FAX30 meaning of SS and SN


Furuno Super Fan
I have difficulty receiving navtex signal on the boat in Eastern Canada but not sure it is the fault of the FAX30 installation. (there are not many stations here). But i wonder what are the diagnosis tool available - apart from using another stations to check. For example are there any minimal value of SS and SN that we might check for in order to receive a valid transmission ?

When we change station, the SS and SN changes, is this a way to choose the better station ?

I have just installed a Fax 30 I have tried using the reactive externally powered antenna at the mast head made by RR. This worked with the previous Fax receiver, which I have now replaced, not working with the fax 30 and giving low numbers particularly on SN. I have tried the SSB antenna which utilizes the backstay about 19m long and insulated, still quite low scores. Any advice?? As the Fax just sticks on standby.
I am having nil success on receiving fax data. Any ideas?? Have tried on auto and manual timer and standby. The machine just seems to be locked in standby
Not familiar with reactive antennas by R&R nor would it be something we would have recommended. It sounds like the noise is either really high (due to bad amplification) or the antenna or cable is bad resulting in little to no signal. We see similar issues when using the Fax 5 amp when not properly installed (grounding or active jumper not set). You might discuss this with your Furuno dealer for options.