[Elecraft] receivers performance data

[Hector Padron]

here is something I found on the net that will help others to understand better the performance data tables:
 





 
Here a few measurements of receivers, using 500Hz filters. 
MDS is a measure of sensitivity. -135dBm is 10dB more sensitive than -125dBm. This number doesn't matter very much in what you actually hear. The real test is if you hear a very noticeable noise increase when you connect an antenna to the receiver.  If you hear an obvious noise increase when you connect an antenna instead of a dummy load, your receiver is sensitive enough! You should check sensitivity at the quietest time with the narrowest selectivity you use on every antenna you use.
Contrary to folklore and hyperbole, there isn't a receiver sold today that can dig into noise more than others on CW based on sensitivity or the use of a DSP or multiple DSP systems. The exceptions are:

Increased selectivity will reduce noise 
Poor AGC design or detector problems can cause mixing of signals and noise 
If you read a review that claims a receiver made weak signals appear from nowhere, you better keep a wary eye on the rest of the review. It is possible for a receiver to be abnormally bad, but it is not possible for a receiver to work better than other properly working receivers based on sensitivity.
BDR is blocking dynamic range. This is the point where a strong signal either 2 or 10kHz just starts to make your receiver lose sensitivity. The bigger the number the better, ESPECIALLY at 2kHz spacing. The number you want here is probably around 80dB or more if you live in a reasonably quiet location and work weak signals on crowded bands. If you run two transmitters on the same band or have a neighbor who operates near your frequency, you almost certainly need more dynamic range. I'm in a very quiet rural location and have very directive antennas, and 80dB blocking DR suits my requirements just fine most of the time.    
IMDR is intermodulation dynamic range. This is the single most important number when comparing receivers. This is where two or more strong close-frequency signals mix and generate a new phantom signal or multiple tones in a adjacent frequency SSB signal mix with themselves and make what sounds like splatter. The measurement is made just at the point where the phantom signal level is high enough to interfere with the weakest signal your receiver can detect. IMDR is a measure of how badly your own receiver causes problems you might blame on other people. Bigger numbers mean better receivers. It is most important the 2kHz number be good. The 10kHz test number doesn't mean nearly as much, because almost any radio is good enough at 10kHz or wider. Some number above 80dB is enough to stay out of trouble 99% of the time. If you are in a noisy location, you obviously need less performance. 85dB keeps my receivers at the point where poor quality external signals
 cause nearly all off-frequency problems. With 85dB IM3DR only a few of the strongest stations cause my receiver to make its own internal problems.


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