QRZ! Ham Radio 3/QRZ Ham Radio Callsign Database - Volume 3.iso/digests/ham_ant/930150.txt

Internet Message Format | 1994-06-04 | 19KB

Date: Wed, 22 Dec 93 04:30:18 PST
From: Ham-Ant Mailing List and Newsgroup <[e-mail]>
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Subject: Ham-Ant Digest V93 #150
To: Ham-Ant


Ham-Ant Digest              Wed, 22 Dec 93       Volume 93 : Issue  150

Today's Topics:
                       Antenna Tuner Questions
                       Autek RF Analyzer Review
                       definition of "matched"
                           Gap v Cushcraft
                  Grounded tower and antenna tuners
                        Help with KLM Beam ???
               Hustler Mobile as Base Antenna (2 msgs)
        need comments on MFJ antennas and accessories (2 msgs)
              Sealant for antenna's connectors (2 msgs)
                      Umbrella for 2m HT Antenna
                                unsub

Send Replies or notes for publication to: <[e-mail]>
Send subscription requests to: <[e-mail]>
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.
----------------------------------------------------------------------

Date: 22 Dec 93 02:06:22 GMT
From: ogicse!cs.uoregon.edu!sgiblab!sdd.hp.com!col.hp.com!srgenprp![e-mail]
Subject: Antenna Tuner Questions
To: [e-mail]

Cecil Moore ([e-mail]) wrote:

: I need the equations governing the
: transfer function of a voltage and/or current balun that is not arcing
: and/or saturating. I can't find them in W2FMI's book, Maxwell's book, or
: any of the ARRL publications that I own. Where the heck are they?

Ideally, the transfer function for a 4:1 balun is R(load) = 4 * R(source)
and X(load) = 4 * X(source), assuming the load is connected to the
"4" side of the balun.

Or perhaps you meant you want to calculate the power-handling capability
with high SWR.  The easy answer to that question is to assume that a balun
designed for the amateur limit can handle 1.5 kW (plus some margin) into
a 50 ohm load.  The worst-case voltage or current will be multiplied by
the square root of the SWR.  (High-impedance loads increase the voltage,
low-Z loads increase the current.)

The upshot of this is that, under worst-case conditions, the power
rating is degrated by a factor equal to SWR.  For example, if the
SWR is 3:1, you can safely use your 1.5 kW balun at 500 watts
without arcing the windings or saturating the core.

AL N1AL

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

Date: 19 Dec 93 19:51:35 GMT
From: sdd.hp.com!cs.utexas.edu!swrinde!dptspd!ephsa![e-mail]
Subject: Autek RF Analyzer Review
To: [e-mail]

Somewhere uptopic, somebody asked about the Autek RF Analyzer.
Mine just arrived in the mail yesterday.  Attached is a summary of its
capabilities.

The Autek Research "RF Analyst" (Model RF-1) is a versatile
mesuring instrument.  For systems used between about 1 MHz and 36
MHz, it will measure and display feedline or antenna SWR,
impedance ("Z"), "L", and "C".  It will also act as a low
distortion sine wave generator.  No nomograms, tables or
calculators need be used.  The LCD display shows frequency (MHz),
SWR, Z (ohms), L (uH), and C (pF).

The RF-1 is approximately the size of a cigarette package, but
twice as thick.  The LCD display is about 1 3/4" x 3/4".
Controls include seven function selection buttons (ON/OFF, BAND,
FREQ, SWR, Z, L and C) and two tuning knobs (TUNE and FINE).
Power is supplied by a 9 volt battery, but it may be run from any
7 to 15 volt DC source.

With this device, the manufacturer claims that  the user can
adjust antenna element lengths, make phased transmission lines,
measure cable loss, check baluns, determine the effect of number
of radials on a vertical antenna's performance, tune outboard
antenna tuners, measure trap resonant frequency, determine
resonant frequency of the proverbial bedspring and/or gutter
antennas, as well as measure coils and capacitors.

Published SWR accuracy is between 10% and 20% (with the poorer
accuracy at high SWR).  Maximum SWR measured is 15:1.  Maximum
impedance measured is about 2000 ohms, and minimum about 8 ohms.

The RF Analyst comes with a nine page instruction manual, an
accessory kit, and a limited one-year warranty.  Price range:
$150.

(Usual disclaimers apply.  I am neither an employee of Autek
Research, nor am I being reimbursed for this review; I'm just a
Ham who purchased what thinks he thinks could be a very useful
device!)

Lou Genco / N5SGL

--
[e-mail] (Lou Genco)
Rivercity Matrix  --  [phone]/21  --  San Antonio, Texas

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

Date: Tue, 21 Dec 1993 21:04:48 GMT
From: swrinde!gatech!udel!news.sprintlink.net!direct!news.direct.net![e-mail]
Subject: definition of "matched"
To: [e-mail]

Quoting from the ARRL Antenna Handbook: "A line terminated in a purely
resistive load equal to the characteristic line impedance is said to
be *matched*...The more that R differs from Z0, the greater the mismatch."

Now is this statement from a recent magazine article true or false?

The antenna tuner "tunes out all mismatches in the system, including
transmission line to antenna mismatch,..."

Please respond to my Internet address at [e-mail] and feel free
to include the reasons that you think the statement is true or false.

I'm going to send the results to the author.

Thanks and 73, Cecil, [e-mail]

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

Date: 19 Dec 1993 23:49:29 -0500
From: digex.net!access2![e-mail]
Subject: Gap v Cushcraft
To: [e-mail]

I've had a Cushcraft R-5 up 3 feet over my (tin) roof in Washington, DC
for three years now, and long for the opportunity to operate below 14
MHz.

Wire antennas for 40 and 80 won't fit (safely, that is) on this city lot,
so I'm considering upgrading to a Cushcraaft R-7 or the small GAP vertical.

Has anyone compared the two?

Email your answers and I'll compile and post here.

Thanks --
Eric


Eric Rosenberg    WD3Q, EI4VPS, ZL0ADG, J20BY, etc.
338 14th Street, NE   voice: [phone]
Washington, DC 20002  USA  fax:   [phone]
[e-mail]   [e-mail]

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

Date: Tue, 21 Dec 1993 18:26:10 GMT
From: news.service.uci.edu!usc.edu!hela.iti.org!widener!dsinc!ub!news.kei.com!sol.ctr.columbia.edu!howland.reston.ans.net!torn!newshost.uwo.ca!julian.uwo.ca![e-mail]
Subject: Grounded tower and antenna tuners
To: [e-mail]

I would like to thank all those that replied to my query some months
ago
about feeding a grounded 12 metre tower (that I removed my tribander
beam and 15 el two metre beam from because of needed roter repairs.

I bought a homebrew tuner at a local hamfest and rigged a gamma match.
I also put up 3 sopers of the lambda/4 variety.

My first contact was on 10.1 with a W5 and nice sigs using the
grounded
tower.  My swr is nearly 1:1 on some frequencies and >3 on other bands
. Because I now have a choice of antennas I can work 3.5 to 28 Mhz
with swr nearly 1:1.

Needless to say I left the tower work too late and nearly froze my
fingers working last week.  I was worth it though.

Many thanks to all those who sent me email.

For those interested in tuners the homebrew one I bought for $35
includes a roller inductor and two high voltage capacitors, one of
which is a two section beast with the sections isolated.  The diagram
is very similar to the one in the ARRL Handbook.

Best of the holiday season to all

Marv Sherebrin VE3FHX

email: [e-mail]

Assoc Professor Medcical Biophysics
U Western Ontario

.

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

Date: 21 Dec 1993 04:27:41 GMT
From: pa.dec.com!nntpd.lkg.dec.com!sousa.ako.dec.com!bobseg.enet.dec.com![e-mail]
Subject: Help with KLM Beam ???
To: [e-mail]

Greetings,

A couple of months back I was wandering through one of the regional ham
fests and had the good fortune to pick up a nice looking 440 beam.  The
fellow that I bought it from said that it was a KLM antenna.

The beam has a 5' long boom with 4'8" between the reflector and further
most director elements.  There are 9 directors and one reflector. Each
element is bolted to the boom through a plastic tee.  The boom has been
drilled for either horizontal or vertical orientation both at the end and
in the middle.  The driven element consists of eight half elements cross
connect with straps in what I believe (from looking in the RSGB VHF book)
is a log-periodic configuration.

Looking in the latest AES catalog I suspect that what I have is a KLM 440-10X
beam.

The problem is that I don't know how to hook the coax up to this beast.
The two foremost driven half-elements had slightly longer bolts and a
second set of nuts.  I connect my coax to these two points and I am getting
a fairly high (a little over 2:1) SWR.

Is this correct?

The RSGB VHF manual seems to show a loop of wire connecting the back end of
the driven element array.  There is no loop of this sort on the antenna I
have.

If anyone has one of these beams and can tell me how it is supposed to be
configured I would very much appreciate some assistance.

Thanks in advance.....

Bob Segrest
KD4PWU

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

Date: Tue, 21 Dec 1993 14:48:34 -0500
From: titan.ksc.nasa.gov!k4dii.ksc.nasa.gov![e-mail]
Subject: Hustler Mobile as Base Antenna
To: [e-mail]

In article <[e-mail]>, [e-mail]
(Victor Tavernini) wrote:
> I happen to have a Hustler mobile antenna and a 40 meter resonator ...
> and was wondering ... is it possible to use it as a base anteenna?
> If so, would I need to add radials?

Victor-

When you use the Hustler on a car, it is only half of the antenna system.
The car's body provides the other half.

If you want to use it as a base antenna, you will need to supply something
else to act as the counterpoise or ground plane.  If you can't come up with
anything, you might consider getting a second mobile antenna, and setting
the two up as a dipole.

The company that makes the "Hamstick" antennas, also sells a bracket to
mount two Hamsticks as a dipole.  The resulting assembly is about 15 feet
long, which may fit where a full-size 40 meter dipole won't.  I think a
pair of Hustlers would work as well, but the Hamstick has a little broader
bandwidth.  (The bandwidth is narrower on the lower bands.)

If you are restricted to using a compact antenna such as this, it is
certainly better than nothing.  But don't kid yourself.  A full half-wave
dipole, or full quarter-wave ground plane with radials, almost certainly
will outperform this dipole arrangement on the lower bands.

73, Fred, K4DII

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

Date: Tue, 21 Dec 1993 21:23:37 GMT
From: swrinde!cs.utexas.edu!howland.reston.ans.net!gatech!udel!news.sprintlink.net!direct!news.direct.net![e-mail]
Subject: Hustler Mobile as Base Antenna
To: [e-mail]

Fred McKenzie ([e-mail]) wrote:
: When you use the Hustler on a car, it is only half of the antenna system.
: 73, Fred, K4DII

Hi Fred, if only it were half of an antenna system I would be happy. I
would say it more like a tenth of an antenna system. :-)

73, Cecil, [e-mail]

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

Date: 21 Dec 93 13:57:33 GMT
From: ogicse!emory!europa.eng.gtefsd.com!howland.reston.ans.net!cs.utexas.edu![e-mail]
Subject: need comments on MFJ antennas and accessories
To: [e-mail]

I need a 2m mobile antenna and like to get comments about the MFJ
5/8 wave magnet mount antenna  MFJ-1728B ($25).

Also, is the MFJ J Pocket Rollup antenna any good  ($15)?

how about telescopic antennas for HT (MFJ-1714, $17) ? how does this
compare to the AEA hot rod ($25) ?

are the MFJ speaker mikes for HTs good ?

please email replies if possible.
thanks in advance.

happy holidays

jerry

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

Date: 21 Dec 93 13:53:12 GMT
From: ogicse!emory!europa.eng.gtefsd.com!howland.reston.ans.net!cs.utexas.edu![e-mail]
Subject: need comments on MFJ antennas and accessories
To: [e-mail]

I need a 2m mobile antenna and like to get comments about the MFJ
5/8 wave magnet mount antenna  MFJ-1728B ($25).

Also, is the MFJ J Pocket Rollup antenna any good  ($15)?

how about telescopic antennas for HT (MFJ-1714, $17) ? how does this
compare to the AEA hot rod ($25) ?

are the MFJ speaker mikes for HTs good ?

please email replies if possible.
thanks in advance.

happy holidays

jerry

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

Date: 21 Dec 93 17:53:10 GMT
From: ogicse!emory!darwin.sura.net!fconvx.ncifcrf.gov![e-mail]
Subject: Sealant for antenna's connectors
To: [e-mail]

In article <thweatt.756429935@mustang18> [e-mail] (John A. Thweatt) writes:
>I am going to be installing some 9913 cable with silver-plated
>connectors this weekend.  It was recommended to me that I should
>assure that a proper seal was between the connector and cable by
>using 3M #23 self valcanizing rubber tape, a layer of Schotchkote,
>followed by another layer of #23.  He also recommended that I
>avoid Coax Seal.  I would like to assure that I don't have any
>moisture problems in this cable so I would like to follow this suggestion
>but I can't find a vendor in the Chicago (Northwest Chicago area) which
>has this 3M product.  Does anyone know where I can get this for my weekend
>installation project?  Is there another type of tape which I could use
>which would provide as much or more protection?  Radio shack sells Archier
>brand rubber tape, would this work as well???  I spent good money on this
>cable and don't wanted it damaged within a few years, so I want to do as
>much as possible to safegard against these problems.
>
>Also I measured the lost of this complete 85 feet of cable with silver-plated
>connectors and obtained 2.54 db loss at 900MHz, .8 db loss at 100MHz, and
>2.7 db at 999MHz. Can't wait to try it out.
>
>Thanks,
>John T.
>
I'm impressed with your (lack of) loss at 900Mhz - Ithought 1/2" hardloine was
3db at 1296.
I don't know where this tape is, but I put a sleeve of heatshrick on the outside of
the coax before I uinstall the connector - this shims the coax out to make the
connector ssnug. I aslo put a plastic boot on the ocax to slide
upover the connectorw when I'm done. After installing the connector and
before sliding the boot up - I put ssilicon glue II (not resgular which
fives off acetic acdi when it cures) around the join of the coax and the connector.
After I couple the connectors together I cover them with movre Si glue II.
When you want to dissasseemble the connectors you can peel the Si glue off .
Works great.
Joe NA3T
[e-mail]
>
>
>

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

Date: 20 Dec 93 23:25:35 GMT
From: news.service.uci.edu!usc.edu!news.isi.edu!headwall.Stanford.EDU!agate!howland.reston.ans.net!cs.utexas.edu!asuvax!ennews!mcdphx!schbbs!mothost!delphinium.cig.mot.com!mustang18!thweatt@network
Subject: Sealant for antenna's connectors
To: [e-mail]

I am going to be installing some 9913 cable with silver-plated
connectors this weekend.  It was recommended to me that I should
assure that a proper seal was between the connector and cable by
using 3M #23 self valcanizing rubber tape, a layer of Schotchkote,
followed by another layer of #23.  He also recommended that I
avoid Coax Seal.  I would like to assure that I don't have any
moisture problems in this cable so I would like to follow this suggestion
but I can't find a vendor in the Chicago (Northwest Chicago area) which
has this 3M product.  Does anyone know where I can get this for my weekend
installation project?  Is there another type of tape which I could use
which would provide as much or more protection?  Radio shack sells Archier
brand rubber tape, would this work as well???  I spent good money on this
cable and don't wanted it damaged within a few years, so I want to do as
much as possible to safegard against these problems.

Also I measured the lost of this complete 85 feet of cable with silver-plated
connectors and obtained 2.54 db loss at 900MHz, .8 db loss at 100MHz, and
2.7 db at 999MHz. Can't wait to try it out.

Thanks,
John T.


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

Date: Sun, 19 Dec 93 15:07:15 PST
From: yeshua.marcam.com!zip.eecs.umich.edu!destroyer!nntp.cs.ubc.ca!mala.bc.ca!oneb!ham![e-mail]
Subject: Umbrella for 2m HT Antenna
To: [e-mail]

[e-mail] writes:

> Anybody ever try an umbrella for a 2m HT antenna?  I guess a 1/4 wave
> radiating element could be stuck up from the top and the spreaders trimmed
> for radial elements.  What else would be needed?   Phil, aa8jo.

Yes. It worked fine. I used to do a lot of parades, etc and it seemed to
rain a lot, so an umbrellatenna seemed a logical choice.

Don't worry about trimming the spreaders. Just find a way to mount a BNC
on the top of the antenna - I used an old nutdriver shaft to mount the
BNC in - and feed the coax down through the handle. I used the real thin
50 ohm cable - can't remember the RG number - and though it's lossier
than say, RG58, it's only a few feet long so what the hey?

Then I just snapped on a 1/4 wave BNC to the top of the antenna. If I was
real close, I could use the rubber duck, and even 5/8 if needed. The
umbrella certainly seemed to provide as good a ground plane as the radio.

Oh, and DON'T use a collapsable handle type umbrella, far too much hassle
to deal with the coax.


Robert Smits                    There is *no* idiotproof filter.
VE7EMD                          Idiots are proof against anything!
Ladysmith B.C.                       - Richard Chycoski, VE7CVS
e-mail: [e-mail]

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

Date: 21 Dec 93 16:15:06 GMT
From: [e-mail]
Subject: unsub
To: [e-mail]

  unsub rontiver.ub.ub.com at smtplink-ub@ccmail

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

End of Ham-Ant Digest V93 #150
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