PVC Yagi Construction

jjessico · 05-17-2004

I am working on building a homebrew directional-yagi with PVC. I have made up a diagram, but I am a little short on information as to dimensions, what they are, and how to calculate them to create a quality antenna. If anyone could be of assistance that would be great. I have a diagram of the setup I am trying to create here:
http://www.cpinternet.com/~jjessico/...i/Pvc.yagi.jpg

Thanks,
Jason

G8tK33per · 05-17-2004

Have you looked thru these?

FAU: Frequently Asked URLs; Antenna Links

jjessico · 05-17-2004

Yes I did go through those.

http://www.turnpoint.net/wireless/an...ypringles.html
This was a nice quick guide to a pringles-yagi, but I'm building one a tad bit larger and I'm not sure how the dimensions would scale.

I've obtained most of my ideas and plans from:
http://www.netscum.com/%7Eclapp/wireless.html
but I am still confused. Also he focuses more on his 18" yagi. Unfortunately the small pipe he uses is harder to come by for me.

Thanks,
Jason

Thorn · 05-17-2004

Quote:

Originally Posted by jjessico

Yes I did go through those.

http://www.turnpoint.net/wireless/an...ypringles.html
This was a nice quick guide to a pringles-yagi, but I'm building one a tad bit larger and I'm not sure how the dimensions would scale.

I've obtained most of my ideas and plans from:
http://www.netscum.com/%7Eclapp/wireless.html
but I am still confused. Also he focuses more on his 18" yagi. Unfortunately the small pipe he uses is harder to come by for me.

Thanks,
Jason

The diameter of the PVC pipe doesn't matter. You don't even need that except for structual stability.

The things which are critical are the distance of the washers, the distance from the reflector and the diameter of the can portion. (Your X dimension.) Lincomatic has a calulator on his site for computing the optimum diameter. Look throught the Antenna FAQs. Most of the other dimensions will be either single 1/4 wavelength or multiples of that. The 1/4 wave at these frequencies is 1.22". So the washers should be 1.22" in diameter, the spacing of the washers should be 1.22" apart, etc.

jjessico · 05-24-2004

I have updated my diagram after taking a look at lincomatics calculator and have come up with the following:
http://www.cpinternet.com/~jjessico/...i/Pvc.yagi.jpg

I am still in search of a V and Z value. Any ideas?

Thanks,
Jason

Apollyon · 05-24-2004

Shouldn't "W" be exactly 1/4 wavelength to cause the amplified effect over the driven element?

Apollyon

jjessico · 05-24-2004

I'm not sure, but I'd like to know. The calculator I was refering to was here:

http://www.geocities.com/lincomatic/....html#cantenna

Apollyon · 05-24-2004

I'm no ham junkie, but check here, too.
http://www.saunalahti.fi/elepal/antenna2.html

Maybe it's because "X" is larger than 1/4 wave.

Apollyon

Thorn · 05-24-2004

Quote:

Originally Posted by Apollyon

I'm no ham junkie, but check here, too.
http://www.saunalahti.fi/elepal/antenna2.html

Maybe it's because "X" is larger than 1/4 wave.

Apollyon

I forget why, but 2.48 works out about right for W. If I recall, it has to do with the standing waves. (But that may not be right; its' been a while since I looked at any of the math for this stuff.)

V can be zero, since this is a yagi, and not a waveguide.

Z should be 1/4 wave seperating the first element (washer) from the driven element.

Apollyon · 05-24-2004

Okay. Basic question about these cantennas: Shouldn't the elements be insulated from each other, like a yagi? Or can you point me in the direction of a page that explains the theory?

Apollyon

wrzwaldo · 05-24-2004

Quote:

Originally Posted by Apollyon

Okay. Basic question about these cantennas: Shouldn't the elements be insulated from each other, like a yagi? Or can you point me in the direction of a page that explains the theory?

Apollyon

I have a couple yagis here and the elements are not insulated from each other. The driven element is insulated but not the others.

Thorn · 05-24-2004

Quote:

Originally Posted by Apollyon

Okay. Basic question about these cantennas: Shouldn't the elements be insulated from each other, like a yagi? Or can you point me in the direction of a page that explains the theory?

Apollyon

I'm pretty sure it doesn't matter that much at these frequencies. There are some logarithmic designs where the elements are all etched out of a continuous trace of printed circuit.

Too be honest though, it's a good question, and I'd recommond getting a copy of the ARRL Antenna Handbook for the definative answer. (Mine is long gone and I really need to replace it...)

As far as theory goes, (again from memory) it has to do with the individual elements resonating at the right frequencies due to their length (or diameter in this design) and little to do with conducting in an electrical fashion. Think more like a tuning fork vibrating at the right sound rather than a wire conducting power to a light bulb and you're starting to get the idea.

Apollyon · 05-24-2004

Quote:

Originally Posted by wrzwaldo

I have a couple yagis here and the elements are not insulated from each other. The driven element is insulated but not the others.

I just remember using broomsticks and the like to make yagi's and thought it was for the insulating properties. I understand the RF resonance factor, but, esp at high freq's, every bit of metal matters, right? Like the design of the traces on a board are important at those freq's because they can have capacitive effects.

Apollyon

Thorn · 05-24-2004

Quote:

Originally Posted by Apollyon

I just remember using broomsticks and the like to make yagi's and thought it was for the insulating properties. I understand the RF resonance factor, but, esp at high freq's, every bit of metal matters, right? Like the design of the traces on a board are important at those freq's because they can have capacitive effects.

Apollyon

Good point. I'm going to have get another copy of the ARRL Handbook now.

lincomatic · 05-25-2004

Quote:

Originally Posted by jjessico

I'm not sure, but I'd like to know. The calculator I was refering to was here:

http://www.geocities.com/lincomatic/....html#cantenna

my calculator is for circular waveguide cantennas such as the one pictured here:

http://www.geocities.com/lincomatic/homebrewant.html

not for the pringles yagi's. btw, i wonder why anyone even bothers w/ the pringles yagi's. they're longer, more expensive, and harder to build, and i've yet to see anyone showing that they perform better.

05-17-2004	#1 (permalink)
jjessico Registered Member Join Date: May 2004 Posts: 7	PVC Yagi Construction I am working on building a homebrew directional-yagi with PVC. I have made up a diagram, but I am a little short on information as to dimensions, what they are, and how to calculate them to create a quality antenna. If anyone could be of assistance that would be great. I have a diagram of the setup I am trying to create here: http://www.cpinternet.com/~jjessico/...i/Pvc.yagi.jpg Thanks, Jason

05-17-2004	#2 (permalink)
G8tK33per Asshole Emeritus Join Date: May 2003 Location: Goomba's Booty Boardwalk Posts: 6,121	Have you looked thru these? FAU: Frequently Asked URLs; Antenna Links __________________ "My mind is aglow with whirling, transient nodes of thought careening through a cosmic vapor of invention." Sons of Confederate Veterans

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05-17-2004	#3 (permalink)
jjessico Registered Member Join Date: May 2004 Posts: 7	Yes I did go through those. http://www.turnpoint.net/wireless/an...ypringles.html This was a nice quick guide to a pringles-yagi, but I'm building one a tad bit larger and I'm not sure how the dimensions would scale. I've obtained most of my ideas and plans from: http://www.netscum.com/%7Eclapp/wireless.html but I am still confused. Also he focuses more on his 18" yagi. Unfortunately the small pipe he uses is harder to come by for me. Thanks, Jason

05-24-2004	#5 (permalink)
jjessico Registered Member Join Date: May 2004 Posts: 7	I have updated my diagram after taking a look at lincomatics calculator and have come up with the following: http://www.cpinternet.com/~jjessico/...i/Pvc.yagi.jpg I am still in search of a V and Z value. Any ideas? Thanks, Jason

05-24-2004	#6 (permalink)
Apollyon WDing the World in BDU's Join Date: Apr 2004 Location: Rural Sin City, USA Posts: 61	Shouldn't "W" be exactly 1/4 wavelength to cause the amplified effect over the driven element? Apollyon

05-24-2004	#7 (permalink)
jjessico Registered Member Join Date: May 2004 Posts: 7	I'm not sure, but I'd like to know. The calculator I was refering to was here: http://www.geocities.com/lincomatic/....html#cantenna

05-24-2004	#8 (permalink)
Apollyon WDing the World in BDU's Join Date: Apr 2004 Location: Rural Sin City, USA Posts: 61	I'm no ham junkie, but check here, too. http://www.saunalahti.fi/elepal/antenna2.html Maybe it's because "X" is larger than 1/4 wave. Apollyon

05-24-2004	#10 (permalink)
Apollyon WDing the World in BDU's Join Date: Apr 2004 Location: Rural Sin City, USA Posts: 61	Okay. Basic question about these cantennas: Shouldn't the elements be insulated from each other, like a yagi? Or can you point me in the direction of a page that explains the theory? Apollyon