Hi,

I have an interesting project! I am using a RF receiver device which has a
50 Ohm RF input. I want to use a PCB printed antenna on FR4 board, not
unusual you say. but I need to pot the whole PCB in resin to make it
waterproof. The receiver only needs to work when floating on water! Has
anyone any experience in PCB antenna who would be so kind to comment on the
effects, and possible actions to counter any effects, of the potting. The
resin is much like araldite.



Any thoughts much appreciated.



Will

On Tue, 14 Oct 2003 18:27:50 +0000 (UTC), "Will Reeve"
wrote:

Hi,

I have an interesting project! I am using a RF receiver device which has a
50 Ohm RF input. I want to use a PCB printed antenna on FR4 board, not
unusual you say. but I need to pot the whole PCB in resin to make it
waterproof. The receiver only needs to work when floating on water! Has
anyone any experience in PCB antenna who would be so kind to comment on the
effects, and possible actions to counter any effects, of the potting. The
resin is much like araldite.



Any thoughts much appreciated.



Will


Hi Will,

Look into conformal coating as an alternative. Or simply mix acetone
and RTV to create one and paint it on. To cut down on water losses,
it would do well to provide an air jacket around the antenna elements
that is roughly a tenth wavelength in diameter (and from the tips).

73's
Richard Clark, KB7QHC

Will Reeve wrote:
Hi,

I have an interesting project! I am using a RF receiver device which has a
50 Ohm RF input. I want to use a PCB printed antenna on FR4 board, not
unusual you say. but I need to pot the whole PCB in resin to make it
waterproof. The receiver only needs to work when floating on water! Has
anyone any experience in PCB antenna who would be so kind to comment on the
effects, and possible actions to counter any effects, of the potting. The
resin is much like araldite.



Any thoughts much appreciated.



Will




The potting compound will act as a dielectric load. My bet is that the
dielectric constant will be about 3. Your antenna will have to shrink.
If you know the dielectric properties of the potting compound, and
your antenna is simple, then I might be able to run a simulation (and
optimization) for you with IE3D.... I work with 900 MHz antennas on FR4
every day

Wayne Shanks
Senior RF and Antenna Engineer, Matrics Inc.

If the antenna is in close proximity to water, the water's dielectric
constant of about 80 will have a profound effect, as will its very high
loss.

Roy Lewallen, W7EL

Wayne Shanks wrote:
Will Reeve wrote:

Hi,

I have an interesting project! I am using a RF receiver device which
has a
50 Ohm RF input. I want to use a PCB printed antenna on FR4 board, not
unusual you say. but I need to pot the whole PCB in resin to make it
waterproof. The receiver only needs to work when floating on water! Has
anyone any experience in PCB antenna who would be so kind to comment
on the
effects, and possible actions to counter any effects, of the potting. The
resin is much like araldite.



Any thoughts much appreciated.



Will




The potting compound will act as a dielectric load. My bet is that the
dielectric constant will be about 3. Your antenna will have to shrink.
If you know the dielectric properties of the potting compound, and your
antenna is simple, then I might be able to run a simulation (and
optimization) for you with IE3D.... I work with 900 MHz antennas on FR4
every day

Wayne Shanks
Senior RF and Antenna Engineer, Matrics Inc.

www.fwt.niat.net

This dielectric embedded antennas are smaller than naturally occurs and yet
have a net gain


"Roy Lewallen" wrote in message
...
If the antenna is in close proximity to water, the water's dielectric
constant of about 80 will have a profound effect, as will its very high
loss.

Roy Lewallen, W7EL

Wayne Shanks wrote:
Will Reeve wrote:

Hi,

I have an interesting project! I am using a RF receiver device which
has a
50 Ohm RF input. I want to use a PCB printed antenna on FR4 board, not
unusual you say. but I need to pot the whole PCB in resin to make it
waterproof. The receiver only needs to work when floating on water! Has
anyone any experience in PCB antenna who would be so kind to comment
on the
effects, and possible actions to counter any effects, of the potting.
The
resin is much like araldite.



Any thoughts much appreciated.



Will




The potting compound will act as a dielectric load. My bet is that the
dielectric constant will be about 3. Your antenna will have to shrink.
If you know the dielectric properties of the potting compound, and your
antenna is simple, then I might be able to run a simulation (and
optimization) for you with IE3D.... I work with 900 MHz antennas on FR4
every day

Wayne Shanks
Senior RF and Antenna Engineer, Matrics Inc.

On Mon, 03 Nov 2003 17:00:58 GMT, "Marc H.Popek"
wrote:

www.fwt.niat.net

This dielectric embedded antennas are smaller than naturally occurs and yet
have a net gain

Hi Marc,

Interesting sentence construction.

A cogent question would reveal some perspective: How much would your
13dBi dielectric embedded antennas for TV Channel 2 weigh?

73's
Richard Clark, KB7QHC

Richard Clark wrote:

On Mon, 03 Nov 2003 17:00:58 GMT, "Marc H.Popek"
wrote:

www.fwt.niat.net

This dielectric embedded antennas are smaller than naturally occurs and yet
have a net gain

Hi Marc,

Interesting sentence construction.

A cogent question would reveal some perspective: How much would your
13dBi dielectric embedded antennas for TV Channel 2 weigh?

73's
Richard Clark, KB7QHC

A lot less than they would for the 160 meter ham band.

--
Many thanks,

Don Lancaster
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
voice: (928)428-4073 email: fax 847-574-1462

Please visit my GURU's LAIR web site at http://www.tinaja.com

Sir Clark,

No work on using the embedded moldable plastic dielectric at 50 Mc... as you
point out the size and weight does not appear to be advantageous.

However, above 900 the size shrink, has an advantage

we have other ideas to use the FWT at lower frequencies.... stay tuned

"Richard Clark" wrote in message
...
On Mon, 03 Nov 2003 17:00:58 GMT, "Marc H.Popek"
wrote:

www.fwt.niat.net

This dielectric embedded antennas are smaller than naturally occurs and
yet
have a net gain

Hi Marc,

Interesting sentence construction.

A cogent question would reveal some perspective: How much would your
13dBi dielectric embedded antennas for TV Channel 2 weigh?

73's
Richard Clark, KB7QHC

"Marc H.Popek" wrote in message
...
www.fwt.niat.net

This dielectric embedded antennas are smaller than naturally occurs and
yet
have a net gain

More correctly, they CLAIM a gain, relative to isotropic.

If the antenna is smaller than a free space antenna, then it looses capture
area.
I would be very interested to know how they recoup that.
I suspect these antennas might need some power to drive an on-board
amplifier, which means that their gain claim is bogus, and what they aren't
telling you is that the noise floor comes up also.

TANSTAAFL.

On Mon, 3 Nov 2003 16:40:59 -0500, "Dave VanHorn"
wrote:


"Marc H.Popek" wrote in message
...
www.fwt.niat.net

This dielectric embedded antennas are smaller than naturally occurs and
yet
have a net gain

More correctly, they CLAIM a gain, relative to isotropic.

They? HE (the CTO in fact). American business has a recent history
of clown elevation.


If the antenna is smaller than a free space antenna, then it looses capture
area.

Capture area is hardly an issue for even the full size antennas they
replace.

I would be very interested to know how they recoup that.
I suspect these antennas might need some power to drive an on-board
amplifier, which means that their gain claim is bogus, and what they aren't
telling you is that the noise floor comes up also.

TANSTAAFL.

Hi Dave,

What is more to the matter is unstated issues of efficiency. I will
let the claims of 8 fold boons pass (which is marketese from the world
of ENRON). Compare these "advantages" of reclaimed volume to the
unanswered query of weight (no claims about density are there?).

Leftover halloween candy.

73's
Richard Clark, KB7QHC