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1994-11-13
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Date: Mon, 13 Jun 94 04:30:18 PDT
From: Ham-Ant Mailing List and Newsgroup <ham-ant@ucsd.edu>
Errors-To: Ham-Ant-Errors@UCSD.Edu
Reply-To: Ham-Ant@UCSD.Edu
Precedence: Bulk
Subject: Ham-Ant Digest V94 #182
To: Ham-Ant
Ham-Ant Digest Mon, 13 Jun 94 Volume 94 : Issue 182
Today's Topics:
'Bending' beverage
2 antennas into receiver?
80 Meter Receiving Loop
<<Best dual band verticals?>> (2 msgs)
beverage???
Curing RF Voltage on Rig case in Mobi (2 msgs)
Dielectric antennas?
help w/antenna/amp problem
Mobile Antennas
moment method
need MFJ-941D tuner manual
seek old CDR rotor (or replacement)
Wind Loading
Send Replies or notes for publication to: <Ham-Ant@UCSD.Edu>
Send subscription requests to: <Ham-Ant-REQUEST@UCSD.Edu>
Problems you can't solve otherwise to brian@ucsd.edu.
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: 12 Jun 1994 14:14:47 GMT
From: ihnp4.ucsd.edu!swrinde!hopper.acm.org!ACM.ORG!SMITHSON@network.ucsd.edu
Subject: 'Bending' beverage
To: ham-ant@ucsd.edu
I just put up a _lot_ of fence on my 4 acre lot (we have horses). This
fence would make an excellent support for a beverage, but I would have to
make some turns to get the kind of length I'd need. does anyone know if
there is a problem in beverages not being straight?
Thanks!
-Brian n8wrl
------------------------------
Date: Sun, 12 Jun 94 10:00:00 -0800
From: ihnp4.ucsd.edu!dog.ee.lbl.gov!agate!iat.holonet.net!megasys!tim.marek@network.ucsd.edu
Subject: 2 antennas into receiver?
To: ham-ant@ucsd.edu
It wont work. I sugest you use a coak switch to switch between the two.
The radio is expecting a 50 Ohm load. The BNC "TEE" is not a Power
divider with 1/4 wavelength lengths between feeds, Its just a adaptor,
NO MORE. If you want broadband cvrg with one feedline I suggest a
broadband Discone or Log Periodic yagi, Both available commercially but
why dont you build them and save 90% of your money for something else.
Besides Homebrewing is fun and you will leard a thing or two about
antennas. Have Fun! See Ya...l. Tim, NC7K...sk
------------------------------
Date: 13 JUN 94 01:17:31 AST
From: newsflash.concordia.ca!nstn.ns.ca!news.unb.ca!UNBVM1.CSD.UNB.CA@uunet.uu.net
Subject: 80 Meter Receiving Loop
To: ham-ant@ucsd.edu
I have been trying to build the Maxi-Loop 80 meter Receiving antenna
described in 73 Amateur Radio of Dec. 1993, pp. 42-48 without much
success.
It is basically a box, 18 inch square, with 6 turns of wire going,
through a 7th turn to a variable capacitor rated 75 pF, for 80 meter
(and 200 pF for 160 m or so). What I built, with a VC that goes up
to 138 pF, does not work better than a dummy load no matter what I
do with the VC. On 20 meters it seems to tune, especially as I get
to the upper limit of 138 pF. Strangely enough, reception was noisy.
I tried another VC that goes from 9 to 305 pF but it is useless.
Can anyone offer some help on this problem?
Luis Nadeau VE9LN
------------------------------
Date: Sun, 12 Jun 1994 14:19:34 GMT
From: ihnp4.ucsd.edu!swrinde!cs.utexas.edu!math.ohio-state.edu!darwin.sura.net!news.Vanderbilt.Edu!news@network.ucsd.edu
Subject: <<Best dual band verticals?>>
To: ham-ant@ucsd.edu
In a former article we saw...
---begin former article---
From: penneys@brahms.udel.edu (Robert Penneys)
Subject: <<Best dual band verticals?>>
Date: 11 Jun 1994 18:38:59 -0400
We are having some debate in the club about the best base station verticals
for 2m/440.
If you have a vote to cast one way or the other in the following categories:
$50-100 100-150 150-200 200-250 250 and up
we would love to hear it.
Tnx Bob
and PFEIFFEM@ctrvx1.Vanderbilt.Edu (PFEIFFEM_1) comments...
If you are going strictly by cost than by performance then you're mistaken!
Better try to poll people based on performance first.
------------------------------
Date: Sun, 12 Jun 1994 21:31:19 GMT
From: ihnp4.ucsd.edu!swrinde!howland.reston.ans.net!usenet.ins.cwru.edu!ncoast!fmsystm.telemax.com!fmsys!macy@network.ucsd.edu
Subject: <<Best dual band verticals?>>
To: ham-ant@ucsd.edu
In article <2tdee3$lgo@brahms.udel.edu> penneys@brahms.udel.edu (Robert Penneys) writes:
>
>We are having some debate in the club about the best base station verticals
>for 2m/440.
We've used several types for the couple local clubs I'm involved with.
What always seems to work best is the Diamond X-500 or X-500RH.
Yes, they wave around a bit in the wind, but they work very well.
(We've tried others, but keep coming back to the Diamond X-500)
Diamonds will not withstand direct lightning strikes. Some commercial
antennas seem to do better with lightning, but offer lesser performance.
Since we can buy a X-500RH (heavy duty version) for around $220, we've
decided to bear with replacing them when they are destroyed by lightning.
Around here, thats about every two years for an tower mounted unit.
Note: for some reason we have not tried the similiar Comet. I hear
other clubs have, and like it. Also, its a good idea to seal up these
fiberglass antennas with silcone seal when you assemble them. Every
once in a while, a leak around a joint will develop, probably from
the flexing in the wind.
Regards,
--
Macy M. Hallock, Jr. N8OBG +1.216.723.3030 macy@telemax.com macy@fms.com
Telemax, Inc. - F M Systems, Inc. 152 Highland Drive Medina, OH 44256 USA
------------------------------
Date: Sun, 12 Jun 1994 15:46:00 GMT
From: newsflash.concordia.ca!vax2.concordia.ca!hirschj@uunet.uu.net
Subject: beverage???
To: ham-ant@ucsd.edu
For the less educated of us, what is a beverage (no jokes
about root beer please).
Keywords: beverage
Message-ID: <12JUN199410465787@vax2.concordia.ca>
Organization: Concordia University
News-Software: VAX/VMS VNEWS 1.41
------------------------------
Date: 13 Jun 1994 04:17:11 GMT
From: ihnp4.ucsd.edu!swrinde!gatech!concert!inxs.concert.net!taco.cc.ncsu.edu!csemail.cropsci.ncsu.edu!samodena@network.ucsd.edu
Subject: Curing RF Voltage on Rig case in Mobi
To: ham-ant@ucsd.edu
In article <2te4d4$g4p@chnews.intel.com> cmoore@ilx018.intel.com (Cecil A. Moore -FT-~) writes:
>
>Hi Steve, Can you explain my problem. I have my bumper mounted mobile
>antenna grounded outside at the bumper with a choke balun on the
>transmission line. That ground was the only one in the system. Inside
>the cab, I have a separate battery and transceiver. I had RF in the cab
>something fierce. A two-foot ground wire from my transceiver to the
>S10 chassis lowered the RF in the cab to a neglible value. Do those
>results agree with what you said above? Where was my RF in the cab
>coming from and where did it go?
>
>73, KG7BK, OOTC, CecilMoore@delphi.com
Cecil-- I'm not sure you are giving me enough info to imagine your setup.
Here's a couple of points:
I don't discourage people from grounding their rig to the
interior/frame of the car...that may be wise *just* for the
rare case of live AC somehow coming in contact with the whip...
AND YOU being the connection to the car via the transmission line.
;^)
I don't discourage people from using chokes on their power cords
or mike leads or on their transmission lines. :^)
I personally prefer--and do, run my mobile rig from a stand-alone
battery that is never connected to the car's charging system...
When I analyse a mobile setup, I start from this logic:
Modern radios can convert battery energy into rf energy *without*
the transmission line/antenna/ground system being involved in
the frequency determination/energy-storage aspects...
(in contrast to arc & spark transmitters...see Communications
Quarterly, Spring 1994, "Arcs and Sparks: Part 1" article).
A good design modern xmtr is a closed system (rf-wise) except for
the coax connector.
Rf can be piped to an antenna via an entirely closed transmission
line--such as 95% coax with wrap.
Supposing that the antenna is mounted on a steel shell vehicle--
that vehicle having no openings greater than a very small
fraction of the wavelength being transmitted, then there is no
expectation that rf emitted external to the vehicle should appear
*within* the vehicle....provided that the coax is routed
correctly and the braid is properly connected to the exterior
of the vehicle in such a way as to assure a connection to a
large *exterior* surface area.
So it follows, that rf circulating on the interior of a steel shell
vehicle *either* originates inside the vehicle via leaks from the xmtr
or transmission line...*or* originates externally and is conducted
back into the interior.
Notice that I've set this up as a bifurcation type logic...I used to
repair cars for a living: a car that won't start has a problem with
(a) spark or (b) fuel...do the appropriate test to decide which...then
determine the next bifurcarted logic step to test..... :^)
Vince gave enough of a description of his roof mounted antenna system
that I'd guessed that the most *likely* solution would begin with
affixing the coax braid to the exterior of the car.
Now Cecil, I think you have an S-10 pickup truck...but I don't know
what antenna you have, how the bumper mount is feed...especially
the routing of the coax, whether you have made any attempt to make
sure the bumper is actually connected to the truck bed via a good
*rf* conductor, what the nature/specs of your "choke" balun is,
or even what band we are talking about....never mind the contrast of
2 M. to 80 M....10 M requires more precautions than 80 M. :^)
So post a good discription of your system...I'm game to think about it...
Someone reading this might think that the problem has already been solved.
But based on the logic I layed out above, Cecil has temporarily
routed the rf problem elsewhere in the cab....it's still there and *that*
is the problem: how is the rf getting into the cab...is it leaking from
the transmitter, from the coax (yes, folks, RF can easily leak from
improperly constructed or damaged coax), or is it coming back from the
exterior by some direct or *circuitous* route?
Remember, rf in the cab means *less* rf radiating! At home and mobile,
more people are running QRP than realize it! :^)
73/Steve/AB4EL nmodena@unity.ncsu.edu.
------------------------------
Date: 13 Jun 1994 04:59:09 GMT
From: ihnp4.ucsd.edu!swrinde!gatech!asuvax!chnews!cmoore@network.ucsd.edu
Subject: Curing RF Voltage on Rig case in Mobi
To: ham-ant@ucsd.edu
S. A. Modena (samodena@csemail.cropsci.ncsu.edu) wrote:
: >Hi Steve, Can you explain my problem. I have my bumper mounted mobile
: >antenna grounded outside at the bumper with a choke balun on the
: >transmission line. That ground was the only one in the system. Inside
: >the cab, I have a separate battery and transceiver. I had RF in the cab
: >something fierce. A two-foot ground wire from my transceiver to the
: >S10 chassis lowered the RF in the cab to a neglible value. Do those
: >results agree with what you said above? Where was my RF in the cab
: >coming from and where did it go?
: So post a good discription of your system...I'm game to think about it...
: 73/Steve/AB4EL nmodena@unity.ncsu.edu.
Thanks Steve, the antenna connector mount fits into the trailer hitch hole.
The bumper is tied to the frame through the double braid from an ethernet
cable. Freq is 10m and I have a dozen cores slipped over the RG-8x for
an RF choke. Inside, battery and transceiver were isolated from any metal.
There was only one frame ground at the base of the antenna. No tail gate
on the S10. If I touched the transceiver case and the S10 frame while
transmitting, I got bit. A two-foot piece of braid from the transceiver
chassis to the S10 chassis solved the problem. The SWR is 1/1 and the
coax is six feet long. Before I installed the ground strap on the transceiver,
I could change the SWR reading by touching the transceiver chassis. Now
the SWR reading is rock solid. Antenna is 98" whip.
Before the inside ground strap was added, a powered speaker connected to
my 2m rig completely isolated from the HF rig would turn on when I keyed
up on 10m. I've solved the problem but I don't know why. What do you think?
73, KG7BK, OOTC, CecilMoore@delphi.com
------------------------------
Date: 13 Jun 1994 05:30:40 GMT
From: ihnp4.ucsd.edu!agate!spool.mu.edu!bloom-beacon.mit.edu!noc.near.net!chaos.dac.neu.edu!chaos.dac!dean@network.ucsd.edu
Subject: Dielectric antennas?
To: ham-ant@ucsd.edu
Hi:
I would like to learn about Dielectric Antennas. Could anyone recommend
some reading materials, books, articles, etc.?
-Dean
------------------------------
Date: Sun, 12 Jun 1994 14:26:28 GMT
From: ihnp4.ucsd.edu!swrinde!howland.reston.ans.net!darwin.sura.net!news.Vanderbilt.Edu!news@network.ucsd.edu
Subject: help w/antenna/amp problem
To: ham-ant@ucsd.edu
In a former article we saw...
---begin former article---
From: koechig@garnet.msen.com (B Koechig)
Subject: help w/antenna/amp problem
Date: 11 Jun 1994 23:50:28 GMT
Here is the problem:
With my homebrew 2 meter j-pole and yaesu ft-23r I get an swr reading of
under 1.5:1 at both power levels. With the rf concepts amp I just
bought, if I use low power coming from the radio I get about 8 watts out
with still a good swr. However if I use the 5 watts out from the radio my
swr rockets to almost 3:1! I would think that both power levels would
reflect the same swr if everything was ok. Does anyone have any insight?
Thanks,
Bill Koechig N8PKA
Pontiac, MI
---end former article---
and PFEIFFEM@ctrvx1.Vanderbilt.Edu (PFEIFFEM_1) comments...
Bill,
My Nye Viking SWR meter requires about 10w to show true (?) SWR. Sounds like
yours too requires a minimum power to read correctly.
Good DX,
K5WIM
------------------------------
Date: Mon, 13 Jun 1994 04:29:27 GMT
From: ihnp4.ucsd.edu!usc!howland.reston.ans.net!europa.eng.gtefsd.com!newsxfer.itd.umich.edu!caen!saimiri.primate.wisc.edu!sal.wisc.edu!zimmer!news@network.ucsd.edu
Subject: Mobile Antennas
To: ham-ant@ucsd.edu
Not long ago I heard in this group about a great antenna made by a
small company in Texas (Austin?) that sells direct (I think the 2m
single band antenna was $19.95) to the public. Can anybody help me by
posting (or e-mailing) the name and phone # of the company. I'm sorry
I can't give more information. I only remember what is above.
Thanks.
73,
Rafael
(waiting for ticket)
------------------------------
Date: Sun, 12 Jun 94 10:02:00 -0800
From: ihnp4.ucsd.edu!dog.ee.lbl.gov!agate!iat.holonet.net!megasys!tim.marek@network.ucsd.edu
Subject: moment method
To: ham-ant@ucsd.edu
The ARRL Antenna Book or the ARRL Handbook would be good places to
start. Have Fun... Tim - NC7K...sk
------------------------------
Date: 13 Jun 1994 07:21:56 GMT
From: ihnp4.ucsd.edu!usc!nic-nac.CSU.net!vfoao0ix@network.ucsd.edu
Subject: need MFJ-941D tuner manual
To: ham-ant@ucsd.edu
Sy Jerry (SYJERRY@duq3.cc.duq.edu) wrote:
> I got a used MFJ-941D versa tuner II and do not have the manual for
> it. I'd appreciate it if someone who has it can send me a copy of it
> (is it a one page instruction sheet ?). or maybe just explain to me
> via email how to use the tuner.
> thanks in advance.
> 73s de jerry N3RKD
------------------------------
Date: 12 Jun 94 04:18:45 GMT
From: ihnp4.ucsd.edu!swrinde!howland.reston.ans.net!noc.near.net!ipswitch!ddlgw!ddl@network.ucsd.edu
Subject: seek old CDR rotor (or replacement)
To: ham-ant@ucsd.edu
I'm looking for an old rotor (model HAM-M) made by Cornell-Dubilier
Electronics (rotor division) once of Fuquay Springs, North Carolina.
The original was from ~1968 and the company has moved or ceased to
exist. I'd appreciate any information about where they are now (if
they are) or about a mechanically compatible replacement. Electrical
compatibility is not particularly important. (The reason mechanical
compatibility is important is that the rotor was mounted using their
custom bottom plated rather than a pole. The plate is well attached
to the tower, and the whole thing is well weathered. Using a different
style of mounting looks like major work. :)
Thanks,
Dan Lanciani
ddl@harvard.*
------------------------------
Date: 12 Jun 1994 21:59:31 -0000
From: news.delphi.com!news.delphi.com!not-for-mail@uunet.uu.net
Subject: Wind Loading
To: ham-ant@ucsd.edu
I am going to try to build the triband quad in the arrl antenna book.
What I need is help figuring the windloading. Does anyone know where I
can find a program that will help me find the loading of the antenna
both for the total load and to calcuate the load on the beam(The one that
holds the spreaders). Thanks Peter
------------------------------
End of Ham-Ant Digest V94 #182
******************************