"Jeff Liebermann" wrote in message
...
On Wed, 30 May 2012 09:08:04 +0200, "Szczepan Bialek"
wrote:

And neither are spacecraft antennas no matter what the type.


# Jeff

Why does anyone answer Skeezix Blutarsky?

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

And the yagi,

http://www.ebay.com.au/itm/Caravan-R...e m2ebd055150

The argument I seemed to have inadvertently triggered reminds me of
disgreement
I had about 40 years ago describing Op Amp inputs as virtual earths.
Odd how equally intelligent and educated people can look at things
differently.
Cheeers
John

"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

On 5/30/2012 10:21 PM, John wrote:
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

I liked the reflector screen on the HW-DT8. It's appears just a bit
sparse for the frequencies it's supposed to cover.

Other than that the driven part is kind of interesting. If it's
reasonably priced enough and shipping isn't out of line I may order one
just to see what mischief they are up to.

tom
K0TAR

Link to the antenna I referenced.

http://www.happywanderer.net.au/page...9&parent2id=71

And of course it will give me a nice new antenna to perform weight and
charge measurements on.

Can't use an old one. See, when the antenna gets used more and more it
gets tired because of electron loss. You have to watch your transmit
and receive balance. If you don't you will end up with too few
electrons around, which makes for an increase in transmit resistance.
Some people think it's impedance, but they don't know it's just because
you haven't got the right length coax.

And the other way around, if you receive all the time you eventually
fill the electron sump, and the antenna must be discarded unless you can
get a good electron sump pump for cheap. Funny thing, that's why the
old AM and FM radios wore out - they were full.

On Wed, 30 May 2012 20:00:55 -0700, "Sal M. O'Nella"
wrote:

Why does anyone answer Skeezix Blutarsky?

Because I'm terrible at resisting temptation. If someone wants to
make themselves a target, it's far too tempting to take a few shots at
the target. Also, I enjoy reading (and writing) science fiction.
However, the real reason is that I haven't seen any decent antenna
related discussions in this newsgroup for a long time.


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

Its why you should never leave a powerpoint switched on. You end up with a
heap of electrons on the floor.
And a hole under the neutral hole.


"tom" wrote in message
. net...
On 5/30/2012 10:21 PM, John wrote:
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

I liked the reflector screen on the HW-DT8. It's appears just a bit
sparse for the frequencies it's supposed to cover.

Other than that the driven part is kind of interesting. If it's
reasonably priced enough and shipping isn't out of line I may order one
just to see what mischief they are up to.

tom
K0TAR

Link to the antenna I referenced.

http://www.happywanderer.net.au/page...9&parent2id=71

And of course it will give me a nice new antenna to perform weight and
charge measurements on.

Can't use an old one. See, when the antenna gets used more and more it
gets tired because of electron loss. You have to watch your transmit and
receive balance. If you don't you will end up with too few electrons
around, which makes for an increase in transmit resistance. Some people
think it's impedance, but they don't know it's just because you haven't
got the right length coax.

And the other way around, if you receive all the time you eventually fill
the electron sump, and the antenna must be discarded unless you can get a
good electron sump pump for cheap. Funny thing, that's why the old AM and
FM radios wore out - they were full.

John wrote:
Many thanks for your time Gents, The antennas were intended for outdoor use
and constant handling. being encased in hard plastic obviously enhances
those functions. My experience has been at the other end of the spectrum so
to speak and I (incorrectly) assumed an antenna picks up an electrical
signal. Putting a layer of insulating plastic on it seemed contradictory. If
antenna is detecting magnetic signals obviously a different story.
When I mentioned impedance I mislead you. Wasnt referring to antenna
impedance but the impedance looking back form the recieving antenna to the
signal source ( thats what us old analogue designers do, Norton/Thevenin
equivalent circuits etc !!!!) and the effect on that a layer of plastic
has.
Your combined efforts have answered a lot of my questions, thanks for your
time.

Unfortunately the clueless idiot from Poland has woken up and is
making his outdated claims again...

What you should know is (and apparently have realized by now) that
the antenna impedance is not an impedance between its elements and
the surrounding air, but a "radiation impedance" that results from
the antenna emitting an electromagnetic field. This field traverses
plastic, a vacuum, air etc without problem so it does not matter if
you coat the elements.

"John" wrote in message
. au...
Its why you should never leave a powerpoint switched on. You end up with a
heap of electrons on the floor.
And a hole under the neutral hole.

Not if you leave a plug in the socket. That'll stop the electrons.
What about the neutrons, protons and croutons?

Regards, Ian.

Ian wrote:
"John" wrote in message
. au...
Its why you should never leave a powerpoint switched on. You end up with a
heap of electrons on the floor.
And a hole under the neutral hole.

Not if you leave a plug in the socket. That'll stop the electrons.
What about the neutrons, protons and croutons?

Croutons are especially nasty when they end up on the floor...

"Rob" wrote in message
...
Ian wrote:
"John" wrote in message
. au...
Its why you should never leave a powerpoint switched on. You end up with
a
heap of electrons on the floor.
And a hole under the neutral hole.

Not if you leave a plug in the socket. That'll stop the electrons.
What about the neutrons, protons and croutons?

Croutons are especially nasty when they end up on the floor...

But you can weight them and they are easy to detect :-)