[HomeBrew] Evaluating an EMI/RFI filter response?

[Ray, W4BYG]

I have acquired several surplus 20 amp EMI/RFI filters for 120 VAC service.
The manufacturer does not publish a graph of performance online.  They do
give a few -dB numbers to 30 MHz at 50 ohms.   I also obtained several
nicely built built EMI/RFI filters on circuit boards with no make or model
ID.
 
I would like to plot some simple tests with an RF generator and use a
Tektronix 485 wideband scope as the detector.  
 
My question: 
 
Is the manufacturer's 50 ohm spec a good dummy load to place at the output
terminals of an AC-EMI/RFI filter and should there also be an input load to
get meaningful results for real life performance?   20 Amps at 120 VAC would
seem to indicate the first filter is designed for a minimum 6 ohm AC load
impedance.  A lower more typical operational load of 10 amps would indicate
a 12 ohm design load impedance, etc.
 
Anyone have experience with testing EMI/RFI filters?
 
Your attention is appreciated.
 

Ray, W4BYG