QRZ! Ham Radio 4/QRZ Ham Radio Callsign Database - Volume 4.iso/digests/antenna/940019.txt

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

Date: Mon, 31 Jan 94 04:30:28 PST
From: Ham-Ant Mailing List and Newsgroup <[e-mail]>
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Subject: Ham-Ant Digest V94 #19
To: Ham-Ant


Ham-Ant Digest              Mon, 31 Jan 94       Volume 94 : Issue   19

Today's Topics:
                          Antenna pre-amps.
                      Computing antenna coverage
                       Dipole supplies (4 msgs)
                    Info on ACE brand base antenna
                RG-58 and Discone ant. problem at VHF
                          RS Rotor (2 msgs)
                    Where can I find copper-weld??

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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, 27 Jan 1994 17:06:34 GMT
From: catfish!cscsun![e-mail]
Subject: Antenna pre-amps.
To: [e-mail]

[e-mail] wrote:
: Hi,

:     Can anyone tell me the disadvantages/advantages of using an antenna
: pre-amp?

Advantages: Better apparent noise figure since the coax attenuation is
no longer a factor (for antenna mounted amps), much higher signal levels,
inproved copy on waek signals.

Disadvantages: Your transmitter output must backwash thru the thing - either
the amp itself must detect the inbound RF and switch itself away, or you
must provide a switching relay and the appropriate signal to do it manually.
Additional risk of lightning damage since you've got to run power up the
coax or a separate cable, and now there's a sensitive little GasFET up there
waiting for a strike.  Greater chance of front end overload on relatively
strong signals (not an issue with an RF gain control.)

--
David Tiller        | Network Administrator    | Voice: [phone]       |
[e-mail]        | Randolph-Macon College| Fax:   [phone]       |
[e-mail]    | P.O. Box 5005        | This space for rent.        |
ICBM: 37 45N 77 45W    | Ashland, Va 23005    |                             |

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

Date: 29 Jan 94 20:19:12 GMT
From: psinntp!psinntp!arrl.org![e-mail]
Subject: Computing antenna coverage
To: [e-mail]

Pages 23-8 to 23-10 of the ARRL Antenna Book discuss this
for VHF.  The RSGB Microwave Handbook volume I and the
VHF/UHF DX book also have useful information on coverage.

Actually, coverage area for an antenna is misleading--it
ignores the capability of the equipment and the effect
atmospheric conditions have on propagation.

For example, there are long line of sight paths that
might be too long for the free space range of simple
wide bandwidth microwave gear.  On the other hand,
the coverage with 1500 watt transmitters and narrow
bandwidth sensitive receivers can be considerably
in excess of line of sight.

Matthew B Cravit ([e-mail]) wrote:
: A friend of mine asked me this question, and I do not know the answer.
: If one has an antenna (say a vertical or something, as opposed to a
: beam) that is x feet above ground level, how does one compute the
: approximate coverage area of that antenna (in square miles)? For
: example, see the following diagram
:         _
:         |     |
:         |     |
:         |     |
:         |    _|_
:         |x    | |
:         |    | |
:         |    | | Tower
:         |    | |
:         |    | |
:         |    | |
:       ----------------------------------------Ground---------

: If we assume that the distance x is, say, 200 feet and that the ground
: around the antenna is relatively flat, is there a way to estimate the
: area of coverage for that antenna?

--
Zack Lau  KH6CP/1           2 way QRP WAS
                           8 States on 10 GHz
Internet: [e-mail]   10 grids on 2304 MHz

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

Date: Sat, 29 Jan 1994 22:16:43 GMT
From: world![e-mail]
Subject: Dipole supplies
To: [e-mail]

In article <[e-mail]> [e-mail] (Cliff Sharp) writes:
>In article <[e-mail]> [e-mail] (Julian Macassey) writes:
>>    As I intend to make various loops, dipoles and Beveridges, I
>>could save a dollar or two if I can find a supplier who can sell me a
>>1,000 ft reel of 14 AWG stranded copper at less than $0.085 per foot.
>>Of course, shipping and tax costs will sway this pricing.
>
>   I would be REALLY surprised if some local electrical supply dealer
>couldn't sell you #14 insulated wire at less than $85/1000 ft. roll.
>
>   No idea on insulators, etc. though.

I buy #14 stranded THHN (teflon coated) insulated wire at Home Quarters
for something like $12 or so for 500'. The teflon is great as snow does
not stick to it too well! (Get black, it is pretty invisible once up).

For insulators, I use budwig center (hi-q labeled) insulators. These are
the same things Kurt Sterba uses and recommends. For the ends, get the matching
small size end insulators. The centers sell for $6 and the end ones for $1.50
a pair or so.

73,

Dan N1JEB
--
---------------------------------------------------------------
Daniel Senie                 Internet:     [e-mail]
Daniel Senie Consulting                    [e-mail]
508-365-5352                 Compuserve:   74176,1347

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

Date: 30 Jan 1994 13:55:02 GMT
From: usc!howland.reston.ans.net!usenet.ins.cwru.edu!magnus.acs.ohio-state.edu![e-mail]
Subject: Dipole supplies
To: [e-mail]

Julian Macassey wrote:

>        And finally the $64,000.00 question. What is recommended as
>the best "rope" to hold up my cheesy antennas? It should be rot and UV
>proof. Nylon I believe will rot in the sun, as will polyester. What is
>the definative word? Any Plastics men on the net who can answer this?

ANY organic material (plastics, hemp, human skin :-) ) is damaged by
UV.  Plastics can be doped with "UV retardant" additives, but that only
slows down the deterioration, it doesn't stop it.  The best "UV
retardant" of all is carbon-black, a pigment that totally absorbs all
light of all wavelengths.  All black plastic (I think) is loaded with
carbon-black pigment, so that is the key.

One source of black polyester rope is Synthetic Textiles, Inc., 2472
Eastman Avenue, Bldg 21-22, Ventura, CA 93003, [phone].  I have
never dealt with them, but received their literature.  For myself, I use
plain nylon rope and replace it every couple of years.

73, Van - W8UOF
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
*   It ain't wot you don't know 't gets you into trouble.   *
*   It's wot you know 't ain't true. - "Mr. Dooley"         *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
[e-mail]

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

Date: Fri, 28 Jan 1994 20:15:36 GMT
From: netcomsv!netcomsv!bongo![e-mail]
Subject: Dipole supplies
To: [e-mail]

    Being a standard radio amateur (parsimonious appliance
operator), I am trying to locate low cost suppliers for wire and
insulators.

    Radio Shack is my pricing reference for dipole supplies. They
have 14 AWG stranded copper wire in 70ft hanks which costs $0.085
per foot. Texas Towers has the same stuff for $0.1 per foot. Mark one
up for Radio Shack.

    As I intend to make various loops, dipoles and Beveridges, I
could save a dollar or two if I can find a supplier who can sell me a
1,000 ft reel of 14 AWG stranded copper at less than $0.085 per foot.
Of course, shipping and tax costs will sway this pricing.

    I am also looking for low rent suppliers (in bulk no doubt) of
egg and dog-bone insulators.

    And finally the $64,000.00 question. What is recommended as
the best "rope" to hold up my cheesy antennas? It should be rot and UV
proof. Nylon I believe will rot in the sun, as will polyester. What is
the definative word? Any Plastics men on the net who can answer this?

--
Julian Macassey, N6ARE  [e-mail] Voice: [phone]
Paper Mail: Apt 225, 975 Hancock Ave, West Hollywood, California 90069-4074

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

Date: 29 Jan 94 17:11:33 GMT
From: library.ucla.edu!csulb.edu!nic-nac.CSU.net!usc!yeshua.marcam.com!news.kei.com!ddsw1!indep1![e-mail]
Subject: Dipole supplies
To: [e-mail]

In article <[e-mail]> [e-mail] (Julian Macassey) writes:
>    As I intend to make various loops, dipoles and Beveridges, I
>could save a dollar or two if I can find a supplier who can sell me a
>1,000 ft reel of 14 AWG stranded copper at less than $0.085 per foot.
>Of course, shipping and tax costs will sway this pricing.

   I would be REALLY surprised if some local electrical supply dealer
couldn't sell you #14 insulated wire at less than $85/1000 ft. roll.

   No idea on insulators, etc. though.

--
+------------------------------------------------------------------------------+
|   Cliff Sharp  |                [e-mail]               |
|     WA9PDM     |                                   |
+------------------------------------------------------------------------------+

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

Date: Sat, 29 Jan 1994 16:11:53 GMT
From: library.ucla.edu!europa.eng.gtefsd.com!howland.reston.ans.net!vixen.cso.uiuc.edu!uwm.edu!psuvax1!news.cc.swarthmore.edu!netnews.upenn.edu!netnews.cc.lehigh.edu!ns1.cc.lehigh.edu!c002@@
Subject: Info on ACE brand base antenna
To: [e-mail]

I am looking for  information on a ACE brand base antenna found in the popular
electronics....

thanks
DAvid
--

:)****************************************************************(:
**                                     **  The Flying HAm         **
**          David Roseman              **  [e-mail]        **
**                                     **                         **
**    Cole's Law:                      **  Les Boules Qui Roulet  **
**           Thinly sliced Cabbage     **  Toutes Les Poules!!    **

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

Date: 29 Jan 1994 17:41:50 -0600
From: usc!cs.utexas.edu![e-mail]
Subject: RG-58 and Discone ant. problem at VHF
To: [e-mail]

> A guy I know recently installed a Discone Antenna (R-S brand) and 50 ft of
> RG 58 for his scanner.  Problem: The rubber duck on the handheld unit, 20

There's your answer right there:  RG58 and UHF don't mix very well.  I
don't have the RS $3 Catalog near me, but I think you'll be surprised at
the dB loss at UHF.  And I don't recall the discone design having much,
if any, gain.

On my indoor discone, I use the RG8/M from RS which has less loss at the
higher frequencies.  You'll find a lot of folks who'll recommend RG6 for
scanner use, too.  (I don't use it 'cause it's ~70 ohm and I like to use
my discone for my 2m HT).

73,

Peter Laws,
Associate Editor - Arkansas,
RCMA _Scanner Journal_,


Peter Laws <[e-mail]> | "That's the President of the United States
n5uwy@ka5bml.#nwar.ar.usa.noam   | you're talking about, pinhead."-VP Al Gore

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

Date: 29 Jan 1994 20:26:00 GMT
From: usc!cs.utexas.edu!swrinde!hopper.acm.org!ACM.ORG![e-mail]
Subject: RS Rotor
To: [e-mail]

Does anyone have any experience with Radio Shack antenna rotors?  I can find
no information about load capacity for weight or wind-area of antennas, etc.
I'm looking for a rotor for a 14 ele 2m beam I plan to build, and wondered
if the RS offering might do.
Thanks for your help!
-Brian
[e-mail]
   -or-
[e-mail]

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

Date: Sat, 29 Jan 1994 22:18:51 GMT
From: world![e-mail]
Subject: RS Rotor
To: [e-mail]

In article <2iegoo$[e-mail]> [e-mail] writes:
>Does anyone have any experience with Radio Shack antenna rotors?  I can find
>no information about load capacity for weight or wind-area of antennas, etc.
>I'm looking for a rotor for a 14 ele 2m beam I plan to build, and wondered
>if the RS offering might do.
>Thanks for your help!
>-Brian
>[e-mail]
>   -or-
>[e-mail]

The RS rotor is also the Alliance U105 (and is sold under the channel master
label as well). You should be able to get loading info from someone who sells
one of these brand labels. Alliance also has a thrust bearing which has guy
anchor spots. So you could guy your installation if needed.

--
---------------------------------------------------------------
Daniel Senie                 Internet:     [e-mail]
Daniel Senie Consulting                    [e-mail]
508-365-5352                 Compuserve:   74176,1347

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

Date: 28 Jan 94 09:45:02 EDT
From: ucsnews!sol.ctr.columbia.edu!howland.reston.ans.net!vixen.cso.uiuc.edu!newsrelay.iastate.edu!destroyer!nntp.cs.ubc.ca!utcsri!newsflash.concordia.ca!sifon!clouso.crim.ca!comback!willow!alexr@
Subject: Where can I find copper-weld??
To: [e-mail]

In article <[e-mail]> [e-mail] (Jan Chojnacki) writes:
> >Subject says it all...
> >
> >I've checked with all the hardware stores and electrical supply
> >houses in my area and nobody has the stuff. Am I looking in the
> >wrong places???
> >
>
> Tried a welding supply house?
>
>  -----------------------------------------------------------------------------
>                             : If you eat a live toad first thing in the
>  [e-mail]  : morning, nothing worse will happen to you all
>                             : day.
>                             : To you or the toad.
>  -----------------------------------------------------------------------------

We sell some. Phone number is [phone]

--

==========================================================================
Alexandre Rousseau                       UUCP:        [e-mail]
                                     Internet: [e-mail]
23 MIPS is still not enough...           Bell:           [phone]
(A2000 + '040 + 20Mb)
==========================================================================

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

End of Ham-Ant Digest V94 #19
******************************