 7-75: “It is essential to feed the equipment at the shack through high-quality mains filters.” In looking for such filters, I have come across the W3NQN AC Line Filter. It seems to be built with quality components, but I have not been able to find any specs on the amount of attenuation it provides to EMI and RFI noise at various frequencies (either common or differential mode). Could someone recommend a “high-quality mains filter” or comment on the W3NQN filter? The author goes on to state: “The bottom side of the operating table in my shack is completely covered with aluminum sheet. This represents a lot of capacitance and virtually zero inductance, which is just what you want! Quality mains filters are bolted directly to those sheets and the mains outlet to which the equipment is connected is connected as well. The ground plane is connected with very short low-inductance wide straps to long copper ground rods.” Would someone please explain to me the purpose of this ground plane and how it helps reduce noise? How does “a lot of capacitance and virtually zero inductance” under a transceiver help reduce noise? Thanks in advance for advice and help for a newcomer. ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Reducing Noise in the Shack
I don't like diff mode only filters because they have diff mode to common mode conversion due to component tolerance. I don't see a fuse in the NQN filter and it us rated for only 7 amps. To be used on a 20 amp circuit without an internal fuse it must be able to handle 20 amps. I assume it's not UL listed? Dave WX7G On Jun 21, 2012 1:07 PM, Guy Olinger K2AV olin...@bellsouth.net wrote: On Thu, Jun 21, 2012 at 2:59 PM, DAVID CUTHBERT telegraph...@gmail.comwrote: The W7NQN line filter is a differential-mode filter. You need a filter that is designed for common-mode filtering. Dave WX7G This is from the web page advertisement: - Compare this with a Brand C filter which only handles common-mode interference problems. The NQN AC power-line filters are optimized for common-mode and differential-mode filtering and have about 3 times the components of brand C. - Seems to specifically include common mode. See http://arraysolutions.com/Products/nqnaclinefilter.htm 73, Guy. ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: radial wire source
I use #14 stranded THHN wire from Home Despot because it's easy work work with. Dave WX7G On Jun 5, 2012 9:23 AM, W2XJ w...@nyc.rr.com wrote: You really do not need stranded wire. Bare solid wire is typically used for grounds. and while the standard of 120 radials spaced 3 degress is a well known standard for ground systems, it is very rare in amateur radio. Anything beyond 12 1/8 wavelength radials is a plus. I would check an electrical wholesaler and price bare copper in bulk. Usually #10 is used but I see no serious reason why #12 or even #14 would work in this application. I prefer a buried ground (or at least on the surface) over elevated for various reasons. Having installed many MW systems, I can tell you the ideal is not always achieved. At the end of the day, get as much wire in the ground wherever it is possible. On 6/5/12 9:01 AM, Dan Bookwalter wrote: I think I asked something similar last fall , but , circumstances changed and I couldn't do anything about it at the time... So , here I am again looking for a source of radial wire I was thinking of either going with K2AV's FCP or a radial field If i go with the radials I was thinking of using #14 stranded for about 15 radials that in theory would help absorb any lightning impulses (per W8JI website) , then I was going to use whatever wire I can find for the remaining 40 or 50 radials. My radial field can only cover from about SW thru North over to East. Is there a better source for wire than Lowes/Home Depot ? I will check with the local electrical distibutor , but , if I recall correctly they weren't much better Lowes currently has 500' of #14 THHN for $50 I would need about 3000 feet. Dan ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Monopole Radiation Patterns, takeoff angles etc
The program W6ELProp gives the take-off-angle needed for any path. Looking at 80 meter paths (it does 801-0 meters) the angles for DX paths are in the range of 3-15 degrees. Dave WX7G ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Monopole Radiation Patterns, takeoff angles etc
If the radiation at 3 degrees is -8.9 dB relative to the maximum amplitude we can still work DX. Dave WX7G On May 8, 2012 9:18 AM, Richard Fry r...@adams.net wrote: Dave WX7G wrote: The program W6ELProp gives the take-off-angle needed for any path. Looking at 80 meter paths (it does 801-0 meters) the angles for DX paths are in the range of 3-15 degrees. Assuming those angles are true for DX paths, note that if the NEC far-field elevation pattern for a 1/4-wave monopole was the only radiation leaving the antenna, the field at 3 degrees elevation would be about 8.9 dB below the field at the center of the so called take-off angle (see link below - note Photobucket stripped the decimal from the 3.9MHz link). The surface wave really needs to be recognized in such evaluations. http://i62.photobucket.com/albums/h85/rfry-100/39MHz_Elepat_6_mS.jpg ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: question about antenna bandwidth
Roy, you didn't specify the vertical length of your inverted-L but I'll assume it is 50' and that your base-referred ground loss is 5 ohms. Using NEC-2 for the 1/4 wavelength inverted-L I get a 2:1 VSWR bandwidth of 51 kHz. Note the base resistance at resonance is 18 ohms. For the 3/8 wavelength inverted-L I get a 2:1 VSWR bandwidth of 30 kHz. Note the base resistance is 44 ohms and a 142 pF series capacitance is used to tune out the inductive reactance. Dave WX7G On Mon, May 7, 2012 at 11:48 AM, Roy royan...@ncn.net wrote: If I were to extend my 1/4-wave inverted-L to a 3/8-wave L, and tune out the inductance with a fixed capacitor at the base, what would this do to the broadbandedness of the antenna? There is an old basic principle to remember about this, The fewer the components in general, the broader the bandwidth. 73, Roy K6XK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: 'the old ways...'
On May 4, 2012 9:43 AM, DAVID CUTHBERT telegraph...@gmail.com wrote: Dan that is how I do it and have measured the base referred ground loss resistance of my 30' vertical to be around 5 ohms. Dave WX7G On May 4, 2012 9:22 AM, Dan Edward Dba East edwards dan.n.edwa...@sbcglobal.net wrote: whatever happened to the 'old way' of measuring ground loss? back in the 80's we would look up the predicted impedance from LaPort, then measure it as accurately as possible with a General Radio 1606..and figure the difference is 'ground loss'... today, with better software ( EZNEC5 ), we can model our antennas over 'perfect ground', and with better hardware ( i like my VNWA2 ), measure with some confidence of reasonable accuracy. and again, figure the difference is 'ground loss'... this at least gives you a clue what is happening, beyond 'just put out as many radials as you can, as long as you can make them'in my case, with scant available real estate for radials, i come up with about 6 ohms of ground loss... respectfully submitted...tell me why this is 'wrong'73 w5xz, dan ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Topband: Fwd: Re: 'the old ways...'
-- Forwarded message -- From: DAVID CUTHBERT telegraph...@gmail.com Date: May 4, 2012 9:43 AM Subject: Re: Topband: 'the old ways...' To: Dan Edward Dba East edwards dan.n.edwa...@sbcglobal.net Dan that is how I do it and have measured the base referred ground loss resistance of my 30' vertical to be around 5 ohms. Dave WX7G On May 4, 2012 9:22 AM, Dan Edward Dba East edwards dan.n.edwa...@sbcglobal.net wrote: whatever happened to the 'old way' of measuring ground loss? back in the 80's we would look up the predicted impedance from LaPort, then measure it as accurately as possible with a General Radio 1606..and figure the difference is 'ground loss'... today, with better software ( EZNEC5 ), we can model our antennas over 'perfect ground', and with better hardware ( i like my VNWA2 ), measure with some confidence of reasonable accuracy. and again, figure the difference is 'ground loss'... this at least gives you a clue what is happening, beyond 'just put out as many radials as you can, as long as you can make them'in my case, with scant available real estate for radials, i come up with about 6 ohms of ground loss... respectfully submitted...tell me why this is 'wrong'73 w5xz, dan ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Fwd: Re: Home Depot LED bulb interference.
My calculations assume that the LED lamp conducted emissions are at the FCC limit at a single frequency in the 160 meter band. This is not real world. I'll buy a lamp and characterize the conducted emissions. Dave WX7G On Apr 6, 2012 4:44 PM, DAVID CUTHBERT telegraph...@gmail.com wrote: -- Forwarded message -- From: DAVID CUTHBERT telegraph...@gmail.com Date: Apr 6, 2012 4:42 PM Subject: Re: Topband: Home Depot LED bulb interference. To: GeorgeWallner aa...@atlanticbb.net LED lamps no doubt comply with FCC conducted emissions. The noise is almost entirely differential mode. Think of a signal on an open wire t-line; it does not radiate (much). But, the asymmetry in the AC power system causes differential to common-mode conversion. Common-mode current on an open wire feedline radiates (a lot). The primary asymmetry I see is the neutral wire to earth ground. I ran a NEC sim of a simplified house AC power with feed wires to a power pole. The signal induced into a 160 meter dipole next door is S-8 from a single LED lamp at the FCC limit of 2 mV differential into 100 ohms. Disconnecting the AC earth ground wire drops the signal by 40 dB. Ferrites clamped onto the earth ground wire could help. This is crude and preliminary but is interesting as I'm an EMC design engineer as well as a ham. Dave WX7G On Apr 6, 2012 4:22 PM, GeorgeWallner aa...@atlanticbb.net wrote: On Fri, 6 Apr 2012 11:57:15 -0700 (PDT) Jim F. j_fit...@yahoo.com wrote: ...Since this bulb complies with part 15 of FCC rules It is marked to comply, but it may not. (Part 15 compliance is self-certified. It would be interesting to test it against Part 15 requirements. I believe that one of our potential defences against the worst offenders is to bring the attention of retailers to the pontial risks of selling non FCC comliant products. The more cautious they get the better off we will be. Returning it to the retailer is a good start in that direction! George ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Home Depot LED bulb interference.
I did some research and Maxim makes ICs for offline LED lamps such as the Home Depot lamps. The switching frequency is 50 to 330 kHz and the incoporate frequency dithering to reduce EMI. The standard they adhere to appears to be EN 55015, Limits and methods of measurement of radio disturbance characteristics of electrical lighting and similar equipment. I found a plot of the limit line and it is in dBuA. In the 160 meter band it is 28 dBuA. From what I gather a standard 50uH/50 ohm LISN is used for the measurement. The standard applies from 9 kHz to 30 MHz. Dave WX7G On Apr 6, 2012 5:02 PM, Garry Shapiro ga...@ni6t.com wrote: George, I suspect your question at the end was tongue-in-cheek. We know from long experience with other notorious consumer noise sources---e.g. plasma TV's, cheap dimmers, touch lamps, fish tank heaters, thermostats--that the FCC has been neither active nor timely in exercising its enforcement prerogatives. Some of this is probably due to the disparity between congressional mandate--i.e. do this--and funding, but we have had little indication of the government's interest in pursuing Part 15 violations, especially against imports of dubious quality. I fear we are facing a tsunami of RFI, speeding toward us as a perfect storm of modern lighting. I have in the past laid in a supply of relatively quiet dimmers and replaced many in the neighborhood. But CF and LED bulbs will be ubiquitous and it is likely to be impossible to deal with this problem---unless we can generate pressure on the FCC to enforce Part 15. Garry, NI6T On 4/5/2012 4:10 PM, GeorgeWallner wrote: On Thu, 5 Apr 2012 16:01:12 -0400 Mike Greenwayk...@bellsouth.net wrote: I wondered how long it would take before they started selling some RFI generating lighting. Soon we can have a complete neighborhood of RFI I have tested compact fluorescent bulbs a couple of years ago and found that they were noisy. I have not tried to quantify the level of noise emitted, but it was about S5 on my K3 at a distance of about 4 feet using a one foot wire for antenna. I have stayed with incandescent, but my neighbor has installed over 50 of them on his house. The noise coming from that direction (NW) is significantly stronger than what I get from any other direction. Since he has installed the CF (and many LED) bulbs, I have not made one JA QSO! Fortunately, my DHDL, which looks towards EU (NE) completely blocks the noise and I am still able to work Europe. On the other hand, I have LED lights installed on my dock, which is only about 20 feet to the East of the RX antenna, but these LED lights are driven by well filtered drivers in metal boxes. No noise from these lights can be detected. It seems to me that we have a very serious threat from noisy switched light sources (and other digital noise generators, like Variable Frequency Drives) that have not been properly filtered. I am wondering the if the LED bulbs bought from Home Depot meet FCC Part 15 specs. Were they marked so? George, AA7JV ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: It is not so much propagation
To me top band seems to be all about DXing. I can find plenty of if folks calling CQ DX but I don't hear many folks calling just plain CQ. Dave WX7G On Mar 19, 2012 9:47 AM, donov...@starpower.net wrote: We really don't need beacons on 160, the reverse beacon network provides good coverage. We just need stations on the air to be detected. http://www.reversebeacon.net The W3AO Field Day will have three transmitters on 160 meters this year, one each on CW, SSB and RTTY. 73 Frank W3LPL Original message Date: Mon, 19 Mar 2012 07:22:09 -0700 (PDT) From: N7DF n...@yahoo.com Subject: Topband: It is not so much propagation To: 160 reflector topband@contesting.com During the summer the storm static is the main obstacle to top band operation here 40 over nine crashes every 30 seconds kind of drown out everything, QRP or QRO In fact the fish beacons still come through around sunrise indicating that propagation paths are open but SWLing them is not that big a thrill Maybe we could get some low power 160 meter beacons operating through the summer to see what is really happening It would be interesting to get more Field Day stations on 160. Maybe our crowd can get 160 included in local club plans a 30 foot high mast with top loading is not to hard to put together and can get out pretty well with two or three readials it might even get some new people interested in top band ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: July Stew Perry Please!!!!
Perhaps during the summer months we should forgo QRP. Dave WX7G On Mar 18, 2012 11:29 AM, Sam Morgan k5oai@gmail.com wrote: I know I tried very hard to participate last year, mother nature had it in for us here in WTX DM91sk if you check that list there were only two '5's listed one was in MS the other in KY but I'll for sure give it another try this year any Stew Perry test, any time, QRPers will be there if thunderstorms permit that is P.S. if you are a QRPer you know the Stew Perry is the ONLY contest 160m or anywhere, that we are treated with any respect by the rest of hamdom. You have it we will come! Nuff said -- GB 73 K5OAI Sam Morgan On 3/18/2012 12:01 PM, Tree wrote: Think of the June Stew as an activity night. No weekend is going to be without conflicts - but maybe the die hard 160 types will show up and hand out some QSOs. Here are the results from last year: http://web.jzap.com/k7rat/SummerStew2011.txt The top QSO total was 94 QSOs. Not a lot - but more than you would have worked on most other evenings.:-) This was the first running of the event - so hopefully, there will be a bit more activity the second time. ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: TB season
I think we need a July contest. Dave WX7G On Mar 15, 2012 9:28 PM, Jim Brown j...@audiosystemsgroup.com wrote: On 3/15/2012 5:01 PM, Jon Zaimes AA1K wrote: I've worked JA's in April and August. Europe and the Mideast can be worked all summer long, as well as VK/ZL and much of the southern hemisphere -- where it's their winter. So the season can be what you make of it. YES! How would North America and EU work VK/ZL or South America if the guys in the lower hemisphere had our parochial attitude about the season? It's another self-fulfilling prophesy -- if you're not on the air, you're not going work anyone who is. 73, Jim K9YC ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: TB season
Thanks Sam, I didn't know about the summer Stew. I'll be there. WX7G On Mar 16, 2012 9:26 AM, Sam Morgan k5oai@gmail.com wrote: are there any plans for a Jine Stew Perry this year? last year it was on 1500Z, Jun 18 to 1500Z, Jun 19, 2011 GB 73 K5OAI Sam Morgan On 3/16/2012 10:09 AM, DAVID CUTHBERT wrote: I think we need a July contest. Dave WX7G ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: 160m dethroned? 600m the new top band?
I believe the proposed rule is 2 watts ERP. The typical 70 x 50 foot top band inverted-L can be base loaded on 500 kHz using a 500 kHz inductor. Given an inductor Q of 300 and ground loss of 20 ohms we have a radiation efficiency of 4%. Drive the antenna with 50 watts and you're on the air at the legal limit. Dave WX7G ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: NCJ Ground Radial Article
Radials do not affect the angle of radiation. Dave WX7G On Sat, Feb 11, 2012 at 4:14 AM, Doug Turnbull turnb...@net1.ie wrote: Bob, I found the NCJ article (http://www.ncjweb.com/k3lcmaxgainradials.pdf) most interesting - thank you. I wonder if there is also an affect on the angle of radiation with ground radial numbers. Is the issue solely one of gain and feed point impedance? At the moment I am helping a friend with his radials for a SteppIR vertical to be used on 80 though 6 so some compromises or overkill will be occurring here depending on the band. I also use a SteppIR for 80, 40 and 30 (120+ ground radials 40 to 60 feet long average length 55 feet) with an inverted L for TB using sixteen raised radials (12 to 16 feet) over the SteppIR radial system which I think serves as the ground screen mentioned in ON4UN's book. This is an interesting topic and one which does not die. There are always those of us coming up who need to learn from our more experienced fellows. Thanks to all. 73 Doug EI2CN ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Radials help
The paper by Rudy Severns, EXPERIMENTAL DETERMINATION OF GROUND SYSTEM PERFORMANCE FOR HF VERTICALS PART 7 GROUND SYSTEMS WITH MISSING SECTORS is illuminating. WX7G On Feb 10, 2012 2:03 PM, Guy Olinger K2AV olin...@bellsouth.net wrote: The 120 comes from the watershed 1937 Brown Lewis and Eppstein study now found in the IEEE journals. There were distinct characteristics to 120 times 0.4 wl (actually 115) that improved results even vs. 60. That a deficient radial system on one side has any significant reduction in that direction alone VS THE OTHER DIRECTIONS is a fairly well debunked idea. That the missing radials reduce radiation in all directions, due to diminished efficiency, is not disputed. 73, Guy. On Fri, Feb 10, 2012 at 2:54 PM, Herb Schoenbohm he...@vitelcom.net wrote: On 2/10/2012 1:11 PM, Milt -- N5IA wrote: If that is the case, WHY do the pro broadcasters install all 120 radials at full length; even bare wire buried a couple of inches underground? Answer: Because the FCC requires it as part of your AM application. Some stations that were required to protect a distant station on the same channel but away from the area they wanted to cover, even applied for a waivers with a deliberately poor ground system in the protected direction ...but the FCC said no way Jose. Another consulting engineer when modeling a slant wire shunt fed and running test FSM noticed some cancellation in the opposite direction of the slant wire shunt fed tower. This appeared a sensible solution to enhanced protection without the addition of another tower and expensive pahser, not to mention the cost of additional real estate. Again the boys at 1919 M Street said no. (The Portals today) With the price of copper skyrocketing the amount of theft in some parts of the country is unbelievable. AM stations are immediate targets as thieves just pull up the systems with a winch or just hook it to the bumper and drive off into seclusion and roll it up in the back of a truck. Some station owners in PR have opted to plow in barbed wire as a lower cost alternative to bare copper. So far none of the barbed wire buried ground systems have not been touched. Herb Schoenbohm, KV4FZ ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Help With Vertical Antenna Matching
100 +j0 or close to it. I can send the file later today. On Feb 6, 2012 10:26 AM, Paul Christensen w...@arrl.net wrote: Dave, What complex Z value do you get after running NEC at 1835 kHz? Can you attach the .NEC input file? Phil, Does your MFJ analyzer give you complex Z results in a R+jX format, rather than just Z magnitude? Not sure if the 259B model will do that or not. Anyway, with complex Z info, it's easy to design either a low-pass or high-pass L network using TLW software. Paul, W9AC - Original Message - From: DAVID CUTHBERT telegraph...@gmail.com To: philcleme...@centurylink.net Cc: topband@contesting.com Sent: Monday, February 06, 2012 12:06 PM Subject: Re: Topband: Help With Vertical Antenna Matching Phil, NEC shows that shortening the radials to 110' will resonate things at 1.8 MHz. The ends are 10' from ground. The radial length can be used to adjust the antenna to resonance. The input impedance is 100 ohms. A balun having a lossy 400 ohm impedance is needed to reduce the worse case feed line shield current to 20 dB below the total radial current. Dave WX7G On Feb 5, 2012 3:49 PM, Phil Clements philcleme...@centurylink.net wrote: I need the help from one of the Guru's here on the group I need to know how to match the 160 meter vertical ground plane here. It worked fine for years until I removed 80 meter 4-square from the tower. I have no modeling capabilities here. The set-up is this: A 200 foot Rohn 25 tower, with insulators at the 60 foot level. Three elevated radials at the 60 foot level; sloping down to about 10 feet off the ground at the far ends. They are c. 110 electrical degrees long. The vertical radiator is c. 140 feet long. There is a large 1:1 balun at the feed point. The feed line is 450 feet of 7/8 helix to the ham shack. The reading on the 259B at the feed point is c. 3:1 VSWR, with a slight dip to 2.7:1 at 2.45 mhz. I am at my wits end here; several trips up the tower produced no good results. There are many systems on Google and YouTube, but the matching systems are for antennas shorter that 1/4 wave length. The old matching system when the 80 m 4-square was co-located was a 600 pf series capacitor from the center of the coax to the base of the vertical element. The three radials are joined together at the feed point, and connected to the coax shield. The VSWR back then was 1.25:1 @ 1835 khz. , and was a killer antenna on 160! Any help will be greatly appreciated; my old knees have about two more climbs left in them! Thanks in advance. (((73))) Phil, K5PC __**_ UR RST IS ... ... ..9 QSB QSB - hw? BK __**_ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Help With Vertical Antenna Matching
Exactly. Dave WX7G On Mon, Feb 6, 2012 at 1:29 PM, ZR z...@jeremy.mv.com wrote: So does simple math when looking for 1/2 wave resonance. This is basically an OCF dipole which is going to have gobs of shield current thet has to be surpressed. Carl KM1H - Original Message - From: DAVID CUTHBERT telegraph...@gmail.com To: philcleme...@centurylink.net Cc: topband@contesting.com Sent: Monday, February 06, 2012 12:06 PM Subject: Re: Topband: Help With Vertical Antenna Matching Phil, NEC shows that shortening the radials to 110' will resonate things at 1.8 MHz. The ends are 10' from ground. The radial length can be used to adjust the antenna to resonance. The input impedance is 100 ohms. A balun having a lossy 400 ohm impedance is needed to reduce the worse case feed line shield current to 20 dB below the total radial current. Dave WX7G On Feb 5, 2012 3:49 PM, Phil Clements philcleme...@centurylink.net wrote: I need the help from one of the Guru's here on the group I need to know how to match the 160 meter vertical ground plane here. It worked fine for years until I removed 80 meter 4-square from the tower. I have no modeling capabilities here. The set-up is this: A 200 foot Rohn 25 tower, with insulators at the 60 foot level. Three elevated radials at the 60 foot level; sloping down to about 10 feet off the ground at the far ends. They are c. 110 electrical degrees long. The vertical radiator is c. 140 feet long. There is a large 1:1 balun at the feed point. The feed line is 450 feet of 7/8 helix to the ham shack. The reading on the 259B at the feed point is c. 3:1 VSWR, with a slight dip to 2.7:1 at 2.45 mhz. I am at my wits end here; several trips up the tower produced no good results. There are many systems on Google and YouTube, but the matching systems are for antennas shorter that 1/4 wave length. The old matching system when the 80 m 4-square was co-located was a 600 pf series capacitor from the center of the coax to the base of the vertical element. The three radials are joined together at the feed point, and connected to the coax shield. The VSWR back then was 1.25:1 @ 1835 khz. , and was a killer antenna on 160! Any help will be greatly appreciated; my old knees have about two more climbs left in them! Thanks in advance. (((73))) Phil, K5PC __**_ UR RST IS ... ... ..9 QSB QSB - hw? BK __**_ UR RST IS ... ... ..9 QSB QSB - hw? BK - No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1424 / Virus Database: 2112/4792 - Release Date: 02/06/12 ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: T Vertical feed
I had considered this case and it is valid with lossless GND or in free space. But over lossy ground one resonant radial with many short radials carries the about the same current. While not entirely accurate this can be explored in NEC-2 by placing the radials close to S-N GND. Dave WX7G On Jan 27, 2012 8:21 AM, Paul Christensen w...@arrl.net wrote: This is a terrible error in logic. Current on the radials will divide based on the impedance of each radial. If the feedline happens to be a pathological length its (outer) shield can carry *all* of the antenna return current. To Joe's point, I don't think we want the feedline to become a radial. It also seems that placement of the line should occur under the radial field and not on top of it, but I have not seen any studies that compare measurements. Anyone have this data? My initial thought for base-fed verticals is to use a CM choke at the base and also at the perimeter of the radial field, unless by placing the line under the field significantly helps to reduce coupling to the line. Paul, W9AC ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: T Vertical feed
Charles, Joe listed some symptoms of excessive feedine common-mode current such as RF bites and RF feedback. If you do not suffer from any of these effects a balun may be of no use. If one does experience CM problems that might be cured by a balun (CM choke) by all means give it a try. In my NEC model a CM choke having an impedance magnitude of 300 ohms reduced the coax CM current by one half. My anecdotal evidence from a dozen vericals is that no balun has been needed. Even in the case of a 12' top loaded 1.8 MHz vertical having a base current of 10 amps. Dave WX7X On Jan 27, 2012 9:40 AM, Charles Moizeau w...@msn.com wrote: My radial field consists of 55 radials, 75' to 150' in length, buried 0.5 to 1 deep. My coax feedline, encased by a 1.25 gray pvc conduit, is 12'' deep and 80' long. It passes beneath several radials between the shack and the antenna base. I don't use a common-mode choke at the base feedpoint of my inverted L, where the only matching element is a series-connected capacitor to cancel out the inductive reactance of the antenna's total length of 170'. I am willing to insert a common-mode choke, but don't know what to measure beforehand to learn if one is needed. Nor do I know what changed indications to look for after such a choke has been installed. I'd be grateful for any advice. 73, Charles, W2SH From: w...@arrl.net To: topband@contesting.com Date: Fri, 27 Jan 2012 10:20:16 -0500 Subject: Re: Topband: T Vertical feed This is a terrible error in logic. Current on the radials will divide based on the impedance of each radial. If the feedline happens to be a pathological length its (outer) shield can carry *all* of the antenna return current. To Joe's point, I don't think we want the feedline to become a radial. It also seems that placement of the line should occur under the radial field and not on top of it, but I have not seen any studies that compare measurements. Anyone have this data? My initial thought for base-fed verticals is to use a CM choke at the base and also at the perimeter of the radial field, unless by placing the line under the field significantly helps to reduce coupling to the line. Paul, W9AC ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: T Vertical feed
No I mean no balun is needed. The coaxial cable external shield current will be roughly that of one radial. With so many radials the shield current will be low. Dave WX7G On Jan 26, 2012 9:49 PM, Jim Brown j...@audiosystemsgroup.com wrote: On 1/26/2012 4:08 PM, DAVID CUTHBERT wrote: No balun is needed. What you mean, I think, is that no IMPEDANCE TRANSFORMATION is needed. Yet another example of why I object to the word balun. And I agree that no impedance transformation is needed at the antenna as long as some sort of matching is used in the shack. But a common mode choke IS a good thing, because it keeps RF off the coax. 73, Jim K9YC ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: T Vertical feed
The radiation resistance is 25 ohms. I estimate your base referred ground loss resistance to be 10 ohms. So, you should expect a VSWR of 1.4:1 fed directly with 50 ohm coax. To obtain a better match you could place a shunt inductor (start with 4 uH) across the feedpoint but you will have to shorten the T wires a bit. Dave WX7G On Jan 25, 2012 12:28 PM, ct1...@sapo.pt wrote: Hi Everyone, just finishing puting up a T Vertical (exactly in T shape) using 2 supports at the ends. The vertical portion is 18m and the T is 17m to each side (34m total). I am laying radials from 20m - 40m (have about 20 right now). My question is regarding the feeding of the antenna, should it be straight with 50 Ohm cable? Should I make some impedance transformer? (I have FT240-61) that I could use. Thanks for help, getting ready here for CQ WW cw 160M. 73's Filipe CT1ILT aka CR6K ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Adding a Ground to Elevated Feed Vertical?
No On Nov 29, 2011 2:08 PM, Mark Adams msadam...@gmail.com wrote: Hi Gang, I've been running my vertical for a couple of weeks now and it plays very nicely. The setup is: 85' up and 42' horizontal. Comtek 1:1 balun at feedpoint 7' off ground. 3 x ~137' radials all between 7 and 13 feet (driveway crossing height) off the ground. Fed with good coax. VSWR at rig end of coax is 1.9:1 at 1830 kHz. The question is whether it is worthwhile to install a ground rod under the feedpoint and connect the neg side of the balun to the ground rod (or maybe the shell of the 259 at the bottom of the balun). I'm asking because with my luck I won't be able to remove the rod once it is in and I cannot convert this antenna to ground radials because it is close to my driveway. OK, I could rent/borrow a horizontal boring rig. 73, Mark K2QO K2 #543 FN03ra** ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Erroneous info on ARRL web site about ARRL 160 contest
The rules are simple and clear: 1.1. Stations located in overseas and non-contiguous U.S. Territories may be worked by DX stations. This includes Alaska KL7, the Caribbean US possessions KP1-KP5, and all of the Pacific Ocean territories KHØ-KH9, including Hawaii KH6. These stations can work BOTH domestic stations (US and VE) as well as DX stations around the world. Check your software *before * the contest to be sure it will accept these QSOs. Dave WX7G ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Counterpoise very interresting
L.B. was a professor of Philosophy and not a degreed engineer. Dave WX7G On Nov 22, 2011 8:08 AM, ZR z...@jeremy.mv.com wrote: Cebik tended to be pedantic. Heck, he was a college professor- duh! He certainly knew his stuff, but his views were not necessarily global at all times. Perception colors our understanding of the world. ** Thats an understatement. I consider him one of the more blatant plaigarizers who knew a lot less about antennas as he misled many to believe. I happend to be in a meeting with him in GA when the company team I was with were making a presentation. His body language and questions gave a strong impression of a blowhard which was somewhat confirmed by the looks others on his side were giving him. The after the meeting discussions on my side were rather emphatic about the above. Carl KM1H - Original Message - From: k...@radioprism.com To: topband@contesting.com Sent: Tuesday, November 22, 2011 8:45 AM Subject: Re: Topband: Counterpoise very interresting Cebik's paper on the counterpoise is interesting and perhaps useful, so far as it goes. I don't remember seeing any mention of voltage-fed antennas, however. If they are in that article, I missed them. Cebik mentions Woodrow Smith in connection with a 1948 antenna book. I don't know if this is the same 'Woody Smith', W6BCX, but I suspect it is. Woody Smith wrote an article in March 1948 CQ Magazine titled Bet My Money on a Bobtail Beam. In that article, he is somewhat vague about the ground return for the center element, but is very clear that 'not much' of a ground is needed. In his Feb/Mar 1983 HR Mag. reprise of the Bobtail/Half Square antennas, he refers to the desirability of a 'ground screen', refraining from calling this small, rectangular grid a 'counterpoise'. But that's what it is, in today's usage. I called it that in my Bobtail pages, and will likely continue doing so. http://www.angelfire.com/md/k3ky/page49.html Moxon, G6XN also refers extensively to the counterpoise in his favored half wave vertical antennas, and in his case, is talking about a pretty tiny piece of metal indeed. See HF Antennas For All Locations. by G6XN. Cebik tended to be pedantic. Heck, he was a college professor- duh! He certainly knew his stuff, but his views were not necessarily global at all times. Perception colors our understanding of the world. Language is a living, growing thing. Cebik was probably right about the concept of the counterpoise having been 'muddied', but OTOH that horse is now long out of the barn. I very much doubt the word is going away any time soon, in ham 'circles'. Or squares or rectangles. Even elongated, skinny rectangles. I find K2AV's FCP (folded counterpoise) most intriguing, and I intend to give it a try here. My inverted L needs help. I am so over with crummy 'sparse radials'. What a waste. Also, I intend to shift more towards a longer L which more approximates voltage feed. Having a quarter wave L with the current point at ground level is just asking for poor performance IMO. 73, David K3KY ___ UR RST IS ... ... ..9 QSB QSB - hw? BK - No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1411 / Virus Database: 2092/4030 - Release Date: 11/21/11 ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Hi Z antenna coupling
There is no need to transmit to test your antenna. Received signal strength will do. With skywave antenna measurements there can be significant measurement variability. Multiple measurements like so should be used. Antenna A,B,C,A,B,C,A,B,C. Plot the data and you can see trends. Dave WX7G On Nov 20, 2011 12:41 PM, w7...@juno.com wrote: being radially impoverished, i have gravitated to high impedance feed antennas, the one at present is a tree mounted 120 up 130 over. i have installed three wall switches to be able to choose (one or all) of two differently configured 5/16 counter poises, and connecting my link coupled tuner tank bottom to the transmitter coax feed. now i have the option of working someone ( if the someone is patient) and getting a signal report comparing the tuner tank coupling options i remember our mathematician ron murata talking about the magic 37 as the number of random events needed for some sort of statistical confidence (was too busy thinking about ham radio or girls to remember exactly what he said) so with a sampling of 10 we shall make a comparison.. mike w7dra Invest in Gold Today Diversify your investment portfolio with Gold and Silver. Get a Free Investor Kit. http://thirdpartyoffers.juno.com/TGL3141/4ec957b4c5a9a29ed13st03vuc ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Another non-traditional antenna working.
For short radials make them equal lengths and load using a single coil. Dave WX7G On Nov 16, 2011 10:49 AM, Richard (Rick) Karlquist rich...@karlquist.com wrote: On 11/15/2011 9:10 PM, Guy Olinger K2AV wrote: field, either buried or elevated. Therefore, presuming that undense irregular radials that would fit would be excessively lossy, per RBN data previously gathered, the +33, -33 foot linear folded counterpoise (FCP) is used instead, elevated at 8 feet. The folds in the counterpoise are designed to self-cancel fields as much as possible, thereby minimizing ground induction, which is loss to skywave. The 66 73, Guy.e It seems to me that the folded counterpoise is equivalent to a couple of loaded short radials, except that linear loading is used instead of lumping loading coils. Thus the ground induction loss is not reduced by the folding. So this is just a non-traditional implementation of 2 short loaded elevated radials. Nothing wrong with that, if implemented carefully. The decrease in gain is probably within the margin of error of RBN. In the described small backyard situation, I would think that making radials out of plain wire and loading them with coils at the feedpoint would be more acceptable from the visual clutter viewpoint. Rick N6RK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Need EZNEC file for 1/4 wave 160 vertical with radial system
Here is how to build a useful NEC-2 model of a ground mounted 160 meter vertical. Place a vertical with four radials 1' over real GND. Use 20 current segments for each of the five wires. Place the RF source in segment 2. Place an RF load representing the counterpoise loss resistance in segment 2. Make this 5 to 15 ohms depending on your radial system. For example, for sixty 1/8 wavelength radials use 5 ohms. Dave WX7G ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: RX Antenna
I'm right in the middle of the search for a receive antenna. I tried an MFJ-1025 noise canceler and it works quite well to null out the one dominant local noise source that comes on from time to time. But it does nothing for the other noise sources. I then tried a short loaded dipole with a good 1:1 current balun to see if the noise was vertically polarized. No improvement. I then (last week) built a 5 x 8 ft rotating terminated loop with a 9:1 balun. A Radio Shack rotator turns it. Not enough signal and so today I ordered a DX Engineering preamp. So far I'm into this receive antenna adventure to the tune of $800 and I'm determined to get something that does the job. Dave WX7G ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: [Topband] DX window for the southern hemisphere
A write up in CQ could be what's needed to foster more souther hemisphere interest. By the way, that's what's missing in the Stew Perry contest; a write up in a major magazine or at least a QST type formatted article online. The present crude online list of scores causes me to skip most Stew's. Dave WX7G On Thu, Feb 10, 2011 at 8:32 PM, Ward Silver hward...@gmail.com wrote: Unfortunately those 160m contest contacts with southern hemisphere stations are likely to become increasingly rare, unless something can be done to encourage operation from here. Vy 73 Steve, VK6VZ I suggest having a contest within a contest for the southern hemisphere operators with plaques, certificates, and a separate writeup by a writer from the region on a web site, possibly posted on the CQ 160 web site. The CQ 160 sponsors obviously have to focus on the main body of participants who are in the northern hemisphere, but there's no reason not to have your own Midsummer's Eve version at the same time. As long as the exchange and rules are compatible with those of the CQ 160 contest, everyone will benefit from the increased activity and the southern hemisphere operators will get their fair share of the fun. 73, Ward N0AX ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Window Yes! -penalized in contest !
Yes there are repercussions. Some stations will not work a domestic station in the DX Window. If everyone followed this rule no domestic station would operate in the DX Window. It takes two to tango. Dave WX7G *IF* the sponsor of the contest says no domestic QSO's in the 1830-1835 DX window, then there should be repercussions for doing so. VE9AA ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
