home brew help for a new guy

home brew help for a new guy

Postby fartmonger » Sat Sep 14, 2002 5:52 am

im in the process of building my first cantenna, i got all the parts and ive been searching for designs that i like so far i like this pvc one i found but its just got a picture and no how to. i hate to sound lame but does there have to be some kind of metal liner in this thing? pleare reply all your input is appreciated.
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PVC linings

Postby l0ckd0wn » Sat Sep 14, 2002 1:22 pm

I don't know which PVC design you're going for, but they're all pretty much the same. The one that I see most commonly referenced is Andrew Clapp's modification of the Seattle Wireless Group's design at http://www.netscum.com/~clapp/wireless.html

The length of the PVC doesn't need to be lined with any metal, you've got the allthread and washer elements set up in the barrel as your collector. The reflector end (where your N-connector is) needs to be metal, so your best bet is just using a can. (see http://seattlewireless.net/index.cgi/DirectionalYagi for clarification)

Some mylar tape over the length of the thing once it's glued, and you've got a clean exterior finish.
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Postby fartmonger » Sat Sep 14, 2002 4:09 pm

thanx those may help im actually looking to make the antenna like this attached photo but im not sure what all is inside. it sounds like the key is in the reflector though and the whole length of the inner pvc does not need to be metal, just the end behind the copper probe (wire) inside the can
Attachments
1.jpg
1.jpg (28.85 KiB) Viewed 2548 times
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Postby l0ckd0wn » Sat Sep 14, 2002 5:54 pm

That's one fat antenna for a PVC. If you're going to go for something in that diameter, save the trouble of the element spacing calculations and such, and just use an empty can (no elements necessary) I'll post the link to the URL with the connector placement calculator when I find it. (Tomorrow, the latest) I've built a few on that design, and they work really well and are a lot easier to build than the multi-element design.
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URL, as promised

Postby l0ckd0wn » Sun Sep 15, 2002 2:50 pm

This is the site that has a waveguide calculator on it. Works great, too. I've built a few very decent gain cans using this calc.

http://www.turnpoint.net/wireless/cantennahowto.html

Just a personal note, the best can that I've used to date is from a can of Munton's Pilsner brewer's wort. (I homebrew b33r, as well as antennas) It's 3.75" diameter, and almost twice as deep as a one pound coffee can, but it's totally smooth inside with a dead flat bottom.
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Postby Chris_Schear » Sun Sep 15, 2002 10:16 pm

I'm sorry, I hate to interupt, but did you just intentionally spell "beer" with elitespeak?
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Postby l0ckd0wn » Mon Sep 16, 2002 3:23 pm

When you triple ferment an oatmeal stout to 10.6% alcohol, maintain the subtle chocolate undertones, and keep it from developing a bitter after flavour, you can spell b33r however you want. If you're ever in Cincinnati, I'll put a few pints in the fridge for ya.

-- l0ckd0wn
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Postby fartmonger » Tue Sep 17, 2002 7:18 am

thanks so much,
however what about the metal linning on the inside wall of the can is it necesary or do i just need it at the bottom?
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Postby Thunderforge » Tue Sep 17, 2002 7:46 am

For the waveguide style antenna it has to all be metal.
Back to the forge,
TF
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Postby l0ckd0wn » Tue Sep 17, 2002 10:11 am

Sorry if I confused you with two different designs there and not much clarification.

PVC/multi-element style: metal for reflector end behind the pickup

Waveguide (empty can) style: whole thing metal
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Postby fartmonger » Thu Sep 19, 2002 12:41 pm

you guys are great! thanx for the help
All for one and one for All !!!
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