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m1bwt:antennas [2012/02/10 21:15]
simon
m1bwt:antennas [2012/04/17 15:40] (current)
simon
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 ====== Station Antennas ======  ====== Station Antennas ====== 
  
-===== Home-brew Fan Dipole - 20/17/15/10m ======+===== Home-brew Fan Dipole - 20/10m ======
  
 <html><div style="margin:0 15px 0 0px;float:left"></html> <html><div style="margin:0 15px 0 0px;float:left"></html>
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 <html><center><i><small>Dipole shown when configured for 10/15/17 & 20m</small></i></center></div></html> <html><center><i><small>Dipole shown when configured for 10/15/17 & 20m</small></i></center></div></html>
  
-I design and construct my main station antennas, making frequent modifications to help improve performance and develop my technical skills.+I design and construct my main station antennas, making frequent modifications to help improve their performance and coverage.
  
-The antenna is currently configured as two independently centre-fed half wave inverted V dipoles for 10m. The elements are configured in a cross, and switchable from the shack to obtain maximum gain from their directivity.+The antenna is currently configured as two independently centre-fed half wave inverted V fan dipoles for 20 and 10m. Each pair of elements are configured in a cross, being switchable from the shack to exploit their directivity.
  
 Past configurations have included various fan dipoles covering 20, 17, 15 & 10m (shown left), and flat-tops for 10m. Past configurations have included various fan dipoles covering 20, 17, 15 & 10m (shown left), and flat-tops for 10m.
  
 I generally run the dipoles cut resonant so no ATU is required for the main bands. For other bands I rely on an ATU for a match, but due to the increased mis-matched coaxial feeder loss when operating at those frequencies, this is not the primary mode of operation. I generally run the dipoles cut resonant so no ATU is required for the main bands. For other bands I rely on an ATU for a match, but due to the increased mis-matched coaxial feeder loss when operating at those frequencies, this is not the primary mode of operation.
-<html><div style="clear:both"><br /></div></html>+
 ==== Antenna Construction ==== ==== Antenna Construction ====
  
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 <html><center><i><small>Balun feeding all antenna elements</small></i></center></div></html> <html><center><i><small>Balun feeding all antenna elements</small></i></center></div></html>
  
-As with all dipoles this antenna is very simple, cheap and easy to construct. I use stranded (pre-stretched) copper wire for the antenna elements (3mm diameter), terminated at each end with ceramic insulators. +As with all dipoles these antennas are very simple, cheap and easy to construct. I use stranded (pre-stretched) copper wire for the antenna elements (3mm diameter), terminated at each end with ceramic insulators. 
  
 When in fan configuration, elements are separated by a number of wooden dowel verticals to reduce unwanted interactions (giving a separation of ~ 180mm). When in fan configuration, elements are separated by a number of wooden dowel verticals to reduce unwanted interactions (giving a separation of ~ 180mm).
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 ==== Component List ==== ==== Component List ====
 +
 +<html><div style="margin:0 15px 0px 0px;float:left"></html>
 +{{:m1bwt:pulley.jpg?200|}}
 +<html><center><i><small>Pulleys used to hoist the centre baluns</small></i></center></div></html>
  
 **__Antenna:__** **__Antenna:__**
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 <html><div style="margin:0 15px 0 0px;float:left"></html> <html><div style="margin:0 15px 0 0px;float:left"></html>
-{{:m1bwt:aid-07_16m_vs_6m.jpg?380|}} +{{:m1bwt:aid-07_16m_vs_6m.jpg?340|}} 
-<html><center><i><small>Elevation radiation pattern for flat top at 16M (black) and 6M (blue)</small></i></center></div></html>+<html><center><i><small>Elevation  pattern for flat top at 16M (black) and 6M (blue)</small></i></center></div></html>
  
 <html><div style="margin:0 0px 0 15px;float:right"></html> <html><div style="margin:0 0px 0 15px;float:right"></html>
-{{:m1bwt:aid-08_16m_vs_6m.jpg?380|}} +{{:m1bwt:aid-08_16m_vs_6m.jpg?340|}} 
-<html><center><i><small>Elevation radiation pattern for inverted-V at 16M (black) and 6M (blue)</small></i></center></div></html>+<html><center><i><small>Elevation pattern for inverted-V at 16M (black) and 6M (blue)</small></i></center></div></html>
  
 <html><div style="clear:both"><br /></div></html> <html><div style="clear:both"><br /></div></html>
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 <html><div style="margin:0 15px 0 0px;float:left"></html> <html><div style="margin:0 15px 0 0px;float:left"></html>
-{{:m1bwt:aid-08_16m_vs_6m_90deg.jpg?380|}} +{{:m1bwt:aid-08_16m_vs_6m_90deg.jpg?340|}} 
-<html><center><i><small>Elevation radiation pattern at 90 degrees for inverted-V at 16M (black) and 6M (blue)</small></i></center></div></html>+<html><center><i><small>Elevation pattern at 90 degrees for inverted-V at 16M (black) and 6M (blue)</small></i></center></div></html>
  
 <html><div style="margin:0 0px 0 15px;float:right"></html> <html><div style="margin:0 0px 0 15px;float:right"></html>
-{{:m1bwt:aid-08.jpg?330|}} +{{:m1bwt:aid-08.jpg?290|}} 
-<html><center><i><small>Dual independently fed crossed 10M inverted-V dipoles</small></i></center></div></html>+<html><center><i><small>Dual independently fed crossed 10/20M inverted-V dipoles</small></i></center></div></html>
  
 <html><div style="clear:both"><br /></div></html> <html><div style="clear:both"><br /></div></html>
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 The picture above right shows the antenna configured as two independently fed crossed inverted-V dipoles for 10m. The picture above right shows the antenna configured as two independently fed crossed inverted-V dipoles for 10m.
  
 +<html><div style="margin:0 15px 0 0px;float:left"></html>
 +{{:m1bwt:antenna_base.jpg?340|}}
 +<html><center><i><small>View looking straight up from the base of the mast</small></i></center></div></html>
 +
 +<html><div style="margin:0 0px 0 15px;float:right"></html>
 +{{:m1bwt:compass.jpg?260|}}
 +<html><center><i><small>Compass showing directions of peak gain</small></i></center></div></html>
 +
 +<html><div style="clear:both"><br /></div></html>
 +
 +The picture to the above left shows the view from the base of the mast looking up at the dual 10/20M fan dipoles. Each element is separated from the others, forming an approximate X on each band which gives good coverage.
 +
 +The separation also helps reduce unwanted near field interactions between the elements, making it easier to tune for resonance.
  
 ==== Antenna Performance ==== ==== Antenna Performance ====
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 The main issue I've come across is problems tuning in the 10m element when configured in a fan under 20/17 and 15m elements. I suspect this was due to interactions between the elements, but was easily solved by offsetting the dipole elements. The main issue I've come across is problems tuning in the 10m element when configured in a fan under 20/17 and 15m elements. I suspect this was due to interactions between the elements, but was easily solved by offsetting the dipole elements.
 +
 +Some more pictures of these antennas are present within my [[http://www.slyware.com/gallery/index.php?/category/11|Picture Gallery]].
  
 <html><div style="margin:0 15px 0 0px;float:left"></html> <html><div style="margin:0 15px 0 0px;float:left"></html>
-{{:m1bwt:10mhorzdipole.jpg?330|}}+{{:m1bwt:10mhorzdipole.jpg?290|}}
 <html><center><i><small>Using PVC horizontal support for flat-top 10M dipole</small></i></center></div></html> <html><center><i><small>Using PVC horizontal support for flat-top 10M dipole</small></i></center></div></html>
  
 <html><div style="margin:0 0px 0 15px;float:right"></html> <html><div style="margin:0 0px 0 15px;float:right"></html>
-{{:m1bwt:dipole_antennas.jpg?380|}}+{{:m1bwt:dipole_antennas.jpg?340|}}
 <html><center><i><small>Previous iterations of the dipole antenna I've been using</small></i></center></div></html> <html><center><i><small>Previous iterations of the dipole antenna I've been using</small></i></center></div></html>
  
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 I'd definitely recommend this antenna, both as a portable and as a small inner-town antenna.  I'd definitely recommend this antenna, both as a portable and as a small inner-town antenna. 
-htmlhtmlhtml/smallhtml/small +/html
-{{:m1bwt:aid-07_16m_vs_6m.jpg?400|}} +
-htmlhtmldiv style=/smallhtml/smallhtmlhtml/smallhtmlsmallhtmlhtmlhtmlhtmlhtml/divhtmlhtml/smallhtmlbr /html/div+
 
m1bwt/antennas.1328908532.txt.gz · Last modified: 2012/02/10 21:15 by simon
 
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