QRZ! Ham Radio 4/QRZ Ham Radio Callsign Database - Volume 4.iso/digests/antenna/940225.txt

Internet Message Format | 1994-11-13 | 15KB

Date: Sun, 17 Jul 94 04:30:08 PDT
From: Ham-Ant Mailing List and Newsgroup <[e-mail]>
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Subject: Ham-Ant Digest V94 #225
To: Ham-Ant


Ham-Ant Digest              Sun, 17 Jul 94       Volume 94 : Issue  225

Today's Topics:
                            Antenna safety
                             GPS antennas
                        kites <--> antennas ?
                           simple antennas
                     Specs, DAIWA Remote Sensor?

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Archives of past issues of the Ham-Ant Digest are available
(by FTP only) from UCSD.Edu in directory "mailarchives/ham-ant".

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: 15 Jul 1994 04:42:40 GMT
From: ihnp4.ucsd.edu!agate!headwall.Stanford.EDU![e-mail]
Subject: Antenna safety
To: [e-mail]

I need to mount an antenna for a 900 MHz spread-spectrum radio link.

According to the manufacturer of the radio equipment, it works best
when antennas are on a direct line of sight. However, because the
building where the antenna will be is only 18' high, and some of the
surrounding buildings are taller, it will need a tall mast or tower.

To figure out how high the antenna needs to be, I made a crude sextant
from a yardstick, a protractor, and a photo tripod. After a few
observations and a little math, I determined that one nearby building
with a flat roof (plus a small shed on top) was about 30' tall at the
roofline, with a chimney about 41' high. (Since local codes require
the chimney to be the tallest part of the building, it should end
higher than the shed.) Another building in the area, an old Victorian
mansion, came out to be about 54' high at its tallest spire.

The area where the antenna will reside is subject to strong winds all
year round, so the mast or tower will have to be steady and strong.
There's an average of one thunderstorm per day during the summer, so
lightning protection needs to be good. The lot on which the building
sits is 66' across, and there are high voltage power lines in the alley
about 6' beyond the property line. The building butts right up against
the opposite end of the property.

The antenna itself will be an omni with 9 dB of gain -- fairly expensive,
but necessary to give it a good reach even when it's iced over.

What's the best method of mounting the antenna safely, securely, and
high enough to work? The local Radio Shack said it had a 39' mast designed
for TV antennas, which could be mounted on the roof using an eave or tripod
mount. (The resulting height would be about 57' -- just about right.)
But of course, I don't trust Radio Shack to know anything about antenna
safety, or mounting it to resist winds. They also drew a blank when I
asked about grounding and lightning protection.

What do I need to know to get the antenna up (and have it stay up)? How
can I avoid having the building burn down if lightning strikes? How can
I protect the digital transceiver at the end of the coax? And what precautions,
if any, need to be taken about the power lines?

Any info, advice, comments, and pointers to literature would be much
appreciated.

--Brett Glass

--
"Beware when the great God lets loose a thinker on this planet.
 Then all things are at risk. It is as when a conflagration has
 broken out in a great city, and no man knows what is safe, or
 where it will end."                   -- Ralph Waldo Emerson

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

Date: Sat, 16 Jul 1994 04:34:04 GMT
From: ihnp4.ucsd.edu!agate!howland.reston.ans.net!gatech!newsxfer.itd.umich.edu!zip.eecs.umich.edu!yeshua.marcam.com!news.kei.com!news.byu.edu!hamblin.math.byu.edu!wicat![e-mail].
Subject: GPS antennas
To: [e-mail]

Roger Corbett <[e-mail]> writes:
>
>Most of the GPS antenna that I have come across are crossed dipoles of
>some sort with the ends turned down and twisted around.
>The other more important thing is that the antenna will have a low
>noise
>preamp in it and this is where the cost comes from...

These are QUADRIFILAR antennas.  They feature circular polarization
with the same direction at all points within a hemisphere.  In other
words exactly what GPS requires.


--
 Keith McQueen, NACT, Inc                               | My opinions are |
 Packet:      n7hmf @ nv7v.UT.USA.NA                    | all mine...     |
 Internet:    [e-mail]                          | ...so there!    |

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

Date: 15 Jul 1994 20:30:02 -0400
From: newstf01.cr1.aol.com!search01.news.aol.com![e-mail]
Subject: kites <--> antennas ?
To: [e-mail]

    I worked a ham in Michigan who was using a helium-filled weather
balloon on the end of a 150 foot peice of wire.  He was S9+ here in West
Virginia on a day when QRM and poor band conditions made most other
stations unreadable.  The advantage to the balloon approach is that it
seems it would require less operator attention then keeping a kite flying.

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

Date: 16 Jul 94 23:30:16 GMT
From: [e-mail]
Subject: simple antennas
To: [e-mail]

----------------------------------------------------------------------
In Volume 94, issue 220 of Ham-ant digest, Tom Ferch asked;

>>Date: 12 Jul 1994 00:10:17 GMT
>>From: netcomsv!netcomsv!tbm128.thomas.com![e-mail]
>>Subject: Simple antenna
>>To: [e-mail]
>>
>>I am interested in making a simple antenna for my Realistic DX - 440.
>>
>>If I set up seperate antenna wires for each frequency band that I
>>am interested in (16, 19, 25, 31, 41, 49 meter bands) can I
>>connect them to my radio with one wire or will that affect their
>>performance?  Should I use coax between my antennas and my radio?
>> What is the best wire to use for my antennas?
>>
>>Any feed back would be greatly appreciated.
>>
>>Tom Ferch
>>
------------------------------


  since I am not sure how much space or what he is looking for,
I offer these two ideas....

1)   The old fashioned longwire, or

2)   Multi band no trap dipole...


    ----------------------------\ || /----------------------------
        ------------------------ \||/------------------------
            ---------------------/||\---------------------
              ------------------/ || \-----------------
                                  ||
                                  ^^
                               Common feedpoint


The wire used in this antenna is tv rotator wire.  This type of antenna
was the first antenna that I used as a swl.

The feedpoint was a hamfest special balun feeding into rg58.


      Regards,
      Vernon Erle Ikeda
      AX25:      ve2mbs@ve2fkb.#mtl.pq.can.noam
      Internet:  [e-mail]

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

Date: Fri, 15 Jul 1994 17:19:52 GMT
From: psinntp!news.rlcn.rl.af.mil![e-mail]
Subject: Specs, DAIWA Remote Sensor?
To: [e-mail]

We are developing an automated test device here that requires input
from a remote power sensor like the Daiwa U-66H,V,orS series devices
that sit in-line with the antenna and provide power information to
their NS-660 series power meters (although we will be taking the
information directly, digitizing it, and processing it from there).
Problem seems to be getting information about the remote attachments; I
have been unable to get any information through the usual vendors.
There doesn't seem to be an easily accessible, knowledgable source for
detailing what the remote devices actually provide to the power meter.
Any assistance from people familiar with these devices is appreciated.
We are presuming that it provides forward and reverse power at the
antenna output, with some scaling factor/transfer function based on the
coupling used in the main device necessary to accurately portray the
true power.  More detailed information would be very helpful.  Any
ideas or suggested contacts out there?

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

Date: Thu, 14 Jul 1994 15:26:25 GMT
From: gatech!kd4nc!ke4zv![e-mail]
To: [e-mail]

References <2vak22$[e-mail]>, <[e-mail]>, <[e-mail]>φ
Reply-To : [e-mail] (Gary Coffman)
Subject : Re: Antenna on my boat??

In article <[e-mail]> [e-mail] (Jeffrey Herman) writes:
>In article <[e-mail]> [e-mail] (Gary Coffman) writes:
>>
>>Probably a better idea though is to use a halfwave radiator so you
>>don't *need* any groundplane. That's an 18 foot whip on 11 meters,
>>and you'll need a matching network to match to the high base impedance,
>....
>
>I wouldn't recommend this type of antenna for a small boat. The
>base of the 18 foot vertical will be subjected to violent torquing
>due to the severe motions which are always encountered on smaller
>boats.

That's a good point, but probably more applicable to salt water
boating than to fresh water river or lake boating where large
waves are uncommon. I think the bigger problem would be bridge
and overhanging tree clearances. A couple of non-metallic stays
should reduce the torquing on the base, if that proved to be a
problem.

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: Sat, 16 Jul 1994 05:21:05 GMT
From: news.Hawaii.Edu!kahuna![e-mail]
To: [e-mail]

References <[e-mail]>, <[e-mail]>, <[e-mail]>
Subject : Re: Antenna on my boat??

In article <[e-mail]> [e-mail] (William Vaughn) writes:
>

I wrote:

>>Of course, being  an ex-Coast Guard Radio Officer I must in good
>>conscience say that one should/must have a VHF marine band radio;
>>the USCG has an excellent coastal/lake VHF radio system and have
>>radiomen listening 24 hours per day to channel 16 (156.80 MHz)
>>just waiting to assist you. The antenna of choice is a 5/8 wave
>>vertical; but a 1/4 wave ground plane atop a mast would suffice.
>
>>Jeff NH6IL
>
>Jeff, buddy. We are talking about a "CB" antenna here. Why waste time on the
>silly thing. Being an ex CG radio officer you are probably aware that the
>coast guard does not monitor CB radio any longer. If there is a CB radio in
>the comms room the radioman(person) has the gain and volume turned all the way
>down. Being an ex CG radio officer how many times have you lost a person who
>had a cb and had to relay thru someone who had a VHF?

Why do you think I suggested getting a VHF radio? Sheesh. But, here in
Hawaii our fishing fleet operates  on CB channel 19, so one's best bet
is having both a CB and a VHF radio here.

Whatever lake the original poster is operating on might be so small
that there is no VHF marine  system in operation there. So, if his
comms are entirely dependent upon his CB radio then he'll want the
best possible antenna. It's possible the lake has a REACT monitor
listening on channel 9.

>I suggested that he buy
>one because they are cheap and he won't get that much better performance
>anyway.  Those vhf antennas you have for your boat, did you make them yourself
>or did you buy one of those compromise fiberglass ones?

We're talking about a  wavelength of 11 meters - commercial antennas
at this wavelength are all compromises (unless they're half wave
length).

On the VHF marine band the wavelength is less than  2 meters so
the commercial antennas are not compromises; they even  provide
a certain amount of `gain' from their lower angle of radiation.

I use a homebuilt 1/4 groundplane atop the mast of my sailboat for
my VHF radio. You want a high angle of radiation off a sailboat
antenna because the wind acting on the sails keeps the boat heeled
over at sometimes drastic angles! Even with the sails  down the
boat is  subject to a  rocking motion due to ocean  swell, so
again one would still want an antenna with a high angle of radiation.

I think we've beat this topic to death.

Jeff NH6IL

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

Date: Fri, 15 Jul 1994 06:58:29 GMT
From: news.Hawaii.Edu!kahuna![e-mail]
To: [e-mail]

References <[e-mail]>, <[e-mail]>, <[e-mail]>
Subject : Re: Antenna on my boat??

In article <[e-mail]> [e-mail] (William Vaughn) writes:
>
>Gary, go down to radio shack or your local marine/bait/hardware store and buy
>a shakespere marine fold down whip for your cb.

This is the second time today that someone has made reference to
`buying' an item that  can easily be built (the earlier item
was an antenna tuner). Gary's idea of a half-wave vertical is
excellent for a base station but might suffer under marine
conditions.

We shouldn't be so quick to direct someone to  buy when we,
as amateurs whom are renowned for our skills of building something
out of nothing, can fabricate many station items ourselves.

If the original poster wanted to buy a ready-to-go antenna that
didn't require a ground he wouldn't have posed his question concerning
a below-the-waterline ground plate.

In general, the best choices of shipboard antennas are:

1. Halfwave wire dipole extending from a mast to the stern or another
   mast (large powerboat or sailboat).
2. Halfwave vertical (heavy displacement ships, or powerboats operated
   in protected waters).
3. Quarter wave vertical in conjunction with a below-the-waterline
   ground plate (any vessel).
4. A random wire between masts, or mast and stern in conjunction with
   a below-the-waterline ground plate (large powerboat or sailboat).

I wouldn't want the commercial fiberglass `compromise' CB antennas on
a boat of mine; my radio is my lifeline to the shore - I want to
make sure my signal is heard!

Of course, being  an ex-Coast Guard Radio Officer I must in good
conscience say that one should/must have a VHF marine band radio;
the USCG has an excellent coastal/lake VHF radio system and have
radiomen listening 24 hours per day to channel 16 (156.80 MHz)
just waiting to assist you. The antenna of choice is a 5/8 wave
vertical; but a 1/4 wave ground plane atop a mast would suffice.

Jeff NH6IL

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

End of Ham-Ant Digest V94 #225
******************************