
The May 1993 cover of QST has a picture of three different boards without
any solder mask (you can tell from the copper colored traces). The box
labeled 2304 transverter has the brown teflon/glass board, while the one
in the center has the grayish board exposed.  On the left is some 
fiberglass board that looks green to me.  I see no reason
for putting solder mask on circuit board used for box covers :-).

I wonder if any manufacturer actually puts a solder mask on their
low noise microwave preamps?  Often, microwave circuits have odd
bits of wire/foil/metal attached to wherever/whatever is necessary
to make the unit work properly (this is a commercial product?).  A
solder mask would certainly make doing this tougher, never mind 
the finding something that minimally degrades the circuits.  (Q dope
for coils *does* not improve the Q--it just holds things together with
minimal loss).

Zack Lau  KH6CP/1

Internet: zlau@arrl.org           "Working" on 24 GHz SSB/CW gear     
			          Operating Interests: 10 GHz CW/SSB/FM
US Mail: c/o ARRL Lab				       80/40/20 CW
	225 Main Street		  Station capability: QRP, 1.8 MHz to 10 GHz
	Newington CT  06111	               modes: CW/SSB/FM/packet
						      amtor/baudot
Phone (if you really have to): 203-666-1541

Zack Lau  KH6CP/1

Internet: zlau@arrl.org           "Working" on 24 GHz SSB/CW gear     
			          Operating Interests: 10 GHz CW/SSB/FM
US Mail: c/o ARRL Lab				       80/40/20 CW
	225 Main Street		  Station capability: QRP, 1.8 MHz to 10 GHz
	Newington CT  06111	               modes: CW/SSB/FM/packet
						      amtor/baudot
Phone (if you really have to): 203-666-1541