Re: Topband: Elevated radial number vs efficiency
On N6LF web page you can find the QEX series on ground mounted radials. And there is a ton of discussion of this topic on the reflector as it seems to come up often (may be mixing it with the towertalk reflector). 73/jeff/ac0c alpha-charlie-zero-charlie www.ac0c.com On 1/1/21 11:28 PM, List Mail wrote: Yes, the antenna modelling is helpful, but by no means definitive. Several years ago I put up a top loaded vertical over a very limited buried radial field, 16 x 20 m. It worked, but nothing exciting. It was very hard work burying wire in very hard ground. I then put up an elevated radial system, starting with a pair, tuning them like a dipole. Same with the second pair. After four, the tuning didn't seem at all sensitive. I ended up with 7 x 1/4 wave radials, plus a shorter one where the property boundary was too close. The radials were about 2.5 m high, just high enough to not touch with my outstretched hand. That seemed to work quite ok, compared with a full wavelength doublet antenna up 20 m. I then moved and set up the top loaded now trapped vertical over elevated 4 x 1/4 wave radials for 160 and 4 x 1/4 radials for 80 m. I quickly tired of repairing fallen radials where a horse had rubbed on a post or where I caught the wire on the tractor exhaust pipe! Again, it worked me a decent amount of DX. And I mean "DX" as nearly everything is a very long way from VK3. Last year, I did the work of burying 60 x 33 m radials, clearing away the mess of overhead wires. Does that work any better than the elevated radials? I cannot know, as there was no means of comparative testing. But, it's a whole lot tidier with the wires under the ground than overhead. My conclusion is that elevated radials do work quite decently, and they are probably a little less work than burying a decent radial field. Wires on the ground were never an option, with livestock in the paddock. My suggestion, and the references too, is to put the elevated radials up as high as practicable (higher than I had them). This allows easy access to vehicles to drive under them, without tearing something down. The aim of the radials is to reduce the effect of ground return path losses, and even with 8 radials, I could drive under them, listening to Radio National on 621 kHz, and the signal would be significantly attenuated. All of the above observations were over fairly poor ground, decomposed granite, with granite rocks floating. There is water underlying, however. 73, Luke VK3HJ _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Elevated radial number vs efficiency
Yes, the antenna modelling is helpful, but by no means definitive. Several years ago I put up a top loaded vertical over a very limited buried radial field, 16 x 20 m. It worked, but nothing exciting. It was very hard work burying wire in very hard ground. I then put up an elevated radial system, starting with a pair, tuning them like a dipole. Same with the second pair. After four, the tuning didn't seem at all sensitive. I ended up with 7 x 1/4 wave radials, plus a shorter one where the property boundary was too close. The radials were about 2.5 m high, just high enough to not touch with my outstretched hand. That seemed to work quite ok, compared with a full wavelength doublet antenna up 20 m. I then moved and set up the top loaded now trapped vertical over elevated 4 x 1/4 wave radials for 160 and 4 x 1/4 radials for 80 m. I quickly tired of repairing fallen radials where a horse had rubbed on a post or where I caught the wire on the tractor exhaust pipe! Again, it worked me a decent amount of DX. And I mean "DX" as nearly everything is a very long way from VK3. Last year, I did the work of burying 60 x 33 m radials, clearing away the mess of overhead wires. Does that work any better than the elevated radials? I cannot know, as there was no means of comparative testing. But, it's a whole lot tidier with the wires under the ground than overhead. My conclusion is that elevated radials do work quite decently, and they are probably a little less work than burying a decent radial field. Wires on the ground were never an option, with livestock in the paddock. My suggestion, and the references too, is to put the elevated radials up as high as practicable (higher than I had them). This allows easy access to vehicles to drive under them, without tearing something down. The aim of the radials is to reduce the effect of ground return path losses, and even with 8 radials, I could drive under them, listening to Radio National on 621 kHz, and the signal would be significantly attenuated. All of the above observations were over fairly poor ground, decomposed granite, with granite rocks floating. There is water underlying, however. 73, Luke VK3HJ _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Elevated radial number vs efficiency
I have taken the liberty to move Jim's most recent reply on the Common mode thread over here where it is more on topic Jim: True enough There is a work around however Dick Weber k5UI ( SK ..I think) published an article in Communications Quarterly in 1999 on an approach using non resonant ( i.e not .25 wavelength ) radials which significantly reduces the impact of unbalanced radial currents. I cant find a link to a copy on the WEB, I have a copy of the article (contact me off list) if you cant find one . Running four 100 foot radials ( ~.2 wavelengths) I am able to have (measured)� radial currents that vary less than 2% over all four radials installed in a heavily wooded environment where some attempt was made to try and keep all of them "around " 7' above ground At .2 wavelengths N6LF's work suggests that I am giving up around .2db ...which suggests I might want to look at going from 100' radials to 150 /160' ? Will have to look at that, it would require I redo all my matching networks not sure I want to go through that for .3db ...8^( NR1DX manu...@artekmanuals.com On 1/1/2021 4:28 PM, Jim Brown wrote: On 1/1/2021 12:09 PM, Mike Waters wrote: I am ONE of the people who claim that four elevated radials can have approximately the same efficiency as 120 buried quarter wavelength radials. N6LF's work on this showed that imbalance of the current in elevated radials can significantly reduce field strength. Imbalance can be caused by differences in heights, lengths, and soil underneath them. Depending on our real estate, hams may find it difficult or impractical to install elevated radials having the symmetry of a broadcast station. Rudy has published work showing that 8 elevated radials are better than 4 for this reason. 73, Jim K9YC On 1/1/2021 4:55 PM, Mike Waters wrote: Thanks for catching that, Dave! I certanly can't argue with Rudy N6LF, but those two λ/4 10' high elevated radials in my old 160m page made that inverted-L a "killer"* in an ARRL 160 contest about 10 years ago. That was using only 100 watts. Broke a number of DX pileups, to my utter amazement. *Having said that, I had nothing else to compare it to in an A/B test! 73, Mike W0BTU On Fri, Jan 1, 2021, 3:37 PM Artek Manuals wrote: Correction that should be N6LF (not N6FL) NR1DX On 1/1/2021 4:26 PM, Artek Manuals wrote: N6FL was quoted earlier ... https://www.antennasbyn6lf.com/design_of_radial_ground_systems/ However N6FL states "The article is primarily intended to show why I (he, N6FL) _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector -- Dave manu...@artekmanuals.com www.ArtekManuals.com -- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Elevated radial number vs efficiency
My experience was not on top band BUT on a 80 meter 4 sq. initially I installed 4 gullwing elevated tuned radials for each of the 4 elements. The array played will but over time it became quit clear on wet rain or even dew conditions the array played much better in transmit and not as much obvious in recive. This prompted me to strip and install 112 ¼ wave radials per element. Wayne ,W3EA Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10 From: Mike Waters<mailto:mikew...@gmail.com> Sent: Friday, January 1, 2021 4:55 PM To: topband@contesting.com<mailto:topband@contesting.com> Subject: Re: Topband: Elevated radial number vs efficiency Thanks for catching that, Dave! I certanly can't argue with Rudy N6LF, but those two λ/4 10' high elevated radials in my old 160m page made that inverted-L a "killer"* in an ARRL 160 contest about 10 years ago. That was using only 100 watts. Broke a number of DX pileups, to my utter amazement. *Having said that, I had nothing else to compare it to in an A/B test! 73, Mike W0BTU On Fri, Jan 1, 2021, 3:37 PM Artek Manuals wrote: > Correction that should be N6LF (not N6FL) > > NR1DX > > On 1/1/2021 4:26 PM, Artek Manuals wrote: > > N6FL was quoted earlier ... > > https://www.antennasbyn6lf.com/design_of_radial_ground_systems/ > > > > However N6FL states "The article is primarily intended to show why I > > (he, N6FL) > _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Elevated radial number vs efficiency
Thanks for catching that, Dave! I certanly can't argue with Rudy N6LF, but those two λ/4 10' high elevated radials in my old 160m page made that inverted-L a "killer"* in an ARRL 160 contest about 10 years ago. That was using only 100 watts. Broke a number of DX pileups, to my utter amazement. *Having said that, I had nothing else to compare it to in an A/B test! 73, Mike W0BTU On Fri, Jan 1, 2021, 3:37 PM Artek Manuals wrote: > Correction that should be N6LF (not N6FL) > > NR1DX > > On 1/1/2021 4:26 PM, Artek Manuals wrote: > > N6FL was quoted earlier ... > > https://www.antennasbyn6lf.com/design_of_radial_ground_systems/ > > > > However N6FL states "The article is primarily intended to show why I > > (he, N6FL) > _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Elevated radial number vs efficiency
Correction that should be N6LF (not N6FL)
NR1DX
On 1/1/2021 4:26 PM, Artek Manuals wrote:
Mike & Bill
Thank you!!! I sometimes think there is too much emphasis on NEC
modelling and never enough real world verification with actual field
measurements
{I have hijacked the original thread and changed the subject. to be
more on point }
N6FL� was quoted earlier in the previous thread, for his work on
studying the effects of elevated radials and he in fact states on his
web page which IS by all means� worthy of reading and close study.� I
am reposting the link here
https://www.antennasbyn6lf.com/design_of_radial_ground_systems/
However N6FL� states "The article is primarily intended to show why I
(he, N6FL)� suggest that 10-12 elevated radials should be used if
possible. " . His own data however is a bit contradictory and his
comment lacks� the context of radial length. Radials of .25
wavelengths (Page 37 figure 12, QEX, March 2012) produces a gain
identical to 16 radials of the same length. His data suggests that if
you lengthen the elevated radials to .6 wavelengths then 16 elevated
radials do indeed produce ~.6db improvement over four radials of that�
same length. Most of us are unlikely to want to invest in the almost a
mile of additional wire on 160M to get that .6db improvement, let
alone the labor involved in stringing it up and keeping it up.
What I also stumbled on in reading that same article is that only two
elevated radials is only down by .4db compared to four radials, which
would suggest that even only two (elevated) radials would perform as
good or better than ground mounted radial fields of a couple of dozen
radial range. A quick google search did not produce a similar study to
N6LF's work for ground mounted radials though I am sure it is out
there and the readers of this thread will find it for everyone's
reading enjoyment !
Cheers and HNY
Dave
NR1DX
On 1/1/2021 3:09 PM, Mike Waters wrote:
This link at to top of that page is a must-read, too.
https://web.archive.org/web/20180923221943/http://lists.contesting.com/_topband/2007-11/msg00248.html.
Guess I might as well include the text...
I am ONE of the people who claim that four elevated radials can have
approximately the same efficiency as 120 buried quarter wavelength
radials.
I have installed such systems at three Standard Broadcast stations in
the
United States, and made field strength measurements that, when
analyzed in
accordance with FCC procedure, showed that the unattenuated field
strength
at one kilometer was essentially the same as the FCC criteria for
broadcast
antennas with 120 buried 90 degree radials (Figure 8 of Part 73 of
the FCC
Rules).
The first station was in 1990 and it was WPCI, 1490 kilohertz,
Greenville,
SC where the height of the tower steel was 93 degrees above the base
insulator and 87.2 degrees above the point of attachment of the four
elevated radials. The radials were horizontal all the way to the tower
where they were attached with an insulator and connected to the outer
conductor of a coax cable. The coax center conductor was connected
to the
tower at that point. The license application containing the field
strength
measurements, measurement analysis and explanations can be found in
the FCC
Public Reference Room under file number 900615AE.
Measurements were made on eight equally spaced azimuths out to three
kilometers using a Nems Clark model 120E field strength meter. 146
measurements were made for an average of over 18 per azimuth. Power
was set
at one kilowatt using a General Radio model 916A RF impedance bridge
for the
radiation resistance and a Delta Electronics precision RF ammeter for
the
antenna current. The measurement data was analyzed with EDX Engineering
program AMDAT which is described in IEEE Transactions on
Broadcasting, Vol.
BC-32, No. 2, June 1986.
The result was an RMS value of the eight radials of 302.7 mV/m/kW at one
kilometer. This compares with the FCC Figure 8 value of 307.8
mV/m/kW for a
93 degree tower with 120 ninety degree buried radials, however, a
tower 87.2
degrees (the height of the WPCI tower above the four horizontal
radials) has
an FCC rated efficiency of 303.7 mV/m/kW, one mV/m more than our
measured
value.
The WPCI radials were number 10 copper wire 90 degrees long and 8.7
degrees
(16 feet) above ground. A coax cable was fed through the inside of the
tower from the T network at the tower base to the point of radial
attachment. The top of the base insulator was approximately five
feet above
ground. The impedance was measured at the input to the coax which
was the
point of current measurement for determination of power. The bridge
measurement was R 78 +j56.4.
The FCC personnel in the Broadcast Bureau were initially reluctant to
entertain the notion of an AM broadcast ground system which was so
radically
different from what had been used from the beginning of vertical
broadcast
antennas in the
Topband: Elevated radial number vs efficiency
Mike & Bill
Thank you!!! I sometimes think there is too much emphasis on NEC
modelling and never enough real world verification with actual field
measurements
{I have hijacked the original thread and changed the subject. to be more
on point }
N6FL was quoted earlier in the previous thread, for his work on
studying the effects of elevated radials and he in fact states on his
web page which IS by all means worthy of reading and close study. I am
reposting the link here
https://www.antennasbyn6lf.com/design_of_radial_ground_systems/
However N6FL states "The article is primarily intended to show why I
(he, N6FL) suggest that 10-12 elevated radials should be used if
possible. " . His own data however is a bit contradictory and his
comment lacks the context of radial length. Radials of .25 wavelengths
(Page 37 figure 12, QEX, March 2012) produces a gain identical to 16
radials of the same length. His data suggests that if you lengthen the
elevated radials to .6 wavelengths then 16 elevated radials do indeed
produce ~.6db improvement over four radials of that same length. Most
of us are unlikely to want to invest in the almost a mile of additional
wire on 160M to get that .6db improvement, let alone the labor involved
in stringing it up and keeping it up.
What I also stumbled on in reading that same article is that only two
elevated radials is only down by .4db compared to four radials, which
would suggest that even only two (elevated) radials would perform as
good or better than ground mounted radial fields of a couple of dozen
radial range. A quick google search did not produce a similar study to
N6LF's work for ground mounted radials though I am sure it is out there
and the readers of this thread will find it for everyone's reading
enjoyment !
Cheers and HNY
Dave
NR1DX
On 1/1/2021 3:09 PM, Mike Waters wrote:
This link at to top of that page is a must-read, too.
https://web.archive.org/web/20180923221943/http://lists.contesting.com/_topband/2007-11/msg00248.html.
Guess I might as well include the text...
I am ONE of the people who claim that four elevated radials can have
approximately the same efficiency as 120 buried quarter wavelength radials.
I have installed such systems at three Standard Broadcast stations in the
United States, and made field strength measurements that, when analyzed in
accordance with FCC procedure, showed that the unattenuated field strength
at one kilometer was essentially the same as the FCC criteria for broadcast
antennas with 120 buried 90 degree radials (Figure 8 of Part 73 of the FCC
Rules).
The first station was in 1990 and it was WPCI, 1490 kilohertz, Greenville,
SC where the height of the tower steel was 93 degrees above the base
insulator and 87.2 degrees above the point of attachment of the four
elevated radials. The radials were horizontal all the way to the tower
where they were attached with an insulator and connected to the outer
conductor of a coax cable. The coax center conductor was connected to the
tower at that point. The license application containing the field strength
measurements, measurement analysis and explanations can be found in the FCC
Public Reference Room under file number 900615AE.
Measurements were made on eight equally spaced azimuths out to three
kilometers using a Nems Clark model 120E field strength meter. 146
measurements were made for an average of over 18 per azimuth. Power was set
at one kilowatt using a General Radio model 916A RF impedance bridge for the
radiation resistance and a Delta Electronics precision RF ammeter for the
antenna current. The measurement data was analyzed with EDX Engineering
program AMDAT which is described in IEEE Transactions on Broadcasting, Vol.
BC-32, No. 2, June 1986.
The result was an RMS value of the eight radials of 302.7 mV/m/kW at one
kilometer. This compares with the FCC Figure 8 value of 307.8 mV/m/kW for a
93 degree tower with 120 ninety degree buried radials, however, a tower 87.2
degrees (the height of the WPCI tower above the four horizontal radials) has
an FCC rated efficiency of 303.7 mV/m/kW, one mV/m more than our measured
value.
The WPCI radials were number 10 copper wire 90 degrees long and 8.7 degrees
(16 feet) above ground. A coax cable was fed through the inside of the
tower from the T network at the tower base to the point of radial
attachment. The top of the base insulator was approximately five feet above
ground. The impedance was measured at the input to the coax which was the
point of current measurement for determination of power. The bridge
measurement was R 78 +j56.4.
The FCC personnel in the Broadcast Bureau were initially reluctant to
entertain the notion of an AM broadcast ground system which was so radically
different from what had been used from the beginning of vertical broadcast
antennas in the 1920s, and as refined by the classic article on broadcast
ground systems in the thirties (Ground Systems as a Factor in Anten
