RF problem caused display to blank

[Dummy]

I have one radio (330Mhz-400MHz), equipped with antenna and remote
speaker mic.
When the radio is transmitting at 4W over a groundplane with LCD
display facing down, display blank problem could be seen occasionally.
The display was totally blank and not functioning. Of course, radio
was still working well. Turning the radio OFF and ON again would have
the display recovered.

A copper tape that applied at the LCD flex solved the problem. But no
display blank issue was not seen at other bands of radios such as from
100MHz-200MHz and 400MHz-500MHz. All radios are using same LCD, same
circuitry and similar platform design. Even though the problem has
been solved, the behaviour of the display blank problem was not
properly understood, especially when it's frequency dependent, and it
happened when display was facing downwards the big groundplane, and it
didn't happen at other bands of radio. Can somebody shed some light on
this?

 

[John Woodgate]

I read in sci.electronics.design that Dummy <ahkit1021@yahoo.com> wrote
(in <74bb84c0.0503090259.7f2f2d4b@posting.google.com&gt about 'RF problem
caused display to blank', on Wed, 9 Mar 2005:

I have one radio (330Mhz-400MHz), equipped with antenna and remote
speaker mic.
When the radio is transmitting at 4W over a groundplane with LCD
display facing down, display blank problem could be seen occasionally.
The display was totally blank and not functioning. Of course, radio
was still working well. Turning the radio OFF and ON again would have
the display recovered.

A copper tape that applied at the LCD flex solved the problem. But no
display blank issue was not seen at other bands of radios such as from
100MHz-200MHz and 400MHz-500MHz. All radios are using same LCD, same
circuitry and similar platform design. Even though the problem has
been solved, the behaviour of the display blank problem was not
properly understood, especially when it's frequency dependent, and it
happened when display was facing downwards the big groundplane, and it
didn't happen at other bands of radio. Can somebody shed some light on
this?

Typical EMC mystery problem. Of course it can be explained. Start with
Maxwell's Equations and go on from there. (;-)

Alternatively, just remember that things like that can happen.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk