"Sal M. O'Nella" wrote in message
...

" Well, with Field Day coming up, I had planned to use last year's 20m
dipole again, but I was on the phone with a guy last night and he dictated
some really easy-sounding plans for a two-element quad. It's supposed to
be good for 6 dB more gain than a dipole. Yes please, I'll take one free
S-unit. We're in the southwest corner of the country, so aiming it is a
no-brainer.

Maybe I can post a diary of the build to amuse you nice folks by
demonstrating my (lack of) skill using hand tools. By the way, we'll be
using N3FJP's "Field Day Network Logger" this year, for the first time.
Last year, one of our guys used N3FJP single-station logger for himself
(400+ contacts) and he registered the network version for the club. I
like it. We've had several good trial runs. Find it at
http://www.n3fjp.com/.

"Sal" (KD6VKW) Club President Club FD Chairman, Principal Elmer
Donation Sales Manager (Jeez -- what am I _not_ doing?)

Hello courteous, dedicated and hard-working (over-worked) Sal.

After that write-up you may get a posting from a certain person telling you
to use a 19th century antenna rather than a modern one. So much better for
throwing those electrons into the aether :-)

I'd be delighted to read your diary. Your hard work will save my hands from
Bandaids and other first-aid treatments. I like to learn through other's
pain. Actually, a two-element quad might be a project for 2013 for me - not
sure if my yagi is still fit for work on 20m - 15m - 10m. Homebrew quads
used to be popular here in the UK some decades ago.

73, Ian.

"John" wrote in message
news
Here is the 'T" antenna I referred to. It is totally plastic.

http://www.happywanderer.net.au/page...9&parent2id=24

If link doesnt work the website is www.happywanderer.net.au and the image
is on first screen. The totally plastic covered yagi I saw was somewhere
in ebay. I,ll see if I can find it again.
Regards
John



"John" wrote in message
. au...
Whilst trying to source a "digital" TV antenna I came across some with
all external surfaces plastic. One was a small yagi with all external
surfaces plastic, hopefully with metal elements embedded. Another a "T"
shape made out of plastic conduit with elements inside conduit.
My question is how do they work?. If they are detecting electrical fields
how does increasing source impedance by 100,s of megohms improve things?.
Capacitive coupling, I suppose at the frequencies involved there would be
some.
If it works as well as all metal why doesn,t every one use it and stop
corrosion?
Hope this is not too off topic.
Many thanks
John

It is probably what is called a "folded dipole."

We used to make them out of common TV twinlead. They have a characterisstic
impedance around 300 ohms, same as the twinlead, so the black block at the
hub is likely to be a 300-75-ohm balun (trannsformer) to match the coaxial
cable lead-in.

You determine the frequency of interest and cut it to size, accordingly.
They're not too great for wide-band coverage, but you might get lucky. (The
wide-band issue is why big, expensive antennas always have elements of many
different sizes. "One Size Fits All" definitely does NOT apply to antennas.

"Sal"

On 5/31/2012 5:43 PM, Sal M. O'Nella wrote:
wrote in message
...

Ah well, I guess that some of us like to try to be helpful. I'm hoping
that
Szczepan might one day read some modern books on radio theory and
practice.
Reminds me of when I had a relative who was unable to accept and
understand modern day life and technology. Tried to help but relative was
incurable.

Methinks this one is incurable, too.

73,
"Sal"
(KD6VKW)



I bet he has an outhouse. Who needs modern plumbing when the negative
15th century stuff has worked so well for 25 centuries?

tom
K0TAR

On Thu, 31 May 2012 15:06:22 -0700, "Sal M. O'Nella"
wrote:

However, the real reason is that I haven't seen any decent antenna
related discussions in this newsgroup for a long time.
Jeff Liebermann

Well, with Field Day coming up, I had planned to use last year's 20m dipole
again, but I was on the phone with a guy last night and he dictated some
really easy-sounding plans for a two-element quad. It's supposed to be good
for 6 dB more gain than a dipole. Yes please, I'll take one free S-unit.
We're in the southwest corner of the country, so aiming it is a no-brainer.

Much better. Field Day is the prime incentive to do last minute
repairs on antennas and equipment. It's also a great place to do
testing that should have been performed before Field Day. Learn by
Destroying at its best. While fatalities and major injuries tend to
be minimal, I can't say the same for equipment and antenna failures.
Somehow, the miracle antenna contrived specifically for Field Day just
doesn't seem to tune or work as expected. Your "easy-sounding plans"
should be an ominous warning of problems to follow.

I'm staying out of Field Day this year. I had planned to deploy my
inflatable antenna design, but decided that doing R&D on top of a
mountain was not a good idea. I plan to visit, but not operate much.
I did my part this morning by customizing one of the Field Day
trailers with my cutting torch. Hopefully, I didn't weaken the
structure so that it will collapse on arrival to the site.

Maybe I can post a diary of the build to amuse you nice folks by
demonstrating my (lack of) skill using hand tools.

Any tool can be used as a hammer. That should be fun to read, and
more fun to watch the video.

By the way, we'll be
using N3FJP's "Field Day Network Logger" this year, for the first time.
Last year, one of our guys used N3FJP single-station logger for himself
(400+ contacts) and he registered the network version for the club. I like
it. We've had several good trial runs. Find it at http://www.n3fjp.com/.

We like to use N1MM, mostly because it's free, but also because it
took the last half dozen Field Days to train the operators in its use.
http://n1mm.hamdocs.com
We also gave up on running CAT5e all over the site because of the RFI
generated, but also because I got tired of dealing with trashed rolls
of CAT5e as everyone seem to enjoy walking on or tripping over the
CAT5 and coax cables. We tried 802.11g wi-fi, but found that high
power transmitters are really good at blocking the receiver front end
of the wireless cards. Since we don't run more than one station on a
band, there's no issue with dupes. So, no network needed.

(Jeez -- what am I _not_ doing?)

Operating?


--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com
# http://www.LearnByDestroying.com AE6KS

On Thu, 31 May 2012 13:21:50 +1000, "John"
wrote:

Here is the 'T" antenna I referred to. It is totally plastic.
http://www.happywanderer.net.au/page...9&parent2id=24

Not quite totally plastic. Inside the ABS or PVC tubing are some
wires. Most likely, a length of twinlead forming a folded dipole.
While not the most sophisticated antenna available, it's probably
sufficient for campers and caravans.

However, there's a small problem. If you cram an antenna into a PVC
tube, the resonant frequency goes down. There's no set value for the
velocity factor for PVC or ABS, so the resonance change will vary with
manufacturer, doping, and the position of the moon. It's not a big
deal for a low-Q minimal gain and wide band antenna such as this
folded dipole. However, as the gain goes up, the tolerances for
element lengths become more critical. This means that changes in
effective length and resonance caused by PVC or ABS pipe becomes an
important consideration.

"John" wrote in message
.au...
Whilst trying to source a "digital" TV antenna I came across some with all
external surfaces plastic. One was a small yagi with all external surfaces
plastic, hopefully with metal elements embedded. Another a "T" shape made
out of plastic conduit with elements inside conduit.
My question is how do they work?. If they are detecting electrical fields
how does increasing source impedance by 100,s of megohms improve things?.
Capacitive coupling, I suppose at the frequencies involved there would be
some.
If it works as well as all metal why doesn,t every one use it and stop
corrosion?

The distance between the metal elements and the dielectric (PVC or
ABS) is also a consideration. Obviously, if the pipe diameter were
fairly large, the effect of the pipe would be minimal. Similarly, if
the pipe were molded around the conductor, the effect of the pipe
would be maximum.

There's nothing magic about coating an antenna to prevent corrosion.
This is an important consideration for trailers, campers, and
caravans. The antenna has to survive freeway speeds and be fairly
aerodynamic. Coating the antenna with smooth plastic does this.

If you feel ambitious, and happen to have either a grid dip meter or
an antenna analyzer, just build any resonant antenna (probably at VHF
frequencies) and watch the resonant frequency change as a PVC or ABS
pipe is slid over the antenna elements. I build a collinear antenna
out of alternating pieces of coax cable. It tuned perfectly, until I
slid the antenna into a PVC pipe. Tuning changed from 146MHz to a
useless 135MHz. Filling the pipe with urethane foam (fence post
compound), lowered the frequency a few more mHz.



--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

"Jeff Liebermann" wrote in message
...


snip

Your "easy-sounding plans"
should be an ominous warning of problems to follow.


Sound warning, indeed. I checked some websites devoted to quads and the
measurements are in the ballpark. The 20m version is fairly close to the
ground,, being suspended from a boom at the top of a 30-foot pole. I'm
going to build it and try it in my yard before taking it to FD. The 30-foot
pole is no problem; I had three of them last year for the dipole.


(Jeez -- what am I _not_ doing?)

Operating?


Club duty only really requires about six hour a week, average. I still get
on the air. :-)

"Sal"

"tom" wrote in message
. net...



I bet he has an outhouse. Who needs modern plumbing when the negative
15th century stuff has worked so well for 25 centuries?

tom
K0TAR


Grin

"Sal"

"Jeff" napisal w wiadomosci
...

A cristal sets has the modern name "rectenna":

No it doesn't, a 'cristal' (sic) set, fails to meet the definition that is
in the first line of the article that you linked to: "A rectenna is a
rectifying antenna, a special type of antenna that is used to convert
microwave energy into direct current electricity"; in that a 'cristal'
(sic) set does not produce direct current; as it also states later in that
article: "it discards the DC component before sending the signal to the
earphones".

And what the electrons do in such instalation:
http://www.telegraph.co.uk/technolog...ectricity.html
"
a.. It is very simple to light a building with power stolen from a nearby
radio transmitter as a farmer once proved with a barn.
b.. 1. Ensure that the building is isolated and near a powerful
transmitter
c.. 2. Fit it with a metal roof (corrugated iron works well)
d.. 3. Connect the lights between the roof and a good earth connection
e.. 4. Bask in the glow
There no the "crystal" or a diode.
What do you think. Will it be working with the diode between the light and
the roof ?

Where come from the electrons?
S*

"Ian" napisa³ w wiadomo¶ci
...
"Szczepan Bialek" wrote in message
.. .
I've a recollection that you've posted your views onto this newsgroup
a
few weeks ago.
I guess that asking you to disregard 19th century understanding and
learn 20th and 21st century understanding is probably an unproductive
approach.

But I hope that you understand that 19th century physics and 21st century
are the same.
In the 20th the all was a top secret.
S*

I don't recall us having nuclear bombs in the 19th century, nor
transistors nor integrated circuits.

All fundamentals were invented in XIX by Faraday, Stokes, Lorenz and Tesla.

The underlying physics may not have changed but man's understanding of it
certainly has.
By analogy, the human body is still the same design as it was in the 15th
/ 16th /17th centuries (and earlier and later). If you need a doctor, will
you go to one practising 21st century medicine or 15th century medicine?
Would you prefer to drive a 21st century car or a 19th century car? Would
you be worried about dropping off the flat earth?
Perhaps you should study the "phlogiston" theory. How about the opposition
that Galileo encountered when he tried to support the theory of Copernicus
that Earth orbits around the Sun? If you'd been around in the time of
Galileo and Copernicus I guess you'd be certain that the Sun orbits the
Earth. After all, that's how Ptolemy said it was and that view lasted a
thousand years or more.

Galileo, Copernicus, Ptolemy. All known that the planets orbit the Sun.
But the teaching program "said" the "the Sun orbits the Earth."

The same is now.
All physics people know that : "Light is the oscillatory flow of
electrons".
But in teaching program are mystery TEM waves.
S*

"Rob" napisa³ w wiadomo¶ci
...
Szczepan Bialek wrote:
Tesla and Marconi proved that antenna must be grounded and that it
emmits/gains electrons.

But later it was found that they had been wrong, and that only a
strange critter named Szczepan Bialek was still writing about it.

Who found that they had been wrong?

S*