Recent measurements have shown that the IC9700 has an RMDR of well over 90dB on both 2m and 70cm at close spacing (~10kHz) and even better further out.
This is a key measurement of a receiver’s dynamic range and is critically dependent on the local oscillator. Conventional superhet architecture receivers can be particularly bad. The fixed LO (clock) of an SDR receiver makes the design of ‘quiet’ local oscillators much easier than with an LOnthat must be tuneable as in VFO.
Older superhet receivers have typically given a RMDR in the 70dB range. More recent designs have improved this into the 90s and even as high as 115dB. However, this performance comes at a price. The SDR direct sampling receiver can achieve high levels of RMDR at a much more acceptable price.
I will be presenting my measurements and those of a number of well-known experts at the RSGB Convention in October.
Sam
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