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.