QRZ! Ham Radio 4/QRZ Ham Radio Callsign Database - Volume 4.iso/digests/antenna/940333.txt

Internet Message Format | 1994-11-13 | 21KB

Date: Thu,  6 Oct 94 04:30:16 PDT
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Subject: Ham-Ant Digest V94 #333
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Ham-Ant Digest              Thu,  6 Oct 94       Volume 94 : Issue  333

Today's Topics:
                        'No ground' verticals?
                         AEA Isoloop (2 msgs)
                 Antennas are prohibited ...!!!!!!..
                           AUTEK RF ANALYST
                        Feeding Yagis (2 msgs)
      FEEDLINE: A Followup Summary. Thanks to all how responded!
              Mobile HF Antennas - the search continues
                  Need help tuning a 2m SSB antenna
                         Recommend a vertical
                        tower salvage question

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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: Tue, 4 Oct 1994 21:39:41 GMT
From: [e-mail] (Gordon Couger)
Subject: 'No ground' verticals?

In article <[e-mail]>,
Daniel T Senie <[e-mail]> wrote:
>In article <36ra19$[e-mail]>,
>Jukka Tapio Sirvi| <[e-mail]> wrote:
>>In article <[e-mail]> [e-mail] (Alan Cooney) writes:
>>>I'd like to make a 'no ground' vertical antenna for six meters (to
>>
>>The vertical doesn't need radials, if you make it 1/2 wave length long. You
>>have match the impedance though since it isn't 50 ohm (can't recall now
>>how much it is).
>>
>A vertical dipole (bring the coax away at 90 degrees) also works well.
>
A vertical dipole feed in the center is easy to match 83 ohms 1.5 to 1
swr accroding to Elnec. 1 inch tubing .47 wavelength long with the low
end .5 wave lengths off the ground will give a 14 degree take off angle
with good radiation from 5 to 52 degrees which should give good preformance
in for both e and f2 skip. A peice of copper pipe with a wood dowel
in the center and on one end stuck in to some conduit with the coax
running down the center of the lower element will make a nice instalation.

Good luck
Gordon AB5DG
                            Gordon Couger
                            Biosystems & Agricultural Engineering
                            Oklahoma State University
                            114 Ag Hall, Stillwater, OK  74074
[e-mail] 405-744-9763 day 624-2855 evenings
    I do not speak for my employer

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

Date: 4 Oct 1994 14:23:11 GMT
From: [e-mail] ()
Subject: AEA Isoloop

In article <[e-mail]>,
Dave van De Kerk <[e-mail]> wrote:
>I could put an AEA Isoloop at about 20
>feet off the ground (roofline) or I can string another long wire.
>
Dave, you can be sure that a lw is by far the better alternative.
The isoloop really is only for people who dont have the alternative.

If you can afford it, get both and compare. There is a market for second-
hand isoloops, if you want to get rid of it.

73, Moritz

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

Date: Wed, 5 Oct 1994 03:47:20 GMT
From: [e-mail] (Alan Bloom)
Subject: AEA Isoloop

Dave van De Kerk ([e-mail]) wrote:
: Hello,
:     I will shortly be moving into an apartment building which
: is somewhat antenna friendly.  I could put an AEA Isoloop at about 20
: feet off the ground (roofline) or I can string another long wire.  ...
: Issues I am interested in are TVI, RFI, RF safety and "getting out." ...
: There are trees in the complex, and I could probably get a long
: wire about 70 to 100 feet long, probably peaking about 25 to 35 feet
: off the ground.
: Goals are reliable, hassle free S7 20 meter ssb operation out
: to about 600 miles and 30 meter CW DX.  ...

The longwire would probably work better, mainly because of the increased
height.  However, it could be more of an RFI problem if it runs close to a
neighbor's house.

:     Grounding for a long wire worries me.  I'd be 20 feet from an
: Earth ground, and this is dry California soil.  I would also string
: counterpoise wires around the shack ... but ...

For RF purposes, you don't need a ground with the Isoloop.  For the
longwire, feed it 1/4 wavelength from one end with a transmission
line.  Coax would probably work -- sure the SWR would be high, but you
won't zap the coax with 50 watts, and a short run on 20 meters won't
lose you much power.  You could also use twinlead or open-wire feedline
if you have a tuner with balanced output.   (The 1/4-wave wire stub
decouples the feedline from the antenna.)

Awhile back I did a side-by-side comparison of an (original model) AEA
Isoloop and an 80 meter inverted vee with the apex at the same height.
I fed the inverted vee on 20 meters with a tuner and compared it with
the Isoloop on 20 meters.  I could never see any significant on-the-air
difference between the two antennas.

AL N1AL

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

Date: 4 Oct 1994 13:30:51 GMT
From: [e-mail] (Todd Little)
Subject: Antennas are prohibited ...!!!!!!..

In article <36q6d6$s60$[e-mail]>, TI Forum <[e-mail]> writes:
|>Don't WE think it is about time we come out of the ATTIC and
|>STAND up for our rights!!!!!
|>I am also stuck with antenna prohibitions. I would like to fight.
|>Alone it will not work ... but as a group!!!!
|>i think we need to lobby our elected officials. Gather support
|>from other Amateur Radio Operators in similar situations.
|>No I don't propose my home owners association allow me to put up
|>a 40M beam on a town house.   or Stacked 15 element 2M beams. But
|> out the the ATTIC reduces RFI.
|>Well any one elese feel this way!!!

Please feel free to lobby anyone and everyone.  I've personally written
much of the League's hierarchy and the only really favorable response I
got was from Wilson.  Sumner went out of his way to suggest that we need
to work with local officials and demonstrate our value.  The fact that
the local RACES (of which I'm an active member), and many disaster related
agencies spoke on our behalf, the local egomaniacs (you know, our local
elected government) still felt that our town shouldn't live under the
specter of high or large or numerous antennas.  Dealing with a bunch
of self appointed demi-gods doesn't always work.

Personally I beleive this is one of the biggest threats to amateur radio,
but I guess those that already have their contest station antenna farms
don't have to worry about it.

73,
Todd
N9MWB

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

Date: Wed, 5 Oct 1994 16:15:46 GMT
From: [e-mail] (Daniel T Senie)
Subject: AUTEK RF ANALYST

In article <hawley.780935613@aries>,
Chuck Hawley <[e-mail]> wrote:
>[e-mail] (Tom Alldread) writes:
>
>>Greetings to All:
>
>>    I wonder if anyone on this conference has any experience with
>>or heard/seen any reports on the Autek Research model RF-1 Antenna
>>Analyst advertized on page 162 of QST? This sure looks like an
>>interesting alternative to some of the other HF antenna analyzers on the
>>market as it appears to offer continuous coverage from 1.2-35 MHZ,
>>provides either SWR or Z measurement up to 2000 Ohms plus an RF LC meter
>>that according to the advertisement can measure very small values of L
>>and C at actual operating frequencies.
>
>>    It sure would be nice to hear from someone who has either first
>>hand experience or seen an independent product review on this
>>instrument.
>
>>73
>>Tom, VE7TMA
>
>>Very Best Regards,
>
>>T.M. Alldread
>
>It works as advertised. It is kind of homebrew in the way it's constructed,
>but the price is homebrew also. I think all Autek's stuff is sort of
>homebrew, but works as advertised. The limit of 2000 ohms is limiting, but
>usually you can switch to some frequency which allows measurments.
>I can't think of any criticism that could be answered without a much higher
>price.
>

I'll second this. It works well. It has some known limits, but it is possible
to work effectively with them. I ordered one after reading about it in the
Kurt Sterba column in World Radio. If he mentions something as being good,
it is nearly always worth taking a look. If he really nukes something it
is nearly always worth listening to why he did. Not that his opinion is
necessarily the be-all and end-all, but it is always worth taking into
account.

Dan


--
---------------------------------------------------------------
Daniel Senie                 Internet:     [e-mail]
Daniel Senie Consulting                    [e-mail]
508-779-0439                 Compuserve:   74176,1347

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

Date: Wed, 5 Oct 1994 14:06:44 GMT
From: [e-mail] (Zack Lau (KH6CP))
Subject: Feeding Yagis

W Luke Hamaty KQ4QO ([e-mail]) wrote:
: This may be a simple question, but what is the best way to bring the feedline
: away from a 2m yagi so as not to disrupt the tuning and pattern? The
: thing needs to rotate, so it isn't practical to run the coax very far
: horizontally. 1/4 wave might not be bad if it would help. I could bring
: it out behind the reflector, but it wouldn't be very convenient.

Yes, when cost is no object, the preferred method is to bring it out behind
the reflector.  An excellent example is the array of Frank Potts, NC1I. You
can see a picture of it on page 184 of the September 1994 QST.  Actually,
you can do even better by running it out through the boom.  Incidentally,
a coil of coax inside the boom forms an excellent balun if you can figure
out how to get it there.

I've heard that Frank is busy on 432.100 MHz every night after 9 PM
looking for troposcatter contacts.  I know he has worked a station
running 200 watts to a single yagi on EME and is undoubtedly interested
in working similar stations.  Guess the array works :-).
--
Zack Lau  KH6CP/1           2 way QRP WAS
                           8 States on 10 GHz
Internet: [e-mail]   10 grids on 2304 MHz

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

Date: 5 Oct 1994 11:47:57 GMT
From: [e-mail] ()
Subject: Feeding Yagis

In article <36somp$[e-mail]>, W Luke Hamaty <[e-mail]> wrote:
>This may be a simple question, but what is the best way to bring the feedline
>away from a 2m yagi so as not to disrupt the tuning and pattern?

You did not say, if the yagi is intended for horizontal or vertical polari-
zation. in the first case no problem: along the boom and down the mast.
If vertically polarized you have the problem of mounting the yagi in the first
place. Any conductors parallel with the elements will have to be behind
the reflector or at least 1wl away, if not more.

73, Moritz DL5UH

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

Date: Wed, 5 Oct 1994 12:15:51 GMT
From: [e-mail] (andrew peter.cropley)
Subject: FEEDLINE: A Followup Summary. Thanks to all how responded!

 Many thanks to all who responded to my original post.

Most folks said to stay away from 9913 (air dialect and water condensation
problems)

Some said that 214 was worth any additional money over 213.

Some said I should check out CATV hardline.

I checked out this last item on my way home. (I drive past the main office
for the local CATV company.) I expected to get stonewalled and screened
by the receptionist but figured I had to try anyway. The receptionist
was very nice. I explained my want and she understood and said "They throw
lots of that stuff out in the dumpster! go around back and ask for Dave
he'll give you what ever you need". Boy what luck I thought. Got around
back and a gruff man with the name "Dave" sewed in his shirt stopped me
at the door. I again explained what I was looking for. He said no way
instantly. Suggested I check out the local radio shack. It was quickly evident
that I would not be beneficary of any "scraps". I'm sure if I had known him
or had a 6-pack under my arm he would have been more receptive. I will
try to talk to the construction engineer on friday (he/she was out til then)
see if I can talk my way into some stuff.
 I left kinda sad, but there is still hope. My brother in law used to work
for a CATV firm and I asked him if there was anything he could do for me.
He said he would try. There is also the prior mentioned CATV's competitor
across the street from where i work.


  Q.  Anyone know of any "ham-friendly" CATV company in New Jersey??

  Q.  Looking for plans to build 50 Ohm to 75 Ohm converters. I read the
      project in the ARRL hand book (1993) Page 34-23  However it says
      it's for 2-30 MHz. I will be looking for 144 primary and 440 Secondary
      anyone built these transformers for VHF/UHF??  I imagine they are
      close to the same design as the one in the ARRL HB.


   Thanks again all,

     Andy Cropley

     N2ZAM


     [e-mail]

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

Date: Tue, 4 Oct 1994 13:26:24 GMT
From: [e-mail] (Charles R. Sufana)
Subject: Mobile HF Antennas - the search continues

David,

I have tried the 4 resonator adapter and had problems right from the start.  I almost
lost all 4 elements when they helicoptered right off of the MO1 mast; I did have one
damaged beyond repair.  I use 2 MO4 masts each with the 3 resonator adapter mounted on a board that hook up temporarily when I want to run HF mobile.  I use an MFJ tuner to
switch between masts.  Hope this helps.

73,
Charlie Sufana AJ9N  [e-mail]

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

Date: 4 Oct 1994 10:48:40 -0500
From: [e-mail] (Andy Whitcroft)
Subject: Need help tuning a 2m SSB antenna

Hi Netlanders,

I am trying to build a 2m SSB dipole antenna for use in my apartment,
but I cannot find any clear answer to the following questions:

1) Do I just cut the wire(s) so the overall length of the element is
equal to 468/144.2 = 39 inches ( and therfore tuned ?? )

-- OR --

2) how do I tune this antenna with an SWR meter?

3) How can a make the antenna more omni directional?

Any and all help with these questions is appreciated.


         T a H d A v N a K n Y c O e U,   Andy  Whitcroft,  N9KWS

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

Date: 4 Oct 1994 08:25 -0500
From: [e-mail] (SODERMAN.WALTER)
Subject: Recommend a vertical

I would appreciate any recommendations for an excellent vertical antenna.  I
used a Hustler 4BTV many years ago as a novice.  Recently got my general to get
back into the ham activity, and I've noticed antennas like the MFJ-1798,
Cushcraft R-5/R-7, and I'd be interested in some input from folks who have used
these, in addition to other suggestions.  I'll be operating HF from 80 to 10
meters.  The two meter option (as on the MFJ-1798) is of interest, also.
Thanks, in advance, for your replies.

Walt
KE4QOH

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

Date: 4 Oct 94 17:25:36 GMT
From: [e-mail] ("Robert F. Enenkel")
Subject: tower salvage question

I salvaged a bunch of antenna tower sections that someone had put out
for the city garbage.  They have three 1-1/4" galvanised metal pipes
connected with horizontal cross-braces, and are in good condition
with no visible rust.  Unfortunately, in addition to unbolting the
sections from one another, the dismantlers have sawn each of the
former 10-foot sections in two, probably so they would fit into the
garbage truck.  Now, if I machine some short metal rods to fit snugly
into the inside of the tower legs, and drill and bolt the sawn sections
back together using these stubs, would the resulting tower be safe?
Thanks, Robert Enenkel

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

Date: 4 Oct 1994 14:34:08 GMT
From: [e-mail]

References<[e-mail]> <36p7vi$[e-mail]>, <[e-mail]>
Subject: Re: HF antenna questions from newbie ham (semi-long)

In article <[e-mail]>,
Robert Adams <[e-mail]> wrote:
>In article <36p7vi$[e-mail]>,
> <[e-mail]> wrote:
>>Hi Robert, it just depends on what you want your antenna to do.
>
>Not at all. The tuner deals with feedline impedance... not the antenna.

Sounds to me like you believe that feedline impedance measured at the
transmitter is independent of the antenna impedance. Actually, the image
of the antenna impedance is mirrored and transformed all along the feedline.
Change the antenna and you _will_ change the transmitter feedline impedance.
Did you know that the transmitter feedline impedance looking into a 450
ohm characteristic impedance feedline is not at all likely to be 450 ohms?

I wanted maximum broadside gain. That pointed to a 10/8 wavelength dipole.
A 10/8 wavelength dipole is not 50 ohms. I_chose_my_antenna_for_what_I_
wanted_it_to_do and that necessitated an antenna tuner. I suggest that you
read "Reflections", chapter 7... "My Transmatch Really Does Tune My
Antenna." Do you understand conjugate matching? Do you understand that
for high SWRs, 450 ohm ladder-line is near-lossless on HF? Do you understand
that common coax turns into a resistor for high SWRs on 20m?

>>The antenna tuner induces less than 0.5db loss according to the Antenna
>>Handbook, neglible on an 'S' meter.
>
>Don't take one of my classes! On second thought... you can't... I retired.
><grin>

You are welcome in my classes any time. :-)

>>My 88 ft CF dipole works all the way from 80m to 10m
>
>That's all well and good, Cecil. But, you're using a balanced feedline and
>it was an _unbalanced_ feedline that was under discussion. Apples & oranges.

Go back and read the original posting. There was no mention of _unbalanced_
feedline. The original poster asked for suggestions. I am suggesting the use
of near-lossless balanced feedline with an all-band dipole.

>>It has a two-lobe 9dbi gain on 20m and a four-lobe 8 dbi gain on 17m over
>>real ground. It has more gain and a lower angle of radiation on 20m than a
>>20m resonant dipole.
>
>Not meaning to sound flippant... but, just how did you arrive at those
>figures? DBI? Sounds like modeling software... not real world data.

Well, you are using binary encoded ASCII characters here in this posting,
so, meaning to sound exactly as flippant as you, :-) you are not using
real world words.

Of course I am using modeling software. Not many of us have an antenna
range in our back yards... do you? Modeling software is a hellava lot
better than ignorance.

>>I feed it with 450 ohm ladder-line from a 4:1 balun.
>
>And, again, what has this to do with 50 ohm unbalanced lines?

And again, what does unbalanced lines have to do with the original posting?

>>There are a lot of advantages to all-band non-resonant dipoles.
>
>That's what people with all-band non-resonant dipoles invariably suggest.
>;->

If you know of a simpler wire antenna that will perform better than
my 88 ft dipole with 450 ohm ladder-line, I sure would like to hear
about it. 450 ohm ladder-line is less lossy and less expensive than coax.
For $25 I have an all-band HF antenna. For $50 (coax) I could have had a
single-band antenna with less gain... go figure the logic in that.

--
73, Cecil, KG7BK, OOTC   (All my own personal fuzzy logic, not Intel's)

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

Date: 5 Oct 1994 12:02:47 GMT
From: [e-mail] ()

References<36eo65$[e-mail]> <[e-mail]>, <[e-mail]>
Subject: Re: HF antenna questions from newbie ham (semi-long)

>So, where is the power going?  Or do you not believe in the conservation
>of energy?
>
Rich,

Just load up a coat hanger, and put out a long call at high power...
you will certainly soon know where the power is going. Dont expect
answers from DX, though.

73, Moritz DL5UH

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

End of Ham-Ant Digest V94 #333
******************************