Can anyone point me at a good book or website that can teach me about
antenna theory from a beginner's standpoint? I'm getting into SWL & feel I
really need to understand this subject well . . .

hi lisa,

check you local library, the arrl antenna books are very good,
also http://www.cebik.com

jake

Lisa Simpson wrote:

Can anyone point me at a good book or website that can teach me about
antenna theory from a beginner's standpoint? I'm getting into SWL & feel I
really need to understand this subject well . . .

The ARRL Antenna Book is very good, and it's a good deal more accurate
than many other beginners' books. There's very likely to be a copy at
your local library.

Roy Lewallen, W7EL

Lisa Simpson wrote:
Can anyone point me at a good book or website that can teach me about
antenna theory from a beginner's standpoint? I'm getting into SWL & feel I
really need to understand this subject well . . .

Thanx all - I'll check this book out!

"Roy Lewallen" wrote in message
...
The ARRL Antenna Book is very good, and it's a good deal more accurate
than many other beginners' books. There's very likely to be a copy at
your local library.

Roy Lewallen, W7EL

Lisa Simpson wrote:
Can anyone point me at a good book or website that can teach me about
antenna theory from a beginner's standpoint? I'm getting into SWL &
feel I
really need to understand this subject well . . .

Is this an explanation of the term 'capture area' I hear a lot of hams
use.

regards, Jer

As a 'rule of thumb' the captured signal power in small loops is
proportional to the area enclosed by the loop. Twice the area = twice
the
power (3 dB).

The typical dimensions given for these loops allow them to be used on
either
160M or 80M -- and as you have surmised, the loop can be larger for 160M
only.

73, Gary
K9AY
_________

Subject: [Antennaware] Shielded loop receive antennas.


In the ARRL antenna handbook (and repeated elsewhere) is a design for
a 160m shielded rx loop antenna with 5ft square sides.

Can anyone advise me how the strength of the recovered signal would
change if the loop was made bigger. By using low-capacity coax I
think I could still resonate a loop that has 7ft square sides. This
would very nearly double the **AREA** of the loop, I would like to
understand how this would affect the received signal.

Any thoughts would be appreciated.

73,

Here is a site for examples of capture areas of antennas

http://www.sommerantennas.com/gain.html

--
CL -- I doubt, therefore I might be !


"k" wrote in message
...
Is this an explanation of the term 'capture area' I hear a lot of hams
use.

regards, Jer

As a 'rule of thumb' the captured signal power in small loops is
proportional to the area enclosed by the loop. Twice the area = twice
the
power (3 dB).

The typical dimensions given for these loops allow them to be used on
either
160M or 80M -- and as you have surmised, the loop can be larger for 160M
only.

73, Gary
K9AY
_________

Subject: [Antennaware] Shielded loop receive antennas.


In the ARRL antenna handbook (and repeated elsewhere) is a design for
a 160m shielded rx loop antenna with 5ft square sides.

Can anyone advise me how the strength of the recovered signal would
change if the loop was made bigger. By using low-capacity coax I
think I could still resonate a loop that has 7ft square sides. This
would very nearly double the **AREA** of the loop, I would like to
understand how this would affect the received signal.

Any thoughts would be appreciated.

73,

Caveat Lector wrote:
Here is a site for examples of capture areas of antennas

http://www.sommerantennas.com/gain.html

--
CL -- I doubt, therefore I might be !

As a 'rule of thumb' the captured signal power in small loops is
proportional to the area enclosed by the loop. Twice the area = twice
the
power (3 dB).


That's all nonsense, including the Sommer site!!

Capture area, more correctly called effective aperture, and gain has
nothing directly to do with physical area of an antenna. It is strictly
a function of the operating wavelength and gain of the antenna.

If I double the size of an antenna the capture area (effective
aperture) might increase, decrease, or stay the same.

If I have a small loop and it has zero loss, the capure area is
effectively very large.

If I have a full size dipole and add enough loss resistance, capture
area is very small.

Capture area is generally an excuse people make to justify using a
larger antenna, even if the antenna does not work as nearly as well.
"My quad works great for receiving because it has large capture area."
Nonsense. If it has the same gain as a Yagi on the same band, it has
exactly the same capture area. If it has less gain than a Yagi (which
many quads do, hence the reason you don't see them in contest stations)
it has less capture area.

I'd be ashamed if I was selling antennas and did not understand what
capture area was.

73 Tom

You can also find many postings explaining capture area by doing a
groups.google.com search of this newsgroup for the phrase "capture
area". I've explained it here several times.

Roy Lewallen, W7EL

Caveat Lector wrote:
Here is a site for examples of capture areas of antennas

http://www.sommerantennas.com/gain.html

Caveat Lector wrote:
Here is a site for examples of capture areas of antennas

http://www.sommerantennas.com/gain.html


Have you got a link to a similar site that covers ferrite rod antennas?

Caveat Lector wrote:
Here is a site for examples of capture areas of antennas

http://www.sommerantennas.com/gain.html

John Popelish wrote:
Have you got a link to a similar site that covers ferrite rod antennas?

I hope this question isn't taken the wrong way, but why would you want
a similar site? That one is terrible for accuracy. The poor fellow who
wrote that page doesn't even know what capture area is.

Wouldn't it be better to find a totally different type of site, one
that at least has some technical accuracy?

73 Tom