[HCARC] When People Ask A Question - Be Careful With The Answer
W4wj at aol.com
W4wj at aol.com
Sat Aug 4 15:37:03 EDT 2012
Kerry...
Excellent response regarding the AS2259 antenna...
To make things short, it appears that it is time that we have turn the
TechCorner into an
OPEN Q&A session... Any questions allowed... and those sitting in can
give their
personal opinions etc on the subject.
So, I will suggest that whenever there is not a specific TechCorner
scheduled, that
we do an OPEN Q&A session... Bring your questions... Someone will have
the answers...
and if not, WE WILL GET THE ANSWER/S...
Gary... Antennas are such a challenge... As Kerry mentions, most of us
"old timers" started
with used gear and very simple antennas. Before I knew better, and while
awaiting for my
novice license back in 1959 (you could wait many many weeks for the FCC
wheels to crank out your
paper license and send it along) I had my used Heathkit DX-35 transmitter
and used Hallicrafters
SX-43 receiver all hooked up. My antenna: a coax end-fed half-wave long
wire for 40 meters.
"Bad choice" said my Elmer buddy K4PVH as he looked at my antenna handy
work. "Better
if we move the coax to the middle of the wire, insert an insulator and
check the SWR. So we
made that change and I was a bit smarter antenna-wise!! ;-)
Cheap wire antenna... but it worked very well for me on 40 meters as I
worked all over the country
with it. As Kerry points out...
To spend nearly $200 for 135 feet of wire and a couple short lengths of
transmission line is, in my opinion, criminal.
Kerry is right on about that. Asking the right questions will save you
BIG $$$...
BTW... 500 feet of #14 insulated house wire is selling right now for about
$60... That would
make three 135 foot dipoles (80 meters) with 100 feet of wire left over!!
;-)
As you will find out Gary... There are many antenna lovers in the
HCARC... Ask questions
and you will get differing but accurate opinions on your options...
Enough soapbox time for me!! Good discussion!
73
Don
W4WJ
In a message dated 8/4/2012 11:14:20 A.M. Central Daylight Time,
kerryk5ks at hughes.net writes:
Gary,
I was happy to meet you at the meeting. I didn't know who you were when
we
started exchanging e-mails.
As far as the question/answer. When you ask a 'simple' question, it may
not
be as simple as you think. The basic question I think was "would the
AS2259
make a good antenna for field day?" Unfortunately the short answer is
yes,
no, sometimes and maybe. I didn't think the short answer would be
particularly useful. The AS2259 antenna is a fine antenna. It has a
couple
limitations; 1- It is designed to use NVIS propagation, 2- It operates
with
a very high SWR, 3- The center support/ transmission line is designed to
plug into a specific military HF transceiver.
What this means is that it is really most useful for daytime propagation
on
80 and 40 meters out to about 200 or so miles. While it will work on the
higher bands, since most of the radiated power goes straight up, the
results
will not be very good. The fact that it was designed to mate with a
specific military transceiver, means it will not be easy to connect it to
a
typical modern ham transceiver with 50 Ohm coaxial output. The fact that
it
operates with a high SWR, probably higher than 10:1, means that even if
you
could connect it to a ham transceiver, the transceiver will not be able to
deliver very much if any power to the antenna becasue of the high SWR.
Even
expensive transceivers with built in auto tuners will not work since they
typically can only handle an SWR of 3:1.
The specific transceiver used with the AS2259 is an AN/PRC47. This a
Collins designed/built transceiver from ~1970. It is mostly solid state
but
uses a PL177WA tube for its final amplifier. This tube is capable of
250-300 W on SSB but is run at ~100W, pretty conservative. The unit uses
a
Pi-L output tuning network which is probably capable of matching antenna
impedances from 10 to several hundred Ohms. This is a huge range compared
to the typical modern ham transceiver. It is more range than modern
transceivers with built-in antenna tuners. The operator 's manual for the
PRC47 talks about a plate on the transceiver that provides tuning setting
for the antennas designed to use with the PRC47. It also has a 'special'
procedure for tuning to match a 50 Ohm load. This pretty clearly
demonstratres that the PRC47 was designed to use antennas with high SWR.
Ultimately, this is what finally convinced me that the AS2259 antenna is a
high impedance antenna over most of its frequency range.
Unless you have some understanding of where the answer comes from and can
refine the question to a particular set of conditions, all the answers -
yes, no, sometimes and maybe - are correct. Unfortunately, most
questions
and answers in ham radio are like that. Ham radio is a lifelong learning
experience. You ask a question, if the answer doesn't make sense, you ask
another question. You read. You listen to other peoples discussions.
You
ask another question. And so it goes.
I personally believe the AS2259 is a good antenna for field day. It will
take some effort to physically connect it to a ham transceiver. You will
have to use a wide range antenna tuner. It is primarily useful for NVIS
propagation on 80 and 40 meters.
One of your early statements is something that greatly concerns me. Too
many people spend to much money on a fancy transceiver and 'special'
antenna that they can never figure out how to work. Most of us old timers
started on the cheap with second hand (or worse) transmitters and
receivers
and a twin lead dipole. No, they didn't work well at all, but we were all
stuck on the novice bands and most of us were in the same boat. Misery
loves company! Most of the guys I worked were less than 100 miles away.
I
was in Mass. at the time. To work Maryland or Ohio or even Pennsylvania
was
a big deal. QST had at least one article a month that was practical
information for new hams to use to help them improve their station. Most
of
the articles didn't require spending large amounts of money. It was only
after a couple years of learning and practicing, that most hams actually
went out and spent any real money on a fancy radio. Unfortunately life is
different now. There are no novice bands. Its not easy to find decent
used
equipment. QST seems to have sold their soul to the manufacturers of
fancy
equipment. CQ, Ham Radio and 73 (old ham magazines) have all
dissappeared.
The problems are still the same. How do you find a group of new hams with
the same ability level that you have so you can learn together? How do
you
find some reasonably priced and performing equipment that you can learn on
until you think you are ready to make that big purchase? How do you know
what you should expect from your station?
These are not easy questions and I don't know the answers. Gale is trying
to get a weekly HF net going. Perhaps that is part of it. It will give
people a chance to try different antennas and settings on their equipment
to
see what makes an improvement. Things like the Tech Corner are part of
the
answer too, but you have to get control of it on your own! If the level
is
too deep, ask questions to move the discussion to your level. When I
talk,
I love questions, it shows someone is interested. Read all you can. Old
ham magazines (1960's 1970's) are great. They are technically readable
and
cover real problems unlike most of what you see today. Read old ARRL
Handbooks, antenna books, VHF handbooks etc. There are a lot of them out
there. They don't change quickly, read ones about 10 years apart and you
will get most of it. Take what the manufacturers say with a lot of salt.
They are just trying to sell you on something they have. Try to find used
equipment locally, ie, Austin and San Antonio. Avoid e-bay, QRZ.com
swapmeet, etc. A lot of the ads I see, the seller is just plain clueless
or
worse.
The G5RV and Carolina Windom antennas are another problem. You will find
a
lot of people who are convinced these antennas are nothing short of
miraculous. Too spend nearly $200 for a 135 feet of wire and a couple
short
lengths of transmission line is, in my opinion, criminal. These antennas
will not work any better than a plain old dipole. The problem with any
antenna is matching to the transmitter. I believe you are much better off
spending your money on a good antenna tuner. My main point in the
comments
on the Carolina Windom and the G5RV is to show they are both derived from
the Windom antenna, pre WW2, and the premise the Windom is based upon, no
longer applies.
I hope this summary does you some good. Again, there is no simple answer
to
your question. Remember, my comments are my opinion, especially on the
G5RV
and Carolina Windom. There are many who would disagree with me , some
violently.
Kerry
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