Quagi - Revision history

Wb6mrq: Added superscript tags to the footnotes in the text.

2010-08-05T20:00:16Z

Added superscript tags to the footnotes in the text.

TimVK4YEH: added pictures fixed table at the end of the page

2009-11-16T16:13:05Z

added pictures fixed table at the end of the page

@@ Line 186: / Line 186: @@
 ----
-''This description is from Gary Bonnor - VK4ZGB, see: http://web.archive.org/web/20071017002252/http://www.geocities.com/garyntricia/quagi.html This page did provide some photos but these appear to have been lost to the October 2009 shutdown of GeoCities.''
+''This description is from Gary Bonnor - VK4ZGB,
 ----
@@ Line 192: / Line 192: @@
 The following are details of a 70CM Quagi I built XMAS 1999. It had a VSWR of 1.3:1 from manufacture, with no tuning.
 Measurements used were those shown for the 432 MHz Quagi in the previous table.
 Materials used were 6mm (1/4 inch) aluminium rod for the directors, 6mm copper tube for the quad elements, 6mm polycarbonate (LEXAN) sheet for the quad spreaders, pultruded fibreglass boom, machined aluminium bar for director mountings.
 The photo shows a section of the boom material. This was sourced from Pacific Composites in Melbourne, Australia. It is used as the support section in fibreglass grate flooring used in harsh environments. (Price was approximately A$4.50 / metre early 1999). Being manufactured using the pultrusion process, it has a high ratio of glass fibres to epoxy resin. There is almost no flexing over a 3 metre length in the vertical plane and a minimal amount in the horizontal plane. The photo shows an end view of this material (on its side). This antenna has a boom length of 1950 mm.
 I wanted this antenna to be portable, so the elements needed to be removeable. I did this by machining bushes for the directors from 19mm aluminium bar and glued these to the boom using epoxy resin. The following photos (hopefully) show enough detail of these bushes. The clamping screws happened to be some from the junk box, but anything with a diameter of about 3mm should do the job.
+[[Image:Quagi bush1.jpg |400px]][[Image:Quagi bush2.jpg |400px]]
 The third photo shows a bush with a director fitted. (There is a lack of definition in this one.)
 Meter 8 Element Quagi
 all measurements in mm
+{|!width = "1200pt"
+|----
+|width = "300pt" | || width = "300pt" |145.5Mhz || width = 300pt |mm/100khz step (250 steps)|| width = 300pt | 147.0 Mhz
-This page was created by Gary Bonnor - VK4ZGB.
+* This page was created by Gary Bonnor - VK4ZGB.Updated 11 May 02

Carlb at 14:51, 16 November 2009

2009-11-16T14:51:15Z

← Older revision		Revision as of 07:51, 16 November 2009
Line 2:		Line 2:
	from an article by Wayne Overbeck, K6YNB in QST April 1977;		from an article by Wayne Overbeck, K6YNB in QST April 1977;
	"Building a 440MHz Quagi" description is from Gary Bonnor - VK4ZGB		"Building a 440MHz Quagi" description is from Gary Bonnor - VK4ZGB
			----

	There have been many half-hearted attempts to combine a Yagi and a Quad. Most have produced questionable results. Well, here are the "true" facts, the real dope, the hot scoop.		There have been many half-hearted attempts to combine a Yagi and a Quad. Most have produced questionable results. Well, here are the "true" facts, the real dope, the hot scoop.

Carlb at 14:49, 16 November 2009

2009-11-16T14:49:03Z

← Older revision		Revision as of 07:49, 16 November 2009
Line 1:		Line 1:
	The VHF Quagi		The VHF Quagi
	from an article by Wayne Overbeck, K6YNB in QST April 1977		from an article by Wayne Overbeck, K6YNB in QST April 1977;
			"Building a 440MHz Quagi" description is from Gary Bonnor - VK4ZGB

	There have been many half-hearted attempts to combine a Yagi and a Quad. Most have produced questionable results. Well, here are the "true" facts, the real dope, the hot scoop.		There have been many half-hearted attempts to combine a Yagi and a Quad. Most have produced questionable results. Well, here are the "true" facts, the real dope, the hot scoop.

Carlb: /* Building a 440MHz Quagi */

2009-11-16T14:31:44Z

Building a 440MHz Quagi

← Older revision		Revision as of 07:31, 16 November 2009
Line 1:		Line 1:
	The VHF Quagi		The VHF Quagi
	from an article by Wayne Overbeck, K6YNB in QST April 1977		from an article by Wayne Overbeck, K6YNB in QST April 1977

	see: http://web.archive.org/web/20071017002252/http://www.geocities.com/garyntricia/quagi.html - this page did provide some photos but these appear to have been lost to the October 2009 shutdown of GeoCities and are no longer available.


	There have been many half-hearted attempts to combine a Yagi and a Quad. Most have produced questionable results. Well, here are the "true" facts, the real dope, the hot scoop.		There have been many half-hearted attempts to combine a Yagi and a Quad. Most have produced questionable results. Well, here are the "true" facts, the real dope, the hot scoop.
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	== Building a 440MHz Quagi==		== Building a 440MHz Quagi==

			----

			''This description is from Gary Bonnor - VK4ZGB, see: http://web.archive.org/web/20071017002252/http://www.geocities.com/garyntricia/quagi.html This page did provide some photos but these appear to have been lost to the October 2009 shutdown of GeoCities.''

			----

	The following are details of a 70CM Quagi I built XMAS 1999. It had a VSWR of 1.3:1 from manufacture, with no tuning.		The following are details of a 70CM Quagi I built XMAS 1999. It had a VSWR of 1.3:1 from manufacture, with no tuning.

Carlb at 14:27, 16 November 2009

2009-11-16T14:27:07Z

← Older revision		Revision as of 07:27, 16 November 2009
Line 2:		Line 2:
	from an article by Wayne Overbeck, K6YNB in QST April 1977		from an article by Wayne Overbeck, K6YNB in QST April 1977

	see: http://web.archive.org/web/20071017002252/http://www.geocities.com/garyntricia/quagi.html - ~~the original~~ page did provide photos but these appear to have been lost to the October 2009 shutdown of GeoCities and are no longer available.		see: http://web.archive.org/web/20071017002252/http://www.geocities.com/garyntricia/quagi.html - this page did provide some photos but these appear to have been lost to the October 2009 shutdown of GeoCities and are no longer available.

Carlb: photos from original page are not recoverable from archive.org

2009-11-16T14:26:19Z

photos from original page are not recoverable from archive.org

← Older revision		Revision as of 07:26, 16 November 2009
Line 2:		Line 2:
	from an article by Wayne Overbeck, K6YNB in QST April 1977		from an article by Wayne Overbeck, K6YNB in QST April 1977

	see: http://www.geocities.com/garyntricia/quagi.html ~~for~~ photos ~~etc~~		see: http://web.archive.org/web/20071017002252/http://www.geocities.com/garyntricia/quagi.html - the original page did provide photos but these appear to have been lost to the October 2009 shutdown of GeoCities and are no longer available.

Carlb: /* References */

2009-11-16T14:22:32Z

References

@@ Line 183: / Line 183: @@
 The following are details of a 70CM Quagi I built XMAS 1999. It had a VSWR of 1.3:1 from manufacture, with no tuning.
 Measurements used were those shown for the 432 MHz Quagi in the previous table.
 Materials used were 6mm (1/4 inch) aluminium rod for the directors, 6mm copper tube for the quad elements, 6mm polycarbonate (LEXAN) sheet for the quad spreaders, pultruded fibreglass boom, machined aluminium bar for director mountings.
 The photo shows a section of the boom material. This was sourced from Pacific Composites in Melbourne, Australia. It is used as the support section in fibreglass grate flooring used in harsh environments. (Price was approximately A$4.50 / metre early 1999). Being manufactured using the pultrusion process, it has a high ratio of glass fibres to epoxy resin. There is almost no flexing over a 3 metre length in the vertical plane and a minimal amount in the horizontal plane. The photo shows an end view of this material (on its side). This antenna has a boom length of 1950 mm.
 I wanted this antenna to be portable, so the elements needed to be removeable. I did this by machining bushes for the directors from 19mm aluminium bar and glued these to the boom using epoxy resin. The following photos (hopefully) show enough detail of these bushes. The clamping screws happened to be some from the junk box, but anything with a diameter of about 3mm should do the job.
@@ Line 289: / Line 262: @@
 .125
 --------------------------------------------------------------------------------

Carlb: /* How to Build a Quagi */

2009-11-16T14:20:54Z

How to Build a Quagi

← Older revision		Revision as of 07:20, 16 November 2009
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	{\|		{\|
	\|Element Lengths		!Element Lengths
	\| 144.5 MHz		! 144.5 MHz
	\| 147 MHz		! 147 MHz
	\| 222 MHz		! 222 MHz
	\| 432 MHz		! 432 MHz
	\| 446 MHz		! 446 MHz
	\|-		\|-
	\|Reflector (all No 12 TW wire, closed)		\|Reflector (all No 12 TW wire, closed)
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	\|colspan="6"\|Spacing		\|colspan="6"\|Spacing
	\|-		\|-
	\|R - DE		!R - DE
	\| 533 mm		\| 533 mm
	\| 521 mm		\| 521 mm
Line 101:		Line 101:
	\| 173 mm		\| 173 mm
	\|-		\|-
	\|DE - D1		!DE - D1
	\| 400 mm		\| 400 mm
	\| 391 mm		\| 391 mm
Line 108:		Line 108:
	\| 130 mm		\| 130 mm
	\|-		\|-
	\|D1 - D2		!D1 - D2
	\| 838 mm		\| 838 mm
	\| 826 mm		\| 826 mm
Line 115:		Line 115:
	\| 272 mm		\| 272 mm
	\|-		\|-
	\|D2 - D3		!D2 - D3
	\| 445 mm		\| 445 mm
	\| 435 mm		\| 435 mm
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	\| 144 mm		\| 144 mm
	\|-		\|-
	\|D3 - D4		!D3 - D4
	\| 663 mm		\| 663 mm
	\| 651 mm		\| 651 mm
Line 129:		Line 129:
	\| 215 mm		\| 215 mm
	\|-		\|-
	\|D4 - D5		!D4 - D5
	\| 663 mm		\| 663 mm
	\| 651 mm		\| 651 mm
Line 136:		Line 136:
	\| 215 mm		\| 215 mm
	\|-		\|-
	\|D5 - D6		!D5 - D6
	\| 663 mm		\| 663 mm
	\| 651 mm		\| 651 mm
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	The directors are mounted through the boom. They can be made of almost any metal rod or wire about 1/8-inch (3mm) diameter. Welding rod or aluminum clothesline wire will work well if straight. The author uses 1/8-inch (3mm) stainless-steel rod secured from an aircraft surplus store.		The directors are mounted through the boom. They can be made of almost any metal rod or wire about 1/8-inch (3mm) diameter. Welding rod or aluminum clothesline wire will work well if straight. The author uses 1/8-inch (3mm) stainless-steel rod secured from an aircraft surplus store.

	A TV type U-bolt mounts the antenna on a mast. The author uses a single machine screw, washers and nut to secure the spreaders to the boom so the antenna can be quickly "flattened" for travel. In permanent installations two screws are recommended.		A TV type U-bolt mounts the antenna on a mast. The author uses a single machine screw, washers and nut to secure the spreaders to the boom so the antenna can be quickly "flattened" for travel. In permanent installations two screws are recommended.

	== Construction Reminders ==		== Construction Reminders ==

Carlb: partial wikify

2009-11-16T13:19:03Z

partial wikify

Show changes

← Older revision		Revision as of 13:00, 5 August 2010
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	Although this is a practical construction article and not a theoretical treatise on antenna design, it would violate the spirit of amateur radio to merely present the dimensions and send people racing off to build a new type of antenna without any discussion of its theoretical basis. The Yagi-Uda antenna with its half-wavelength linear elements was very popular before amateurs began experimenting with parasitic beams made of full-wavelength wire loops. However, it became apparent in the 1940's and 1950's that the cubical quad rivalled the performance of a conventional Yagi.		Although this is a practical construction article and not a theoretical treatise on antenna design, it would violate the spirit of amateur radio to merely present the dimensions and send people racing off to build a new type of antenna without any discussion of its theoretical basis. The Yagi-Uda antenna with its half-wavelength linear elements was very popular before amateurs began experimenting with parasitic beams made of full-wavelength wire loops. However, it became apparent in the 1940's and 1950's that the cubical quad rivalled the performance of a conventional Yagi.

	An excellent history and theoretical explanation of the quad appears in Orr's "Quad Antennas"1. In fact, Orr provided some of the inspiration for the quagi when he suggested that a two-element quad had an edge over a two-element Yagi because of the loop gain (perhaps an extra 1.5 dB). However, he found that quads seemed to lose this advantage as more elements were added.		An excellent history and theoretical explanation of the quad appears in Orr's "Quad Antennas"<sup>1</sup>. In fact, Orr provided some of the inspiration for the quagi when he suggested that a two-element quad had an edge over a two-element Yagi because of the loop gain (perhaps an extra 1.5 dB). However, he found that quads seemed to lose this advantage as more elements were added.

	Others have disputed that conclusion, notably ~~Bergen2~~, ~~Lindsay3~~ and more recently ~~Harrison4~~. Lindsay's studies at the Denver University antenna range in the 1960s suggested that, for any given boom length, a quad would outperform a Yagi by about 2 dB. Harrison summarized two scholarly antenna studies and concluded that a loop-Yagi (i.e., a quad type antenna) with any number of elements probably outperforms a similar size Yagi by 1 dB or more.		Others have disputed that conclusion, notably Bergen<sup>2</sup>, Lindsay<sup>3</sup> and more recently Harrison<sup>4</sup>. Lindsay's studies at the Denver University antenna range in the 1960s suggested that, for any given boom length, a quad would outperform a Yagi by about 2 dB. Harrison summarized two scholarly antenna studies and concluded that a loop-Yagi (i.e., a quad type antenna) with any number of elements probably outperforms a similar size Yagi by 1 dB or more.

	Lindsay reported that a Yagi must have nearly twice the boom length of a quad to achieve the same gain. This author took advantage of the high gain per foot of boom of the quad to build and extremely compact and lightweight moonbounce array of 16 three-element quads for a recent 2-meter DXpedition to Alaska. A description of this small high-gain antenna appears in a moonbounce application note published by ~~Eimac5~~. The Alaskan moonbounce expedition itself was recently described in ~~QST6~~.		Lindsay reported that a Yagi must have nearly twice the boom length of a quad to achieve the same gain. This author took advantage of the high gain per foot of boom of the quad to build and extremely compact and lightweight moonbounce array of 16 three-element quads for a recent 2-meter DXpedition to Alaska. A description of this small high-gain antenna appears in a moonbounce application note published by Eimac<sup>5</sup>. The Alaskan moonbounce expedition itself was recently described in QST<sup>6</sup>.

	== The Birth of the Quagi ==		== The Birth of the Quagi ==
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	"It's the gamma match. They don't work at 432 MHz," a veteran of many vhf antenna measuring sessions said knowingly. "In fact, few amateurs can put together any kind of feed system that works well at that frequency," he added.		"It's the gamma match. They don't work at 432 MHz," a veteran of many vhf antenna measuring sessions said knowingly. "In fact, few amateurs can put together any kind of feed system that works well at that frequency," he added.

	That was a bit of an overstatement, of course. Several true Yagi designs have now been published that work well at 432 MHz - including the W1HDQ classic "Tilton Yagi,"7 and newer designs by ~~Knadle8~~ and ~~Hilliard9~~. However, all three use matching systems that require considerable skill to tune. Having read what Orr, Lindsay and others have said about quads and Yagis, the author wondered if a quad type of feed might be the answer.		That was a bit of an overstatement, of course. Several true Yagi designs have now been published that work well at 432 MHz - including the W1HDQ classic "Tilton Yagi,"<sup>7</sup> and newer designs by Knadle<sup>8</sup> and Hilliard<sup>9</sup>. However, all three use matching systems that require considerable skill to tune. Having read what Orr, Lindsay and others have said about quads and Yagis, the author wondered if a quad type of feed might be the answer.

	Before the next West Coast VHF Conference, the ill-performing, store-bought Yagi was modified in only one way. the driven element was removed and replaced with a quad type loop of no. 12 wire. There was no matching of any kind. A type-N connector was soldered in the center of the quad loop bottom side, and it was fed directly with RG-8/U. Now the SWR and gain both looked better. In the gain contest at the next VHF Conference, this antenna was measured at 9.8 dB over a dipole. Simply eliminating the gamma-matched dipole and adding a quad loop had increased the gain 3.4 dB!!!		Before the next West Coast VHF Conference, the ill-performing, store-bought Yagi was modified in only one way. the driven element was removed and replaced with a quad type loop of no. 12 wire. There was no matching of any kind. A type-N connector was soldered in the center of the quad loop bottom side, and it was fed directly with RG-8/U. Now the SWR and gain both looked better. In the gain contest at the next VHF Conference, this antenna was measured at 9.8 dB over a dipole. Simply eliminating the gamma-matched dipole and adding a quad loop had increased the gain 3.4 dB!!!
Line 44:		Line 44:
	Many, many antennas later, we had an eight-element quagi whose element lengths and spacing seemed about right, with an overall antenna size that seemed to be a good compromise between bulk and gain.		Many, many antennas later, we had an eight-element quagi whose element lengths and spacing seemed about right, with an overall antenna size that seemed to be a good compromise between bulk and gain.

	The rest is history. The quagi has won three consecutive 2-meter antenna-gain contests at West Coast VHF Conferences with measured gains up to 14.2 dB over a ~~dipole10~~. The 220-MHz version has won two out of three measurements (losing once to a much bigger log-periodic Yagi). Even on 432 MHz, where the quagi with it's four-foot 10-inch (1.47M) boom is usually one of the smallest parasitic antennas measured, it finishes high in the standings, not far behind the 10-foot (3.0M) Yagis.		The rest is history. The quagi has won three consecutive 2-meter antenna-gain contests at West Coast VHF Conferences with measured gains up to 14.2 dB over a dipole<sup>10</sup>. The 220-MHz version has won two out of three measurements (losing once to a much bigger log-periodic Yagi). Even on 432 MHz, where the quagi with it's four-foot 10-inch (1.47M) boom is usually one of the smallest parasitic antennas measured, it finishes high in the standings, not far behind the 10-foot (3.0M) Yagis.

	In presenting this information, the author does not mean to imply that the 2-meter version of the eight-element quagi will outperform some of the largest antennas, such as the popular 16-element collinear. Both are a bit big to enter in gain contests, but bother probably outperform the quagi by 1.5 to 2.0 dB on 144 MHz. On 432 MHz a 12-foot (3.66M) log-periodic Yagi described by ~~Holladay11~~ and made commercially by KLM Electronics tops the four-foot 10-inch (1.47M) quagi by about 2.8 dB. (But it costs and weighs at least 6 dB more!!!!)		In presenting this information, the author does not mean to imply that the 2-meter version of the eight-element quagi will outperform some of the largest antennas, such as the popular 16-element collinear. Both are a bit big to enter in gain contests, but bother probably outperform the quagi by 1.5 to 2.0 dB on 144 MHz. On 432 MHz a 12-foot (3.66M) log-periodic Yagi described by Holladay<sup>11</sup> and made commercially by KLM Electronics tops the four-foot 10-inch (1.47M) quagi by about 2.8 dB. (But it costs and weighs at least 6 dB more!!!!)

	== New Ideas, Anyone? ==		== New Ideas, Anyone? ==
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	The boom is wood or any other nonconductor (e.g., fiberglass). If you use a metal boom, you'll have to redesign the whole thing and come up with new element lengths. Many vhf antenna builders go wrong by failing to follow this rule: If the original uses a metal boom, use the same size and shape metal boom when you duplicate it. If it calls for a wood boom, use a nonconductor. Many amateurs dislike wood booms, but in the author's salt-air environment they outlast aluminum, ( and surely cost less). Varnish the boom if you wish.		The boom is wood or any other nonconductor (e.g., fiberglass). If you use a metal boom, you'll have to redesign the whole thing and come up with new element lengths. Many vhf antenna builders go wrong by failing to follow this rule: If the original uses a metal boom, use the same size and shape metal boom when you duplicate it. If it calls for a wood boom, use a nonconductor. Many amateurs dislike wood booms, but in the author's salt-air environment they outlast aluminum, ( and surely cost less). Varnish the boom if you wish.

	The 2-meter version is usually built on a 14 foot (4.27M) 1" (25mm) x 3" (75mm) boom, with the boom cut down to taper it to one inch (25mm) at both ends. Clear pine is best because of its light weight, but construction grade Douglas fir works well. At 220 MHz, the boom is under 10 feet (3.05M) long and most builders use 1 (25mm) x 2 (50mm) or (preferably) 3/4 (20mm) by 1-1/4 inch (30mm) pine molding stock. On 432 MHz the boom must be 1/2-inch (12mm) thick or less. Most builders use strips of 1/2-inch (12mm) exterior plywood for ~~43212~~.		The 2-meter version is usually built on a 14 foot (4.27M) 1" (25mm) x 3" (75mm) boom, with the boom cut down to taper it to one inch (25mm) at both ends. Clear pine is best because of its light weight, but construction grade Douglas fir works well. At 220 MHz, the boom is under 10 feet (3.05M) long and most builders use 1 (25mm) x 2 (50mm) or (preferably) 3/4 (20mm) by 1-1/4 inch (30mm) pine molding stock. On 432 MHz the boom must be 1/2-inch (12mm) thick or less. Most builders use strips of 1/2-inch (12mm) exterior plywood for 432<sup>12</sup>.

	{\|		{\|