QRZ! Ham Radio 4/QRZ Ham Radio Callsign Database - Volume 4.iso/digests/antenna/940240.txt

Internet Message Format | 1994-11-13 | 24KB

Date: Wed, 27 Jul 94 04:30:13 PDT
From: Ham-Ant Mailing List and Newsgroup <[e-mail]>
Errors-To: [e-mail]
Reply-To: [e-mail]
Precedence: Bulk
Subject: Ham-Ant Digest V94 #240
To: Ham-Ant


Ham-Ant Digest              Wed, 27 Jul 94       Volume 94 : Issue  240

Today's Topics:
                  Best HF mobile antenna?? (2 msgs)
                          Channel 6 (2 msgs)
                 Constucting 11 meter band Antennas??
                    How to match 2-meter 1/2 wave
                          Information on GAP
            Mobile 2M SSB antenna suggestions??? (2 msgs)
                      R.Shack FM > 2M mod - Help
            What coax feed to use for 2m antenna (2 msgs)

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: Tue, 26 Jul 1994 04:18:26 GMT
From: ihnp4.ucsd.edu!dog.ee.lbl.gov!agate!howland.reston.ans.net!europa.eng.gtefsd.com!darwin.sura.net!isdnlin.mtsu.edu!perot.mtsu.edu!raider!theporch!jackatak![e-mail]
Subject: Best HF mobile antenna??
To: [e-mail]

[e-mail] (Greg Montllor) writes:
> In article <30grit$[e-mail]>, [e-mail] (David Baker) writes:
> |> I am thinking about getting into HF mobile operation, and have been
> |> looking at the available options.  So far this includes the OUTBACKER,
> |> BUG CATCHER, and HUSTLER series, as well as many home brew options.
> |> I would like 10/20/40M operation if possible, and therefore I am
> |> particularly interested in comments (good and bad!) about the OUTBACKER.

Rather than tear into what Greg reports from his empirical
observations, I think it is important to find out what kind of
operation Dave sees for himself: casual? A little HF'ing while driving
on weekends? What are your goals and objectives? Without knowing what
Dave wants from his installation, none of us can really help him
much... save to make up his mind we are all biased and a bit nuts. ;^)

>   Outbacker:  Sorry, I have no experience with these to offer you.
I do. It is a broadband (low "Q") solution that looks neat and does OK
when conditions are good and a wet string would also work.

>   BugCatcher: My first mobile antenna was a homebrew bugcatcher; built it fro
>      a QST article back around '82. It worked quite well on 20 meters,
>      my main band of interest, and on 40 as well.
I have a "full-size" BugCatcher. It is possible, by carefully
selecting components, to achieve some very respectible efficiency.
Forget "gain" as a consideration in mobile antennas... it does NOT
exist... what does exist are ways of reducing loss and improvong
efficiency -- use large guage wire, silver plated copper and #10 are
better than steel #16 for coils...

Unless Dave is willing to have a 13'6" tall monster on his car, his
radiation resistance will not be much above 1 ohm on 75 meters (40
Meters will be more like 75 than 20M for mobile antennas), so an
efficiency of 20% will be significantly louder than one of 5%... at
least 6dB, a full S-unit or more...

However, the antenna requires getting out to change taps when moving
more than 6KHz of the frequency it is tuned for... if Dave is willing
to sacrifice performance for the convenience of sitting inside, then
other antennas than the BugCatcher are better.

Consider a well-constructed version of Don Johnson's DK-3 system. It
is a good design, with a 12VDC screwdriver motor to move the coil up
and down for great front seat tuning for every frequency from 3.5 - 30MHz.

>    Hustler:  After a few months of hassle with the bugcatcher, I installed a
>      Hustler, and have been using them in daily service for over 12 years.
>      Usually I just mount the 20m resonator.
For most 20M operation from a car, the Hustler will work what it can
hear, assuming the other operator has good ears and is willing to work
to make the contact. As conditions go marginal, the Hustler becomes a
good heater.... if Dave wants to be serious about things, he will need
a better antenna.

My emperical evidence: a friend who drives a cross-country "Big Rig"
runs a hustler and likes to work 75Meters. His signal is marginal much
of the time, although the good operators with full-sized elevated
antennas work him effortlessly.

My signal, (and especially the receive aspects of operating) is
significantly stronger from similar locations, both long and short
haul. I have a WAS from my mobile on 75, using a serious antenna
(13'6" and lots of "stuff" in the air, complete with guys to hold
things together ;^) and submitted no report of less than 4 x 4 -- for
the record, Alaska and Hawaii were both 5 x 5 ... not spectacularly
strong, but a neighbor got a 5 x 9 report from the Hawaiian station
the same go-around that I snagged my 5 x 5, and the home based station
was unable to HEAR the Hawaiian! He was 5x7 to me...

>       The main problem with hustlers are their bandwidth
First, bandwidth is NOT, of neccessity, a "problem"... second, your
experience is counter to mine and everyone else's. The Hustler does
NOT exhibit the "Q" that would sharply limit bandwidth to 15KHz "at
best"... it is more like 25 - 40KHz

>       Keep those little
>       Hustler resonator wrenchs handy if you like to spin that dial :)!
Convenience is a strongly seductive attractor, but Dave needs to
define his needs and wants better before he makes a trade-off.

My entire ham shack in on wheels, so I went for the best I could
muster, and it was a full-sized BugCatcher with primo components and a
few important modifications.
> Hope this helps
Me, too!  ;^)
73,
Jack, W4PPT/Mobile (75M SSB 2-letter WAS #1657 -- all from the mobile! ;^)

+--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--+
| Jack GF Hill        |Voice: [phone] -             Ham Call: W4PPT |
| P. O. Box 1685      |Modem: [phone] -  Bicycling and SCUBA Diving |
| Brentwood, TN  37024|Fax:   [phone] -          Life Member - ARRL |
| [e-mail]  -   "Plus ca change, plus c'est la meme chose" |
+--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--+

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

Date: 26 Jul 1994 17:28:35 GMT
From: ihnp4.ucsd.edu!agate!howland.reston.ans.net!usc!nic-nac.CSU.net!charnel.ecst.csuchico.edu!yeshua.marcam.com!news.kei.com!ssd.intel.com!chnews!scorpion.ch.intel.com![e-mail]
Subject: Best HF mobile antenna??
To: [e-mail]

In article <[e-mail]>,
Jack GF Hill <[e-mail]> wrote:

>Forget "gain" as a consideration in mobile antennas... it does NOT
>exist...

Hi Jack, my S10 pickup is almost exactly a quarter-wave on 17m and I use
a 13 ft. bumper mounted whip. By accident I discovered that I gain
an extra 'S' unit when I point the front of the truck toward a station
that previously was directly behind me. I modeled it using ELNEC and sure
enough, it agreed with what I had experienced.

>However, the antenna requires getting out to change taps when moving
>more than 6KHz of the frequency it is tuned for...
>Jack, W4PPT/Mobile (75M SSB 2-letter WAS #1657 -- all from the mobile! ;^)

Gosh Jack, it must be pretty hard "getting out to change the taps when
moving..." :-)

One doesn't have to change taps if one uses a mobile antenna tuner. If the
SWR is less than 2/1, use the direct path through the tuner. If the SWR
is more than 2/1, switch in the tuner. You may lose a half a dB but you
won't get wet. Your bug-catcher with a high SWR will radiate better than
those low-Q, broad-band antennas with a low SWR!

73, Cecil, KG7BK, OOTC  (Not speaking for Intel)

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

Date: 25 Jul 94 21:28:46 CDT
From: equalizer!timbuk.cray.com!walter.cray.com!renaissance![e-mail]
Subject: Channel 6
To: [e-mail]

In article <20JUL199400062225@metgem>, cbarrere@metgem (CHIP BARRERE) writes:
|>
|> I am trying to receive television Channel 6 from a distant station which
|> is roughly 110 miles away from my location. It is well beyond
|> line-of-site and I usually need a good low-level temperature inversion
|> in order for the signal to be ducted to my location. Does anyone have
|> any experience with television DX'ing? What are the audio and video
|> carrier frequencies and what would be a good antenna/preamp combination?

In the San Francisco Bay area, the VHF frequencies are dominated by
San Francisco and Sacramento stations.  I live in the South Bay, so
SF is about 60 miles and Sacramento is well over 100 miles.  Many
of the transmitters are located on hilltops, however some are also
blocked at my QTH by hills/mountains (like channel 11 in south San Jose).

I use a Wineguard CA-8200 LPDA - which has about a 15' boom.  It is
mounted on my roof on a 20' mast, making the total height about 35 feet.
I also use a Wineguard preamp.  I chose the preamp in the Wineguard catalog
with the lowest noise figure and highest overload figure (I am a ham...)
I didn't worry much about gain.  Best VHF DX is on channel 12 where I can
routinely pick up Redding - over 200 miles north of here.

One problem with this setup is the local FM stations *really* overload
the TV on channel 6.  Especially KQED (high power at the low end of the
FM band).  The Wineguard preamp has a FM trap to nuke a lot of this.
I turned on the trap, and it cured the problem.

If you are only interested in channel 6, I would recommend a single
channel yagi, with an adjustable FM trap.  The Wineguard catalog has
both of these.

In retrospect, I probably should have installed a smaller VHF-only
antenna since the other 11 VHF stations around here are pretty easy
catches.  Then use a large UHF antenna, with UHF-only preamp, for DXing.

(BTW, I've logged over 30 TV stations from the South Bay.  How does
this compare with others?)

Walt
----
Walt Spector                             "Today is the dawn of a new age,
([e-mail])                   if only (click!)"
Sunnyvale, California                The Biederbecke Affair
_._ _._ _.... _. ._.

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

Date: Tue, 26 Jul 1994 19:27:56 GMT
From: newsfeed.pitt.edu!gatech!kd4nc![e-mail]
Subject: Channel 6
To: [e-mail]

[e-mail] (Walter Spector) writes:

>In article <20JUL199400062225@metgem>, cbarrere@metgem (CHIP BARRERE) writes:
>|>
>|> I am trying to receive television Channel 6 from a distant station which
>|> is roughly 110 miles away from my location. It is well beyond
>|> line-of-site and I usually need a good low-level temperature inversion
>|> in order for the signal to be ducted to my location. Does anyone have
>|> any experience with television DX'ing? What are the audio and video
>|> carrier frequencies and what would be a good antenna/preamp combination?

>In the San Francisco Bay area, the VHF frequencies are dominated by
>San Francisco and Sacramento stations.  I live in the South Bay, so
>SF is about 60 miles and Sacramento is well over 100 miles.  Many
>of the transmitters are located on hilltops, however some are also
>blocked at my QTH by hills/mountains (like channel 11 in south San Jose).

>I use a Wineguard CA-8200 LPDA - which has about a 15' boom.  It is
>mounted on my roof on a 20' mast, making the total height about 35 feet.
>I also use a Wineguard preamp.  I chose the preamp in the Wineguard catalog
>with the lowest noise figure and highest overload figure (I am a ham...)
>I didn't worry much about gain.  Best VHF DX is on channel 12 where I can
>routinely pick up Redding - over 200 miles north of here.

>One problem with this setup is the local FM stations *really* overload
>the TV on channel 6.  Especially KQED (high power at the low end of the
>FM band).  The Wineguard preamp has a FM trap to nuke a lot of this.
>I turned on the trap, and it cured the problem.

>If you are only interested in channel 6, I would recommend a single
>channel yagi, with an adjustable FM trap.  The Wineguard catalog has
>both of these.

>In retrospect, I probably should have installed a smaller VHF-only
>antenna since the other 11 VHF stations around here are pretty easy
>catches.  Then use a large UHF antenna, with UHF-only preamp, for DXing.

>(BTW, I've logged over 30 TV stations from the South Bay.  How does
>this compare with others?)

>Walt
>----
>Walt Spector                             "Today is the dawn of a new age,
>([e-mail])                   if only (click!)"
>Sunnyvale, California                The Biederbecke Affair
>_._ _._ _.... _. ._.

Walt (and the other guy) ... we (my family and I) dropped cable and went to a
satellite system and we reinstalled an antenna at our location.  Since we were
'cable lovers' we had rg-6 running to every room in the house, the kitchen, the
study, everywhere ... with this mess (installed by me at age 14 or so - Iam
23 now) we had loss everywhere ... lots of splitters and combiners and crap
like that ... to make things short, when the antenna was installed, about 10
feet off the roof, but our house is on a nice hill in Gainesville, GA (53 mi
ne of atlanta) we were able to get a plethura of good stations, but only on
one TV, as the loss was incredible ... I installed some of Radio Shack's
stuff in the house, with a 4 output distribution amp with FM trap upstairs,
with the gain wide open, and then a inline signal amp downstairs just on
the outside of the Satellite IRD ... the IRD is also fed to a UHF modulator
that sends it's signal on the antenna line on CHannel 26.   Anyway, the
first night this was all instaled, we picked up some 23 channels ... normally
only the Atlanta stations were available, and 11 of those are received on
a regular basis.... but thru the use of a rotor and stuff, we were swinging
all that around, and I was receiving the full complement (ABC-CBS-NBC-FOX-and
an independant) from the Columbus, GA area, Macon, Albany, GA, Augusta,GA,
Asheville, NC, Greenvile, SC, and more ... it was a lot of fun, and my first
real introduction to TV dxing ... the first tv on the upstairs line has about
40 dB of gain coming to it ...with the 2 preamps in series....

73 de John

--
John Reed - Gainesville, GA      |   Internet:  [e-mail]
N4TII - AFA2FH - Redstar 204     |   Packet  :  [e-mail]
 "That which can make you can also break you." - Mr. Rhythm's Good Advice

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

Date: Tue, 26 Jul 94 02:19:12 GMT
From: spcuna!starcomm.overleaf.com!n2ayj![e-mail]
Subject: Constucting 11 meter band Antennas??
To: [e-mail]

In article <30s37l$[e-mail]> [e-mail] writes:
>
>Any help or plans for 11 meter band antenna or beams would be appreciated

Get the ARRL Antenna Book. The basic theory will help you design them.
You might be able to modify some of the 10 meter designs.
Check rec.radio.cb, too.

--
Stan Olochwoszcz, N2AYJ - [e-mail]
"This whole dot-dash concept sounds interesting, Mr. Vail. Why don't you let
me look over your notes on the train to the Patent Office?" - S.F.B. Morse?

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

Date: Tue, 26 Jul 1994 00:10:50 GMT
From: ihnp4.ucsd.edu!sdd.hp.com!hp-pcd!hpcvsnz![e-mail]
Subject: How to match 2-meter 1/2 wave
To: [e-mail]

J.D. Cronin ([e-mail]) wrote:

: How does one match a 1/2 wave antenna to 50 ohms?  I'd like
: to try a 1/2 wave on the HT, but want to avoid the bulk of
: a J-pole type match.

You can use an "L" network.  One form is an inductor in series
from the feedpoint "hot" to the radiator base and a capacitor
from radiator base to feedpoint "ground".  It's nice to have
some place for the return current to go:  if the HT case is
about 1/4 wave long, that should do the trick; three or four
radials attached to the feedpoint "ground" would also work.  A
good starting estimate of the feedpoint impedance is 1000 ohms;
this depends on the radiator diameter.  Of course the feedpoint
will look resistive if you are at resonance (a couple percent
short of full 1/2 wave freespace distance), but will look
inductive if short and capacitive if long.  I've found the "L"
networks to be easy to tune up, given that you use a variable
cap, but I also don't deal with such high ratios (50:1000) and
so the Q that I work with is lower ---> easier tuning.  You can
work out the required values for the L and C from a Smith chart
or simple equations.

73,  K7ITM

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

Date: Tue, 26 Jul 1994 04:07:58 GMT
From: ihnp4.ucsd.edu!dog.ee.lbl.gov!agate!howland.reston.ans.net!europa.eng.gtefsd.com!darwin.sura.net!isdnlin.mtsu.edu!perot.mtsu.edu!raider!theporch!jackatak![e-mail]
Subject: Information on GAP
To: [e-mail]

[e-mail] (Jim Hoffman - Special Programs Manager) writes:

> I am in the process of buying a vertical antenna.  I would like to have one
> vertical with as much bandwidth as possible.
Geee, maximizing bandwidth, presumably at the expense of performance,
as the primary parameters of a vertical antenna....

How about mounting a Heath Cantenna on a pole?  ;^)

Bandwidth is somewhat a function of circuit "Q" (inverse, to make
things more fun) and circuit "Q" directly impacts antenna performance.

You can tune an antenna and find a match that will permit satisfactory
results on all bands from 160-10... but it isn't likely to be vertical,
it won't cost a whole lot, and it will performa lots better than a
store-bought antenna... make a dipole, and cut the legs to NOT be a
quater-wave (or multiple of a quarter wave) on any frequency of
interest. Put the money you save from not buying a fancy aluminum pole
into good open-wire/ladder feedline and a tuner, and enjoy operating.
73,
Jack, W4PPT/Mobile (75M SSB 2-letter WAS #1657 -- all from the mobile! ;^)

+--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--+
| Jack GF Hill        |Voice: [phone] -             Ham Call: W4PPT |
| P. O. Box 1685      |Modem: [phone] -  Bicycling and SCUBA Diving |
| Brentwood, TN  37024|Fax:   [phone] -          Life Member - ARRL |
| [e-mail]  -   "Plus ca change, plus c'est la meme chose" |
+--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--*--+

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

Date: Tue, 26 Jul 94 10:57:23 -0500
From: news.delphi.com![e-mail]
Subject: Mobile 2M SSB antenna suggestions???
To: [e-mail]

I am comparing antenna designs for working 2M ssb mobile.
Obviouslu a horizontal polarization component and omni
pattern are goals here.  I am working on a horizontal loop
and an eggbeater, and am looking for feedback from
any experienced folks, or just any other interested
parties.

thanks,
pete n1qdq

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

Date: 26 Jul 1994 19:07:44 GMT
From: hplextra!news.dtc.hp.com!col.hp.com![e-mail]
Subject: Mobile 2M SSB antenna suggestions???
To: [e-mail]

    PLEASE POST RESULTS...........THANKS J0HN, N0KICQwq

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

Date: 26 Jul 1994 19:20:53 GMT
From: news.sprintlink.net!tequesta.gate.net!inca.gate.net![e-mail]
Subject: R.Shack FM > 2M mod - Help
To: [e-mail]

I was following a couple of threads several weeks ago on the mods to the
Radio Shack FM antenna for 2 meter yagi.  Seeing notes from many people
building these, I never saw the final posts of the results.  Would
someone please e-mail me the final plans for this.  It sounded like a
great project, I'd like to hear how it worked out for you.

Bob Bronson   [e-mail]   KE4PGM
.

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

Date: 26 Jul 1994 05:38:51 GMT
From: ihnp4.ucsd.edu!news.cerf.net!gopher.sdsc.edu!nic-nac.CSU.net!charnel.ecst.csuchico.edu!yeshua.marcam.com!news.kei.com!ssd.intel.com!chnews!scorpion.ch.intel.com![e-mail]
Subject: What coax feed to use for 2m antenna
To: [e-mail]

In article <310mc0$[e-mail]>,
Vinod Narayanan <[e-mail]> wrote:
>1. What type of coax should I put up?

Hi Vinod,

Matched line losses for 100 ft of coax at 150 MHz:
RG-58 6 dB,  RG-8(213) 3.2 dB,  RG-8F 2.1 dB,  9913 1.6 dB

100 ft of ladder-line has about 0.8 dB loss and is a lot cheaper than
coax but the baluns at each end would probably add up to the cost and
loss of 9913.

I use 9913 with type N connectors if I have to splice the coax. I doubled
my radiated power when I switched from RG-8X to 9913.

73, Cecil, KG7BK, OOTC

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

Date: Tue, 26 Jul 1994 12:22:10 GMT
From: pacbell.com!att-out!cbnewsl!cbnewsj!cbnewsi!cbnewsh!cbnewse!cbnewsd!cbnewsc!cbfsb!cbnewsf.cb.att.com![e-mail]
Subject: What coax feed to use for 2m antenna
To: [e-mail]

In article <3127hb$[e-mail]> [e-mail] writes:
>In article <310mc0$[e-mail]>,
>Vinod Narayanan <[e-mail]> wrote:
>>1. What type of coax should I put up?
>
>Hi Vinod,
>
>Matched line losses for 100 ft of coax at 150 MHz:
>RG-58 6 dB,  RG-8(213) 3.2 dB,  RG-8F 2.1 dB,  9913 1.6 dB
>
>  ...
>
>73, Cecil, KG7BK, OOTC
>

   Cecil,

       Have you ever tried 9880? We had lots of this stuff laying around from
 an old ethernet network. I was always curious if this would also be very
 good. it's 50 Ohm. looks like a Urathane dialectic. solid copper conductor
 (looks about 12 gauge). a foil layer followed by a 95%+ stranded weave
 followed by another foil layer followed by yet another 95%+ stranded weave.

   I would think this stuff is pretty good.

   comments are very much welcomed from all readers.

    Andy Cropley

    [e-mail]

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

Date: Tue, 26 Jul 1994 02:06:28 GMT
From: rit!isc-newsserver!ultb![e-mail]
To: [e-mail]

References <[e-mail]>, <[e-mail]>, <[e-mail]>cam.
Subject : Re: How to match 2-meter 1/2 wave

In article <[e-mail]> [e-mail] (Ross Alexander) writes:

>Or, if mechanical considerations eliminate that option,
>try using a tuned autotransformer - a parallel resonant
>LC circuit with one side to ground, one side to the
>end of the 1/2 lambda, and the feedline a turn or so up
>from the ground end of the coil.
>
>regards,
>Ross ve6pdq
>--
>Ross Alexander VE6PDQ    [e-mail],
>[phone]        [e-mail]
>
>Television is chewing gum for the eyes. -- Frank Lloyd Wright

The ARRL Handbook shows a 1/2 wave fed this way, but doesn't go
into specifics.  Since there are any number of combinations of
inductance and capacitance for a given resonant frequency, how
does one pick an appropriate combination?

Since this is a matching circuit, doesn't it depend on the
coax impedence (50 ohms) and the actual load (unknown, but
believed to be high)?

73...Jim  N2VNO

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

End of Ham-Ant Digest V94 #240
******************************