QRZ! Ham Radio 4/QRZ Ham Radio Callsign Database - Volume 4.iso/digests/antenna/940351.txt

Internet Message Format | 1994-11-13 | 17KB

Date: Fri, 21 Oct 94 04:30:25 PDT
From: Ham-Ant Mailing List and Newsgroup <[e-mail]>
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Subject: Ham-Ant Digest V94 #351
To: Ham-Ant


Ham-Ant Digest              Fri, 21 Oct 94       Volume 94 : Issue  351

Today's Topics:
                                (none)
                         7db for $7 (2 msgs)
                         ACURATE ROTATORS ???
                             AEA Isoloop
                   Best wire for dipoles? (4 msgs)
                           Diapole antenna
                          flat plate antenna

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Archives of past issues of the Ham-Ant Digest are available
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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: 20 Oct 94 23:22:57 GMT
From: [e-mail] (James Hurt)
Subject: (none)

subscribe

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Date: Thu, 20 Oct 1994 13:13:16 GMT
From: [e-mail] (Bill Splaine)
Subject: 7db for $7

I was listening to a conversation on 2m last nite and should have, but didn't,
break in... they wer talking about an antenna found in a somewhat recent (?)
publication.  The article title is about a simple antenna, yagi type I think,
that is supposed to be pretty good and only $7 (less, I guess w/ good  junk
box).... Has anyone else seen this article?  Where was it?

--
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
\         Bill Splaine                E-MAIL  > [e-mail]         /
/        Hewlett Packard              VOICE   > [phone]             \
\      Santa Rosa, CA 95403           FAX     > [phone]             /
/ ALL STANDARD DISCLAIMERS APPLY      PACKET  > N6GHG@KC6PJW               \
\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/

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Date: Thu, 20 Oct 94 23:13:25 -0500
From: John Sokol <[e-mail]>
Subject: 7db for $7

the reference is to the April 1993 issue of QST magazine.(page 54 and 55) I
have built this antenna myself and am quite happy with the results. I live
in a basement apartment and when the antenna is used, I place the unit on
my porch railing and communications are in order. My total cost was less than
20 bucks, only because I do not have a junk box---everything new from the
local hardware/home superstore.
Good luck with the build.......I'll fax a copy to you in the a.m.

John Sokol
KE4KPV

NO .sig applicable

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Date: Thu, 20 Oct 1994 07:11:04 +0000
From: [e-mail] ("Anthony R. Gold")
Subject: ACURATE ROTATORS ???

In article <[e-mail]>
           [e-mail] "Keith Laaks" writes:
>
> I read somewhere that most of the 'commercial' rotators is not capable of
> rotating with an acceptable accuracy for EME. Apparently you need the
> rotator to be able to rotate to within 0.5 or 0.25 of a degree (in both
> planes).
>

Nothing like that with a yagi with something like a 10 degree beam
width! Now if you were steering a 40 ft cable system head satellite dish,
THEN you'ld need that sort of accuracy!

What ARE you planning on trying to point at the moon?

--
Tony, G3SKR & AA2PM

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

Date: 20 Oct 1994 08:45:03 -0400
From: [e-mail] (WA8MSF)
Subject: AEA Isoloop

In article <[e-mail]>, [e-mail] (Don Anderson)
writes:

I have been using the newer AEA Iso-Loop for about a year here in Ohio.
It is mounted on a 2" O.D. pipe that sticks out sideways at about 110' on
my
VHF/UHF SSB/CW tower.  It is horizontally polarized and placed about 7'
away horizontally from the mass of the tower structure.

I also have a 75 meter 1-wavelength quasi-horizontal loop for 75/40
regional
nets and chit-chat.  My radio's tuner can make the wire loop work from 80
thru
10, at least it takes the power.

In no instance has the wire loop (80',40',45',50' at corners) ever
exceeded the
Iso-Loop in received signal strength.  About 5% of the time they are
exactly
equal.  20% of the time the Iso-Loop @ 110' is more than 15dB better than
the
wire antenna being operated on higher modes.

Many will say that this is comparing apples with bumble-bees and they are
quite right.  But I don't think that it matters for purposes of
illustration.

The only thing that has ever gone wrong with the Iso-Loop was a nearby
lightning strike that took out the control box and wall-power-supply.  I
have been
using the controller that came with my unused "original" Iso-Loop.  The
"original" had compression joints in the loop that would go
high-resistance
(an extra milli-Ohm or two was real bad) so I didn't put it way up on the
tower
where it would be difficult to service.  The new one has been up since
July '93.

The present installation looks like a Godzilla fly swatter sticking out
near
the top of the tower.  It works great.  I had a JA come back to me on 10
right as I was testing the installation and he refused to believe I was
using only
a compact loop.  Said I was 20dB louder that any other W/K he was hearing.
That doesn't prove anything except maybe I had the lowest radiation angle
of any station that he had tuned across just then. (Height helps alot)

In sum, the only hadicap is that it won't take any more power than the
FT-1000D.  If it had 150KV tuning cap, it would be even neater, but I
won't
hold my breath for someone to make one like that.

73
Mike - WA8MSF
Cincinnati, Ohio

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

Date: 20 Oct 1994 11:22:20 GMT
From: [e-mail] (Mike Staples)
Subject: Best wire for dipoles?

For 1/2 wavelength wire dipoles in the 10 - 80 meter range, whats the best
type of wire to use? Solid? Stranded? Insulated? Non-insulated?  Also, what's
"Copperweld" and what does "hard drawn" mean?


                                            Thanks!

                                                 Mike

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

Date: 20 Oct 94 15:34:15 GMT
From: [e-mail] (hamilton on BIX)
Subject: Best wire for dipoles?

[e-mail] (Mike Staples) writes:



>For 1/2 wavelength wire dipoles in the 10 - 80 meter range, whats the best
>type of wire to use? Solid? Stranded? Insulated? Non-insulated?  Also, what's
>"Copperweld" and what does "hard drawn" mean?

Most folks, I think, choose Copperweld, which refers to a steel wire
with a copper plating.  It combines terrific strength (no drooping
from stretch) with the electrical characteristics of copper.  Next
choice is hard-drawn, which refers to a copper wire that's hardened
so it won't stretch as much as ordinary copper wire.  (I'm no
metalurgist, so don't ask me how it's done.)

The one slight advantage of hard-drawn over Copperweld is that a
steel wire is a little harder to work with:  it's springier, tends
to kink more easily and just generally more of what it wants, not
necessarily what you want.  That said, both my wire antennas are
Copperweld and I got them up without too much trouble.

What you should not choose is ordinary copper wire.  It's just
going to stretch too much.  Also, do not use a solid wire.  You
must use a stranded wire or it'll break too easily.  (The idea
here is that if part of the metal fatigues and begins to crack,
it'll go thru that whole strand.  If that's the only strand, the
wire breaks.  But if there are multiple strands, the crack has
no way to just continue right on thru.)

Re: insulation or enameling, the ARRL antenna book does recommend
this if you're in an area with acid rain, but otherwise it makes
little difference.

Regards,
Doug Hamilton  KD1UJ  [e-mail]  Ph 508-358-5715  FAX [phone]
Hamilton Laboratories, 13 Old Farm Road, Wayland, MA  01778-3117, USA

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

Date: Fri, 21 Oct 1994 00:20:24 GMT
From: [e-mail] (Michael A McCarthy)
Subject: Best wire for dipoles?

hamilton on BIX ([e-mail]) wrote:
: [e-mail] (Mike Staples) writes:
: >For 1/2 wavelength wire dipoles in the 10 - 80 meter range, whats the best
: >type of wire to use? Solid? Stranded? Insulated? Non-insulated?  Also, what's
: >"Copperweld" and what does "hard drawn" mean?

: The one slight advantage of hard-drawn over Copperweld is that a
: steel wire is a little harder to work with:  it's springier, tends
: to kink more easily and just generally more of what it wants, not
: necessarily what you want.  That said, both my wire antennas are
: Copperweld and I got them up without too much trouble.

   The disadvantages of Copperweld are that it tends to "rust" out over
time.  Pure hard drawn copper forms a green oxidation on the surface and
forms a protective barrier.  I have a piece of #10 solid hard drawn copper
that has been in use off and on since 1963 (handed down from my dad).
A copperweld dipole I had up rusted out after about 6 years.

: What you should not choose is ordinary copper wire.  It's just
: going to stretch too much.  Also, do not use a solid wire.  You
: must use a stranded wire or it'll break too easily.  (The idea
: here is that if part of the metal fatigues and begins to crack,
: it'll go thru that whole strand.  If that's the only strand, the
: wire breaks.  But if there are multiple strands, the crack has
: no way to just continue right on thru.)

   I'll agree with most of the above with the exception of solid vs.
stranded.  Stranded copperweld is a good choice and is available from
many outlets at reasonable prices.  Solid copperweld is almost impossible
to deal with.  Solid hard drawn copper is my 1st choice but is usually
very difficult to obtain at reasonable cost.  Solid normal copper will
stretch more than I would like.  Stranded copper is a better choice if
that is all that's lying around.

: Re: insulation or enameling, the ARRL antenna book does recommend
: this if you're in an area with acid rain, but otherwise it makes
: little difference.

Most normal PVC insulation will melt at high power levels.  Stranded, tinned
#10 or 12 copper wire makes a great dipole and can usually be found
at very reasonable prices at flea markets, as long as you don't mind the
insulation melting off the first time you fire it up with 1.5KW.

I guess the bottom line is use something in the #10 to #14 range.  I use
whatever I happen to find at the flea market at a good price.

--
============================ Give every man his Dew ==========================
--... ...-- Michael A. McCarthy
Everest Engineering Corp., Consultants, 4 Barnes Circle, Marlborough, MA 01752
Voice [phone] - E-mail to [e-mail]

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

Date: 21 Oct 1994 04:25:09 GMT
From: [e-mail] (Gary T. Schwartz)
Subject: Best wire for dipoles?

Mike Staples ([e-mail]) wrote:


: For 1/2 wavelength wire dipoles in the 10 - 80 meter range, whats the best
: type of wire to use? Solid? Stranded? Insulated? Non-insulated?  Also, what's
: "Copperweld" and what does "hard drawn" mean?


:                                             Thanks!

:                                                  Mike
******************************************************************************

Hi Mike!

I would definitely use the stranded,  it is much less prone to breaking.
As far as the type, it depends on your situation.  If the antennas are
going to be strung between two supports such as towers and/or trees, with
nothing in between, then I would opt for the copper-weld.  It will last
forever.  If, on the other hand, you will be stringing this through trees
the hard drawn will be much easier to handle.  A word of warning about
copperweld:  Be careful and wear safety glasses!!  This stuff is so
springy that it WILL snap back like a spring when you cut it or if you
accedently let go of an end.  You could very easily get an end stuck in
your eye.  Be CAREFUL!

Regarding insulation, my experience has shown that if the antennas are
going to be strung through trees, the insulation is necessary.  I once had
an 80M dipole made of un-insulated stranded wire strung through the trees.
 It worked awful!!  I rebuilt it using the same size wire, the same
lengths and the same supports and it worked much better, like night and
day!  I think this may be due to the moisture in the trees providing a
lower impedance path to ground.  I'm still not sure.  I have also noticed
that the time of year makes a difference.  In the spring/summer the trees
have much more moisture in them near the surface of the limb than in the
fall/winter.  Nothing real scientific here, just observations.
Finally, I prefer to use Teflon insulation.  It is so slippery that snow
and ice tend to slide off rather than accumulate.

Good luck!!
73
Gary K9GS
[e-mail]

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

Date: Thu, 20 Oct 1994 12:27:06 -0400
From: [e-mail] (Steve Byan)
Subject: Diapole antenna

Unless your receiver is unusually insensitive, you do not need a resonant
antenna for SWL receiving. Therefor an end-fed random-wire antenna is
fine. The trap dipole isn't necessary.

You are unlikely to get a horizontal dipole mounted high enough for good
reception of low-angle DX stations on the tropical bands. A horizontal
dipole has to be mounted at least 1/2 wavelength above ground to have good
sensitivity at a low angle. That's 30 meters or about 100 feet for the 60
meter band.

Regards,
-Steve

--
Steve Byan                                  internet: [e-mail]
Hitachi Computer Products (America), Inc.
1601 Trapelo Road                           phone: [phone]
Waltham, MA 02154                           FAX: [phone]

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

Date: Fri, 21 Oct 1994 00:28:40 GMT
From: [e-mail] (Ron Jamtgaard)
Subject: flat plate antenna

  I am looking for a flat plate antenna to receive DBS tv
signals( 12 GHz ).  This is for research into mobile communications.
I read about a 350mm flat plate antenna with a gain of 31dbi, but the
book I read about this in made no reference to the manufacturer.
I think the book was called DBS Satellite Systems.
--
                                             [e-mail]

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

Date: Thu, 20 Oct 1994 16:41:26 +0000
From: [e-mail] (Ian G3SEK)

References<37vjjc$[e-mail]> <[e-mail]>, <[e-mail]>
Reply-To: [e-mail]
Subject: Re: Antenna Analyzers/Old QST magazines

In article: <[e-mail]>  [e-mail] (Gary Coffman)
writes about the AEA version:

> What I *meant* to say was that it can't display VSWR over 10:1 *or*
> return losses > 50db. The former is more of a limitation than the
> latter.

Since the errors in VSWR/return loss measurements increase rapidly at
both low and high VSWRs (high and low return losses, respectively)
it seems very likely that the readings are unreliable long before they
hit the limits built into the display software.

After all, it needs precision lab equipment to measure *real* return
losses better than 35-40dB, and the same applies at the opposite end of
the scale too.

Question is: what kind of bridge or other vector impedance sensor circuit
is inside the Autek and AEA instruments? Maybe it's different at HF
and VHF, but the RF circuit is the interesting part - the rest is just an
ADC and software.

Come on, Gary, let's see your company break one open!


 73 from Ian G3SEK               |  Editor,  _The_VHF/UHF_DX_Book_
 Abingdon, England               |
 [e-mail]       | "In Practice" columnist for RadCom (RSGB)

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End of Ham-Ant Digest V94 #351
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