[Lowfer] Will an LF UpConverter Really be worth the effort, and expense

[JD]

I'm not familiar enough with the 450S to offer an opinion based on the 
receiver's published specs, Andy, but from the quality of your captures, I'd 
say it is no slouch!

My first thought for anyone considering upconversion would be to first try a 
modest gain pre-amp, properly matched to the 50 ohm receiver input and 
possessing plenty of output capability (it's surprising how many designs you 
find on the Web that nominally "work into" 50 ohms, but only up to a few 
millivolts before distortion sets in), preceded by a good LPF to prevent 
broadcast band IM products from being generated in either the pre-amp or 
receiver front end.  Jay's pre-amp at his Web site is one of the most robust 
around.  If it has more gain than you need with your radio (which could be 
the case here) then you might also need a bit of attenuation.

If a radio has shortcomings beyond sensitivity, such as too many spurious 
responses in the LF range or an inability to tune low enough for the signals 
you want to hear, an upconverter can be tremendously helpful in overcoming 
those difficulties.

But upconversion has one inherent drawback that even the best designed and 
built converter cannot overcome: the receiver's own stability.  You can have 
an ovenized oscillator for the upconverter and it may be absolutely perfect, 
but if the radio is not similarly stabilized, you WILL see unacceptable 
drift on very slow signals.  A radio with a master oscillator that wanders 
as little as 1 ppm would show errors up to 0.19 Hz when tuned directly to a 
LowFER signal, but will drift nearly 3.2 Hz when tuned to a dial frequency 
of 3.190 MHz!  That can push desired signals right off an Argo screen.

John