



March 4, 1987



To: N. Kelly


From: R. Briody


Subject: FCC testing of VMI monitors in various configurations


Definitions: 
	1) ISI CRT tube - The standard tube supplied by VMI coated with
	Electrodag 437 (a conductive copper paint).
	2) VMI CRT tube - The standard tube supplied by VMI. This tube appears
	to be coated with a high resistance dag coating, possibly graphite.
	3) NBI CRT tube - A tube purchased by NBI from Clinton Electronics that
	has a proprietary EMI/RFI coating and a rubber/monel gasket around the 
	perimeter of the tube.
	4) Shield #1 - A one-piece shield with Be-Cu spring fingers fastened
	in such a way as they will contact any EMI coating on a CRT tube.
	5) Shield #2 - A two-piece yoke shield which fits over the CRT neck and
	fastens to the sides and floor of the enclosure.
	6) Shield #3 - A two piece shield mounted to the top of the existing
	enclosure.

Test Conditions:
	1) All test were performed on monitor chassis' with the following
	modifications:
		A) The gap around three sides of the CRT was sealed with 
		an adhesive backed copper tape.
		B) A ferrite torroid was placed on the internal 110 VAC wires
		at the line filter.
		C) The 25 pin "D" connector on the Monitor Breakout PCB was 
		screwed down to the PCB using #4 hardware.
		D) Be-Cu spring fingers were placed along the bottom of the
		rear panel. There was inadequate contact area between the base
		and rear panel.
		E) A ferrite bead was placed on the ground lead of the Video
		Driver PCB.

The VMI monitor configurations tested at NBI were as follows:

	  |	VMI CRT  |		NBI CRT  |		ISI CRT
-------------------------------------------------------------------------------
Shield #1 | 	Fail	 |	   Untested	 |	 Pass - 2 db margin
	  |		 |			 |
  	  |		 |			 |
-------------------------------------------------------------------------------
Shield #2 |	Fail	 |	   Untested	 |	 Pass - 2 db margin
	  |		 |			 |
	  |		 |			 |	
-------------------------------------------------------------------------------
Shield #3 | 	Fail	 |   Pass - >8 db margin |	 Fail
	  |		 |			 |
	  |		 | 			 |
-------------------------------------------------------------------------------

The FCC emission testing done at NBI did NOT involve raising or lowering the 
antenna per FCC test requirements and thus may NOT be worst case.
The two test conditions in which the monitor passed with a 2 db margin can NOT 
be considered as fixes because 1) the test conditions are not known to be worst
case and 2) 2 db of margin is not a manufacturable margin.

