I tried a search and could not find this topic discussed. Sorry if it has been addressed before.
Could I use a digital multimeter( such as a FLUKE 12B) to test for signal strength if I set it to millivolts/ac? Is there anything else I could use that I probably already own? (signal meter/ swr meter for HAM Radio) I'm at a critically low WAF right now and trying to improve at minimal cost.
Ah, a Ham operator(?)
No, Fluke won't work. Do you have an O'scope?
The X10 "signal" is 120KHz bursts, imposed on the AC sine a few milliseconds past the 0 cross point. ELK used to make a nice signal level meter for under $80, you may still be able to find one on eBay. Jeff Volp may be bringing one to the market, but I think it is a ways off.
90% of X10 problems are either electrical "noise", predominately from switching power supplies knocking out the X10 signal, OR signal coupling problems between the two 120V phases in your home, and IMHO to a lessor degree, "signal suckers" (surge strips, UPS's, some computer power supplies, etc. any circuit that has a very low impedance across the AC line at 120KHz). Search these terms on this forum, and you will get enough free information to find your problem.
http://forums.x10.com/index.php?topic=7951.0