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1994-11-13
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Date: Sun, 6 Nov 94 04:30:16 PST
From: Ham-Ant Mailing List and Newsgroup <ham-ant@ucsd.edu>
Errors-To: Ham-Ant-Errors@UCSD.Edu
Reply-To: Ham-Ant@UCSD.Edu
Precedence: List
Subject: Ham-Ant Digest V94 #367
To: Ham-Ant
Ham-Ant Digest Sun, 6 Nov 94 Volume 94 : Issue 367
Today's Topics:
Copper Pipe Yagis? (2 msgs)
Dipole question's
Dual Band J-Pole?
J-Pole for 2 meters
Need Info:Multi Band Dipole
Twinax for feedline
x-beam vs yagi, ELNEC
Send Replies or notes for publication to: <Ham-Ant@UCSD.Edu>
Send subscription requests to: <Ham-Ant-REQUEST@UCSD.Edu>
Problems you can't solve otherwise to brian@ucsd.edu.
Archives of past issues of the Ham-Ant Digest are available
(by FTP only) from UCSD.Edu in directory "mailarchives/ham-ant".
We trust that readers are intelligent enough to realize that all text
herein consists of personal comments and does not represent the official
policies or positions of any party. Your mileage may vary. So there.
----------------------------------------------------------------------
Date: Thu, 3 Nov 1994 17:45:37 GMT
From: clifto@indep1.chi.il.us (Clifton T. Sharp)
Subject: Copper Pipe Yagis?
In article <CyLMyn.1BF@hpcvsnz.cv.hp.com> tomb@lsid.hp.com (Tom Bruhns) writes:
>How about a baby blue beam??
Naw, make it red... for maximum rediation.
--
Cliff Sharp Never get into fights with ugly people.
WA9PDM They have nothing to lose.
clifto@indep1.chi.il.us --The Fourth Law of Reality
------------------------------
Date: Fri, 4 Nov 1994 19:56:22 -0500
From: Tony Stalls <rstalls@access4.digex.net>
Subject: Copper Pipe Yagis?
Hi Jerry,
> 1. Cost. Copper pipe is a lot more expensive then aluminum, but you already
> know this.
I figured the cost of bringing in aluminum tubing from Texas v. getting
the Cu tubing from the handyman store, and especially adding in the
instant gratification factor, it isn't that much more expensive.
> 2. Weight. Copper weighs a lot more than aluminum.
True, and I realized that too. For a small VHF Yagi (6 meters even), I
don't think it's enough heavier to make that much difference.
The real incentive is the "instant gratification" part. I sometimes
decide on a quick antenna project and by the time I get around to ordering
up the tubing and so on, the moment has passed and nothing gets done.
However, a visit to the local Home Depot (etc.) can yield the tubing and
fittings within a half-hour and the thing can be up and working in an
afternoon. The other part is that working with copper is easy and I can
experiment my little heart's content.
It's obviously not the most practical thing to do, but what the heck. The
ultimate bottom line for doing it is the reason I've been playing with
amateur radio all these years: Fun! ;-)
Thanks for the input!
73,
Tony
K4KYO
------------------------------
Date: Thu, 3 Nov 1994 20:27:47 +0000
From: chasr@parc.demon.co.uk (charles rodgers)
Subject: Dipole question's
In article <38u6vm$mf@chnews.intel.com>
cmoore@scorpion.ch.intel.com "Cecil A. Moore -FT-~" writes:
> I chose 88 ft for my multi-band dipole
Hi Cecil,
I'd be very interested to know what the feeder you use with that dipole.
I assume that you mean 44 ft each side.
I have used such a dipole in inverted V formation with an open wire feeder
and it performed very well on 20m but not so on 17m.
--
charles rodgers
chasr@parc.demon.co.uk
------------------------------
Date: 5 Nov 1994 12:44:44 GMT
From: wvanho@infinet.com (W. E. Van Horne)
Subject: Dual Band J-Pole?
Rafael Solis (rafaels@zimmer.CSUFresno.EDU) wrote:
: Folks!
: Is it possible to build a 2m/73cm dual band J-Pole?
Ken, N9YIR called attention to the recent QST article. The gist of the
article is that the 73 cm. band is the third harmonic of the 2 m. band.
The antenna described was cut for 2 m. and operated on both the
fundamental and third harmonic. From that, I assume that ANY full-size
J-Pole antenna will do the same thing.
Cautionary note: I am NOT speaking from experience. Perhaps others can
correct me if I am wrong. Note my signature, below. :-)
73, Van - W8UOF
* * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* It ain't wot ya don't know 't gets ya into trouble. *
* It's wot ya know 't ain't true. - "Mr. Dooley" *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * *
wvanho@infinet.com
------------------------------
Date: Thu, 3 Nov 1994 03:44:04 GMT
From: wa2ise@netcom.com (Robert Casey)
Subject: J-Pole for 2 meters
In article <3Anjkep56dTS066yn@calvin.stemnet.nf.ca> ydawe@calvin.stemnet.nf.ca (Yvonne M. Dawe) writes:
>I have saved several examples of construction plans for 2m copper
>cactus and 300 ohm twin-lead j-poles with the intention of eventually
>making one, however, upon closer inspection of the details I notice that
>at least two individuals say to connect the sheild to the 1/4 wave matching
>stub, while in other "plans" they say to connect the sheild to the other
>side. Who is wrong? Or are both right? Can anyone please tell
>me: What side does the sheild go to, and what side does the center
>conductor go to..?
As I understand it, it works either way. One should place some ferrite
beads or make a few turns of coax in the feedline near the feedline
connection to the Jpole. These beads or coil act as a sort of balun.
The shield passing thru it is no longer "RF" ground. The center con-
ductor doesn't "notice" the balum, nor does the *inside* of the coax
shield. The outside of the shield having passed thru the balun
acquires something like -1/2 the transmitted RF voltage. This
minus 1/2 gets added to the shield to center 1 x RF from transmitter
to give a +1/2 the transmitted RF voltage. You're effectively going
from 50 ohm unbalanced to 50 ohm balanced. The Jpole is across the
-1/2 RF to +1/2 RF terminals described above. So, it doesn't really
matter which side gets the center conductor. Whichever is more
convenient mechanically.
It's similar to the coax feeding a dipole, with ferrite beads or a coil of
coax at the feedpoint trick. Keeps RF off the *outside* of the coax
and avoiding a messed-up radiation pattern.
------------------------------
Date: 5 Nov 1994 09:42:07 -0800
From: teixeira@ccnet.com (TEIXEIRA)
Subject: Need Info:Multi Band Dipole
Back in my novice days I built a multi band dipole. The antenna was a 1/2
wave dipole with a seperate wire for 40m,15m & 10m. The swr on 40 was 1.5
but it was above 3.0 on 15 & 10. I never could get it down. Now my
neighbor who is a new Ham wants to use this design. Any info on tuning
this beast. Does it require a tuner? It worked excellent on 40M.
Tnx-Don N6FNL
------------------------------
Date: 6 Nov 1994 03:33:09 GMT
From: choffman@pinot.callamer.com (Christopher R. Hoffman)
Subject: Twinax for feedline
--
TNX - 73's
Chris Hoffman
KO6GA ex. KD6VLY
choffman@slonet.org
------------------------------
Date: 4 Nov 1994 09:48:31 -0500
From: jimn0oct@aol.com (JimN0OCT)
Subject: x-beam vs yagi, ELNEC
In article <395q8l$ic3@ornews.intel.com>, zardoz@ornews.intel.com (Jim
Garver) writes:
about different antennas for rs/10. I have used a dipole and others, but
keep coming back to the dipole. Two might be nice, one E/W the other N/S.
They're simple, and you don't have to keep rotating them.. They work
great on rs12/13 too.
72, jim
------------------------------
End of Ham-Ant Digest V94 #367
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