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.

Richard wrote:
http://cgi.ebay.co.uk/ws/eBayISAPI.d...tem=3077597082


Are the 'tubes' solid, or hollow and contain mercury?

All the vertical part of the antenna is made of
aluminum tubing. B is a short peice of fatter
aluminum tubing than either A or C. C
electrically connects with A, so I presume
there is a coil within aluminium tube B. Tube
B, at the bottom, looks rivited to tube C.

So I'm saying B is like:

| | A
_____|__|_____
| | | |
|____|__|_____|
| | | |
| x |
| x |
| x | B
| x |
| x |
| x |
| x |
|____|__|_____|
| | |-----| Rivet
|____| |_____|
| | C
| |



There are insulated collarsat both ends of B.

X represents assumed coil connecting A to C.


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Richard wrote:
All the vertical part of the antenna is made of
aluminum tubing. B is a short peice of fatter
aluminum tubing than either A or C. C
electrically connects with A, so I presume
there is a coil within aluminium tube B. Tube
B, at the bottom, looks rivited to tube C.

So I'm saying B is like:

| | A
_____|__|_____
| | | |
|____|__|_____|
| | | |
| x |
| x |
| x | B
| x |
| x |
| x |
| x |
|____|__|_____|
| | |-----| Rivet
|____| |_____|
| | C
| |



There are insulated collarsat both ends of B.

X represents assumed coil connecting A to C.


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Okay I removed tube B and made measurements. Here are
the details that ought to allow someone to do
calculations for the vertical part of the antenna:


| |-------------------
| | |
| | |
| | |
| | |
| | p 19" (48 Cm)
| | A |
_____|__|_____ --- |
| | | | | |
| | | | | |
| | | | q 1.25" |
|____|__|_____| | (3Cm) |
| | | |------------|
| x |
| x |
| x | B
| x |
| x |
| x |
| x |
| | | |------------------
| | | | | |
|____|__|_____| r 1" (2,5 Cm) |
| | | | | |
| | |ooooo|--- Rivet |
|____| |_____| connecting |
| | tube B |
| | to tube C |
| | |
| | s 60" (153 Cm)
| | C |
| | |
| | |
| | |
| |------------------------
^ Feedpoint

Tube B is a 4"(10 Cm) long tube.

Tube B connects to tube C 1" (2,5 Cm)from the
top of tube C. Tube B in fact shrouds the top
1" of tube C. Top of tube C connects to the
bottom end of a coil shown by x's. The top end
of the coil connects to tube A which is 19"
(48 Cm)long.The top part of tube B shrouds
over the bottom part of tube A by 1.25"(3Cm).


I got the inductance of the coil to be appx 3uH.

Length: 24mm
O.D. coil: 23mm
Turns:13
Spacing: Closewound
Wire diameter:1.5mm

So I suppose next task is to calcuate
the resonant frequency of the vertical part
of the antenna. Thing is,is it meant to
be a quarter wave half wave 5/8th wave or
what. The feedpoint impedance I reckon will
be 50 or 75 Ohms. I don't know how to calculate
this.

The 3 radials are 28" (71 Cm)long, but appear
to have small coils at the beginning of the
radials. The coils on two of the radials look
the same, and the coil on the third radial looks
about twice as long as the other two coils. The
smaller coil inductances seems to be very
approximately 0.330 uH, so the inductance of the
larger coil on the third radial is about 0.660 uH.

Smaller radial coils data:

Length: 7.5mm
O.D. of coil: 12mm
Turns: 5
Spacing: Closewound
Wire Diameter: 1.5mm

larger radial coil data:

Length: 7.5mm
O.D. of coil: 24mm
Turns: 5
Spacing: Closewound
Wire Diameter: 1.5mm

Perhaps now these data might help figure
out what frequency this antenna is for.I hope.

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Richard wrote:
Richard wrote:
All the vertical part of the antenna is made of
aluminum tubing. B is a short peice of fatter
aluminum tubing than either A or C. C
electrically connects with A, so I presume
there is a coil within aluminium tube B. Tube
B, at the bottom, looks rivited to tube C.

So I'm saying B is like:

| | A
_____|__|_____
| | | |
|____|__|_____|
| | | |
| x |
| x |
| x | B
| x |
| x |
| x |
| x |
|____|__|_____|
| | |-----| Rivet
|____| |_____|
| | C
| |



There are insulated collarsat both ends of B.

X represents assumed coil connecting A to C.


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Okay I removed tube B and made measurements. Here are
the details that ought to allow someone to do
calculations for the vertical part of the antenna:


| |-------------------
| | |
| | |
| | |
| | |
| | p 19" (48 Cm)
| | A |
_____|__|_____ --- |
| | | | | |
| | | | | |
| | | | q 1.25" |
|____|__|_____| | (3Cm) |
| | | |------------|
| x |
| x |
| x | B
| x |
| x |
| x |
| x |
| | | |------------------
| | | | | |
|____|__|_____| r 1" (2,5 Cm) |
| | | | | |
| | |ooooo|--- Rivet |
|____| |_____| connecting |
| | tube B |
| | to tube C |
| | |
| | s 60" (153 Cm)
| | C |
| | |
| | |
| | |
| |------------------------
^ Feedpoint

Tube B is a 4"(10 Cm) long tube.

Tube B connects to tube C 1" (2,5 Cm)from the
top of tube C. Tube B in fact shrouds the top
1" of tube C. Top of tube C connects to the
bottom end of a coil shown by x's. The top end
of the coil connects to tube A which is 19"
(48 Cm)long.The top part of tube B shrouds
over the bottom part of tube A by 1.25"(3Cm).


I got the inductance of the coil to be appx 3uH.

Length: 24mm
O.D. coil: 23mm
Turns:13
Spacing: Closewound
Wire diameter:1.5mm

So I suppose next task is to calcuate
the resonant frequency of the vertical part
of the antenna. Thing is,is it meant to
be a quarter wave half wave 5/8th wave or
what. The feedpoint impedance I reckon will
be 50 or 75 Ohms. I don't know how to calculate
this.

The 3 radials are 28" (71 Cm)long, but appear
to have small coils at the beginning of the
radials. The coils on two of the radials look
the same, and the coil on the third radial looks
about twice as long as the other two coils. The
smaller coil inductances seems to be very
approximately 0.330 uH, so the inductance of the
larger coil on the third radial is about 0.660 uH.

Smaller radial coils data:

Length: 7.5mm
O.D. of coil: 12mm
Turns: 5
Spacing: Closewound
Wire Diameter: 1.5mm

larger radial coil data:

Length: 7.5mm
O.D. of coil: 24mm
Turns: 5
Spacing: Closewound
Wire Diameter: 1.5mm

Perhaps now these data might help figure
out what frequency this antenna is for.I hope.

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This post is perfect for this group. Now that I've posted all the necessary
the data it ought to be fathomable..

Reg, you must be able to work this antenna out.

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.