QRZ! Ham Radio 4/QRZ Ham Radio Callsign Database - Volume 4.iso/digests/antenna/940090.txt

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

Date: Mon,  4 Apr 94 04:30:16 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 #90
To: Ham-Ant


Ham-Ant Digest              Mon,  4 Apr 94       Volume 94 : Issue   90

Today's Topics:
                            "The Pounder"
                2-meter J Pole Antenna PLans (3 msgs)
                       AEA Hot Rot whip for HT
                         CQ Article on HS-100
                         CQ Article on TH11DX
                        Cushcraft R7 Vertical
                 How to base-feed half-wave vertical?
                      Info wanted on HT antennas

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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.
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Date: 3 Apr 1994 07:44:57 -0400
From: ihnp4.ucsd.edu!usc!howland.reston.ans.net!news.intercon.com!news1.digex.net!access.digex.net![e-mail]
Subject: "The Pounder"
To: [e-mail]

In the current edition of the ARRL's Antenna Book, there is an article on
the construction of a log periodic antenna called "The Pounder."  Because
it's small, lightweight, has some gain and can be directed, it would suit
several of my needs.
  How-some-ever.
  It also looks like a dead short.
  I've read the article several times and cannot understand how the left
side is kept separated from the right.  I know that the construction
calls for a 1/4 inch peice of Plexiglas between the two pieces of
aluminum angle, but nowhere does it tell how to attach the aluminum angle
to the Plexiglas without touching the other peice of aluminum.
  Has anyone made this antenna and can you help with my question?

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Date: Sun, 3 Apr 1994 07:48:37 GMT
From: news.doit.wisc.edu!saimiri.primate.wisc.edu!hpg30a.csc.cuhk.hk!uxmail!dma039.ust.hk![e-mail]
Subject: 2-meter J Pole Antenna PLans
To: [e-mail]

Robert C. Walker ([e-mail]) wrote:


: Anybody suggest to me a good place to find the plans for a 2-meter J
: Pole antenna...I know it's not that difficult to build but need measure-
: ments, etc.

    Please refer to ARRL Handbook.

: If possible, an e-mail reply would be great since I don't check inot
: this group all the time..

: Thanks

Michael Lo

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Date: Sun, 3 Apr 1994 19:36:25 GMT
From: ihnp4.ucsd.edu!library.ucla.edu!csulb.edu!csus.edu!netcom.com![e-mail]
Subject: 2-meter J Pole Antenna PLans
To: [e-mail]

The 2M twinlead J pole plans probably should be in this newsgroup's FAQ
file (if it isn't already!).  Also note that you can scale up or down
the lengths to do other bands like 222 and 440.  I even made one for
the 100MHz FM broadcast band.  You just need 3/4 and 1/4 wavelength, just
do a ratio 2M_lengths/freq = new lenghts for freq.  Worked for me.

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Date: 4 Apr 94 02:42:30 GMT
From: dog.ee.lbl.gov!hellgate.utah.edu!cc.usu.edu!NewsWatcher![e-mail]
Subject: 2-meter J Pole Antenna PLans
To: [e-mail]

In article <[e-mail]>, [e-mail]
(Michael Lo) wrote:

> Robert C. Walker ([e-mail]) wrote:
>
>
> : Anybody suggest to me a good place to find the plans for a 2-meter J
> : Pole antenna...I know it's not that difficult to build but need measure-
> : ments, etc.
>
>     Please refer to ARRL Handbook.
>

can you tell me what page in the 1994 ARRL Handbook I can find it ?


> : If possible, an e-mail reply would be great since I don't check inot
> : this group all the time..
>
> : Thanks
>
> Michael Lo

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Date: 3 Apr 1994 18:18:20 GMT
From: ihnp4.ucsd.edu!usc!sol.ctr.columbia.edu!newsxfer.itd.umich.edu!ncar!csn!col.hp.com![e-mail]
Subject: AEA Hot Rot whip for HT
To: [e-mail]

Stephen C. Trier ([e-mail]) wrote:
: In article <ah301-290394073455@sy_j.pgh.wec.com>,
: Jerry Sy <[e-mail]> wrote:
: >I tested it on an swr meter and its swr is > 3, my rubber duck is < 1.5 !

: You can tune it by adjusting the length, checking it on the meter until
: you find something < 1.5.  Scribe that length into the side of the antenna
: so you can find it again without the meter.

: BTW, there is usually no need to cross-post so widely.  I've set followups
: to just rec.radio.amateur.antenna.

  When I evaluated the Hot Rod (tm) some years ago, its tuning was
  quite broad, so I would expect that fine tuning it with the length
  should not be necessary.  (Evaluation was performed by sweeping it
  with a network analyzer.)

  Also, when I checked a variety of rubber ducks for SWR they never
  had anything close to SWR<1.5, so I suspect that measurement is erroneous.
  Typically, they had SWR below 2.0 at some frequency for about 1 usec,
  then any movement or shift in the ether caused the resonant frequency
  to jump outside the ham band. Has to do with a shortened 1/4-wave without
  a real ground plane.

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

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

Date: 3 Apr 94 15:07:02 GMT
From: agate!howland.reston.ans.net!gatech!wa4mei!ke4zv![e-mail]
Subject: CQ Article on HS-100
To: [e-mail]

In article <[e-mail]> Cecil Moore <[e-mail]> writes:
>Here's a quote from W1ICP's review of the $290 HS-100 mobile antenna
>in CQ, April '94 issue:  "In my long career of working with antennas
>I have only seen a few that were completely tuned from the operating
>position.  By tuned, I mean an antenna that is tuned to resonance so
>that all reactance in the antenna feedpoint is cancelled out at the
>antenna."
>
>Doesn't the conjugate match provided by my antenna tuner cause
>maximum power transfer and tune the antenna system to resonance "so
>that all reactance in the antenna feedpoint is cancelled out at the
>antenna", (assuming near lossless transmission lines).  The antenna
>tuner does not change the SWR on the transmission line but it does
>neutralize the reactance at the antenna feedpoint because the local
>conjugate match at the antenna tuner is transformed all the way to
>the antenna.  Anywhere you look, up and down the transmission line,
>you see -jX one direction and +jX the other.  As Maxwell said,
>"My Transmatch Really Does Tune My Antenna."

Maxwell is, as usual, correct. The problem is that people have become
fixated on the idea that a 1:1 SWR indicates resonance, and fixated
on the related idea that a 1:1 SWR on the transmission line is required
for *matching* the transmitter to the load. Neither is necessarily true.
Instead both are very special cases of more general resonating and
matching solutions. You can indeed tune out the reactance of an antenna
by introducing, at the transmitter end, a reactance of the appropriate
sign, and allowing for the transforming action of the feedline as transformer,
so that a reactance of the right magnitude and sign appears at the antenna
feedpoint to resonate the antenna. And you can match the transmitter
to the antenna with a non-unity SWR on the transmission line. That
just means you're using the transmission line as *part of the matching
network* in the form of a transmission line transformer.

The last time this came up, people complained that you can't use 50
ohm line as a transmission line transformer to match a 50 ohm load,
but of course you can. That's just the degenerate case where the
transformer action is 1:1. In all other cases, the antenna *isn't*
a 50 ohm load (that's the problem), so the 50 ohm cable does act
as *part* of the matching network in transforming the impedance to
match whatever the antenna *is* presenting as its input impedance
to the transmitter's output impedance. (The plate and load controls
on the transmitter, or the adjustments on the tuner which replace
those controls on the current generation of adjustment deficient
radios, does the rest.)

Additional losses due to SWR on the transmission line are almost
always less than the losses incurred by inserting a lumped coil
in the antenna, or using other forms of fixed lumped networks
at the antenna for matching. That's assuming decent quality
coax, of course. RG-58 need not apply.

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     |                     |

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

Date: 3 Apr 94 19:47:47 GMT
From: dog.ee.lbl.gov!agate!news.Brown.EDU!noc.near.net!news.delphi.com![e-mail]
Subject: CQ Article on TH11DX
To: [e-mail]

Someone also reminded me that if you really want a multiband beam, a Quad
has more gain at 1/3 the price of the TH11DX.

73, KG7BK, [e-mail]

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

Date: 3 Apr 94 23:26:22 GMT
From: dog.ee.lbl.gov!ihnp4.ucsd.edu!sdd.hp.com!hpscit.sc.hp.com!cupnews0.cup.hp.com![e-mail]
Subject: Cushcraft R7 Vertical
To: [e-mail]

Jeffrey D. Angus ([e-mail]) wrote:

: In article <2ncmtr$[e-mail]> [e-mail] writes:

:   >  I am intertested in hearing from people who own or use the Cushcraft
:   > R7 Vertical antenna.  I am seriously considering buying one, and I would
:   > like to know what success, if any you have had  with this  antenna.

:   I have their AP-8, it is the one onebody knows about...

:   > It is my understanding that the R7 is designed especially for those who don't
:   > have room for a ground system, like in a condo or 2nd story apartment.
:   >
:   > I DO have room for a ground system, so perhaps there is a different
:   > vertical that would suit  me better.  I am interested in 80-10.

:   They claimed it didn't need radials either. But it assembled with the 10
:   meter section (the one closest to the connector) 3 feet shorter than the
:   chart before it would load correctly on all 8 bands. Once I got that
:   straightened out it still didn't radiate very well. The power must have
:   been going somewhere, but it sure wasn't going towards any radios I knew
:   about.

:   I bought their radial kit (APR-8 I think) and suddenly the antenna works
:   just like you would expect from a vertical. Poorly, but still better than
:   terrible. And yes, I had to add the 3 feet back to the bottom section.

:   73 es GE from Jeff

The AP-8 doe not need radials? interesting. The AP-8 is a quarter wave vertical
and DOES need radials very much. Otherwise it does not work.  The R-7 on
the other hand is a half wave antenna and radials are not needed. I know an
owner of a R-7. It works, but the 30-m and 40-m traps blow and he has trouble
with them. I own a R-5. It works fine, but then the TA-33 gets 1 to 2 S units
more signal.  I can work stations on the TA-33 that I can't even hear on
the R-5. I also use a HF-2V, a quarter wave vertical for 80/40. I have 16
radials and it works ok, but a beam at 70 foot will beat me.

The bandwidth of the R-7 is very narrow on 40 meters, you will need a tunner.
Given limited space, I would opt for the R-7 over the AP-8. If I can lay
down 16 or more radials, at least 30 foot long, I would opt for a AP-8 or
the like. Do not expect much on 80, 40 will be better, the higher bands
should play ok.  But you will never beat a beam.

Jim Hollenback, WA6SDM
[e-mail]

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

Date: 3 Apr 94 19:17:07 GMT
From: dog.ee.lbl.gov!agate!news.Brown.EDU!noc.near.net!news.delphi.com![e-mail]
Subject: How to base-feed half-wave vertical?
To: [e-mail]

Rajiv Dewan <[e-mail]> writes:

>>I'm looking for advice on the best way to match coax to the bottom of a
>>half-wave vertical.  Cushcraft does this for the multi-band R-5 with some type

W5GYJ's method is a great way to feed this antenna. A not as great way but
easier method is to end feed the antenna with 450 ohm ladder line with one
conductor open. This is like the Zeppelin airships used. Be sure to keep
the transmission line a few feet above ground and use an antenna tuner.
Or you could use a 1:4 balun (Hi-imped un/Lo-imped bal) at the antenna base
with a ground under the antenna and then use 450 ohm ladder-line.

73, KG7BK, [e-mail]

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

Date: Sun, 3 Apr 1994 13:54:18 GMT
From: ihnp4.ucsd.edu!usc!cs.utexas.edu!geraldo.cc.utexas.edu!portal.austin.ibm.com!awdprime.austin.ibm.com![e-mail]
Subject: Info wanted on HT antennas
To: [e-mail]

I have a FT-530, and I would like to upgrade the antenna. I'm interested in finding out what others have upgraded to before putting
any money down on a new antenna. I'm interested in a dual-band
antenna, but performance is my primary concern.

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End of Ham-Ant Digest V94 #90
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