QRZ! Ham Radio 4/QRZ Ham Radio Callsign Database - Volume 4.iso/digests/antenna/940274.txt

Internet Message Format | 1994-11-13 | 18KB

Date: Mon, 22 Aug 94 04:30:28 PDT
From: Ham-Ant Mailing List and Newsgroup <[e-mail]>
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Reply-To: [e-mail]
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Subject: Ham-Ant Digest V94 #274
To: Ham-Ant


Ham-Ant Digest              Mon, 22 Aug 94       Volume 94 : Issue  274

Today's Topics:
                         AEA IsoLoop (2 msgs)
               Are you experienced: With CABL-X-PERTS?
                       Isoloop problems anyone?
                         MFJ vs. AEA IsoLoop?
                        Self-supporting masts
                             SG-Smartuner
                        Should feedline lengh
               Should feedline length change the VSWR?

Send Replies or notes for publication to: <[e-mail]>
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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: 21 Aug 1994 20:47:35 GMT
From: ihnp4.ucsd.edu!swrinde!howland.reston.ans.net!wupost!udel!news.sprintlink.net!tequesta.gate.net!inca.gate.net![e-mail]
Subject: AEA IsoLoop
To: [e-mail]

I am moving to a community where the antennas is a (no)^2. But I am planning
to buy an AEA IsoLoop and set it up in my attic (This is a single story in
Orlando, FL).  I would like to hear your experiences (good and bad) of the
IsoLoop.

TNXs de Jose
KP4FMD Orlando, Fl.

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

Date: 21 Aug 1994 19:11:01 -0400
From: ihnp4.ucsd.edu!swrinde!howland.reston.ans.net!sol.ctr.columbia.edu!news.kei.com!eff!wariat.org!malgudi.oar.net!swiss.ans.net!newstf01.cr1.aol.com!search01.news.aol.com!not-for-mail@@.
Subject: AEA IsoLoop
To: [e-mail]

In article <338eh7$[e-mail]>, [e-mail] (Jose Rivera)
writes:

Well, I have had my ISOLOOP 2 weeks, and am satisfied with it.  I live in
a condo, and am on the third floor, and I use my ISOLOOP indoors, and have
worked both coasts with it.  I have experienced RF getting into things
though, which I hear is common with all indoor antennas.

Jon - KB5IAV

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

Date: 21 Aug 1994 22:11:09 GMT
From: ihnp4.ucsd.edu!swrinde!howland.reston.ans.net!math.ohio-state.edu!magnus.acs.ohio-state.edu!csn!yuma![e-mail]
Subject: Are you experienced: With CABL-X-PERTS?
To: [e-mail]

In article <[e-mail]> [e-mail] writes:
>Howdy.  I'm looking for feedback on your experiences with an
>outfit called  CABL-X-PERTS, purveyors of cable and wire.
>Specifically, they sell  14 GUAGE SOLID COPPERWELD  for $0.06/ft
>in qtys > 500'.  Anyone have any experience with their products?
>73 de Walt

They're fast shippers.  I called them on Monday morning, I had it Thursday
afternoon (to Colorado).
I don't know about the #14 wire, but the RG-8 foam hasn't given me any
problems.
73, KF0YJ

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

Date: Sun, 21 Aug 1994 14:36:26 GMT
From: ihnp4.ucsd.edu!swrinde!howland.reston.ans.net!wupost!udel!news.sprintlink.net!primenet!slip227.primenet.com![e-mail]
Subject: Isoloop problems anyone?
To: [e-mail]

I am a fairly happy isoloop owner. I have about 87 countries on 10m in 1.5
yrs, two state Novice Roundup (Tech) First places and doing fairly well on
IOTA.

But, the antenna case keeps cracking. First it was around the u-clamp
attaching it to the mast. One the case was replaced it happened again within a
few months. AEA has now added a modification of a metal device so the clamp
has more than plastic to press against.

Now the plastic around the end bolts is cracked.

Let me say that AEA has fixed all my problems at no cost to me. I also live in
Arizona and it gets up into the high 110's during the summer.

Anyhow, just wanted to see it my experience is an isolated event or not.

73, Dean

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

Date: 21 Aug 1994 19:06:02 -0400
From: newstf01.cr1.aol.com!search01.news.aol.com![e-mail]
Subject: MFJ vs. AEA IsoLoop?
To: [e-mail]

In article <[e-mail]>, [e-mail]
(Andy Domonkos) writes:

Andy, thanks for the response,  I didn't say I didn't like the antenna, in
fact I think it's O.K.  The NC ham told me I had a great signal!  I do
have one complaint, it seems that when I try to work phone, I set off my
smoke alarm.
I don't know why this is, it just seems to happen.  Is there a way to
remedy this?  I have tried improving my ground with wires cut to the
appropriate length spread across the room, but no luck.  Would the MFJ 931
artificial ground help? Let me know what you think.

Jon - KB5IAV

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

Date: 21 Aug 1994 11:04:12 GMT
From: ihnp4.ucsd.edu!library.ucla.edu!europa.eng.gtefsd.com!news.umbc.edu!eff!wariat.org!malgudi.oar.net!infinet![e-mail]
Subject: Self-supporting masts
To: [e-mail]

: I would like to avoid using guy wires on the masts.  Does anyone have some
: ideas or experience with self-supporting small masts 20-25 ft. high?  The
: "system" should: 1. be inexpensive, 2. fairly easy to put up, 3. use
: readily availabel materials (eg. lumber yard, etc.).  I have a nice
: post-hole digger that will dig down 5 ft.  I don't plan on mounting
: anything else on these masts.  Thanks in advance for any suggestions.

: 73 Mark KA3LFG

Mark -

I believe a wooden "H" beam made of a 2 x 4 with "flanges" of 1 x 4 would
do the job nicely.  Use construction grade glue, plus nails, to hold it
together.  To splice lengths of 2 x 4, I would use short pieces of 1 x 4
on each side of the splice, glued and nailed.  Also, be sure that the
1 x 4 flanges are continuous over the splice in the 2 x 4.

Coat the bottom end, the part that will be buried, with liberal coatings
of asphalt roofing compound.  Paint the rest with several coats of house
paint.

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"       *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * *

[e-mail]

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

Date: Sun, 21 Aug 1994 08:51:14
From: ihnp4.ucsd.edu!usc!howland.reston.ans.net!wupost!udel!news.sprintlink.net!nwnexus!olympus.net!olympus.net![e-mail]
Subject: SG-Smartuner
To: [e-mail]

In article <3377pi$[e-mail]> [e-mail] (Matti Jokinen) writes:


>QST reported the SG-230 Smartuner to be a good choice for an automatic
>tuner. I am thinking of using it with an IC-735 rig and 15' backstay
>longwire as the antenna in a sailing boat. Does anyone has experiences
>of a similar installation or of that tuner in general?

>________________________
>Matti Jokinen
>Institute of Dentistry
>University of Helsinki
>[e-mail]
>-------------------------

Matti, I have installed dozens of these critters on sailboats and I have never
had a problem, before or after. Just be sure to seal all the cable entrances
so that no water can enter the box. Be sure that no one is hanging on to the
backstay while you are transmitting it really cuts down on your
radiation,very bothersome you know. Also it would improve your radiation a lot
if you installed a ground shoe. I don't know the technical term for this
device (Gary Coffman probably does, sigh.) But it is a ground that attaches to
your hull  and is connected to your rf ground with a thru hull bolt. Get the
largest one you are willing to stick on your hull. The shoe with apprx. 15 sq
ft of ground plane gives the best performance,price ,size ratio. Good luck and
be careful.

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

Date: 22 Aug 1994 02:26:56 GMT
From: ihnp4.ucsd.edu!usc!nic-nac.CSU.net!charnel.ecst.csuchico.edu!yeshua.marcam.com!news.kei.com!ssd.intel.com!chnews!scorpion.ch.intel.com![e-mail]
Subject: Should feedline lengh
To: [e-mail]

In article <[e-mail]>,
Art Harris <[e-mail]> wrote:

>The SWR does not change with line length. >Art N2AH

Hi Art, sounds like you mean well but please reference the definition of
SWR. The reflection coefficient is part of the definition of SWR and
is defined as the square root of the reflected power divided by the
forward power (measured at any point on a transmission line).

Assume a transmission line with 3db loss. Assume half the power at the
antenna is reflected. The reflection coefficient at the antenna will be
the square root of 1/2. The reflection coeffieicnt at the transmitter
will be the square root of 1/8. Clearly the SWR is different at the antenna
and the transmitter. If you transmit 8 watts, 4 watts reach the antenna,
2 watts are reflected at the antenna, and one watt of reflected power
reaches the transmitter end (assume that watt is not re-reflected).
If my 1+rho/1-rho math is correct the _actual_ SWR at the antenna is 5.8
and the _actual_ SWR at the transmitter is 2.1 and a properly functioning
SWR meter will yield those SWR readings. Add another equal length of
transmission line and the SWR measured at the transmitter will be 1.4

The SWR _does_ change with line length. If one doesn't believe it, one
should replace the 70 ft. of RG-58 on a G5RV with the same electrical
length of 9913... both 50 ohms. Especially on the higher frequency bands,
the SWR at the transmitter end will measurably increase, the antenna tuner
will work a little harder, and more power will be radiated. I know... that
was my first step in improving my G5RV.

73, Cecil, KG7BK, OOTC  (Not speaking for Intel)
--
 Intel, Corp.
 5000 W. Chandler Blvd.
 Chandler, AZ  85226

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

Date: 21 Aug 1994 16:14:40 GMT
From: ihnp4.ucsd.edu!sdd.hp.com!col.hp.com![e-mail]
Subject: Should feedline length change the VSWR?
To: [e-mail]

Hank Riley ([e-mail]) wrote:

  <snip>
:
: These SWR *truths* are excerpted from the original series
: of QST articles (beginning April 1973) entitled "Another Look at
: Reflections" by Walt Maxwell, noted RCA space satellite antenna
: designer.  This incredibly well written and technicallly rigorous
: debunking of SWR and transmission line myths was made into a book
: which is available from the ARRL, as well as companion software.
:
  I've got a copy of Maxwell's book and generally agree that its
  pretty good. There are a couple of things to watch out for

  1. There was a significant errata sheet published after the book
     went into print. I believe it was printed in QST. I don't
     know if the book has been revised yet. Maxwell deserves credit
     for making the corrections public, as there is probably no
     book in print today that does not have some error in it.

  2. Maxwell often assumes a conjugate match at the transmitter (generator).
     While this assumption is often true for transmitters operating
     at HF (with the use of antenna tuners and the like), most VHF/UHF
     transmitters have output impedances fixed at a nominal 50 ohms.
     (Yeah, I know, there is no perfect 50 ohms.)


Bob Witte / [e-mail]  / Hewlett Packard PMO / KB0CY  / [phone]

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

Date: 21 Aug 1994 16:06:13 GMT
From: ihnp4.ucsd.edu!sdd.hp.com!col.hp.com![e-mail]
To: [e-mail]

References <32um8c$[e-mail]>, <[e-mail]>, <332bp9$[e-mail]>
Subject : Re: Should feedline length change the VSWR?

John F. Woods ([e-mail]) wrote:
: [e-mail] (C. C. (Clay) Wynn, N4AOX) writes:
: >As you undoubtedly know, all of those rules, principles, and laws are just
: >abstract mathematical descriptions of relationships that one thinks one
: >observes in nature.  Sometimes they're accurate and longlasting, other times
: >not.

: You are cordially invited to list concrete examples where classical E&M fails
: to predict the behavior of antennas as used by hams, with special attention
: to where it mistakenly predicts the purely classical effect called SWR.  Assume
: that one is running sufficient power that the classical approximation holds.

: >Try explaining RF
: >propagation to an avant garde particle physicist using classical
: >electromagnetic theory.  In the end he may think you are talking folklore and
: >you may think he is talking magic.

   This is what makes the technical fields so interesting and challenging..
   knowing when/how/if to apply the right model to a problem. For example,
   someone writing microcontroller code would be hampered by (only) a detailed
   model of the microcontroller's switching transistors (too much detail
   in the model for the problem at hand). On the other extreme, the
   designer of the switching transistor probably needs a darn good model
   for the subtle effects that can occur.  And the person who developed
   the semiconductor fab process probably needs a model on a different
   level.

   No one model is "right". On the other hand, if the software designer
   starts blaming coding defects on, say, breakdown of the gate oxide
   of the transistor, look out :-)

Bob Witte / [e-mail]  / Hewlett Packard PMO / KB0CY  / [phone]

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

Date: Sun, 21 Aug 1994 23:02:16 +0000
From: ihnp4.ucsd.edu!swrinde!pipex!demon!arkas.demon.co.uk![e-mail]
To: [e-mail]

References <[e-mail]>, <332quu$[e-mail]>, <[e-mail]>
Reply-To : [e-mail]
Subject : Re: Does 73 Magazine have

Ham Radio magazine.  Haven't picked up a copy for years.  Is it still published?

--
Michael J Dower
                                    'Quoth the raven, "Never more".'  ... Poe

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

Date: 21 Aug 1994 22:21:03 GMT
From: ihnp4.ucsd.edu!sdd.hp.com!col.hp.com!csn!yuma![e-mail]
To: [e-mail]

References <330m0d$[e-mail]>, <[e-mail]>, <332quu$[e-mail]>
Subject : Publishing (was Re: Does 73 Magazine have

In article <332quu$[e-mail]> [e-mail] (Jim Garver) writes:
>I don't think
>QST would publish my stuff because they don't have room and are too picky.
>I'm not a contester so CQ is out.  That leaves Wayne's rag.

You forgot Internet.  Publish it here.  No editors!
Maybe fax diagrams to those who want them.

Galen, KF0YJ

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

Date: Mon, 22 Aug 1994 04:13:33 GMT
From: ihnp4.ucsd.edu!swrinde!howland.reston.ans.net!sol.ctr.columbia.edu!news.kei.com!ub!freenet.buffalo.edu![e-mail]
To: [e-mail]

References <330m0d$[e-mail]>, <[e-mail]>, <332quu$[e-mail]
Reply-To : [e-mail] (Kurt Rieder)
Subject : Re: Does 73 Magazine have


In a previous article, [e-mail] (Michael J Dower) says:

>Ham Radio magazine.  Haven't picked up a copy for years.  Is it still published?
>
>--
>Michael J Dower
>                                    'Quoth the raven, "Never more".'  ... Poe
>
No,  not for 3 -4 years.  The key person died suddenly and shortly thereafter
the staff started to peel away.  Finally, the publication together with all
the rights were sold to CQ magazine.  At the time it was said that CQ would
carry on the tradition... what a joke that was.

I thought it was a great publication, have about 90 % of the issues, and
still use them.

Kurt
--

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

Date: Mon, 22 Aug 1994 01:44:57 GMT
From: ihnp4.ucsd.edu!swrinde!emory!wa4mei!ke4zv![e-mail]
To: [e-mail]

References <332quu$[e-mail]>, <[e-mail]>, <[e-mail]>
Reply-To : [e-mail] (Gary Coffman)
Subject : Re: Does 73 Magazine have

In article <[e-mail]> [e-mail] writes:
>Ham Radio magazine. Haven't picked up a copy for years. Is it still published?

Sadly, no. CQ bought it and closed it. All they wanted was to assume the
subscriber list to temporarily boost their circulation figures and enhance
ad revenue. I suspect few _Ham Radio_ subscribers renewed CQ after their
subscriptions ran out.

CQ did throw us a sop though. They publish _Communications Quarterly_.
As the name suggests, it comes out 4 times a year, and it's of moderately
good technical quality. About the best US amateur publication still in
print as a matter of fact. Of course the $9.95 cover price is somewhat
off putting.

If your interest in radio is even moderately technical, your best bet
is to subscribe to the RSGB magazine, or if you read Japanese, to the
Japanese _Ham Radio_ magazine. Both are much superior to any of the
remaining US publications.

That leads me to a question for our non-US readers. What is the best
amateur radio magazine in the world? Capsule reviews of non-US magazines
would be most welcome.

Gary
--
Gary Coffman KE4ZV          |    You make it,     | gatech!wa4mei!ke4zv!gary
Destructive Testing Systems |    we break it.     | uunet!rsiatl!ke4zv!gary
534 Shannon Way             |    Guaranteed!      | emory!kd4nc!ke4zv!gary
Lawrenceville, GA 30244     |                     | [e-mail]

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End of Ham-Ant Digest V94 #274
******************************