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<DIV>Com todos os detalhes.<BR>Espero que seja util.<BR><A
title=http://www.qsl.net/kp4md/144_mhz_halo.htm
href="http://www.qsl.net/kp4md/144_mhz_halo.htm">http://www.qsl.net/kp4md/144_mhz_halo.htm</A><BR><BR></DIV>
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<H1><B><FONT face="Times New Roman">144 MHz Halo
Antenna</FONT><BR></B></H1>
<H2><I><FONT face="Times New Roman">Construction and Analysis of a Low
Cost Omnidirectional Horizontally Polarized Antenna for 144
MHz</FONT><BR></I></H2>
<P><FONT face="Times New Roman">by Dr. Carol F. Milazzo, KP4MD (posted 23
May 2012)<BR>E-mail: kp4md@arrl.net</FONT></P>
<UL>
<LI><A
style='href: "http://www.qsl.net/kp4md/144_mhz_halo.htm#construction"'><FONT
face="Times New Roman">Construction</FONT></A>
<LI><A
style='href: "http://www.qsl.net/kp4md/144_mhz_halo.htm#analysis"'><FONT
face="Times New Roman">Model Analysis and Measurements</FONT></A>
<LI><A
style='href: "http://www.qsl.net/kp4md/144_mhz_halo.htm#stacking"'><FONT
face="Times New Roman">Stacking Halo Antennas</FONT></A>
<LI><A
style='href: "http://www.qsl.net/kp4md/144_mhz_halo.htm#comparison"'><FONT
face="Times New Roman">Gain and Polarization Comparisons</FONT></A>
<LI><A
style='href: "http://www.qsl.net/kp4md/144_mhz_halo.htm#references"'><FONT
face="Times New Roman">References</FONT></A>
<LI><A style='href: "http://www.qsl.net/kp4md/index.html"'><FONT
face="Times New Roman">Return to KP4MD Home
Page</FONT></A><BR></LI></UL></TH>
<TH style="VERTICAL-ALIGN: top" align=center text-align:=""
center;?=""></TH></TR>
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</TD></TR>
<TR>
<TH style="VERTICAL-ALIGN: top" width="33%" text-align="left;"><A
style="name: construction"></A>
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/IP3z93Xmcgoo-aPjijnuyNMTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="144 MHz Halo Antenna" style="HEIGHT: 300px; WIDTH: 400px" border=2
alt="144 MHz Halo Antenna"
src="https://lh6.googleusercontent.com/-AvVseXEIza0/T7STNUvEYwI/AAAAAAAAAoU/L6pDZnYvnWw/s720/IMG_1022.JPG"
width=720 height=540></A></P></DIV>
<P><FONT face="Times New Roman">1. Here is one of the pair of 2 meter Halo
antennas I built this week. I needed a horizontally polarized antenna for
a</FONT><A style='href: "http://www.qsl.net/kp4md/144_mhz_wspr.htm"'><FONT
face="Times New Roman">144 MHz WSPR propagation study</FONT></A><FONT
face="Times New Roman"><SPAN class=Apple-converted-space> </SPAN>and
planned to stack these to increase omnidirectional gain. I will use it
with my</FONT><A style='href: "http://www.qsl.net/kp4md/xv144.htm"'><FONT
face="Times New Roman">Elecraft XV144 transverter</FONT></A><FONT
face="Times New Roman"><SPAN class=Apple-converted-space> </SPAN>with
20 watts peak output power and lower loss RG-8/U coaxial cable feed line.
The materials for this one antenna cost about $6. Commercial versions cost
about $50 or more.</FONT></P></TH>
<TH style="VERTICAL-ALIGN: top" width="33%" align=left>
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/CLwwvSrtnzbVOLIkxaL-vtMTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="144 MHz Halo Antenna" style="HEIGHT: 300px; WIDTH: 400px" border=2
alt="144 MHz Halo Antenna"
src="https://lh3.googleusercontent.com/-rmqC5YWIdcs/T7STJCnii5I/AAAAAAAAAnc/e334B_zkkqs/s720/IMG_1015.JPG"
width=720 height=540></A></P></DIV>
<P><FONT face="Times New Roman">2. The boom is an 18 inch piece of the
1/2" Carlon "Plus 40" Rigid PVC Conduit that my husband had in the garden
shed. I bought the 10 foot roll of 1/4 inch copper tubing for $9 at Home
Depot. It comes coiled in nearly the required diameter. I cut a 41 inch
length of it and easily formed it into the 13-1/8 inch diameter shape. The
loop is continuous except for a gap between the open ends at the right end
of the boom.</FONT></P></TH>
<TH style="VERTICAL-ALIGN: top" width="33%" align=center>
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/AzWiLpZQ31fgOoRKaAsyeNMTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="The open ends of the loop here are separated by 1.5 inches. The resonant frequency of the antenna will vary with the distance between these open ends. The open ends of the boom will later be sealed for weatherproofing."
style="HEIGHT: 300px; WIDTH: 400px" border=2
alt="The open ends of the loop here are separated by 1.5 inches. The resonant frequency of the antenna will vary with the distance between these open ends. The open ends of the boom will later be sealed for weatherproofing."
src="https://lh4.googleusercontent.com/-UAhUMgvIR70/T8EbCl3IJQI/AAAAAAAAA1E/epfzMRsZRT4/s720/IMG_1082.JPG"
width=720 height=540></A></P></DIV>
<P align=left><FONT face="Times New Roman">3. The open ends of the loop
here are separated by 1.5 inches. The resonant frequency of the antenna
will vary with the distance between these open ends. The open ends of the
boom will later be sealed for weatherproofing.</FONT></P></TH></TR>
<TR>
<TH style="VERTICAL-ALIGN: top" width="33%" text-align="left;">
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/i8R9YI8OWXn7FCq6oCk2dNMTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="Detail of the 6-32 x 1" style="HEIGHT: 300px; WIDTH: 400px"
border=2 alt="Detail of the 6-32 x 1"
src="https://lh5.googleusercontent.com/-MCSYopApOZ8/T7STN98tokI/AAAAAAAAAoc/vvxdNj6P-dY/s720/IMG_1023.JPG"
width=720 height=540 to SO-239 screw ready be soldered
center pin SO-239 connector.? of the to soldered></A></P>
<DIV align=left><FONT face="Times New Roman">4. Detail of the 6-32 x 1"
screw ready to be soldered to the center pin of the SO-239
connector.</FONT></DIV></DIV></TH>
<TH style="VERTICAL-ALIGN: top" width="33%" align=left>
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/Tslo95-dctYnj6J87_XCANMTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="144 MHz Halo Antenna" style="HEIGHT: 300px; WIDTH: 400px" border=2
alt="144 MHz Halo Antenna"
src="https://lh3.googleusercontent.com/-b_9Z_htKOa8/T7hB7BzGp3I/AAAAAAAAArQ/TA-HTPMdE2E/s720/IMG_1024.JPG"
width=720 height=540></A></P></DIV>
<P><FONT face="Times New Roman">5. The 6-32 x 1" screw is soldered to the
center pin of the SO-239 connector.</FONT></P></TH>
<TH style="VERTICAL-ALIGN: top" width="33%" align=center>
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/v0VHMf23Q5HBsbpl-mbWCdMTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="The PVC Boom is drilled for the SO-239 antenna connector. The center pin is 1-7/8"
style="HEIGHT: 300px; WIDTH: 400px" border=2
alt="The PVC Boom is drilled for the SO-239 antenna connector. The center pin is 1-7/8"
src="https://lh4.googleusercontent.com/-HKt8mO1Fers/T7hB7QvCcOI/AAAAAAAAArU/4bekRX3FTdc/s720/IMG_1026.JPG"
width=720 height=540 of the away center point tubing.? copper
from></A></P></DIV>
<P align=left><FONT face="Times New Roman">6. The PVC Boom is drilled for
the SO-239 antenna connector. The center pin is 1-7/8" away from the
center point of the copper tubing.</FONT></P></TH></TR>
<TR>
<TH style="VERTICAL-ALIGN: top" width="33%" text-align="left;">
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/0ws73KWBqbQIG6QE9-g0-NMTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="Several #6 washers were placed under a #6 nut to securely maintain its position and to prevent traction on the solder joint when the mica trimmer capacitor is secured onto the screw."
style="HEIGHT: 300px; WIDTH: 400px" border=2
alt="Several #6 washers were placed under a #6 nut to securely maintain its position and to prevent traction on the solder joint when the mica trimmer capacitor is secured onto the screw."
src="https://lh3.googleusercontent.com/-32dgryzkWMA/T7hB9pDIDgI/AAAAAAAAAr0/3BY-FSLeQlw/s720/IMG_1029.JPG"
width=720 height=540></A></P></DIV>
<P><FONT face="Times New Roman">7. Several #6 washers were placed under a
#6 nut to securely maintain its position and to prevent traction on the
solder joint when the mica trimmer capacitor is secured onto the
screw.</FONT></P></TH>
<TH style="VERTICAL-ALIGN: top" width="33%" align=left>
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/g_8OU8LpLMDCYewTt_2gw9MTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="The SO-239 antenna connector is secured to the PVC boom with two 6-32 x 1½"
style="HEIGHT: 300px; WIDTH: 400px" border=2
alt="The SO-239 antenna connector is secured to the PVC boom with two 6-32 x 1½"
src="https://lh3.googleusercontent.com/-uBJ4a9lEx30/T7hB9gBYJXI/AAAAAAAAArw/wYNObjDQLd8/s720/IMG_1028.JPG"
width=720 height=540 screws.?></A></P></DIV>
<P><FONT face="Times New Roman">8. The SO-239 antenna connector is secured
to the PVC boom with two 6-32 x 1½" screws.</FONT></P></TH>
<TH style="VERTICAL-ALIGN: top" width="33%" align=center>
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/sOKQCua3mYeIdvA_h1Ey8dMTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="The shell of the SO-239 connector is connected to the copper tubing with 12 AWG bare copper wire which is soldered to the tubing."
style="HEIGHT: 300px; WIDTH: 400px" border=2
alt="The shell of the SO-239 connector is connected to the copper tubing with 12 AWG bare copper wire which is soldered to the tubing."
src="https://lh4.googleusercontent.com/-zzRysydHBkw/T7hB-NEDjII/AAAAAAAAAsA/G1MgIri_tzg/s720/IMG_1030.JPG"
width=720 height=540></A></P></DIV>
<P align=left><FONT face="Times New Roman">9. The shell of the SO-239
connector is connected to the copper tubing with 12 AWG bare copper wire
which is soldered to the tubing.</FONT></P></TH></TR>
<TR>
<TH style="VERTICAL-ALIGN: top" width="33%" text-align="left;">
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/A1COAbM9WRoipEEoX3bnANMTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="The side of the boom behind the SO-239 antenna connector with the mica compression trimmer capacitor with a 6-32 nut onto the 6-32 screw that is soldered to the center pin of the SO-239 connector."
style="HEIGHT: 300px; WIDTH: 400px" border=2
alt="The side of the boom behind the SO-239 antenna connector with the mica compression trimmer capacitor with a 6-32 nut onto the 6-32 screw that is soldered to the center pin of the SO-239 connector."
src="https://lh3.googleusercontent.com/-z9vMCY4SyTU/T7hB--tXgsI/AAAAAAAAAsI/MMAqW4Smusg/s720/IMG_1031.JPG"
width=720 height=540></A></P></DIV>
<P><FONT face="Times New Roman">10. The side of the boom behind the SO-239
antenna connector with the mica compression trimmer capacitor secured with
a 6-32 nut onto the 6-32 screw that is soldered to the center pin of the
SO-239 connector.</FONT></P></TH>
<TH style="VERTICAL-ALIGN: top" width="33%" text-align="left;">
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/f9BkbamSmYS-5HlAm1REANMTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="Close-up view of the mica compression trimmer capacitor connected between the gamma match rod and the screw on the center pin of the SO-239 antenna connector."
style="HEIGHT: 300px; WIDTH: 400px" border=2
alt="Close-up view of the mica compression trimmer capacitor connected between the gamma match rod and the screw on the center pin of the SO-239 antenna connector."
src="https://lh5.googleusercontent.com/-oUcH7PzIBf4/T7STJevnNeI/AAAAAAAAAnk/RUopCf7rN5s/s720/IMG_1017.JPG"
width=720 height=540></A></P></DIV>
<P><FONT face="Times New Roman">11. Close-up view of the mica compression
trimmer capacitor connected between the gamma match rod and the screw on
the center pin of the SO-239 antenna connector.</FONT></P></TH>
<TH style="VERTICAL-ALIGN: top" width="33%" align=left>
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/TgIXnhh2WsBfIXM0tArNq9MTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="I investigated several feed methods and selected a gamma match with a 30-180 pF mica compression trimmer capacitor (Arco 463 type) soldered to a 6 inch length of the ¼"
style="HEIGHT: 300px; WIDTH: 400px" border=2
alt="I investigated several feed methods and selected a gamma match with a 30-180 pF mica compression trimmer capacitor (Arco 463 type) soldered to a 6 inch length of the ¼"
src="https://lh3.googleusercontent.com/-ay7gCiA9jck/T7STJQdBb7I/AAAAAAAAAno/CTilGJn8SNA/s720/IMG_1016.JPG"
width=720 height=540 the tubing. maximum the 50 The
back-to-back temporary tubing. At maximum capacitance, it barely
brought 50 zero reactance. The back-to-back alligator clips are
temporary bar.? a ohms impedance shorting and></A></P></DIV>
<P><FONT face="Times New Roman">12. I investigated several feed methods
and selected a gamma match with a 30-180 pF mica compression trimmer
capacitor (Arco 463 type) soldered to a 6 inch length of the ¼" tubing. At
maximum capacitance, it barely brought the impedance 50 ohms and zero
reactance. The back-to-back alligator clips are a temporary shorting
bar.</FONT></P></TH></TR>
<TR>
<TH style="VERTICAL-ALIGN: top" width="33%" align=center>
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/JSpiUAQr6MCwjWKkdpNaltMTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="The original ¼"
style="HEIGHT: 300px; WIDTH: 400px" border=2
alt="The original ¼"
src="https://lh5.googleusercontent.com/-kUkBF3GFrjU/T7hB7ewX4CI/AAAAAAAAArY/asQvHUYgRlU/s720/IMG_1025.JPG"
width=720 height=540 of="" the="" to="" soldered="" copper="" from="" a=""
ohms="" impedance="" shorting="" and="" tubing="" gamma="" match="" arm=""
was="" replaced="" with="" length="" awg="" bare="" wire="" spaced=""
radiator="" element.="" this="" decreased="" capacitance="" required=""
pf="" achieve="" non-reactive="" match.="" tuning="" antenna=""
requires="" three="" gap="" bar="" location="" these="" all=""
interact.="" capacitor="" at="" mid="" i="" first="" adjusted="" for=""
lowest="" swr="" then="" moved="" position="" swr.="" repeated=""
procedure="" until="" finding="" where="" achieved="" mhz=""
in=""></A></P></DIV>
<P align=left><FONT face="Times New Roman">13. The original ¼" tubing
gamma match arm was replaced with a 7" length of 10 AWG bare copper wire
spaced 1-7/8" from the radiator element. This decreased the capacitance
required to 80 pF to achieve the non-reactive 50 ohms impedance match.
Tuning the antenna requires three adjustments: the gap space, the shorting
bar location and the capacitor, and these all interact. With the capacitor
at mid range, I first adjusted the gap for lowest SWR at 145 MHz, then
adjusted the capacitor and moved the shorting bar position for lowest SWR.
I repeated this procedure until finding the "sweet spot" where 1:1 SWR was
achieved at 145 MHz and then soldered the shorting bar in
place.</FONT></P></TH>
<TH style="VERTICAL-ALIGN: top" width="33%" align=left>
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/7nbkyLOEC_8qcKZsaGrqEdMTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="20 May 2012 - The 144 MHz halo antenna was mounted at 80 inches (1 λ) above the roof and fed with Belden 8214 foam type RG-8/U coaxial cable. At first, the antenna resonance was unstable and sensitive to the routing of the feed line until 5 turns of it were wound to form a 8 inch diameter choke balun. The standing wave ratio was then measured as 1:1 at 145.0 MHz."
style="HEIGHT: 300px; WIDTH: 400px" border=2
alt="20 May 2012 - The 144 MHz halo antenna was mounted at 80 inches (1 λ) above the roof and fed with Belden 8214 foam type RG-8/U coaxial cable. At first, the antenna resonance was unstable and sensitive to the routing of the feed line until 5 turns of it were wound to form a 8 inch diameter choke balun. The standing wave ratio was then measured as 1:1 at 145.0 MHz."
src="https://lh6.googleusercontent.com/-Bv1hJq-VPaA/T7mk0X7DghI/AAAAAAAAAtM/3GKHSyxxIHE/s720/IMG_1066.JPG"
width=720 height=540></A></P></DIV>
<P><FONT face="Times New Roman">14. 20 May 2012 - The 144 MHz halo antenna
was mounted at 80 inches (1 λ) above the metal roof and fed with Belden
8214 foam type RG-8/U coaxial cable. At first, the antenna resonance was
unstable and sensitive to the routing of the feed line until 5 turns of it
were wound to form a 8 inch diameter choke balun. The standing wave ratio
was then measured as 1:1 at 145.0 MHz.</FONT></P></TH>
<TH style="VERTICAL-ALIGN: top" width="33%" align=center>
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/mdE8372IBNEWwhGutca5s9MTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="A closer view of the 144 MHz halo antenna. The entire antenna was weatherproofed with clear acrylic spray paint. The open ends of the boom and the PL-259 connector were sealed with a self sealing silicone tape called Rescue Tape. Both open ends of the copper loop were outside the boom with approximately 1.5"
style="HEIGHT: 300px; WIDTH: 400px" border=2
alt="A closer view of the 144 MHz halo antenna. The entire antenna was weatherproofed with clear acrylic spray paint. The open ends of the boom and the PL-259 connector were sealed with a self sealing silicone tape called Rescue Tape. Both open ends of the copper loop were outside the boom with approximately 1.5"
src="https://lh3.googleusercontent.com/-80anYKByDg4/T7mk03ki1AI/AAAAAAAAAtU/yZgtGZWRpAo/s720/IMG_1067.JPG"
width=720 height=540 gap at for distance for resonance 145
mhz.?></A></P></DIV>
<P align=left><FONT face="Times New Roman">15. A closer view of the 144
MHz halo antenna. The entire antenna was weatherproofed with clear acrylic
spray paint. The open ends of the boom and the PL-259 connector were
sealed with a self sealing silicone tape called Rescue Tape. Both open
ends of the copper loop were outside the boom with approximately 1.5" gap
distance for resonance at 145 MHz.</FONT></P></TH></TR>
<TR>
<TH style="VERTICAL-ALIGN: top" width="33%" text-align="left;">
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/EzR--xDMiy9ADunN_c09b9MTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="Close up view of the PL-259 antenna connector sealed with Rescue Tape. The open spaces between the boom and the SO-239 connector were sealed with GOOP Plumbing contact adhesive and sealant, selected as it does not release corrosive acetic acid during curing."
style="HEIGHT: 300px; WIDTH: 400px" border=2
alt="Close up view of the PL-259 antenna connector sealed with Rescue Tape. The open spaces between the boom and the SO-239 connector were sealed with GOOP Plumbing contact adhesive and sealant, selected as it does not release corrosive acetic acid during curing."
src="https://lh5.googleusercontent.com/-L7uPXSfiVj4/T7mk2HZPzII/AAAAAAAAAtk/esCOsyXsHJ0/s720/IMG_1069.JPG"
width=720 height=540></A></P></DIV>
<P><FONT face="Times New Roman">16. Close up view of the PL-259 antenna
connector sealed with Rescue Tape. The open spaces between the boom and
the SO-239 connector were sealed with GOOP Plumbing contact adhesive and
sealant, selected as it does not release corrosive acetic acid during
curing.</FONT></P></TH>
<TH style="VERTICAL-ALIGN: top" width="33%" align=left><A
style="name: analysis"></A>
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/Pi_xTtWANrbpe2QtB4dw3NMTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="144 MHz Halo antenna NEC model calculated SWR vs. Frequency."
style="HEIGHT: 300px; WIDTH: 400px" border=2
alt="144 MHz Halo antenna NEC model calculated SWR vs. Frequency."
src="https://lh5.googleusercontent.com/-1jwiCgU7scE/T7s0MZycFnI/AAAAAAAAAxI/c3kYSHdrL7I/s509/2m_halo_nec_swr.jpg"
width=509 height=329></A></P></DIV>
<P><FONT face="Times New Roman">17. 144 MHz Halo antenna NEC model
calculated SWR vs. Frequency.</FONT></P></TH>
<TH style="VERTICAL-ALIGN: top" width="33%" align=center>
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/TRSuYPwKmNUpI4UKj_jivNMTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="144 MHz Halo antenna measured SWR vs. Frequency. The SWR measured at the feed point was 1.3:1 or less over the 144.0 to 146.4 MHz range."
style="HEIGHT: 300px; WIDTH: 400px" border=2
alt="144 MHz Halo antenna measured SWR vs. Frequency. The SWR measured at the feed point was 1.3:1 or less over the 144.0 to 146.4 MHz range."
src="https://lh4.googleusercontent.com/-j-wC662aNRU/T7nVPgww4oI/AAAAAAAAAvQ/k0h6XWpTDCk/s524/2m_halo_swr.jpg"
width=524 height=310></A></P></DIV>
<P align=left><FONT face="Times New Roman">18. 144 MHz Halo antenna
measured SWR vs. Frequency. The SWR measured at the feed point was 1.3:1
or less over the 144.0 to 146.4 MHz range.</FONT></P></TH></TR>
<TR>
<TH style="VERTICAL-ALIGN: top" width="33%" text-align="left;">
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/CcgcHykeeNeM8wB2i4VvddMTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="144 MHz Halo Antenna 4nec2 Calculations using the high-pass L-network to simulate the gamma match."
style="HEIGHT: 494px; WIDTH: 364px" border=2
alt="144 MHz Halo Antenna 4nec2 Calculations using the high-pass L-network to simulate the gamma match."
src="https://lh5.googleusercontent.com/-21gH9uad7uM/T75UGOiGnkI/AAAAAAAAAys/3GOpF3_vEJU/s494/2m_halo_nec_calculations.jpg"
width=364 height=494></A></P></DIV>
<P><FONT face="Times New Roman">19. 144 MHz Single Halo Antenna 4nec2
Calculations. As the gamma match is not amenable to accurate NEC
modeling<SUP>1</SUP>, I used the high-pass L-network under the RLC
matching function (F10) of 4nec2 when generating the frequency sweep
curves in Figures 17 and 20.</FONT></P></TH>
<TH style="VERTICAL-ALIGN: top" width="33%" align=left>
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/zBxC_Ypi80YF8Na0PBWIetMTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="144 MHz Halo antenna NEC Model calculated Resistance and Reactance vs. Frequency."
style="HEIGHT: 300px; WIDTH: 400px" border=2
alt="144 MHz Halo antenna NEC Model calculated Resistance and Reactance vs. Frequency."
src="https://lh6.googleusercontent.com/-dVy35ZzWQ_w/T7s0MYYZtzI/AAAAAAAAAxE/hMU2u9US-c8/s509/2m_halo_nec_impedance.jpg"
width=509 height=329></A></P></DIV>
<P><FONT face="Times New Roman">20. 144 MHz Halo antenna NEC Model
calculated Resistance and Reactance vs. Frequency.</FONT></P></TH>
<TH style="VERTICAL-ALIGN: top" width="33%" align=center>
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/tqY2KJSwj-H7LO7SRMCFgdMTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="144 MHz Stacked Halo antennas Resistance and Reactance vs. Frequency measured with a miniVNA Pro vector network analyzer."
style="HEIGHT: 300px; WIDTH: 400px" border=2
alt="144 MHz Stacked Halo antennas Resistance and Reactance vs. Frequency measured with a miniVNA Pro vector network analyzer."
src="https://lh6.googleusercontent.com/-PRrtO-VllSM/UkJ1ItmZtcI/AAAAAAAAHZE/zS_Y9R5nIdw/s744/144%2520MHz%2520Stacked%2520Halos%2520Rs%2520%2526%2520Xs%2520vs%2520Frequency.gif"
width=744 height=394></A></P></DIV>
<P align=left><FONT face="Times New Roman">21. 144 MHz Stacked Halo
antennas Resistance and Reactance vs. Frequency measured with a miniVNA
Pro vector network analyzer.</FONT><BR></P></TH></TR>
<TR>
<TH style="VERTICAL-ALIGN: top" width="33%" text-align="left;">
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/xM6mBGoFZPjQcyyj7sS4lNMTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="144 MHz single Halo Antenna azimuth pattern calculated by NEC Model."
style="HEIGHT: 344px; WIDTH: 302px" border=2
alt="144 MHz single Halo Antenna azimuth pattern calculated by NEC Model."
src="https://lh3.googleusercontent.com/-PqnS4tERuIo/T7nZ4OHpEEI/AAAAAAAAAwA/qCPOvuFJRn0/s344/2m_halo_az_pattern.jpg"
width=302 height=344></A></P></DIV>
<P><FONT face="Times New Roman">22. 144 MHz single Halo Antenna azimuth
pattern calculated by NEC Model.</FONT></P></TH>
<TH style="VERTICAL-ALIGN: top" width="33%" align=left>
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/nwvkRJEaV8Uqonp86iBHkdMTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="144 MHz single Halo Antenna elevation pattern calculated by NEC Model."
style="HEIGHT: 344px; WIDTH: 302px" border=2
alt="144 MHz single Halo Antenna elevation pattern calculated by NEC Model."
src="https://lh4.googleusercontent.com/-G9IV1epZUxY/T7nZ19n3uaI/AAAAAAAAAv4/9IBjBz2_fgQ/s344/2m_halo_el_pattern.jpg"
width=302 height=344></A></P></DIV>
<P><FONT face="Times New Roman">23. 144 MHz single Halo Antenna elevation
pattern calculated by NEC Model.</FONT></P></TH>
<TH style="VERTICAL-ALIGN: top" width="33%" align=center>
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/Y5mjQHYvDR0ovyLm_d6D6NMTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="144 MHz single Halo Antenna 3D Radiation Pattern calculated by NEC Model."
style="HEIGHT: 353px; WIDTH: 400px" border=2
alt="144 MHz single Halo Antenna 3D Radiation Pattern calculated by NEC Model."
src="https://lh3.googleusercontent.com/-X-sLWfzDvMY/T7nZ7Mx11xI/AAAAAAAAAwI/ztawk1ijhfk/s640/2m_halo_3d_pattern.jpg"
width=640 height=564></A></P></DIV>
<P align=left><FONT face="Times New Roman">24. 144 MHz single Halo antenna
3 dimensional radiation pattern calculated by NEC Model.</FONT></P></TH></TR>
<TR>
<TH style="VERTICAL-ALIGN: top" width="33%" text-align="left;">
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/tnRZeCgNkZl0EDx3z93lUtMTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="144 MHz 2 stacked Halo Antennas azimuth pattern calculated by NEC Model."
style="HEIGHT: 344px; WIDTH: 302px" border=2
alt="144 MHz 2 stacked Halo Antennas azimuth pattern calculated by NEC Model."
src="https://lh4.googleusercontent.com/-dSw-F3tREHE/T7_lHDacPwI/AAAAAAAAAzI/M1W31hn56M4/s344/2m_halo_stack_az_pattern.jpg"
width=302 height=344></A></P></DIV>
<P><FONT face="Times New Roman">25. 144 MHz 2 stacked Halo Antennas
azimuth pattern calculated by NEC Model.</FONT></P></TH>
<TH style="VERTICAL-ALIGN: top" width="33%" align=left>
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/3mLIyQpVum3zgMVBXXAq7dMTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="144 MHz 2 stacked Halo Antennas elevation pattern calculated by NEC Model."
style="HEIGHT: 344px; WIDTH: 302px" border=2
alt="144 MHz 2 stacked Halo Antennas elevation pattern calculated by NEC Model."
src="https://lh4.googleusercontent.com/-nE6MohIuKhc/T7_lHCtMwrI/AAAAAAAAAzM/d6-0g1eVjJo/s344/2m_halo_stack_el_pattern.jpg"
width=302 height=344></A></P></DIV>
<P><FONT face="Times New Roman">26. 144 MHz 2 stacked Halo Antennas
elevation pattern calculated by NEC Model.</FONT></P></TH>
<TH style="VERTICAL-ALIGN: top" width="33%" align=center>
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/NpU8dQ8TZokDmL8yvkZ0vtMTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="144 MHz 2 stacked Halo Antennas 3D Radiation Pattern calculated by NEC Model."
style="HEIGHT: 353px; WIDTH: 400px" border=2
alt="144 MHz 2 stacked Halo Antennas 3D Radiation Pattern calculated by NEC Model."
src="https://lh5.googleusercontent.com/-yA7MP54GhCY/T7_lHdh0nRI/AAAAAAAAAzQ/khDj-TZ0yZw/s702/2m_halo_stack_3d_pattern.jpg"
width=702 height=619></A></P></DIV>
<P align=left><FONT face="Times New Roman">27. 144 MHz 2 stacked Halo
Antennas 3 dimensional radiation pattern calculated by NEC
Model.</FONT></P></TH></TR>
<TR>
<TH style="VERTICAL-ALIGN: top" width="33%" text-align="left;">
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/PshqEmRqMcSoLBT3YV7GuNMTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="144MHz 2 stacked Halo Antennas 4nec2 Calculations."
style="HEIGHT: 494px; WIDTH: 364px" border=2
alt="144MHz 2 stacked Halo Antennas 4nec2 Calculations."
src="https://lh4.googleusercontent.com/-pMj9QY4DlI4/T7_lHxw5X3I/AAAAAAAAAzg/8fd1PfhjClo/s494/2m_halo_stack_nec_calculations.jpg"
width=364 height=494></A></P></DIV>
<P><FONT face="Times New Roman">28. 144 MHz 2 stacked Halo Antennas 4nec2
Calculations.</FONT></P></TH>
<TH style="VERTICAL-ALIGN: top" width="33%" align=left>
<DIV align=center>
<P align=left><SMALL><FONT face="Times New Roman">CM 144 MHz Halo Antenna
NEC model by Carol F. Milazzo, KP4MD<BR
style="FONT-WEIGHT: normal"><SPAN>CM Horizontal orientation (using GH
command)</SPAN><BR style="FONT-WEIGHT: normal"><SPAN>CM Frequency =
145.000 MHz</SPAN><BR style="FONT-WEIGHT: normal"><SPAN>CM Impedance 50
ohms</SPAN><BR style="FONT-WEIGHT: normal"><SPAN>CM 26-side polygon (40
inch loop with 1.5 inch gap)</SPAN><BR
style="FONT-WEIGHT: normal"><SPAN>CM Simulated good ground</SPAN><BR
style="FONT-WEIGHT: normal"><SPAN>CM Use the high-pass L-network to
simulate the gamma match</SPAN><BR
style="FONT-WEIGHT: normal"><SPAN>CE</SPAN><BR
style="FONT-WEIGHT: normal"><SPAN>SY frq=145 'frequency
MHz</SPAN><BR style="FONT-WEIGHT: normal"><SPAN>SY
cir=40.00758 'Input loop circumference inches (loop +
gap)</SPAN><BR style="FONT-WEIGHT: normal"><SPAN>SY
r=0.5*cir/3.1415926 'Calculate loop radius</SPAN><BR
style="FONT-WEIGHT: normal"><SPAN>SY dia=0.25 'Input
loop wire dia. inches</SPAN><BR style="FONT-WEIGHT: normal"><SPAN>SY
rad=0.5*dia 'Calculate loop wire radius</SPAN><BR
style="FONT-WEIGHT: normal"><SPAN>SY n=26 'Input n-side
polygon of loop + gap</SPAN><BR style="FONT-WEIGHT: normal"><SPAN>SY
h=81.74 'Input height to loop inches</SPAN><BR
style="FONT-WEIGHT: normal"><SPAN>SY g=1.5 'Input gap
size in inches</SPAN><BR style="FONT-WEIGHT: normal"><SPAN>SY
gseg=int(n*g/cir+0.5) 'Calculate gap length in
segments</SPAN><BR style="FONT-WEIGHT: normal"><SPAN>GH
1 n-gseg 1e-300
1e-300*(n-gseg)/n r
r r r rad</SPAN><BR
style="FONT-WEIGHT: normal"><SPAN>GM 0
0 0 0
gseg*180/n 0 0
h 0</SPAN><BR
style="FONT-WEIGHT: normal"><SPAN>GS 0
0 0.0254</SPAN><BR
style="FONT-WEIGHT: normal"><SPAN>GE 1</SPAN><BR
style="FONT-WEIGHT: normal"><SPAN>LD 5
0 0 0
58000000 '1/4 inch copper tubing</SPAN><BR
style="FONT-WEIGHT: normal"><SPAN>GN 2
0 0 0
4 0.01</SPAN><BR
style="FONT-WEIGHT: normal"><SPAN>EK</SPAN><BR
style="FONT-WEIGHT: normal"><SPAN>EX 0
1 (n-gseg)/2 0
1. 0 0 'Feed
point</SPAN><BR style="FONT-WEIGHT: normal"><SPAN>FR
0 0 0
0 frq 0</SPAN><BR
style="FONT-WEIGHT: normal"><SPAN>EN</SPAN></FONT></SMALL></P></DIV>
<P><FONT face="Times New Roman">29. 144 MHz Single Halo Antenna NEC
model.</FONT></P></TH>
<TH style="VERTICAL-ALIGN: top" width="33%" align=left>
<DIV align=center>
<P align=left><SMALL><FONT face="Times New Roman">CM 144 MHz 2 Stacked
Halo Antennas at 40 and 80 inches NEC model by Carol F. Milazzo,
KP4MD<BR>CM Horizontal orientation (using GH command)<BR>CM Frequency =
145.000 MHz<BR>CM Impedance 50 ohms<BR>CM 26-side polygon (40 inch loop
with 1.5 inch gap)<BR>CM Simulated good ground<BR>CE<BR>SY
frq=145 'frequency MHz<BR>SY
cir=40.21493 'Input loop circumference inches (loop +
gap)<BR>SY r=0.5*cir/3.1415926 'Calculate loop
radius<BR>SY dia=0.25 'Input loop wire dia. inches<BR>SY
rad=0.5*dia 'Calculate loop wire radius<BR>SY
n=26 'Input n-side polygon of loop + gap<BR>SY
h=81.74 'Input height to loop inches<BR>SY
g=1.5 'Input gap size in inches<BR>SY
gseg=int(n*g/cir+0.5) 'Calculate gap length in
segments<BR>GH 1
n-gseg 1e-300
1e-300*(n-gseg)/n r
r r r
rad<BR>GM 0 0
0 0 gseg*180/n
0 0 h/2
1<BR>GM 1 1
0 0 0
0 0 h/2
1<BR>GS 0 0
0.0254<BR>GE 1<BR>LD
5 0 0
0 58000000 '1/4 inch copper
tubing<BR>GN 2 0
0 0 4
0.01<BR>EK<BR>EX 0 1
(n-gseg)/2 0 0.5
0 0 'Feed
point<BR>EX 0 2
(n-gseg)/2 0 0.5
0 0 'Feed
point<BR>FR 0 0
0 0 frq
0<BR>EN</FONT></SMALL><BR></P></DIV>
<P><FONT face="Times New Roman">30. 144 MHz 2 stacked Halo Antennas NEC
model.</FONT></P></TH></TR>
<TR>
<TH style="VERTICAL-ALIGN: top" width="33%" text-align="left;"><A
style="name: stacking"></A>
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/rOXEv6kwgd7e_VVl_ttIftMTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="Two identical 0.75 λ lengths of RG-11/U 75 ohm coaxial cable were prepared for the stacking harness. After trimming to achieve zero ohms reactance over 144 to 145 MHz, each of my cables measured exactly 40.25 inches from tip to tip. This measurement may vary slightly due to variations in the velocity factors among different batches and manufacturers of cable."
style="HEIGHT: 300px; WIDTH: 400px" border=2
alt="Two identical 0.75 λ lengths of RG-11/U 75 ohm coaxial cable were prepared for the stacking harness. After trimming to achieve zero ohms reactance over 144 to 145 MHz, each of my cables measured exactly 40.25 inches from tip to tip. This measurement may vary slightly due to variations in the velocity factors among different batches and manufacturers of cable."
src="https://lh4.googleusercontent.com/-93bREItZA8c/T8EBi-gzVwI/AAAAAAAAA0Y/DAQutH2hx8A/s720/IMG_1081.JPG"
width=720 height=540></A></P></DIV>
<P><FONT face="Times New Roman">31. Two identical 0.75 λ lengths of
RG-11/U 75 ohm coaxial cable were prepared for the stacking harness. After
trimming to achieve zero ohms reactance at 145 MHz, each of my cables
measured exactly 40.25 inches from tip to tip. This measurement may vary
slightly due to variations in the velocity factors among different batches
and manufacturers of cable.</FONT></P></TH>
<TH style="VERTICAL-ALIGN: top" width="33%" align=left>
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/FUpvSSgJBe9eLyQftv5MKtMTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="The two lengths of RG-11/U cable are joined with a UHF Tee connector to form the stacking harness. When measured from either end of the assembled stacking harness, the SWR analyzer should indicate zero ohms reactance and over 300 ohms resistance at 145 MHz. When erected, the free end of each RG-11/U cable will be connected to a halo antenna and the 50 ohm feed line connected to the center of the Tee connector."
style="HEIGHT: 300px; WIDTH: 400px" border=2
alt="The two lengths of RG-11/U cable are joined with a UHF Tee connector to form the stacking harness. When measured from either end of the assembled stacking harness, the SWR analyzer should indicate zero ohms reactance and over 300 ohms resistance at 145 MHz. When erected, the free end of each RG-11/U cable will be connected to a halo antenna and the 50 ohm feed line connected to the center of the Tee connector."
src="https://lh4.googleusercontent.com/-StQ3JC_Y2Bk/T8EBisccKcI/AAAAAAAAA0Q/GkenOx6BGQk/s720/IMG_1077.JPG"
width=720 height=540></A></P></DIV>
<P><FONT face="Times New Roman">32. The two lengths of RG-11/U cable are
joined with a UHF Tee connector to form the stacking harness. When
measured from either end of the assembled stacking harness, the SWR
analyzer should indicate zero ohms reactance and over 300 ohms resistance
at 145 MHz. When erected, the free end of each RG-11/U cable will be
connected to a halo antenna and the 50 ohm feed line connected to the
center of the Tee connector.</FONT></P></TH>
<TH style="VERTICAL-ALIGN: top" width="33%" align=center>
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/0VnNEtZJ2yGsOElGlbATsdMTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="The lower halo is mounted at 40 inches height (0.5 λ) above the roof and the upper halo is mounted 40 inches above it (1 λ). The gamma match sections should be oriented on the same side of both halo antennas."
style="HEIGHT: 300px; WIDTH: 400px" border=2
alt="The lower halo is mounted at 40 inches height (0.5 λ) above the roof and the upper halo is mounted 40 inches above it (1 λ). The gamma match sections should be oriented on the same side of both halo antennas."
src="https://lh6.googleusercontent.com/-PAM3_TN5BgU/T8GwW0EpgAI/AAAAAAAAA1o/pRPpy9SV5d8/s720/IMG_1090.JPG"
width=720 height=540></A></P></DIV>
<P align=left><FONT face="Times New Roman">33. The lower halo is mounted
at 40 inches height (0.5 λ) above the roof and the upper halo is mounted
40 inches above it (1 λ). The gamma match sections should be oriented on
the same side of both halo antennas.</FONT></P></TH></TR>
<TR>
<TH style="VERTICAL-ALIGN: top" width="33%" text-align="left;">
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/RfNvN0hsQmeVjecSoL1d_9MTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="A weather shield was fashioned from a recyclable plastic container and glued to the PVC boom of the upper halo antenna. Its purpose is to protect the feed point and the gamma match capacitor from rain."
style="HEIGHT: 300px; WIDTH: 400px" border=2
alt="A weather shield was fashioned from a recyclable plastic container and glued to the PVC boom of the upper halo antenna. Its purpose is to protect the feed point and the gamma match capacitor from rain."
src="https://lh3.googleusercontent.com/-E5c0Nsl28q4/UIxqDoHQdgI/AAAAAAAACuw/CGDKmVLxTh4/s720/IMG_1685.JPG"
width=720 height=540></A></P></DIV>
<P><FONT face="Times New Roman">34. A weather shield was fashioned from a
recyclable plastic container and glued to the PVC boom of the upper halo
antenna. Its purpose is to protect the feed point and the gamma match
capacitor from rain.</FONT></P></TH>
<TH style="VERTICAL-ALIGN: top" width="33%" align=left>
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/U0urF_JEwYGggs8mByZ799MTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="A similar weather shield was placed on the lower halo antenna. The spaces in and around the mating surfaces of all the connectors were filled with petroleum jelly and the connectors wrapped with self-sealing silicone tape."
style="HEIGHT: 300px; WIDTH: 400px" border=2
alt="A similar weather shield was placed on the lower halo antenna. The spaces in and around the mating surfaces of all the connectors were filled with petroleum jelly and the connectors wrapped with self-sealing silicone tape."
src="https://lh6.googleusercontent.com/-scrssi4uvx4/UIxqDWa0mNI/AAAAAAAACuw/ur0y5HENaLQ/s720/IMG_1686.JPG"
width=720 height=540></A></P></DIV>
<P><FONT face="Times New Roman">35. A similar weather shield was placed on
the lower halo antenna. The spaces in and around the mating surfaces
of all the connectors were filled with petroleum jelly and the connectors
wrapped with self-sealing silicone tape.</FONT></P></TH>
<TH style="VERTICAL-ALIGN: top" width="33%" align=center>
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/iI3XWBYWolgLmXDSm4P4vdMTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="The blue line indicates the standing wave ratio for the stacked 2 meter halo antennas is less than 1.3:1 over the 144 through 146 MHz frequency range, measured with a miniVNA Pro vector network analyzer."
style="HEIGHT: 300px; WIDTH: 400px" border=2
alt="The blue line indicates the standing wave ratio for the stacked 2 meter halo antennas is less than 1.3:1 over the 144 through 146 MHz frequency range, measured with a miniVNA Pro vector network analyzer."
src="https://lh5.googleusercontent.com/-QirQTTlHW4s/UkJ1Itlsd6I/AAAAAAAAHZA/OzGiDMW8HeM/s744/144%2520MHz%2520Stacked%2520Halos%2520SWR%2520%2526%2520RL%2520vs%2520Frequency.gif"
width=744 height=394></A></P></DIV>
<P align=left><FONT face="Times New Roman">36. The blue line indicates the
standing wave ratio for the stacked 2 meter halo antennas is less than
1.3:1 over the 144 through 146 MHz frequency range, measured with a
miniVNA Pro vector network analyzer.</FONT><BR></P></TH></TR>
<TR>
<TD style="VERTICAL-ALIGN: top" colSpan=2>
<H2><FONT face="Times New Roman">NOTES ON HALO ANTENNA
STACKING</FONT><BR></H2>
<UL>
<LI><FONT face="Times New Roman">Figure 30. The separation
distance of stacked halo antennas can be optimized for either gain or
radiation pattern. Using my NEC model analysis, a 48 inch separation
yielded 8.7 dBi gain at 15° elevation angle and a -8 dBi minor lobe at
90° elevation. The 40.5 inch separation yielded 7.9 dBi gain at 15°
elevation and a -40 dBi sharp null at 90° elevation. I selected
the latter model to optimize the signal to noise ratio through both
maximizing the gain toward the horizon while minimizing the gain toward
noise sources from the undesired higher elevation angles.</FONT>
<LI><FONT face="Times New Roman">Figure 31. One method to
determine the velocity factor of a coaxial cable is to attach one end
of the cable to an antenna analyzer with the far end open, and to find
the lowest frequency at which the measured impedance is zero. Then
divide the cable length by the free space length of a quarter
wave. My RG-11/U coaxial cable's measured velocity factor was
0.66. I used this calculated velocity factor to cut each of my 75 ohm
stacking harness sections to slightly longer than 3/4 wavelength at 145
MHz. With one end of each section attached to the antenna analyzer, I
trimmed the far end until the analyzer read zero ohms reactance at the
145 MHz frequency with the PL-259 attached on both ends. To
account for the additional conductor length inside the Tee connector,
the analyzer should read zero ohms reactance and over 300 ohms
resistance when measuring from either end of the assembled stacking
harness. Fedler demonstrated an alternative method using an
oscilloscope and function generator.<SUP>8</SUP></FONT>
<LI><FONT face="Times New Roman">Figure 33. The proximity of each
halo antenna to the other affects the tuning of both. With each of my
halos mounted in its final location on the mast on the roof, I tuned
each individually for minimal SWR at 145 MHz. When I then connected both
of the antennas to the stacking harness, the SWR was 1.3:1 or lower from
144 MHz through 146 MHz (Figure 36) and no further adjustment was
necessary.</FONT>
<LI><FONT face="Times New Roman">Figure 33. My RG-11/U stacking
harness only allowed a single turn loop at the feed point of each halo,
so my choke balun consisted of several turns of the 50 ohm coaxial cable
at the Tee connector. The choke balun decouples the antenna from the
feed line and stabilizes the tuning of the antenna that otherwise would
be affected by any movement and the proximity of the feed line to other
structures.</FONT></LI></UL></TD>
<TH style="VERTICAL-ALIGN: top" width="33%" align=center>
<DIV align=center>
<P><A
style='href: "https://picasaweb.google.com/lh/photo/g1ApJUz2eWJQ3Q7RtmqfJNMTjNZETYmyPJy0liipFm0?feat=directlink"'><IMG
title="Radio Mobile predicted line of sight signal strength for stacked halo antennas at KP4MD station in Citrus Heights, CA. Signal strength (0.004 µV) -30 dB to -20 dB SNR in orange area, greater than -20 dB SNR in yellow area. Transmitter power 50 watts, antenna height 6 meters."
style="HEIGHT: 361px; WIDTH: 400px" border=2
alt="Radio Mobile predicted line of sight signal strength for stacked halo antennas at KP4MD station in Citrus Heights, CA. Signal strength (0.004 µV) -30 dB to -20 dB SNR in orange area, greater than -20 dB SNR in yellow area. Transmitter power 50 watts, antenna height 6 meters."
src="https://lh4.googleusercontent.com/-hGYDmV-ApRA/UMwc9A7LPGI/AAAAAAAADGE/RTqY9UtDP9E/s640/wspr_kp4md_2m.jpg"
width=400 height=361></A></P></DIV>
<P align=left><FONT face="Times New Roman">37.<SPAN
class=Apple-converted-space> </SPAN></FONT><A
style='href: "http://www.ve2dbe.com/rmonline.html"' target=_blank><FONT
face="Times New Roman">Radio Mobile Online</FONT></A><FONT
face="Times New Roman"><SPAN
class=Apple-converted-space> </SPAN>predicted line of sight signal
strength for stacked halo antennas at KP4MD station in Citrus Heights, CA.
Limit of WSPR reception at signal strength (0.004 µV) -30 dB to -20 dB SNR
in orange area, greater than -20 dB SNR in yellow area. Transmitter power
50 watts, antenna height 6 meters.</FONT></P></TH></TR>
<TR>
<TD style="VERTICAL-ALIGN: top" colSpan=2><A style="name: comparison"></A>
<H2><FONT face="Times New Roman">COMPARISON OF J-POLE VS. SINGLE AND
STACKED HALO ANTENNAS</FONT></H2>
<DIV align=center><SMALL></SMALL>
<UL style="TEXT-ALIGN: left"><SMALL></SMALL>
<LI><FONT face="Times New Roman">Figures 19 and 22 through 24 show the
expected performance with a single halo antenna at 80 inches (1 λ) above
the metal roof (effective ground).</FONT><SMALL></SMALL>
<LI><FONT face="Times New Roman">Figures 25 through 28 and 39 through 41
show the expected performance with two stacked identical halo antennas,
one at 40 inches (½ λ) and the other at 80 inches (1 λ) above the metal
roof (effective ground).</FONT><SMALL></SMALL>
<LI><FONT face="Times New Roman">Figures 42 through 44 show the
predicted radiation patterns of the J-pole
antenna.</FONT><BR><SMALL></SMALL>
<LI><FONT face="Times New Roman">The video clips at Figure 38
demonstrate the effect on received signal strength when antenna
polarization is matched or mismatched.</FONT><BR><SMALL></SMALL>
<LI><FONT face="Times New Roman">The predicted increase in RDF
(receiving directivity factor), the increased gain at 15º elevation and
the suppression of the radiation lobes at 45º with the stacked halo
antennas did improve the overall performance over the single halo
antenna.</FONT><BR><SMALL></SMALL></LI></UL><SMALL></SMALL></DIV>
<HR width="100%">
<UL><SMALL></SMALL><SMALL>
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<li><big><font face="Times New Roman">test signal source - horizontally polarized<span class=apple-converted-space> </span></font><a style='href: "http://users.innercite.com/kj6ko/beacon.htm"' target=_blank><font face="Times New Roman">beacon station kj6ko/b</font></a><font face="Times New Roman"><span class=apple-converted-space> </span>on bald mountain, ca</font><br></big></li>
<li><big><font face="Times New Roman">compared a vertically polarized j-pole antenna vs. the horizontally polarized single and dual stacked halo antennas</font><br></big></li>
<li><big><font face="Times New Roman">arrow osj 146/440 j-pole antenna at 20 feet - signal to noise ratio (snr) = 23 db</font></big></li>
<li><font face="Times New Roman"><big>single halo antenna at 18 feet<span class=apple-converted-space> </span></big><big>with major lobe oriented 90º away from kj6ko/b - snr = 38 db</big></font></li>
<li><big><font face="Times New Roman">two stacked halo antennas at 18 feet with major lobe oriented 90º away from kj6ko/b - snr = 40 db</font></big></li>
<li><big><font face="Times New Roman">two stacked halo antennas at 18 feet with major lobe oriented toward kj6ko/b - snr = 44 db</font></big></li></style="TEXT-ALIGN:></SMALL></UL></TD>
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<p align=left><font face="Times New Roman">38. video clips comparing noise floor and received signals from kj6ko/b on 144.283 mhz on bald mountain, ca.</font><br></p></th></tr>
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<p><a style='href: "https://picasaweb.google.com/lh/photo/rDAl-34qvrMv1Iia5V8eEdMTjNZETYmyPJy0liipFm0?feat=directlink"'><img title="144 MHz 2 stackedHalo Antennas 3D Radiation Pattern calculated by NECModel." style="HEIGHT: 353px; WIDTH: 400px" border=2 alt="144MHz 2 stacked Halo Antennas 3D Radiation Patterncalculated by NEC Model." src="https://lh6.googleusercontent.com/-mkLt0COtKQ0/UCf8xqEw3-I/AAAAAAAACHI/VwsByroC4RM/s640/2m_halo_stack_3d_patterna.jpg" width=640 height=564></a></p></div>
<p align=left><font face="Times New Roman">39. 144 mhz 2 stacked halo antennas 3 dimensional radiation pattern calculated by nec model. composite of horizontal and vertical polarization components.</font><br></p></th>
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<p><a style='href: "https://picasaweb.google.com/lh/photo/OETygW8z8J9-4wgq-OB4B9MTjNZETYmyPJy0liipFm0?feat=directlink"'><img title="144 MHz 2 stacked Halo Antennas 3 dimensional radiation pattern calculated by NEC Model. Horizontal polarization component only." style="HEIGHT: 353px; WIDTH: 400px" border=2 alt="144 MHz 2 stacked Halo Antennas 3 dimensional radiation pattern calculated by NEC Model. Horizontal polarization component only." src="https://lh5.googleusercontent.com/-fJLFXJVinX0/UCf7OvW77RI/AAAAAAAACGg/HX6F8SgZGBY/s640/2m_halo_stack_3d_horizontal_pattern.jpg" width=702 height=619></a></p></div>
<p align=left><font face="Times New Roman">40. 144 mhz 2 stacked halo antennas 3 dimensional radiation pattern calculated by nec model. horizontal polarization component only.</font><br></p></th>
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<p><a style='href: "https://picasaweb.google.com/lh/photo/Tvf9oCpjw3lhowLm-wrUH9MTjNZETYmyPJy0liipFm0?feat=directlink"'><img title="144 MHz 2 stacked Halo Antennas 3 dimensional radiation pattern calculated by NEC Model. Vertical polarization component only" style="HEIGHT: 353px; WIDTH: 400px" border=2 alt="144 MHz 2 stacked Halo Antennas 3 dimensional radiation pattern calculated by NEC Model. Vertical polarization component only" src="https://lh4.googleusercontent.com/-tvF3z9DO_2I/UCf7POZE5II/AAAAAAAACGg/9CQZzIIMgCI/s640/2m_halo_stack_3d_vertical_pattern.jpg" width=640 height=564></a></p></div>
<p align=left><font face="Times New Roman">41. 144 mhz 2 stacked halo antennas 3 dimensional radiation pattern calculated by nec model. vertical polarization component only.</font></p></th></tr>
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<p><a style='href: "https://picasaweb.google.com/lh/photo/QTnycBB5gLL-bNL5vys9N9MTjNZETYmyPJy0liipFm0?feat=directlink"'><img title="144 MHz Arrow OSJ 146/440 J-Pole Antenna 3 dimensional radiation pattern calculated by NEC Model" style="HEIGHT: 353px; WIDTH: 400px" border=2 alt="144 MHz Arrow OSJ 146/440 J-Pole Antenna 3 dimensional radiation pattern calculated by NEC Model" src="https://lh3.googleusercontent.com/-9UDbTCiPlXM/UCf4YjIh4HI/AAAAAAAACFs/v7EIlSpkqc8/s640/2m_jpole_3d_pattern.jpg" width=640 height=564></a></p></div>
<p align=left><font face="Times New Roman">42. 144 mhz<span class=apple-converted-space> </span></font><a style='href: "http://www.qsl.net/kp4md/modeling.htm#osj146440"'><font face="Times New Roman">arrow osj 146/440 j-pole antenna</font></a><font face="Times New Roman"><span class=apple-converted-space> </span>3 dimensional radiation pattern calculated by nec model. composite of horizontal and vertical polarization components.</font></p></th>
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<p><a style='href: "https://picasaweb.google.com/lh/photo/bJBae8UvF98NNcxJT85FfNMTjNZETYmyPJy0liipFm0?feat=directlink"'><img title="144 MHz Arrow OSJ 146/440 J-Pole Antenna 3 dimensional radiation pattern calculated by NEC Model. Horizontal polarization component only" style="HEIGHT: 353px; WIDTH: 400px" border=2 alt="144 MHz Arrow OSJ 146/440 J-Pole Antenna 3 dimensional radiation pattern calculated by NEC Model. Horizontal polarization component only" src="https://lh4.googleusercontent.com/-TIxYCTHTznI/UCf7PZurlUI/AAAAAAAACGg/8Ve9ZzaNwxA/s640/2m_jpole_3d_horizontal_pattern.jpg" width=640 height=564></a></p></div>
<p align=left><font face="Times New Roman">43. 144 mhz<span class=apple-converted-space> </span></font><a style='href: "http://www.qsl.net/kp4md/modeling.htm#osj146440"'><font face="Times New Roman">arrow osj 146/440 j-pole antenna</font></a><font face="Times New Roman"><span class=apple-converted-space> </span>3 dimensional radiation pattern calculated by nec model. horizontal polarization component only.</font></p></th>
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<p><a style='href: "https://picasaweb.google.com/lh/photo/BOZ3wO_8O_afuwcuX0ukb9MTjNZETYmyPJy0liipFm0?feat=directlink"'><img title="144 MHz Arrow OSJ 146/440 J-Pole Antenna 3 dimensional radiation pattern calculated by NEC Model. Vertical polarization component only" style="HEIGHT: 353px; WIDTH: 400px" border=2 alt="144 MHz Arrow OSJ 146/440 J-Pole Antenna 3 dimensional radiation pattern calculated by NEC Model. Vertical polarization component only" src="https://lh3.googleusercontent.com/-Tyqdbh90CdY/UCf7Pqp12vI/AAAAAAAACGg/BrjtvAA1Kn8/s640/2m_jpole_3d_vertical_pattern.jpg" width=640 height=564></a></p></div>
<p align=left><font face="Times New Roman">44. 144 mhz<span class=apple-converted-space> </span></font><a style='href: "http://www.qsl.net/kp4md/modeling.htm#osj146440"'><font face="Times New Roman">arrow osj 146/440 j-pole antenna</font></a><font face="Times New Roman"><span class=apple-converted-space> </span>3 dimensional radiation pattern calculated by nec model. vertical polarization component only.</font></p></th></tr>
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<h3><a style="name: references"></a><font face="Times New Roman">references</font></h3>
<ol>
<li><a style='href: "http://w4rnl.net46.net/gamma.html"'><font face="Times New Roman">some preliminary notes on the gamma match</font></a><font face="Times New Roman">, cebik, lb, w4rnl</font></li>
<li><a style='href: "http://w4rnl.net46.net/ao16.html"'><font face="Times New Roman">horizontally polarized omni-directional antennas: some compact choices</font></a><font face="Times New Roman">, cebik, lb, w4rnl</font></li>
<li><a style='href: "http://fedler.com/radio/stacked_loops.htm"'><font face="Times New Roman">stacking 2 meter halo antennas</font></a><font face="Times New Roman">, fedler m., n6tww</font></li>
<li><a style='href: "http://www.kr1st.com/2mhalo.htm"'><font face="Times New Roman">a tree friendly 2 meter halo antenna</font></a><font face="Times New Roman">, krist, a., kr1st</font></li>
<li><a style='href: "http://home.comcast.net/~buck0/2m_halo.htm"'><font face="Times New Roman">mobile 2-meter 144 mhz ssb/cw "Halo"</font></a><font face="Times New Roman">, merrill s., kb1dig</font></li>
<li><a style='href: "http://www.qsl.net/kp4md/50_mhz_halo.htm"'><font face="Times New Roman">50 mhz halo antenna</font></a><font face="Times New Roman">, milazzo cf, kp4md</font><br></li>
<li><a style='href: "http://www.qsl.net/d/dk7zb/Stacking/coax.htm"'><font face="Times New Roman">stacking with coax cables as transformation lines</font></a><font face="Times New Roman">, steyer m., dk7zb</font></li>
<li><a style='href: "http://ea4eoz.ure.es/halo144.html"'><font face="Times New Roman">a 144 mhz halo</font></a><font face="Times New Roman">, vallejo, miguel a., ea4eoz</font></li>
<li><a style='href: "http://www.youtube.com/watch?v=Fhhh_CTL7_8"' target=_blank><font face="Times New Roman">2 meter halo antenna part 12 -- "Phasing Harness understanding & calculations"</font></a><font face="Times New Roman">, fedler m., n6tww</font></li>
<li><a style='href: "http://www.youtube.com/watch?v=WAK3_CmPZ8w&list=ULIKCPUykbwcA"' target=_blank><font face="Times New Roman">2 meter halo antenna project video series parts 1-14</font></a><font face="Times New Roman">, fedler m, n6tww</font><br></li></ol></td>
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<h3><font face="Times New Roman">appendix: nec model files</font></h3>
<ol>
<li><a style='href: "http://www.qsl.net/kp4md/2_meter_halo.nec"'><font face="Times New Roman">144 mhz halo antenna 4nec2 model</font></a></li>
<li><a style='href: "http://www.qsl.net/kp4md/2_meter_stacked_halos.nec"'><font face="Times New Roman">144 mhz 2 stacked halo antennas </font></a><a style='href: "file:///C:/Users/Carol/WebPages/kp4md/2_meter_halo.nec"'><font face="Times New Roman"><span class=apple-converted-space> </span>4nec2</font></a><a style='href: "http://www.qsl.net/kp4md/2_meter_stacked_halos.nec"'><font face="Times New Roman"><span class=apple-converted-space> </span>model</font></a></li>
<li><a style='href: "http://www.qsl.net/kp4md/2_meter_stacked_turnstiles.nec"'><font face="Times New Roman">144 mhz 2 stacked turnstile antennas </font></a><a style='href: "file:///C:/Users/Carol/WebPages/kp4md/2_meter_halo.nec"'><font face="Times New Roman"><span class=apple-converted-space> </span>4nec2</font></a><a style='href: "http://www.qsl.net/kp4md/2_meter_stacked_turnstiles.nec"'><font face="Times New Roman"><span class=apple-converted-space> </span>model</font></a></li>
<li><a style='href: "http://www.qsl.net/kp4md/modeling.htm#osj146440"'><font face="Times New Roman">arrow osj 146/440 j-pole antenna </font></a><a style='href: "file:///C:/Users/Carol/WebPages/kp4md/2_meter_halo.nec"'><font face="Times New Roman"><span class=apple-converted-space> </span>4nec2</font></a><a style='href: "http://www.qsl.net/kp4md/modeling.htm#osj146440"'><font face="Times New Roman"><span class=apple-converted-space> </span>model</font></a><br></li></ol>
<h3><font face="Times New Roman">links</font></h3>
<ol>
<li><a style='href: "https://picasaweb.google.com/114032640816757126398/2MeterHaloAntenna"'><font face="Times New Roman">144 mhz halo antenna photo album</font></a></li>
<li><a style='href: "http://www.youtube.com/playlist?list=PL3A573BD8EF5264BC&feature=view_all"'><font face="Times New Roman">144 mhz halo antenna test videos</font></a></li>
<li><a style='href: "http://www.qsl.net/kp4md/omnihoriz.htm"'><font face="Times New Roman">144 mhz omnidirectional horizontal antennas - nec model comparisons of stacked halo, turnstile and eggbeater omnidirectional horizontally polarized antennas for 144 mhz</font></a></li>
<li><a style='href: "http://www.qsl.net/kp4md/xv144.htm"'><font face="Times New Roman">building the elecraft xv transverter kit</font></a></li>
<li><a style='href: "http://www.qsl.net/kp4md/144_mhz_wspr.htm"'><font face="Times New Roman">144 mhz wspr propagation study</font></a></li></ol></th></tr></tbody></table></embed></span>
<div style="FONT-SIZE: 12pt; FONT-FAMILY: 'Calibri'; COLOR: #000000">73's de Carlos CT1GFQ<BR>SKCC#466C <A href="http://www.skccgroup.com">www.skccgroup.com</A><BR>REP#1406 <A href="http://www.rep.pt">www.rep.pt</A></DIV>
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