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940179.txt
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1994-11-13
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Date: Sat, 11 Jun 94 04:30:15 PDT
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 #179
To: Ham-Ant
Ham-Ant Digest Sat, 11 Jun 94 Volume 94 : Issue 179
Today's Topics:
2 antennas into receiver?
Newbie Continues Pondering J-Poles...
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: 10 Jun 1994 16:42:20 GMT
From: lll-winken.llnl.gov!overload.lbl.gov!agate!msuinfo!netnews.upenn.edu!eniac.seas.upenn.edu!depolo@ames.arpa
Subject: 2 antennas into receiver?
To: ham-ant@ucsd.edu
In article <brett_miller.290.0008C5D5@ccm.hf.intel.com> brett_miller@ccm.hf.intel.com (Brett Miller - N7OLQ) writes:
>I have an AOR AR3000A that has coverage from about 100KHz to 2 GHz. It only
>has one BNC connector on the back so I am wondering if there are any
>disadvantages to hooking a BNC T connector to it with one end going to a
>discone, while the other end goes to a random wire antenna (w/tuner).
Not exactly an omptimal way of doing things, but in your receive-only
configuration, it may work tolerably well. There are several issues here,
including impedance matching and constructive/destructive interference.
Although, with a random longwire, impedance concerns go out the window.
A better approach would be to either have a coaxial switch to select
between the two antennas, or to combine the two using a combiner.
A combiner for this type of application could be built fairly easily.
Basically, it would consist of a high-pass and low-pass filter connected
to a common output, with the discone and the longwire feeding the inputs
respectively.
I can't see the logic in a scanner with coverage that wide that they
didn't bother to put seperate antenna connections on in the first place.
Bad design IMHO.
--- Jeff
--
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Jeff DePolo WN3A Twisted Pair: (215) 337-7383H 387-3059W
depolo@eniac.seas.upenn.edu RF: 443.800+ MHz 442.400+ MHz 24.150 GHz
------------------------------
Date: 10 Jun 1994 09:39:07 -0700
From: agate!howland.reston.ans.net!europa.eng.gtefsd.com!sundog.tiac.net!news.sprintlink.net!news.world.net!seatimes.seatimes.com!seatimes.seatimes.com!not-for-mail@ames.arpa
Subject: Newbie Continues Pondering J-Poles...
To: ham-ant@ucsd.edu
: Q: I am unclear on one small point... are the two rods meant to be
: electrically continuous or should they be isolated from each other?
: Based on the many design suggestions forwarded to me, I would guess
: that they should NOT be insulated from each other.
You are correct. They should be electrically and physically connected at
the bottom with the feed point at some elevated position to make the
appropriate matching.
Since the bottom is electrically neutral, it can be grounded to earth
ground providing a very easy path for the static buildup from rain, wind,
snow, etc to drain off rather than create noise for the receiver.
+----------------------------------------------------+
| Steve Butler Voice: 206-464-2998 |
| The Seattle Times Fax: 206-464-2905 |
| PO Box 70 Internet: sbut-is@seatimes.com |
| Seattle, WA 98111 Packet: KG7JE @N7FSP.WA.NA |
+----------------------------------------------------+
------------------------------
End of Ham-Ant Digest V94 #179
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