QRZ! Ham Radio 5/QRZ Ham Radio Callsign Database - Volume 5.iso/digests/antenna/940368.txt

Internet Message Format | 1994-11-13 | 19KB

Date: Mon,  7 Nov 94 04:30:35 PST
From: Ham-Ant Mailing List and Newsgroup <[e-mail]>
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Subject: Ham-Ant Digest V94 #368
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Ham-Ant Digest              Mon,  7 Nov 94       Volume 94 : Issue  368

Today's Topics:
                       2m/70cm/cellular antenna
                               2m bev.?
               Antenna question!!!!!! PLease HELP!!!!!
                      Best vertical - Butternut?
                        High Sierra Antennas?
          How much directionality to slightly inverted vee?
                     How much range on 80m? 40m?
                    Just say NO to RG58! (2 msgs)
                       RG8 vs "Thick Ethernet"
                         Twinax for feedline

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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: 6 Nov 1994 16:36:14 -0600
From: [e-mail] (William Biggs)
Subject: 2m/70cm/cellular antenna

I noted an earlier post to this newsgroup about the Comet    SB-83
Tri-Band 146/446/cellular antenna. I am considering this as an
alternative to my present Comet B20 plus glass mount cellular.

The stats on the SB83 are better than the B20 for both 146 and 446, plus
my present glass mount supposedly give 3db gain, whereas the SB83 is
listed as 8.4 db with VSWR less than 1.5 .

                B20 + cellular       SB83
146                   2.15 dBi       3.0 dBi
446                   5.0            6.0
cellular              3 (glass mnt)  8.4

Thus, if I can believe the manufacturer's own comparisons , there should
be better reception on cellular that my present glass mount, even
factoring in the effect of 0.25db loss from a duplexer. There may be a
trivial improvement on 2m/70cm plus only 1 antenna defacing my car.

Better cellular reception would be a real plus for me, since I frequently
travel in rural West Texas where the only cellular POPs would be a few
thousand head of cattle. Thus cellular coverage can get thin.

Anybody using this antenna than can verify whether it works as
advertised, and whether transmitting on cellular + amateur simultaneously
would have any problems with equipment ?

William Biggs
KC5JIF

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

Date: 6 Nov 1994 06:02:41 -0500
From: [e-mail] (Michael Christie)
Subject: 2m bev.?

If memory serves, the Beverage antenna is only a satisfactory
performer up to about 7 MHz. It was originally designed [as I
recall] as a mediumwave and longwave receiving antenna. Hams
being hams adopted it for 160m, 80m and 40m..which pushed its
physics some. 73,

Michael Christie, K7RLS/4
Crawfordville, Florida

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

Date: 2 Nov 1994 11:21:29 -0500
From: [e-mail] (Peter Rimmel)
Subject: Antenna question!!!!!! PLease HELP!!!!!

Zack Lau (KH6CP) ([e-mail]) wrote:
: Scott Darragh KE6MGW ([e-mail]) wrote:
: : I am trying to figure out a way to put up a low profile antenna.  I have a
: : little room to play with in regards to how profile it is.  I asked if I
: : could put up an antenna on the rain gutter and she said keep it as low
: : profile as possible.

: Surprisingly, a *full size* open wire fed dipole may fall into the
: *low profile* category.  Depending on your landlord's eyesight,
: she may or may not find it obtrusive.  Paying your rent on time
: each month may also help change the definition.  I added a full
: wave 80 meter loop last year around the 2nd floor apartment
: that I rent (actually, its around the entire building... :-)  )

: On the other hand, things like traps, loading coils, and coax
: do tend to be easier to see.

When I was young and foolish, a friend and fellow novice loaded up his
gutters! worked well on 40 M.  What band you want to get on?
You could gamma match a section of gutter on most bands if you work at it
--
                                             \_\_\__\__\__\     -.-.
Have Fun! 73, dah-di-dah                      \ \ \ |\  \  \        --.-
                                                   |X|
Peter Rimmel                                       |X|
[e-mail]                   |X|
K8UNP@N4HHP.#HWDFL.FL.USA.NOAM (packet)     _______|X|______

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

Date: 7 Nov 1994 04:08:51 GMT
From: [e-mail] (ALAN CHURCHILL )
Subject: Best vertical - Butternut?

Re best vertical...
You may thinks this is nuts but I have tested my mobile screwdriver
antenna against my Hustler 5 band full size vertical.  The screwdriver
works better even without any radials.  (Radials on a mobile rig are
really hard to control around curves).  The screwdriver method can get
your antenna resonated rather than "tuning" out the reactance.  I'm no
engineer but I know what works for me.  I got mine from Henry Stewart,
WB7WMW, H. Stewart Designs, P.O. Box 643, Oregon City, OR  97045 or phone
503-654-3350.  Hope this helps.
Alan Churchill AA7CV

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

Date: 7 Nov 1994 03:56:29 GMT
From: [e-mail] (ALAN CHURCHILL )
Subject: High Sierra Antennas?

Hi James,
I have been using one of the screwdriver antennas for nearly 3 years now
and I love it.  Just yesterday I was working in the shack and responded
to the  America3 special events station about 20 times over 2 hours.  No
response.  I then went for a drive, gave them a call and got a reply on
my first call.  The antenna really WORKS.
I took a really good look at the High Sierra at the SeaPac convention
last summer in Seaside, OR.  It is well built but I wanted one that was a
little more "finished".  I found that the screwdriver antenna is being
built by Henry Stewart, WB7WMW. He spent years as a machinist and does
spectacular work.  I have had many complements on the unit and the price
wasn't much more than High Sierra.  You can contact Henry at H. Stewart
Designs, P. O. box 643, Oregon City, OR 97045 or phone him at 503-654-
3350.  By the way, before I had Henry's antenna, I MELTED another one
with a 400 watt amp.  That was an interesting day.  You'll love mobiling
and changing bands on the go.  Good luck.  Alan Churchill AA7CV.

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

Date: Sun, 6 Nov 1994 14:56:38 GMT
From: Rick Zabrodski <[e-mail]>
Subject: How much directionality to slightly inverted vee?

Keep the ladder line, put the antenna up higher.
Remember, unless the average height is close to a half wavelengh or
higher you will be mainly radiating up with negligible directivty.
Classic inverted vees tend to be more omnidirectional as well.
My "reference antenna" and second recevier antenna in contests is an
inverted vee with apex up 62 feet. There is definate directivity noted 30
thru 10 meters, almost none on 40, none at all on 80.  The directivity
never means I cannot hear a station, it just 1 to 4 s units down from
another antenna I might be using at that time.
I have no problems with the ladder line and have used balun and balanced
line link tuners. (The latter works a little better but is more finicky
to tune generally.)  The inverted vee legs are 42 feet each.  This gives
me some gain on 20 towards the US plus reasonable effiency on 40 and 80.
My shunt loaded tower works better on 80 meter dx as does the full sized
3 elemement monobander on 20 m ......no surprises there.  However, the
difference is not always that great......propogation is always more
important than a given antenna design!

****************************************************************************
Dr. Rick Zabrodski BSc, MD, CCFP(E)       *               VE6GK
EMAIL:  [e-mail]          *
Packet: VE6GK@VE6YYC.#cgy.ab.can.na       *      "Power is no subsititute
Phone: [phone]   Fax: [phone]     *               for skill."
****************************************************************************


On 5 Nov 1994, Peter Rimmel wrote:

> David Jenkins ([e-mail]) wrote:
> : I've put up a ladder-fed dipole--the included angle between its legs is
> : about 170 deg. in the horizontal plane, and about 160 deg. in the
> : vertical.  It is oriented roughly NW to SE, with the "vee" pointing to the
> : SW.  The apex of the vee (such as it is) is at about 22'.
>
> : The center is suspended from a 18" PVC standoff attached to
> : the mast that holds our TV antenna.  The mast stands off from the house
> : about 24"  I have been running QRP, and the only
> : TVI we experienced was slight and on Chan 2--it was cured with filter
> : at TV.
>
> : I have heard exactly zero from the South and West--all
> : transmissions I have had are from North (mostly) and East (to some
> : extent).
>
> : Given the orientation I've described, is this directional performance
> : that I should expect? Is the house boogering the performance to S and W?
> : At what angles might I expect to get more equal performance to the South
> : (mostly) andWest? Do I need to move the house?
>
> : TIA--I'm really new at this, but I know that there's lots of gotchas out
> : there, and I've probably triggered a whole raft of 'em.
>
> : David F. Jenkins
> : Decision and Information Sciences
> : University of Houston
> : KC5JRR
>
> You have very close to a classic dipole arrangement...  the 10 or 20
> degrees are minor in the ways of the pattern... BUT... how many hams are
> to the south and west of Houston???  At the low  22 foot height, you are
> not going to work much of the south pacific. I suggest you get it up
> higher at the apex and get that angle to 90-100 degrees, feed it with 50
> ohm coax and use a tuner with it.  You will be happy with the
> difference... good luck with it, 73, Pete K8UNP
> --
>                                              \_\_\__\__\__\     -.-.
> Have Fun! 73, dah-di-dah                      \ \ \ |\  \  \        --.-
>                                                    |X|
> Peter Rimmel                                       |X|
> [e-mail]                   |X|
> K8UNP@N4HHP.#HWDFL.FL.USA.NOAM (packet)     _______|X|______
>
>

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

Date: 3 Nov 1994 08:30 -0500
From: [e-mail] (SODERMAN.WALTER)
Subject: How much range on 80m? 40m?

I realize that a dipole should be up 1/2 wave for optimum performance, but if I
have an 80 meter dipole only 12 to 15 feet up, and no surrounding interfering
structures, should I be able to get "acceptable" performance for a range of
say, 200 miles?  That's really all I need for my application.

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

Date: Sun, 6 Nov 1994 04:43:27 GMT
From: [e-mail] (David Michael Moore)
Subject: Just say NO to RG58!

In article <[e-mail]>,
[e-mail] (Gary Coffman) wrote:

> I just had to troubleshoot a piece of Andrew hardline at a packet node.
> It was open circuited. You guessed it, bad connector at the top. (Of
> course it *couldn't* be the connector on the ground end could it?)


Isn't there an FCC regulation that requires all antenna and feedline problems
to be atleast 50 feet up the tower?  I believe it comes right after the
regulations that require all antenna and feedline problems to occur on a rainy
day or with temperatures below 30 degrees, and all repairs must be done in
similar weather, and preferably at night time.  Rumor has it that they are
preparing to ban all artificial lighting from the repair site...

[Oh yeah, I guess I better drop in a few :-) :-) :-) for the humor impaired]


David  KD4RMW
[e-mail]

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

Date: Mon, 7 Nov 1994 00:16:08 GMT
From: [e-mail] (Jeffrey Herman)
Subject: Just say NO to RG58!

When you feed a dipole with coax the coax is supposed to be fed through
the center insulator in such a way that it forms an upside-down J so
no moisture can enter:



                            _
                           / \
                          |  |
                        __|__|___ Split center conductor and braid here
                       /  |      \
                      /   |       \
<--------------------+--#########--+----------------------->
                          |
                          |  Coax taped to center insulator
                          |
                          ~

Well, you get the idea.... The coax will last for years configured
in this manner.

73,
Jeff NH6IL


--
Jeffrey Herman, NH6IL (ex: WA6QIJ, ex: NMO CW operator)
Mathematics Lecturer and tenured Ph.D. student
University of Hawaii, Central Pacific Ocean

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

Date: 4 Nov 1994 16:19:23 -0500
From: [e-mail] (Larry Brandt)
Subject: RG8 vs "Thick Ethernet"

I have been using standard Ethernet thick cable for HF for a year.
I have not had any problems. This is "normal" 50 Ohm teflon coated
coax. I got some ends of a big roll that had not be chewed up by
Ethernet vampire taps.

Is there a reason this is a bad idea? I tried to see someone 20ft
once and he said it was bad cable! I find it as good as 9913 or
other highpriced cable.

Any comments?
tnx es 73
AA1EA
Larry

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

Date: 6 Nov 1994 06:28:00 GMT
From: [e-mail] (Christopher R. Hoffman)
Subject: Twinax for feedline

Christopher R. Hoffman ([e-mail]) wrote:
Can anyone tell me if Networking TWIN-AX can be used as an unbalanced
feeder? I salvaged a few hundred feet from a network overhaul this
summer.

For those of you who don't know, This is comparable to RG8, accept that
it has TWO inner conductors instead of one. This is used primarily for
IBM networks.

: --
: TNX - 73's
: Chris Hoffman
: KO6GA ex. KD6VLY
: [e-mail]


--
TNX - 73's
Chris Hoffman
KO6GA ex. KD6VLY
[e-mail]

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

Date: 5 Nov 1994 15:29:33 GMT
From: [e-mail]

References<[e-mail]> <38u6vm$[e-mail]>, <[e-mail]>
Subject: Re: Dipole question's

In article <[e-mail]>,
charles rodgers <[e-mail]> wrote:

>I'd be very interested to know what the feeder you use with that dipole.

Hi Charles, I use 300 ohm ladder-line but 450 ohm ladder-line is even less
lossy and usually gives a lower SWR for non-resonant antennas.

>I assume that you mean 44 ft each side.

Yup, 44 ft each side. According to ELNEC, around 1.3 wavelength yields
maximum broadside radiation, 3db higher than a half-wave dipole. That
gives maximum broadside radiation on 20m with 88 ft. At 1.5 wavelengths
there are six lobes about 1db down from the two lobes in a half-wave
dipole. At 1.7 wavelengths the pattern has become a 4 lobe cloverleaf
pattern with each lobe about 2db higher than a half-wave dipole. 88 ft
is 1.7 wavelengths on 17m. This antenna also has a lower angle of radiation
than a half-wave dipole.

>I have used such a dipole in inverted V formation with an open wire feeder
>and it performed very well on 20m but not so on 17m.

With an 88 ft dipole, one does not get the same coverage on 17m as on 20m.
A lot of hams assume that a dipole gives a broadside radiation pattern no
matter what the frequency and that is not true. I chose 88 ft to get broad-
side East/West radiation on 20m _AND_ almost no broadside radiation on 17m.
On 17m, the radiation is NE/SW/NW/SE. On those two DX bands, that gives me
coverage of most of the land areas of the world with a single fixed wire
antenna. And let's face it, under the present sunspot situation, 20m is a
lot better than 17m. The Maximum Usable Frequency often seems to hover
around 16MHz.

Also an 88 ft inverted-V dipole would work well on 20m but not on 17m
because the inverted-V configuration screws up the cloverleaf radiation
pattern. Inverted-V's longer than 1.5 wavelength do not work very well.
Dipoles longer than 1.5 wavelength should be horizontal.
--
73, Cecil, KG7BK, OOTC   (All my own personal fuzzy logic, not Intel's)

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

Date: 5 Nov 1994 04:27:10 GMT
From: [e-mail]

References<27OCT199408150377@ewirb-wr> <38v4q7$[e-mail]>, <31OCT199415115205@ewirb-wr>
Subject: Re: How well will it work?

In article <31OCT199415115205@ewirb-wr>,
SODERMAN.WALTER <soderman@ewirb-wr> wrote:

>With the inverted vee arrangement, the ends
>would be about 12 to 15 feet up, and the apex would be on a mast around 30 or
>35 feet up.  Any ideas on this?  Who makes a good mast for this?

Hi again, Walt. My masts are made out of 2x4s, 2 20' ones on bottom and
one 20' one on top. Cost was neglible. My advice is to put up two of them.

>And, insofar as the 450 ohm ladder line is concerned...how do I connect a
>balanced line like the ladder line to my coax port on my xcvr which already
>has a built-in antenna tuner? Walt  KE4QOH

Coax to a 4:1 balun like the Amidon HBHT200 and ladder-line from there on.
But don't be surprised if your built-in antenna doesn't match the antenna
system on all bands. External antenna tuners usually have a wider range
of matching capabilities than the built-in ones. You may also need to
change the length of the ladder-line as that will change the _measured_ SWR
between your transmitter stage and your built-in antenna tuner. Good luck.
--
73, Cecil, KG7BK, OOTC   (All my own personal fuzzy logic, not Intel's)

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

End of Ham-Ant Digest V94 #368
******************************