Homebrew antenna (well, a copy of anyway)

tomjones · 07-29-2002

I have been working on creating the 18" directional yagi shown in:

http://www.netscum.com/~clapp/wireless.html

I purchased some parts (close to what is described in the reading) and began assembly. I have a few questions to those who have done this already. Before I get to that, here is what I have done so far.

6/32 x 36 threaded rod
cut into 2 18" pieces (only one piece used)

1/4" O.D. Copper Coil (0.030" Wall)
3 cm pieces cut (12 total) and placed between fender washers
*both sides of tubing were filed for better contact on the washers)

1/8" x 1" Fender Washers
13 used and placed between copper coil spacers

6/32 Machine Screw Nut
2 nuts used...one on each side of threaded rod to hold tubing and washers in place

I have the skeleton complete and have a few questions:

-in the outline of what is needed for the 18", he states:

1) some length of 1" abs/pvc cut to 17-1/4" pieces.

I hope that means 1 whole pvc pipe cut into a 17 1/4 piece and not multiple (17 pieces 1/4" long)

-the image shown here:

http://www.netscum.com/~clapp/images...pringles-1.gif

I couldn't find the measurements for the last nut to the plastic pvc cover (upper most side of antenna in picture), or for that matter, the distance from the nut at the bottom to the end of the threaded rod.

-also, how is the plastic pvc cover attached to the threaded rod?

Does it sound like I am missing anything? The most time consuming part was cutting the copper tubing into 12 pieces and filing them down. I would just like to know if anyone notices any huge flaws in what I have done so far. Overall, the site does a great job of explaining what to do. I just want to make sure that I'm not wasting time or resources in going the wrong direction.

Thanks for any help you may offer.

Thorn · 07-29-2002

You have it right.

One comment, you don't need to worry about the contact between the tubing and the washers: "*both sides of tubing were filed for better contact on the washers)"

Those pieces of tubing are just spacers. What is critical is that there be 1.22" from washer to washer. The spacing is 1/4 wave of the center frequency of the ISM band. (Ch. 6) So every 4 of these make a full wave.

The only parts that need to be metal are the washers. The rod and tubing is just a structure to space the washers, and could be non-conductive if you so desired.

As far as attaching the pvc cap, you can use use anything. Attach it using the first nut; Attach it with epoxy; Hot glue; Press fit it; Whatever. It doesn't really matter for the function. It is just there to keep the antenna dry.

lincomatic · 07-29-2002

Quote:

Originally posted by Thorn
Those pieces of tubing are just spacers. What is critical is that there be 1.22" from washer to washer. The spacing is 1/4 wave of the center frequency of the ISM band. (Ch. 6) So every 4 of these make a full wave.

The only parts that need to be metal are the washers. The rod and tubing is just a structure to space the washers, and could be non-conductive if you so desired.

thorn,
when calculating the 1/4 wave, does one have to take the thickness of the washers into consideration? seems to me like the phase would change if the thickness changed.
just wondering...

Thorn · 07-29-2002

Everything I've ever seen, sort of ignored this point, or at least made the center of the element (ie. washer) the point to measure to/from. I'm sure a very thick washer would introduce some distortion, but there are probably a lot of other things which will cause more problems in these designs. For instance, the lack of a proper size reflector in many of these things.

In theory, or at least the theory I've read, the elements should be exactly spaced to 15 decimal places, and all be of infinite thinness. Stuff that never happens in the Real World.

ARPAN3T · 07-30-2002

Quote:

Originally posted by Thorn
Stuff that never happens in the Real World.

Those MTV kids are smart when it comes to constructing a homemade Yagi.

Thorn · 07-30-2002

I was wondering if anyone would comment on "Real World."

Sorry, ARPAN3T, but I was using that expression long before someone at MTV decided they could make TV shows using a bunch of idiots in an apartment.

I guess it worked- Hell, CBS is using the same concept with "Big Brother." Which just proves they were right in Sex and Death: "Give me a rotting corpse, put it on TV, and people will watch it!"

tomjones · 07-30-2002

Thank you for your replies. Good to know that I'm doing something right (even if it's going to take me a while to figure out why I'm doing it.) I need to do some reading on wavelengths...

Should I be concerned about the question below, or does it matter?
........................................
I couldn't find the measurements for the last nut to the plastic pvc cover (upper most side of antenna in picture), or for that matter, the distance from the nut at the bottom to the end of the threaded rod.
.........................................

Thanks again.

Thorn · 07-30-2002

No. You don't have to be concerned with the distances of the nuts. The critical measurements are the spacing of the elements. (The washers.) They are the only things that are active from a radio standpoint.

If you're going to continue fooling around with this stuff, get the ARRL book on antenna design. It will help.

lincomatic · 07-30-2002

tomjones,
after you finish building it, please upload some pics and let us know any tricks/pitfalls you learned during its construction.
thx.

tomjones · 07-31-2002

Finished last night. I'll throw some pics up tonight. Thanks for all of your advice.

tomjones · 08-05-2002

Here are some pics from my first antenna. It's still pretty rough looking and needs to be fine tuned, but works well now.

www15.brinkster.com/oldcrow/pics/103-0310_IMG.JPG

www15.brinkster.com/oldcrow/pics/103-0308_IMG.JPG

I'm fairly sure the Sweet Mesquite BBQ flavor has something to do with the gain. I will be testing numerous reflective surfaces...I've heard the can should be 3 - 3.25 inches in diameter. I'll repost after I try some out.

lincomatic · 08-05-2002

nice job

is the performance good?

tomjones · 08-05-2002

I've only done minimal testing (pointing it out of my window at the city...) I was able to pick up more than my 5 dbi omni and I think more than my 9 dbi omni. The APs are pretty far away and I wasn't too patient waving it around, so I'm sure I missed some. I plan to test it shortly (getting an AP for myself shortly).

Thanks again to everyone for their help and for taking the time to post "step by step" instructions.

Thunderforge · 08-05-2002

Quote:

Originally posted by tomjones
Here are some pics from my first antenna. It's still pretty rough looking and needs to be fine tuned, but works well now.

www15.brinkster.com/oldcrow/pics/103-0310_IMG.JPG

www15.brinkster.com/oldcrow/pics/103-0308_IMG.JPG

I'm fairly sure the Sweet Mesquite BBQ flavor has something to do with the gain. I will be testing numerous reflective surfaces...I've heard the can should be 3 - 3.25 inches in diameter. I'll repost after I try some out.

WHOOPS! Have to check out the pics tomorrow. Looks like the forums chewed up your traffic bandwidth for the day.

bmoore314 · 08-08-2002

Looks like you are about as good as cutting copper tubing at perfect 90 degree angles as I am

A dremel tool and a vice sure doesnt work all that well heh. Just a note: using 2 kinds of metals tends to corrode at the junction, my pringles antenna is kinda coroded like, (though its pretty old now - over 5 or 6 months i think). I think im gonna destroy it to reclaim the N connector, as I am currently out of them.

07-29-2002	#1 (permalink)
tomjones Registered Member Join Date: May 2002 Posts: 61	Homebrew antenna (well, a copy of anyway) I have been working on creating the 18" directional yagi shown in: http://www.netscum.com/~clapp/wireless.html I purchased some parts (close to what is described in the reading) and began assembly. I have a few questions to those who have done this already. Before I get to that, here is what I have done so far. 6/32 x 36 threaded rod cut into 2 18" pieces (only one piece used) 1/4" O.D. Copper Coil (0.030" Wall) 3 cm pieces cut (12 total) and placed between fender washers *both sides of tubing were filed for better contact on the washers) 1/8" x 1" Fender Washers 13 used and placed between copper coil spacers 6/32 Machine Screw Nut 2 nuts used...one on each side of threaded rod to hold tubing and washers in place I have the skeleton complete and have a few questions: -in the outline of what is needed for the 18", he states: 1) some length of 1" abs/pvc cut to 17-1/4" pieces. I hope that means 1 whole pvc pipe cut into a 17 1/4 piece and not multiple (17 pieces 1/4" long) -the image shown here: http://www.netscum.com/~clapp/images...pringles-1.gif I couldn't find the measurements for the last nut to the plastic pvc cover (upper most side of antenna in picture), or for that matter, the distance from the nut at the bottom to the end of the threaded rod. -also, how is the plastic pvc cover attached to the threaded rod? Does it sound like I am missing anything? The most time consuming part was cutting the copper tubing into 12 pieces and filing them down. I would just like to know if anyone notices any huge flaws in what I have done so far. Overall, the site does a great job of explaining what to do. I just want to make sure that I'm not wasting time or resources in going the wrong direction. Thanks for any help you may offer.

07-29-2002	#2 (permalink)
Thorn Did you do the math? Join Date: Apr 2002 Location: Villa Straylight Posts: 10,358	You have it right. One comment, you don't need to worry about the contact between the tubing and the washers: *"both sides of tubing were filed for better contact on the washers)"** Those pieces of tubing are just spacers. What is critical is that there be 1.22" from washer to washer. The spacing is 1/4 wave of the center frequency of the ISM band. (Ch. 6) So every 4 of these make a full wave. The only parts that need to be metal are the washers. The rod and tubing is just a structure to space the washers, and could be non-conductive if you so desired. As far as attaching the pvc cap, you can use use anything. Attach it using the first nut; Attach it with epoxy; Hot glue; Press fit it; Whatever. It doesn't really matter for the function. It is just there to keep the antenna dry. __________________ Thorn "Read Altas Shrugged. Compare it to today. Repeat as necessary"

07-29-2002	#4 (permalink)
Thorn Did you do the math? Join Date: Apr 2002 Location: Villa Straylight Posts: 10,358	Everything I've ever seen, sort of ignored this point, or at least made the center of the element (ie. washer) the point to measure to/from. I'm sure a very thick washer would introduce some distortion, but there are probably a lot of other things which will cause more problems in these designs. For instance, the lack of a proper size reflector in many of these things. In theory, or at least the theory I've read, the elements should be exactly spaced to 15 decimal places, and all be of infinite thinness. Stuff that never happens in the Real World. __________________ Thorn "Read Altas Shrugged. Compare it to today. Repeat as necessary"

07-30-2002	#6 (permalink)
Thorn Did you do the math? Join Date: Apr 2002 Location: Villa Straylight Posts: 10,358	I was wondering if anyone would comment on "Real World." Sorry, ARPAN3T, but I was using that expression long before someone at MTV decided they could make TV shows using a bunch of idiots in an apartment. I guess it worked- Hell, CBS is using the same concept with "Big Brother." Which just proves they were right in Sex and Death: "Give me a rotting corpse, put it on TV, and people will watch it!" __________________ Thorn "Read Altas Shrugged. Compare it to today. Repeat as necessary"

07-30-2002	#8 (permalink)
Thorn Did you do the math? Join Date: Apr 2002 Location: Villa Straylight Posts: 10,358	No. You don't have to be concerned with the distances of the nuts. The critical measurements are the spacing of the elements. (The washers.) They are the only things that are active from a radio standpoint. If you're going to continue fooling around with this stuff, get the ARRL book on antenna design. It will help. __________________ Thorn "Read Altas Shrugged. Compare it to today. Repeat as necessary"

07-30-2002	#7 (permalink)
tomjones Registered Member Join Date: May 2002 Posts: 61	Thank you for your replies. Good to know that I'm doing something right (even if it's going to take me a while to figure out why I'm doing it.) I need to do some reading on wavelengths... Should I be concerned about the question below, or does it matter? ........................................ I couldn't find the measurements for the last nut to the plastic pvc cover (upper most side of antenna in picture), or for that matter, the distance from the nut at the bottom to the end of the threaded rod. ......................................... Thanks again.

07-30-2002	#9 (permalink)
lincomatic Squaaawk! WiFi! WiFi! Join Date: Apr 2002 Location: Tinsel Town Posts: 1,682	tomjones, after you finish building it, please upload some pics and let us know any tricks/pitfalls you learned during its construction. thx. __________________ ~lincomatic

07-31-2002	#10 (permalink)
tomjones Registered Member Join Date: May 2002 Posts: 61	k Finished last night. I'll throw some pics up tonight. Thanks for all of your advice.

08-05-2002	#11 (permalink)
tomjones Registered Member Join Date: May 2002 Posts: 61	Pics Here are some pics from my first antenna. It's still pretty rough looking and needs to be fine tuned, but works well now. www15.brinkster.com/oldcrow/pics/103-0310_IMG.JPG www15.brinkster.com/oldcrow/pics/103-0308_IMG.JPG I'm fairly sure the Sweet Mesquite BBQ flavor has something to do with the gain. I will be testing numerous reflective surfaces...I've heard the can should be 3 - 3.25 inches in diameter. I'll repost after I try some out.

08-05-2002	#12 (permalink)
lincomatic Squaaawk! WiFi! WiFi! Join Date: Apr 2002 Location: Tinsel Town Posts: 1,682	nice job is the performance good? __________________ ~lincomatic

08-05-2002	#13 (permalink)
tomjones Registered Member Join Date: May 2002 Posts: 61	I've only done minimal testing (pointing it out of my window at the city...) I was able to pick up more than my 5 dbi omni and I think more than my 9 dbi omni. The APs are pretty far away and I wasn't too patient waving it around, so I'm sure I missed some. I plan to test it shortly (getting an AP for myself shortly). Thanks again to everyone for their help and for taking the time to post "step by step" instructions.

08-08-2002	#15 (permalink)
bmoore314 Stumbly Stumbly Join Date: Jun 2002 Location: south bay area, california Posts: 35	Looks like you are about as good as cutting copper tubing at perfect 90 degree angles as I am A dremel tool and a vice sure doesnt work all that well heh. Just a note: using 2 kinds of metals tends to corrode at the junction, my pringles antenna is kinda coroded like, (though its pretty old now - over 5 or 6 months i think). I think im gonna destroy it to reclaim the N connector, as I am currently out of them.

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