I thought I would repost this answer to a query on Racal backlighting for
those that might be interested in adding backlight to their HF-150. I have
no interest in doing the work, but creative individuals should be able to
duplicate my results:

While I have never done a backlight for the Racal, I have done numerous Lowe
HF-150. There, the procedure involves removing the foil backing from the
display while being careful not to remove the polarizing film that lies
directly beneath the foil.
Next a plexiglass sheet the size of the area to be illuminated is uniformly
sanded on one side with very fine grit paper- the idea is to frost the
surface allowing light to escape from this front surface. A pair of slots
are milled into each end of the sheet that will allow a T1 3/4 LED to press
axially
into the sheet. (each LED will be "looking" towards the middle of the
sheet). Finally
an Avery self adhering white label is adhered to the back side of the plexi
sheet. I also polish all edges so that light will only escape out the
frosted front. The sheet is finally sandwiched between the back of the
display and its socket.
Here is a Lowe HF-150 after backlighting:
http://www.parelectronics.com/pics/hf150bl.jpg

73,

Dale W4OP
for PAR Electronics, Inc.