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940039.txt
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1994-11-13
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Date: Sat, 19 Feb 94 04:30:26 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: Bulk
Subject: Ham-Ant Digest V94 #39
To: Ham-Ant
Ham-Ant Digest Sat, 19 Feb 94 Volume 94 : Issue 39
Today's Topics:
6 Mtr Loop Skywire??
Antenna gain: dB,dBi,dBic ??
folded dipole dimensions
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, 17 Feb 1994 19:24:20 GMT
From: ucsnews!sol.ctr.columbia.edu!howland.reston.ans.net!europa.eng.gtefsd.com!library.ucla.edu!csulb.edu!csus.edu!netcom.com!henrys@network.ucsd.edu
Subject: 6 Mtr Loop Skywire??
To: ham-ant@ucsd.edu
I want to construct a horizontally polarized, omni directional antenna
for six meters.
The big wheel for six meters is a consideration but it is fairly
complicated to build.
How about a Loop Skywire for six meters?
The Loop Skywire is simply a square loop antenna erected horizontal
to the earth and fed with 50 Ohm coax.
The perimeter of the loop is L = 1005 / f, where f is the frequency. For
six meters, f would be 50.25 and L would be 20 feet. Each side of
the loop would be 5 feet.
At 5 feet on a side, a simple loop could be constructed using PVC or
somthing similar. It would even be feasible to stack the loops for
more gain.
Since most of the articles that I have read describe Loop Skywires
for 80 or 40 meters, I am not sure what the characteristics would be
on six meters.
Would anybody care to comment? What do your antenna modeling programs
say?
Thanks,
Smitty, NA5K
--
-----------------------------------------------------------------------
| Henry B. Smith - NA5K henrys@netcom.com |
| Dallas, Texas |
| |
| "I'm not sure I understand everything that I know" |
-----------------------------------------------------------------------
------------------------------
Date: 18 Feb 1994 09:04:27 -0600
From: agate!howland.reston.ans.net!cs.utexas.edu!not-for-mail@network.ucsd.edu
Subject: Antenna gain: dB,dBi,dBic ??
To: ham-ant@ucsd.edu
Hello,
Can anyone help me. I am trying to interpret various antenna gain specs for
a variety of circularly polarized antennas. The specs usually use dB, dBi
or dBic.
What is the definition of these units and how are they related to each
other ?? Does dBi mean the gain relative to an isotropic radiator ?
Does dBic mean the gain relative to an isotropic circularly polarized
radiator. Can one meaningfully convert from one to the other ?
For instance, a 4 ft. parabolic dish is spec'd at 24 dB. Should this be dBi
? I have some information on a patch antenna which has a gain of 16-17
dBic. How do I compare the two gains ??
Any help or pointers to reference books which discuss this would be
appreciated.
Thanks,
Jim
------------------------------
Date: 18 Feb 94 15:19:09 GMT
From: news-mail-gateway@ucsd.edu
Subject: folded dipole dimensions
To: ham-ant@ucsd.edu
The ARRL handbook shows the folded dipole has a 300 ohm feed point
impedance, independent of conductor diameter and spacing, as long as the
two conductors are equal diameter.
Other literature shows the full wave square loop to have approx. 100 ohm feed
point impedance.
The first question is this: How far apart can the conductors of a folded dipole
be spaced before the antenna looks electrically more like a full wave
rectangle loop, rather than a folded dipole?
The handbook also states that the folded dipole, compared to the regular
75 ohm dipole, has greater bandwidth due to the two parallel conductor
arrangement.
The second question is this: Does increasing the spacing of the parallel
conductors in a folded dipole increase the bandwidth? If so, what is the
optimum spacing for maintaing an approx. 300 ohm feed and maximizing the
bandwidth in a folded dipole arrangement?
Please answer or discuss on the net.
--Clay
------------------------------
End of Ham-Ant Digest V94 #39
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