QRZ! Ham Radio 4/QRZ Ham Radio Callsign Database - Volume 4.iso/digests/antenna/940068.txt

Internet Message Format | 1994-11-13 | 14KB

Date: Wed, 16 Mar 94 04:30:31 PST
From: Ham-Ant Mailing List and Newsgroup <[e-mail]>
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Subject: Ham-Ant Digest V94 #68
To: Ham-Ant


Ham-Ant Digest              Wed, 16 Mar 94       Volume 94 : Issue   68

Today's Topics:
                          Field Day Antennas
                       looking for comments...
                      NOAA Antenna Advice please
                              Subscribe
                            test (2 msgs)
            Thick Ethernet as Transmission Line? (3 msgs)

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Problems you can't solve otherwise to [e-mail].

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.
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Date: 14 Mar 94 14:31:05 GMT
From: ncrgw2.ncr.com!ncrhub2!tdbunews!nsc32![e-mail]
Subject: Field Day Antennas
To: [e-mail]

Last year one of the guys in our club brought a weather balloon and a long wire.
The wind got too much to keep the balloon up, so the long wire, was stung from
tree to lamp pole to lamp pole, etc.  A tuner matched the wire from 160m through
10m.  It is my understanding that the balloon will be tried again this year.  We are
hoping for less wind.

Bill

-----------------------------------------------------------------
Bill Starkgraf                          [e-mail]
AT&T Global Information Solutions       [phone]
El Segundo, CA                          [phone] x5754

Call: KD6UQB                            Simi Settlers ARC
                                        Simi Valley, CA
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Date: 15 Mar 1994 17:30:56 GMT
From: ihnp4.ucsd.edu!dog.ee.lbl.gov!agate!howland.reston.ans.net!usc!elroy.jpl.nasa.gov!swrinde!sgiblab!cs.uoregon.edu!news.uoregon.edu!oregon.uoregon.edu![e-mail]
Subject: looking for comments...
To: [e-mail]

Terry Burge asked about perhaps putting up a 5/8 wave vertical for 20 mtrs.,
mounted with about 60 radials, only 20 or so feet long.I used a cheapo MFJ
tuner at the feedpoint and got a good match across the entire 20 meter band.
It would also load up well on 40 with the same settings: I still don't know
why or how. This was an excellent Dx performer on 20 and 40, and was medio-
cre on 80. I later moved the tuner into the shack, using heliax for a feeder,
about 30 feet, and noticed little or no difference.  BTW, the strong low-
angle on 20 meters from the antenna caused some big-time telefone RFI, which
I had to fix for a few neighbors right after the first big springtime night
opening over the pole into Europe. Good luck!

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Date: Tue, 15 Mar 1994 14:48:48 GMT
From: catfish!cscsun![e-mail]
Subject: NOAA Antenna Advice please
To: [e-mail]

Herb Dieben ([e-mail]) wrote:

: Please comment on the following;
: I have been trying to get NOAA and or Meteor data using a simple 137 Mhz
: J-pole with an antenna mounted GasFet pre-amp.The feed line is about 40 feet
: of RG8.Results of 24hrr/day monitoring for about 8 days has yielded nothing
: at all.
: If the antenna is the problem,how much better do I have to be??A computer
: controlled 20 element Yagi seems a bit much to make but could be done.
: Problem is that I have no assurance that that is good enough.So what should
: be the next step?
: Any advice would be much appreciated.Thanks in advance.Herb.


Seeing as I can get NOAA and Meteor birds on my scanner with a rubber duck
antenna, I'd say there's something else wrong....what freq are you trying?
Some birds are turned off periodically to prevent interference or because
their light angles are bad.  There are regular postings about them on one
on the rec.radio groups - have a look, if you've never seen one.
--
David Tiller           | Network Administrator | Voice: [phone]   |
[e-mail]        | Randolph-Macon College| Fax:   [phone]   |
"Drunk, [Beowulf] slew | P.O. Box 5005         | ICBM:  37d 42' 43.75" N |
no hearth companions." | Ashland, Va 23005     |        77d 31' 32.19" W |

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Date: 16 Mar 94 05:03:49 GMT
From: [e-mail]
Subject: Subscribe
To: [e-mail]

subscribe

wish to partake in antenna forum, TNX

Jim, K1ZX

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Date: Tue, 15 Mar 1994 09:40:21
From: ihnp4.ucsd.edu!galaxy.ucr.edu!library.ucla.edu!europa.eng.gtefsd.com!darwin.sura.net!spitfire.navo.navy.mil!nrl7350.nrlssc.navy.mil![e-mail]
Subject: Test
To: [e-mail]

This is a test

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Date: 15 Mar 1994 13:50:57 -0800
From: ihnp4.ucsd.edu!dog.ee.lbl.gov!agate!apple.com!apple.com![e-mail]
Subject: test
To: [e-mail]

[e-mail] (Victor Chen) *keeps* posting:

>testing



What is this?  The Internet equivalent of a kerchunk?


Kok Chen, AA6TY                [e-mail]
Apple Computer, Inc.

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Date: 14 Mar 94 14:36:17 GMT
From: ncrgw2.ncr.com!ncrhub2!tdbunews!nsc32![e-mail]
Subject: Thick Ethernet as Transmission Line?
To: [e-mail]

In article [e-mail], [e-mail] (NX7U) writes:
-->only for LOW power applications.
-->Probably stamped on the side of the cable somewhere is "30V MAX".  These cables
-->are not designed for any degree of current/voltage stress or heat dissipation.
-->Other than that, they're fine!


When in doubt, one coluld always call Belden.  I have some thin wire Ethernet cable
and did not know if it could be used with 2m and 70cm, so I called Belden (I don't
have the number now - it is an 800 number) and explained what I wanted to do.
They assured me it would work just fine since they use such frequencies to test their
cables.

Bill

-----------------------------------------------------------------
Bill Starkgraf                          [e-mail]
AT&T Global Information Solutions       [phone]
El Segundo, CA                          [phone] x5754

Call: KD6UQB                            Simi Settlers ARC
                                        Simi Valley, CA
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Date: 15 Mar 1994 08:25:57 -0800
From: ihnp4.ucsd.edu!usc!howland.reston.ans.net!usenet.ins.cwru.edu!eff!news.kei.com!ssd.intel.com!chnews!ornews.intel.com!ornews.intel.com![e-mail]
Subject: Thick Ethernet as Transmission Line?
To: [e-mail]

In article <[e-mail]> [e-mail] (Jack GF Hill) writes:
>[e-mail] (Phil Graham) writes:
>
>> 2) At about 100MHz the attenuation starts to increase.   I would not recommen
>> it for 2M or 70cm... Great for HF!
>
>*THAT* is what I said, and opined that the additional capacitance of
>teh multi-layer shield coverage might be the reason... I was booed and
>shoved aside.
>
>So, I am now curious. How did you make your measurements? What data
>led you to conclude your attenuation was poor above 100 MHz?

Let me jump in here and say that I've also found it to be lossy above about
100 Mhz.  I don't use it for anything above 30Mhz now.  I've tried both the
yellow jacket stuff and some harse environment orange jacket.  I don't have
my Belden book here but it is 50 ohms and has no specs on VHF line loss.
Since it wasn't working to my expectations on 2 meters, I removed the 100'
piece and made some measurements.  I used a dummy load/watt meter at the
far end for the first test and the other test was made with the far end
open while I checked the SWR at the driven end.  The same tests with a
similar length of RG-213 confirmed my suspicions that the Ethernet is lossy.
I don't understand why because its got Teflon(tm) insulation, a copper
coated, fat and solid center conductor, and is double shielded.  Oh well.
I probably shouldn't even be using it for 10 meters.
While I don't remember the figures, I made the measurements when the line
was fairly new and it had no Vampire taps in it.  The yellow jacket has
faded now.  I had no trouble putting N connectors or PL-259's on it.
Lately I've been using some 3/4" hardline that is surplus cable TV stuff.
This is really good stuff but matching the 75 ohms is interesting and
putting connectors on it is really a bitch.



--
[e-mail]  WA7LDV

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Date: Tue, 15 Mar 1994 20:16:38 GMT
From: ihnp4.ucsd.edu!dog.ee.lbl.gov!agate!howland.reston.ans.net!vixen.cso.uiuc.edu!sdd.hp.com!hpscit.sc.hp.com!cupnews0.cup.hp.com!news1.boi.hp.com!hp-pcd!hpcvsnz![e-mail]
Subject: Thick Ethernet as Transmission Line?
To: [e-mail]

Jim Garver ([e-mail]) wrote (about Thick Ethernet cable):

: Let me jump in here and say that I've also found it to be lossy above about
: 100 Mhz.  I don't use it for anything above 30Mhz now.  I've tried both the
: yellow jacket stuff and some harse environment orange jacket.  I don't have
: my Belden book here but it is 50 ohms and has no specs on VHF line loss.
: Since it wasn't working to my expectations on 2 meters, I removed the 100'
: piece and made some measurements.  I used a dummy load/watt meter at the
: far end for the first test and the other test was made with the far end
: open while I checked the SWR at the driven end.  The same tests with a
: similar length of RG-213 confirmed my suspicions that the Ethernet is lossy.
: I don't understand why because its got Teflon(tm) insulation, a copper
: coated, fat and solid center conductor, and is double shielded.  Oh well.

Very interesting!  I have 300 feet of the foam Teflon insulated LAN
cable, foil/braid/foil/braid shielded, which I measured at 2M and 440,
and found to be almost exactly the attenuation I would predict from
the cable geometry.  It was better on both bands than RG-213/U (specs
_and_ measured same way), and worse than 9913 -- which is exactly what
I expected.

What's going on here?  Anyone else out there measured the stuff?  Like
Jim notes, if there is higher loss at VHF-UHF, what is the loss mechanism?
Though the catalog specs (Belden) don't go above 100MHz, they do follow
the expected sqrt(f) pattern that far.  Could some lengths have enough
local impedance variation with distance that they start acting like
filters above 100MHz?

73, K7ITM

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Date: 15 Mar 1994 21:01:26 GMT
From: ihnp4.ucsd.edu!dog.ee.lbl.gov!agate!howland.reston.ans.net!cs.utexas.edu!swrinde!sdd.hp.com!hpscit.sc.hp.com![e-mail]
To: [e-mail]

References <2lo8jt$[e-mail]>, <[e-mail]>, <[e-mail]>p.com
Subject : Re: Field Day Antennas

Pete Rossi ([e-mail]) wrote:

: Use the wind as an advantage.  If your FD location has steady dependable
: winds then use a kite.

: Last year I operated FD from the beach were there was a nice steady 10-15 MPH
: breeze all day.  A 3 ft delta kite kept 33 feet of #22 wire (for 20 meters)
: vertical for several hours.  No problems.   Worked great.  I may try the
: same setup with 66 feet of wire for 40 meters this year.

: Pete Rossi - WA3NNA                  [e-mail]
: =================================================================

This is a great idea if you have a steady wind. I happen to be looking at
a kite catalog that has a thing called a stratoscoop. A member of the airfoil
family. You are supposed to use 250 lb line! I have a small 9sqft parafoil
that will really pull. This stratohoister should haul up an antenna. So,
what is the breaking point for RG-8 ? :)


Bill
wb6rzg

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Date: 15 Mar 1994 17:39:43 GMT
From: ihnp4.ucsd.edu!pacbell.com!sgiblab!swrinde!cs.utexas.edu!howland.reston.ans.net!wupost!bigfoot.wustl.edu!cec3![e-mail]
To: [e-mail]

References <[e-mail]>, <[e-mail]>, <[e-mail]>wustl.
Subject : Re: Grounding and lightning protection

Gary Coffman ([e-mail]) wrote:
: All I've seen are summaries, in Broadcast Engineering articles and
: in Roger Block's book The Grounds for Lightning and EMP Protection.
: He mentions a video tape the FAA made of the tests showing the
: dissipation grids receiving repeated lightning strikes, and heavier
: than normal strikes at that.

: Mobile Radio Technology had a series in the April and October 1988,
: and January 1989 issues about lightning prevention systems. They
: tried to give both sides equal time, but it's clear that the dissipation
: arrays are at best only minimally preventative, if at all.

Now I have no technical expertise here, but I'd like to ask a couple
of questions: 1) Does the Corona effect prevent strikes, 2) do spline
balls work, 3) what about "feeler" charges?  The reason I ask is that
Richardson Wireless Klub (K5RWK) had a meeting last night in which
a Richardson ham (I think) who works for TU Electric came and gave a
~1.5 hour lecture on lightning, prevention, and RF grounding.  He
brought up some of the above-mentioned issues, and also said at the
end that he submitted an article to "one of the ham magazines."
Your thoughts???

--jesse

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End of Ham-Ant Digest V94 #68
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