Richard,

Why don't you go to the web site you referenced, and click on "Ask seller a
question", or doesn't he know? I did not read the whole thing. With the
loading coils, it might be an 11 meter antenna.

TYam/WB2TT
"Richard" wrote in message
...
http://cgi.ebay.co.uk/ws/eBayISAPI.d...tem=3077597082

This antenna is a mystery. No-one can identify it from the picture. It's
made in Japan and model number is CA-815.

I now have this antenna and can give the dimentions.

|
| A variable appx 17" (43 Cm)
|
| | B 4" (10 Cm)
| |
|
|
| C 59" (150 Cm)
|
|
-------------X--------------
D D 28" (71 Cm)

Tube A is adjustable it's about 17" long when in mid position.

B from the outside looks like a 4" long metal tube. A enters the "tube"
from the top, but is insulated from it. Likewise C enters the "tube" from
below and also insulated from it. I wonder if within B is a coil.

Tube C is 59" long.

Radials D are 28" long, but it looks to me as if they have a loading coil
which is located at the beginning. Coils not equal length for eachground
plane radial.

On the information sheet it shows a picture of a radio set they call "BASE
UNIT" It highlights an antenna select switch and tells you to select
external. So, to me, it looks like this antenna is meant for a receiver.

This antenna is ground plane type, it looks like a ground plane.

Hope it can now be identified. I've no idea what it's for. Is it either
an
AM or FM outdoor antennna? Or both?

TIA.

Rich.

"Tam/WB2TT" wrote in message
...
Richard,

Why don't you go to the web site you referenced, and click on "Ask seller
a
question", or doesn't he know? I did not read the whole thing. With the
loading coils, it might be an 11 meter antenna.


The seller does not know.

Funny, but figuring out what frequency an antenna might be for, even with
the physical and electrical parameters spelled out must be more difficult
than I imagined. I'm really surprised that after giving these details lower
down in the thread, the antenna cannot be figured. I'm gobsmacked.

On Sun, 29 Feb 2004 12:58:41 -0000, "Richard"
wrote:


"Tam/WB2TT" wrote in message
...
Richard,

Why don't you go to the web site you referenced, and click on "Ask seller
a
question", or doesn't he know? I did not read the whole thing. With the
loading coils, it might be an 11 meter antenna.

The seller does not know.

Funny, but figuring out what frequency an antenna might be for, even with
the physical and electrical parameters spelled out must be more difficult
than I imagined. I'm really surprised that after giving these details lower
down in the thread, the antenna cannot be figured. I'm gobsmacked.

You are right in the case of a simple antenna.

Loading coils and similar make a determination without actually
examining it far more difficult. You may not have provided every bit
of data required for people to VOLUNTARILY provide you with an answer.

An antenna design book might help, as would some careful testing.

You don't need to determine exactly what it is, you just need a "go/no
go" test for your frequencies of interest. Low power Xmit and an SWR
meter would help.

Happy trails,
Gary (net.yogi.bear)
------------------------------------------------
at the 51st percentile of ursine intelligence

Gary D. Schwartz, Needham, MA, USA
Please reply to: garyDOTschwartzATpoboxDOTcom

Have you tried to put the model number (I couldn't read it in the
picture) into Google to see what it returns?

"Stevens" wrote in message
...
Have you tried to put the model number (I couldn't read it in the
picture) into Google to see what it returns?

Yea, done that and nuthin'.

I wonder what the quarter wave frequency would be for a length of wire 30"
long with a base coil of approximately 0.330uH. Same wonder with a 0.660 uH
coil.

I wonder what the quarter wave frequency would be for a length of wire 30"
long with a base coil of approximately 0.330uH. Same wonder with a 0.660
uH
coil.
====================================

Rich, wonder no longer.

Download program BOTLOAD2.

For a 30" rod -

With base loading coil 0.33 uH, Fres = 69.1 MHz.

With a base loading coil 0.66 uH, Fres = 55.7 MHz.

----
Reg, G4FGQ
.................................................. ..........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
.................................................. ..........

"Reg Edwards" wrote in message
...
I wonder what the quarter wave frequency would be for a length of wire
30"
long with a base coil of approximately 0.330uH. Same wonder with a
0.660
uH
coil.
====================================

Rich, wonder no longer.

Download program BOTLOAD2.

For a 30" rod -

With base loading coil 0.33 uH, Fres = 69.1 MHz.

With a base loading coil 0.66 uH, Fres = 55.7 MHz.

The antenna has three radials, and each has a loading coil right at the
begining.

Now I would have thought that at the feedpoint, the impedance would be low,
so I think then one would assume the radials are suppossed to acting as 1/4
wavelength radials. If that were true, then the freqency at which the
radials are quarter wavelength would be the operating frequency of the
antenna.

I've remeasured the coils after removing the rubber insulation to get a
better look.

For Radial #1

Length: 6mm
O.D.: 11mm
Turns: 9
Pitch: closewound


For Radial #2

Length: 6mm
O.D.: 11mm
Turns: 9
Pitch: closewound


For Radial #3

Lenngth: 13mm
O.D.: 11mm
Turns: 20
Pitch: closewound

I wonder if the coils should all be different, but by mistake the radials 1
& 2 are identical. I just don't know.

The new length of the radial is 72mm orabout 28.5". They are 2mm diameter
stainless steel rods.

I tried to use Botload2, but not sure what I'm doing. Can you please do the
two calculations again Reg? Ta.

"Richard" wrote in message
...

"Tam/WB2TT" wrote in message
...
Richard,

Why don't you go to the web site you referenced, and click on "Ask
seller
a
question", or doesn't he know? I did not read the whole thing. With the
loading coils, it might be an 11 meter antenna.


The seller does not know.

Funny, but figuring out what frequency an antenna might be for, even with
the physical and electrical parameters spelled out must be more difficult
than I imagined. I'm really surprised that after giving these details
lower
down in the thread, the antenna cannot be figured. I'm gobsmacked.


It can be figured out, but it is a lot of work. If you have the actual
antenna, I would measure the SWR at some frequencies, starting at 10 or 11
meters. Of course, if you have access to an MFJ Antenna analyzer, you are in
luck.

Tam/WB2TT

On Sun, 29 Feb 2004 12:58:41 -0000, "Richard"
wrote:
I'm really surprised that after giving these details lower
down in the thread, the antenna cannot be figured. I'm gobsmacked.

Hi Richard,

You would be even more so if you had sat through a cycle of
correspondence of trying to make sense of the Patent for that same
antenna. We get a lot of that too, and at that point, some may
respond briefly because Patents don't have to make sense. Would you
care to delve into the mysteries of a Faster than Light antenna? Just
needs magnets in the right place (or was that for better gas
mileage?). Some details just don't add up to better understanding.

We even get Patent holders who come here to proclaim their latest
invention, and then ask us how it works - or worse, proclaim it does
work and it is our bound obligation and duty to prove it.

73's
Richard Clark, KB7QHC

Richard Clark wrote:
"---patents don`t have to make sense."

A search to show the patent application is for something not already
patented is, I think, a part of the process.

This patent search may favor the impractical to the extent that sane
knowing people choose not to pursue the impractical, so no prior patent
may be found.

The patent office may issue a patent for a Yagi / Uda antenna in which
the director is longer than the driven element and the reflector is
shorter than the driven element.

Many patents either don`t work as claimed or have such limited utility
that they aren`t imitated.

Best regards, Richard Harrison, KB5WZI