QRZ! Ham Radio 4/QRZ Ham Radio Callsign Database - Volume 4.iso/digests/antenna/940079.txt

Internet Message Format | 1994-11-13 | 23KB

Date: Fri, 25 Mar 94 04:30:13 PST
From: Ham-Ant Mailing List and Newsgroup <[e-mail]>
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Subject: Ham-Ant Digest V94 #79
To: Ham-Ant


Ham-Ant Digest              Fri, 25 Mar 94       Volume 94 : Issue   79

Today's Topics:
                        144/440 antenna ideas?
                             Attic Dipole
                 Battle creek special info needed !!
               CELLULAR PHONES-How increment reception?
             Designing Ferrit-Antennas for TX/RX (2 msgs)
                  Discone vs 5/8 wave for 2m packet?
                      glass mounted cb antenna?
                      Impedance of Ethernet Coax
              Motorola GPS engine group purchase update
               Question about hatch lip mounts (2 msgs)
            Question about mobile antenna 40/80m (2 msgs)
                            RF systems MLB
                               Umbrella

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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: Thu, 24 Mar 1994 17:50:40 GMT
From: rit!sunsrvr6![e-mail]
Subject: 144/440 antenna ideas?
To: [e-mail]

Having joined the dual-band HT set, I'm looking for info on
building two antennas:  one to replace the rubber duckie, and
something for the car.  The ARRL Antenna Book has the discone,
which isn't suitable for either application, but not much else.
(I actually built a discone antenna.  It would be quite a sight
on top of the car, or attached to the top of an HT...)

Any ideas?  I was thinking of a 1/4 or 5/8 wave cut for 2-meters,
perhaps with a coil in the middle to isolate the top section at 440.
But the 5/8 wave's matching coil would mess things up at 440.

I examined a commercial dual band mag mount.  The bottom section
is 15", with a 3-turn 3/4" diameter coil, then a 19" top section.
There was no DC continuity between the whip and coax center
conductor, just a small amount of capacitance.  The meter gave a
dead short reading from whip to coax cable shield, so it must
have been a coil.

What is this beast?  Is this the oft-rumored 1/2 wave?  If so, how
does the impedence matching work at both 2-meters and 440?

73...Jim N2VNO

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

Date: 24 Mar 94 19:53:12 GMT
From: ihnp4.ucsd.edu!swrinde!emory!news-feed-2.peachnet.edu!umn.edu!dawn.mmm.com!mmm.com![e-mail]
Subject: Attic Dipole
To: [e-mail]

[e-mail] (Troyce) writes:

>Living in a duplex, I can't put an outside antenna up, so I have been
>considering designs involving hiding a dipole in the attic.  I have about
>50 feet of length to work with.  Right now I am considering a trap dipole
>for 10-80 meters, 82' long.  This would entail running 50 feet straight
>across the peak of the attic roof, then sloping down 16 feet on each end.
>I know this is certainly not an optimum configuration, but is it still a
>viable method?  If the bend ends are a big problem, I do have the
>alternative of a 45 foot 10-40 meter dipole, but would like the option of
>80 meter use (for when I upgrade to general from Tech plus).

>Troyce
>KC5CBI

As one who lived in many apartments for many years (back in my youth)
I will offer what experience I had.

First, the most important thing to remember is that anything will work...
It's just a matter of how well.

Second, anything is better than nothing.

Third, try it! That is half the fun a amateur radio, the chance to experiment.

Having said that, my preference ended up being a random length wire... as
long as I had room for, as high as I could get it... matched with a L-type
matching network. (look in the ARRL antenna handbook, or regular handbook)
For best results you need a decent ground, but it will
work without one. I operated on 80meters from a second floor room while in
college and it worked ok.Just don't touch your lips to a metal microphone or the
Chassis... they are hot without a good ground. Bend the ends around to get as
much wire up as possible.

Thin, hard copper-coated steel electric fence wire, 26 gauge I think, makes
a great antenna wire. It is very hard to see, doesn't stretch much and is cheap.
I used it for the above mentioned 2nd floor room. Oh, one pointer. I ran it
from my window to a fellow ham's house across the street. It's important
if you are running across a street to make sure it is higher than a
semi truck's exhaust pipes. Mine wasn't. One night I was laying in bed and
and I heard rrrrrr-RRRRR-PING! and my antenna was gone... probably in
Georgia by now.

The method you mention will work. Bending the ends will upset the resonance
point and raise the VSWR some, but it will probably be acceptable.
Try to keep it as straight as possible.


Hope this helps some

   Steve  WA0ODF

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

Date: 24 Mar 1994 11:21:56 GMT
From: ihnp4.ucsd.edu!usc!howland.reston.ans.net!EU.net!sun4nl!news.nic.surfnet.nl!tuegate.tue.nl!blade.stack.urc.tue.nl![e-mail]
Subject: Battle creek special info needed !!
To: [e-mail]

Hello there,

The HAM club of the University of Technology of Eindhoven is going on its
FIRST dx-pedition to HB0 around the IARU HF Championship Contest in July
this year.

We will set up a HF-VHF-UHF station on top of a mountain at 2010 meters
above sealevel. The plateau is about 18 by 8 meters. After hearing so many
good reports on the BATTLE CREEK SPECIAL being used successfully by some
major dx-peditions we decided to use that antenna on the low bands. Going
through various antenna books has not brought up any info on that antanna.

So we would appreciate any detailed info on the Battle Creek Special.

Many thanks in advance!


73 from Aurelio-PA3EZL operator at PI5EHV and PI4TUE

ax25 packet mail to: [e-mail]
e-mail to:           [e-mail]

-----------------------------------------------------------------------------
ESRAC - Eindhoven Student Radio Amateur Club |
EH 13.19 PI5EHV/PI4TUE                       | Kom naar de ECHTE hemel van
email: [e-mail]                | electro!!!
BBS-mail: PI5EHV @ PI8ZAA                    |
----------------------------------------------------------------------------
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Do a 'finger [e-mail]' for more information.

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

Date: 24 Mar 1994 02:42:03 -0500
From: hp81.prod.aol.net!search01.news.aol.com![e-mail]
Subject: CELLULAR PHONES-How increment reception?
To: [e-mail]

In article <[e-mail]>,
[e-mail] (Brett Miller - N7OLQ) writes:

>Most rural areas use non-sectored cell sites so this should NOT be a problem
>the fringe of a rural area.

I don't see how sectoring affects the problem I'm discussing, unless you're
calling "sectoring" what I'm calling "frequency reuse".
If you have no reuse in a rural area, then yeah, yagi's fine.  That's not
inconsistent with my comments.  It's when your yagi can see two (or more)
cochannel cells at more-or-less the same distance that problems will occur.
Cells could be cochannel whether they're omni or sectored.

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

Date: 24 Mar 1994 14:11:11 GMT
From: usc!howland.reston.ans.net!pipex!uknet!EU.net!Germany.EU.net!netmbx.de!zrz.TU-Berlin.DE!cs.tu-berlin.de!zib-berlin.de!news.belwue.de!news.uni-stuttgart.de![e-mail]
Subject: Designing Ferrit-Antennas for TX/RX
To: [e-mail]

Hi there, this is Peter   DH1IAR,

are there any good books, papers or any other form of information
abt designing Ferrit-Antennas which are usable for TX and RX ?
Favorite frequency area should be in 10-50KHz.

tnx es 73 de Peter

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

Date: Thu, 24 Mar 94 21:05:00 -0800
From: ihnp4.ucsd.edu!dog.ee.lbl.gov!agate!library.ucla.edu!csulb.edu!paris.ics.uci.edu!news.claremont.edu!kaiwan.com!ledge![e-mail]
Subject: Designing Ferrit-Antennas for TX/RX
To: [e-mail]

I doubt that ferrite is a good material to use in a transmitting
antenna.  Due to its nonlinear magnetic characteristics, it will
cause detuning and, worse, harmonic generation.

73 DE K6DDX

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

Date: Thu, 24 Mar 1994 08:47:09
From: ihnp4.ucsd.edu!swrinde!gatech!news-feed-1.peachnet.edu!hobbes.cc.uga.edu!kcs.rx.uga.edu![e-mail]
Subject: Discone vs 5/8 wave for 2m packet?
To: [e-mail]

I just got on packet for the first time last nite, and find that I'm marginal
into the local BBS.  I'm using an Antenna Specialists "Discan" antenna which I
originally used for a scanner, but which I have recently used quite
successfully on 2 meter FM - I can hit repeaters out to about 40 miles or so
with a  5 watt HT.  A/S says "not for transmitting" but the SWR appears ok and
I doubt I'll burn the antenna up on 5 watts.  I have a 5/8 ground plane
availible, which promises something like 3.6 db gain.  I believe that a
discone is supposed to be unity gain.  So the question is, will there be
enough difference between these antennas to make the trip to the roof worth
while?  I doubt 3.6 db would get me solid in something I wasn't hitting at
all, but will it likely improve a marginal situation?   I'd like to put up
something bigger or perhaps a beam, but I have covenant problems and need to
stay real low profile.

Any comment, advice, etc. will be appreciated.

73 de N4NFI


Ken Schroder
Logistical Support Manager
The University of Georgia
College of Pharmacy
Athens, Georgia  30602

e-mail: [e-mail]
phone : [phone]
FAX   : [phone]

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

Date: Fri, 25 Mar 1994 05:52:26 GMT
From: ihnp4.ucsd.edu!agate!howland.reston.ans.net!torn!blaze.trentu.ca!TrentU.CA![e-mail]
Subject: glass mounted cb antenna?
To: [e-mail]

         I've got a real problem, I recently bought a glass mounted cb
antenna for my car, the cellular phone model except for CB units. I've
installed the thing correctly but cannot get a match for either my 23 or 40
channel cb's. I hooked it up to a match meter but cannot get the thing
below 2.5......I've tryed adjusting the whip with an allen key so that it
would slid further down into the housing of the antenna...the problem is
that it does not go any further into the antenna. I'm wondering if I should
clip a little off the bottom of the whip so it is a bit shorter and thus
will go deeper into the antenna assembly......any ideas...should I cut it a
bit or should I do something else....I'm wondering if I shorten the length
of the coax lead will it get a better match.....I don't know that much
about cb's so any advice would be cool.


thanks ...and keep your sticks on the ice.
Joe.

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

Date: Thu, 24 Mar 1994 11:56:47 -0500
From: ihnp4.ucsd.edu!usc!yeshua.marcam.com!hookup!ukma!hsdndev!NewsWatcher![e-mail]
Subject: Impedance of Ethernet Coax
To: [e-mail]

There seem to be two separate uses of coax in computer networking.  The
most common seems to involve rg58/59 type with a terminator at the end
and coax tee feeds to individual users.  I am told that 52 ohm cabling
is the standard for "thinnet" type connections.  There MAY also be a
separate standard for long runs between routers with larger 0.5-1.0
inch coax between machines, routers, etc.  Is this typically 52 or 75 ohm
cable?  I have been told that the larger cables are typically 75 ohm.
Thanks
Frank K1MOQ
--
Frank H. Duffy, MD                     e-mail: [e-mail]
Neurology, Childrens Hospital     workstation: [e-mail]
& Harvard Medical School                  FAX: [phone]
300 Longwood Avenue                     voice: [phone] / 7846
Boston, MA 02115  USA           amateur radio: K1MOQ

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

Date: 25 Mar 1994 00:47:53 GMT
From: ihnp4.ucsd.edu!usc!elroy.jpl.nasa.gov!wp-sp.nba.trw.com!newswire.etdesg.TRW.COM![e-mail]
Subject: Motorola GPS engine group purchase update
To: [e-mail]

(lot of stuff deleted)
> Motorola GPS core engine

What is a GPS core engine?

   --wayne   W5GIE

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

Date: Sun, 20 Mar 1994 13:04:41 GMT
From: ihnp4.ucsd.edu!swrinde!gatech!darwin.sura.net!perot.mtsu.edu!raider!theporch!jackatak![e-mail]
Subject: Question about hatch lip mounts
To: [e-mail]

[e-mail] (Kerry Kurasaki) writes:

> Any net concensus on how the radiation pattern is distorted if a 5/8 wave
> is mounted using a lipmount on the R or L side edges of a trunk?
I am not sure that pattern distortion is as much the issue with a
mount such as you propose...

The *best* solution is to drill a hole, use an NMO mount, and relax
and enjoy hamming.

All the normal worries about devaluing the car for resale have been
anecdotally addressed here. The NMO is an industry standard mount and
renders your vehicle "Cellular Ready" when sold.... One guy even told
of a friend, major league Fox-Hunt DF type who cut a "huge" hole in
the roof for rotatable arrays...when he told the dealer about the hole
in the roof, the response wasn't even lukeworm, and didn't change the
value 1cent: "So?"

> Or are most of the effects not really worth worrying about?
If you worry about not doing as well as you might, drill the hole.
Drive your car to a mall and let a few people slam their doors into
your new car, and then carefully drill the hole. It doesn't bother as
much if teh car isn't totally brand new, cherry...   ;^)
73
Jack, W4PPT/Mobile (75M SSB 2-letter WAS #1657 -- all from the mobile! ;^)

+--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--+
| Jack GF Hill        |Voice: [phone] -             Ham Call: W4PPT |
| P. O. Box 1685      |Modem: [phone] -  Bicycling and SCUBA Diving |
| Brentwood, TN  37024|Fax:   [phone] -          Life Member - ARRL |
| [e-mail]  -   "Plus ca change, plus c'est la meme chose" |
+--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--+

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

Date: 24 Mar 94 20:25:03 GMT
From: ihnp4.ucsd.edu!dog.ee.lbl.gov!agate!howland.reston.ans.net!cs.utexas.edu!swrinde!sgiblab!rtech!ingres![e-mail]
Subject: Question about hatch lip mounts
To: [e-mail]

In article <[e-mail]> [e-mail] (Jack GF Hill) writes:
>[e-mail] (Kerry Kurasaki) writes:
>
>> Any net concensus on how the radiation pattern is distorted if a 5/8 wave
>> is mounted using a lipmount on the R or L side edges of a trunk?
>I am not sure that pattern distortion is as much the issue with a
>mount such as you propose...
>
>The *best* solution is to drill a hole, use an NMO mount, and relax
>and enjoy hamming.

[lotsa stuff deleted]

While drilling the hole is the best solution, your post still did not answer
my question.

After talking to a few elmers, their impression was that the ground plane
effect of the body was less and less the higher in frequency you went.
I've now concluded that it is a non-issue.

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

Date: Sun, 20 Mar 1994 13:18:15 GMT
From: ihnp4.ucsd.edu!swrinde!gatech!darwin.sura.net!perot.mtsu.edu!raider!theporch!jackatak![e-mail]
Subject: Question about mobile antenna 40/80m
To: [e-mail]

[e-mail] (Cecil Moore) writes:

> But I wonder about a bumper-mounted 5/8 vs a top-of-pickup-cab
> mounted 1/4 wave on 10m.
> I've heard that the bumper mount loses a more than neglible amount of power
> because of the parallel car body. I've also heard that a 5/8 without a
> large ground plane directly underneath is inferior to a 1/4 wave with a
> large ground plane directly underneath.
First, may I examine the hypothesis: a 1/4 with a large ground
plane...and mounted on the roof of a pickup truck? Wait one!

The roof of a pickup truck does NOT extend out in ANY direction for
8 1/2 feet...hence there is NO large ground plane. Unless you bond the
pickup truck together VERY carefully, you do not have an effective
groundplane at all...

As for the 5/8 wave bumper mount... Granted that reactances are
frequency dependent, but a 1/4 on 75M operating over virtually NO
ground can not be dismissed as irrelevent when talking about a 10M 5/8
wave operating over a *slightly* better ground.

My point is, Cecil, that NEITHER the 1/4 wave truck mount NOR the 5/8
bumper mount is operating over anything approaching a "good" ground
plane...and hence, the 5/8 wave (NO traps) would seem to have an
advantage (significant?) over the 1/4 wave, whether a full 8 1/2 foot
whip or trapped/loaded unit.

> Have you ever made any field strength
> measurements directly in front of the car vs directly behind it?
> I'll bet I radiate more energy directly ahead on 10m than you do
> (running the same power).
Well, I do not work for anyone with great instrumentation, nor do I
have a range for making those measurements. That said, just the
intuitive feel of your claim doesn't fit, so I guess I'll take your
bet... wanna meet at Dayton and take some measures???  ;^) Love to see
you there, antenna measuring not withstanding... ;^)
73,
Jack, W4PPT/Mobile (75M SSB 2-letter WAS #1657 -- all from the mobile! ;^)

+--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--+
| Jack GF Hill        |Voice: [phone] -             Ham Call: W4PPT |
| P. O. Box 1685      |Modem: [phone] -  Bicycling and SCUBA Diving |
| Brentwood, TN  37024|Fax:   [phone] -          Life Member - ARRL |
| [e-mail]  -   "Plus ca change, plus c'est la meme chose" |
+--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--+

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

Date: Sun, 20 Mar 1994 13:31:02 GMT
From: ihnp4.ucsd.edu!swrinde!gatech!darwin.sura.net!perot.mtsu.edu!raider!theporch!jackatak![e-mail]
Subject: Question about mobile antenna 40/80m
To: [e-mail]

[e-mail] (Cecil Moore) writes:
> my friend W5GYJ just pointed out that a 5/8 wavelength
> at 29.5 MHz is 21'7". Exactly how are you tuning your antenna in
> "approaching a full 5/8 wave on 10 meters"?
By being a tad generous with my measurements: 13' 6" plus 48" equals
17' 6" which approaches 5/8 or 21'7"... it is actually much closer to
a half wave without the center loading coil, but a few turns of coil
make for a better load and match, hence my comment. I was probably
stretching things just a bit... forgive me, I don't fish and have no
other outlet!  ;^)

> Also, shouldn't your antenna have capacitive reactance on 10m?
I would guess it does... though I have no mechanism to accurately
measure it.

> Do you use an antenna tuner by any chance?
No. can NOT find a small effective tuner that has a by-pass to permit
the antenna to function without the tuner... I did some measurements
with an MFJ and discovered my signal went to hell when fed through the
tuner at the self-resonant frequency of the antenna.

Granted I could get a wider deltaF, but bandwidth isn't that
importqant to me...shoving all the RF I can into the ether is... and
the tuner detuned the system more than I would tolerate.

BTW, the measures were taken using a pair of high-isolation 2-pos
antenna switches fore and aft of the tuner like this:
    ______    SW1 ________________________________ SW2
    |     |   ___/                                \___
    | RIG |---| |        ____________              | |---> ANT
    |     |   |_|       |            |             |_|
    |_____|     \-------|  TUNER     |------------/
                        |____________|

Signal strength with the tuner was measureably different at 300 miles
(Nashville to Indianapolis) and 450 miles (Nashville to Andora, IN) by
an S-unit or more below the signal strength without the tuner in a
blind A/B comparison. A shorter path to Kentucky yeilded noticeable
(1/2 S-unit approximate and noticeable audio difference) reduction in
signal strength... There was not enough opportunity for longer range
tests, but I sent the tuner back and get out to change taps... it
works for me!  ;^)
73,
Jack, W4PPT/Mobile (75M SSB 2-letter WAS #1657 -- all from the mobile! ;^)

+--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--+
| Jack GF Hill        |Voice: [phone] -             Ham Call: W4PPT |
| P. O. Box 1685      |Modem: [phone] -  Bicycling and SCUBA Diving |
| Brentwood, TN  37024|Fax:   [phone] -          Life Member - ARRL |
| [e-mail]  -   "Plus ca change, plus c'est la meme chose" |
+--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--+

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

Date: Thu, 24 Mar 1994 14:08:04 GMT
From: ihnp4.ucsd.edu!usc!howland.reston.ans.net!EU.net!julienas!nenuphar.saclay.cea.fr!titania![e-mail]
Subject: RF systems MLB
To: [e-mail]

Did anybody try the Magnetic Longwire Balun from RF systems ? BTW are there any
method to connect properly a coax cable to a random lenght antenna ?
Thanks in advance
73 de F1GOC

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

Date: 25 Mar 1994 09:10:05 GMT
From: ihnp4.ucsd.edu!dog.ee.lbl.gov!agate!howland.reston.ans.net!pipex!uknet!EU.net!sun4nl!fwi.uva.nl![e-mail]
Subject: Umbrella
To: [e-mail]

I'm planning to build a vertical for 160m and I'm looking
for the perfect compromise. Should I use:

1) Umbrella toploading, since the mast is of PVC piping (10m) it
   has to be guyed so this is easy, however:
   - what are the optimal lengths of the topload wires ?
   - how many wires should I use (perhaps 4) ?

2) Coil loading, because the mast is of PVC the coil can be placed
   anywhere, however:
   - what is the optimal position of the load coil (mid ?)
   - what are optimal length/dimension ratios of the coil ?

3) Both toploading and coil ?

Any suggestions are welcome.

Dirk.

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

End of Ham-Ant Digest V94 #79
******************************