QRZ! Ham Radio 4/QRZ Ham Radio Callsign Database - Volume 4.iso/digests/antenna/940293.txt

Internet Message Format | 1994-11-13 | 14KB

Date: Sat,  3 Sep 94 04:30:12 PDT
From: Ham-Ant Mailing List and Newsgroup <[e-mail]>
Errors-To: [e-mail]
Reply-To: [e-mail]
Precedence: Bulk
Subject: Ham-Ant Digest V94 #293
To: Ham-Ant


Ham-Ant Digest              Sat,  3 Sep 94       Volume 94 : Issue  293

Today's Topics:
                   AC House wiring used as antenna?
                         CT:Power Handling of
                        Matching 50 ohms to 2
                 Secret's of the Collinear Vertical?

Send Replies or notes for publication to: <[e-mail]>
Send subscription requests to: <[e-mail]>
Problems you can't solve otherwise to [e-mail].

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: 2 Sep 94 08:28:47
From: ihnp4.ucsd.edu!news.cerf.net!nntp-server.caltech.edu!netline-fddi.jpl.nasa.gov!news.byu.edu!gatech!newsxfer.itd.umich.edu!news1.oakland.edu!rcsuna.gmr.com!rcsuna.gmr.com!vbreault@network.
Subject: AC House wiring used as antenna?
To: [e-mail]

In article <343l6l$[e-mail]> [e-mail] (Russ Blaine) writes:

   I have seen adapters that plug into an AC outlet in a house which use the
   houses's AC wiring as an antenna. Would this work? I am interested in
   this mainly for use on a CB, but I'm also interested in it for general
   scanner use. Any advice or comments appreciated.

I don't recommend it.

Some people spend a great deal of time and effort engineering antennas.
The elements' length, spacing and their angular placement all contribute
to the design goals.  Those goals are usually to work well at the
frequency(ies) of interest and to reject other (noise) frequencies.

Household wiring is not installed with those goals in mind.

Furthermore, household wiring is the best place to receive electrical
noise from your own and your neighbors' electrical appliances.  Things
like aquarium heaters, vacuum cleaners, light dimmers and other typical
appliances make the electrical wiring a very noisy signal source.

I work part-time for Radio Shack.
Radio Shack markets those adapters.
I have refused to sell them.

--
Val Breault - N8OEF - [e-mail]   \      /|
Instrumentation dept  GM NAO R&D Center   \    / |
My opinions are not necessarily those of   \  /__|
GMR nor of the General Motors Corporation   \/   |___

------------------------------

Date: Thu,  1 Sep 94 15:19:00 -0500
From: ihnp4.ucsd.edu!dog.ee.lbl.gov!agate!iat.holonet.net!cencore![e-mail]
Subject: CT:Power Handling of
To: [e-mail]

TO>: Precisely.  The situation I was referring to, and the one Zack was
TO>: discussing is one in which the loss per unit length is so high as
TO>: to bring about melting of the insulation material.  Assuming the

TO>??  That sure isn't the way I interpret it!  If you soften
TO>polyethelene, particularly if the length of line is being flexed,
TO>or is under some stress from taking a sharp corner, then the center
TO>conductor can move off-center.  This can result in reflections
TO>which contribute to further degradation.  This is not necessarily a
TO>catastrophic failure but can be a gradual one.  Polyethelene does
TO>not suddenly turn from solid to liquid at some temperature.

Melting, softening.  What's the difference whether sudden or
gradual?  Cable whose central conductor has wandered off center
is junk cable.   I call that failure produced by operating
it beyond its capability.  My main point is that by the time
you have stressed the cable to arrive at this condition,
I believe you have certainly exceeded its *temperature*
rating as a result of having exceeded its voltage rating.

BTW most polyethylene cables are rated at a top temperature of
80-85deg. C.   This below the softening temperature.

TO>So why would it be unimportant to understand how to operate a
TO>line to _avoid_ failures, either sudden or gradual?  This only
TO>convinces me the more that Zack's original question was a very
TO>reasonable one.

To avoid failures operate below the manufacturer's maximum ratings.

---
 │ SLMR 2.1a │ Any academic pursuit with "Science" in its name isn't one

------------------------------

Date: Thu,  1 Sep 94 15:38:00 -0500
From: ihnp4.ucsd.edu!dog.ee.lbl.gov!agate!iat.holonet.net!cencore![e-mail]
Subject: Matching 50 ohms to 2
To: [e-mail]

MA>Another option is to use 50-ohm coax from each antenna to your switch
MA>box, and then include the quarter-wave 75-ohm matching sections as
MA>part of the switch box.  When you are using them individually, you do
MA>not use the 75-ohm sections.  When you feed them both, go through the
MA>75-ohm sections.

MA>As long as the antennae are 50 ohms, an arbitrary length of 50 ohm
MA>coax will not affect the impedance matching properties of the 75 ohm
MA>quarter-wave sections.

So long as the antennas are operated separately this is OK.
All bets are off when operating them together if you calculate
impedances as you have.

If the two antennas are in proximity of each other the effect
of mutual impedance must now be considered.  Now you get input
impedances quite different from what you expect nor is it likely
the phase difference will be the same as the electrical length
of the interconnecting line.

--k2bt

---
 │ SLMR 2.1a │ The paper is always strongest at the perforations.

------------------------------

Date: Thu, 1 Sep 1994 17:31:44 GMT
From: news.cerf.net!gopher.sdsc.edu!nic-nac.CSU.net!charnel.ecst.csuchico.edu!yeshua.marcam.com!zip.eecs.umich.edu!newsxfer.itd.umich.edu!europa.eng.gtefsd.com![e-mail]
Subject: Secret's of the Collinear Vertical?
To: [e-mail]

Gene Wolford ([e-mail]) wrote:
: Secrets of the ultimate antenna?
: (For uhf / vhf repeater use)

: Since everybody and their brother seems to be bragging about their super gain
: Japanese dual band collinear antenna, I thought I'd read up on them.
: Sadly, though they are incredibly popular, such designs don't appear in the
: ARRL antenna book. (I wonder why?)

: Anyway, digging back, I found that there was an antenna called the
: "Collinear-Coaxial vertical" in the 1974, 13th edition of the ARRL
: antenna book, page 248. It's also referenced in the Oct. 1984 QST, page 39.
: It is a multi-element, stacked half wave vertical with gain on the order of
: that claimed by the Japanese verticals, single band only.

: Has anyone built this thing?
: Why was it dropped from the Antenna Handbook?
: Why isn't something updated in it's place?

I've built them for 2m and 440.  I wrote up my notes and posted them
here a couple months ago.  If enough folk want them again, I'll post
them; otherwise, I'd prefer to email them.  The ARRL writeup makes
some assumptions that aren't always valid and doesn't tell you much
about just _how_ the antenna works, so you don't know what to do if you
want to use fewer or more sections or feed the antenna in the middle
instead of the end (for a better pattern as frequency changes).  The
writeup I did tries to make things like that clearer, and explains what to
do to use things like foam coax and gives an alternate matching method or
two.  The design is a single-band one; I think for homebrew for most hams,
it's best to stick to that.  The coaxial collinear is particularly cheap
to build from readily available materials (mostly just coax, plus some
method of support), and I think it would be much trickier if you must have
it be dual-band with good gain on each band.  In fact, my writeup should
let you build one for lower bands like 10 or 15 meters:  if you can hang
about 60 feet of coax vertically and away from other conductors, it
could give you 4 or 5 half-waves on 10 meters, not a bad omnidirectional
antenna.

73, Tom -- K7ITM
[e-mail]

------------------------------

Date: Thu, 01 Sep 1994 18:32:48 -0400
From: ftpbox!mothost!lmpsbbs!NewsWatcher![e-mail]
To: [e-mail]

References <Pine.3.89.9408240648.A17522-0100000@netcom>, <[e-mail]>, <[e-mail]>e
Subject : Re: Lightning

In article <[e-mail]>, [e-mail] (Warren Gay) wrote:

>
> When I last moved, I put 110VAC relays in a power distribution box for
> this purpose. The relay switches via heavy duty contacts, 3 lines -
> 2 - 110VAC + 1 Neutral. This of course switches the 220VAC for my
> linear (that I don't have yet) in the process.  The relay was one of
> two lucky finds at a ham-fest.
>

It's a good thing that you are located in Canada, but not safe.  Here in
the USA you are not permitted to ever interrupt the neutral lead, since it
is the grounded side (center, actually) of the feed.

> The relay is wired such that it latches itself on. You push one button
> to activate the shack, and the relay holds itself on, as long as the
> one live wire is alive (relay is tied to one side only).  Push another,
> and the relay drops out, and everything in the shack goes out. This
> sooths the XYL, in case something starts smoking!  Also conveniant when
> I go away for a while.
>
> The feature I like about this the best is not the buttons. Its the fact
> that when the hydro goes OFF on me, it STAYS OFF, until I get home and
> reset it.  This protects my computer and packet gear, if I should leave
> it running that day.  There is nothing worse than the power company
> thumping the power on and off.
>
> Finally, although I don't always do it, I do disconnect my antenna. But
> with the relay setup, I can disconnect the shack from the lines with a
> press of the button. If I forget, then the first little power glitch
> will drop the self latching relay out.
>
> The system is not perfect, but I must say that it works very well for
> me.  The hydro dropout feature has saved me on many occasions.
>
> The current setup has a couple of draw backs however:
>
>     1. if only the "other" line drops, then there is the chance
>        that the relay will stay holding.  I doubt this happens
>        often in practice.
>

 I suggest a 220VAC coil so that loss of voltage on either line will drop
the load, but ALWAYS leaving the neutral connected.

>     2. If you lose power in only one line coming into the house for
>     a long length of time (like during winter ice storms!), there
>        is a chance that I cannot use it in the shack if it happens
>        to be the "other" line. That is, the line that is not used
>        for the self latching relay.
>
>        I havn't done it yet, but I could add a cross over switch for the
>        relay's benefit, so I could at least use the one live line
>        in this kind of emergency.
>
> Anyhow, I would highly recommend this setup to anyone else that is
> wiring up their shack.  I have the relay box feed all the outlets
> in the shack. The only exception was one outlet, that I wanted on
> all the time (for light/clock etc.).
>
> Not exactly lightning protection to the max, but it helps. I particularly
> like being around when my systems come back up.  This way I can deal with
> the damaged file systems etc. first, before they go back into use (assuming
> it boots itself up ok).
>
> 73s.
>
> --------------------
> Warren W. Gay VE3WWG        John Coutts Library Services Limited
> [e-mail]            Niagara Falls, Ontario, Canada
> (or [e-mail], [e-mail])


I used that same system, including two other NC safety switches in series
with the relay coil, for over twenty years.   I found the circuit in the
1956 ARRL handbook where I'm sure it had been resident for many years
before.

--
Karl Beckman, P.E.                  <     If our English language is so  >
Motorola LMPS.RNSG.Analog Data      <  precise, why do you drive on the  >
(Square waves & round corners)      <  parkway and park on the driveway? >
   Opinions expressed here do not belong to or represent Motorola Inc.
Amateur radio WA8NVW                        NavyMARS NNN0VBH @ NOGBN.NOASI

------------------------------

Date: 2 Sep 1994 14:55:49 GMT
From: ihnp4.ucsd.edu!agate!howland.reston.ans.net!math.ohio-state.edu!jussieu.fr!univ-lyon1.fr!swidir.switch.ch!scsing.switch.ch!news.dfn.de!news.belwue.de!news.uni-stuttgart.de!deap1032@network.
To: [e-mail]

References <33l9l3$[e-mail]>, <33v088$[e-mail]>, <[e-mail]>r
Subject : Re: One-way propagetion?

In article <[e-mail]>,
Steve (Stephen) G. Miller <[e-mail]> wrote:
>
>Chapter 7.12.2 of Ionospheric Radio by Kenneth Davies states non-reciprocal
>propagation on HF may occur because of the interaction between the magnetoionic
>waves and the antennas.
>
...I am sure there is a misprint, should read electromagnetic wave and not
antenna. Anyway, Faraday rotation may cause strange fading effects, which could
be non-reciprocal (the natural circulator). Giving the high frequency
selectivity of fading, observation of such effects would require
full bk operation and the exchange of accurate signal reports. May be just
transmit the others stations s-readings... would be nice to try.

73, Moritz

------------------------------

End of Ham-Ant Digest V94 #293
******************************