G'day to the Group
Copied this message by VK4ZSS from the Perseus list...thought it might be of interest here.
73, Bill W4ZV
http://groups.yahoo.com/group/perseus_SDR/message/5124Guy has just blogged on Rob Sherwood's updating of his receiver comparison tests
with the Perseus receiver noting that only the Elecraft K3 beats the Perseus in
the key narrow spaced dynamic range test.
Guys blog is here:
http://perseus-sdr.blogspot.com/Rob's test results are here:
http://www.sherweng.com/table.htmlFirstly let me say, Rob's tests are highly professional and we owe Sherwood
Engineering and Passport to Worldband Radio an enormous debt for naming and
shaming the many manufacturers that have been foisting inferior receivers upon
us for several generations of solid state equipment over 4 decades. Nothing
following detracts from that.
As I understand it, Perseus' SDR architecture, together with very low phase
noise LO, results in no degradation of wide spaced dynamic range (100kHz) to
narrow spaced (2kHz) dynamic range and Rob's tests support this (99dB for both).
The K3 relies for its excellent narrow figures upon multipole crystal filters
and only pips the Perseus with a 200Hz filter (101/96/95dB for 200/400/500Hz).
So if we extended the tests for very narrow spaced (say 200Hz) dynamic range the
Perseus would certainly be top of the list. Having said that for medium wave
reception, these narrow spaced figures are not quite so relevant as for hams
using CW. The broadcast signals' modulation is so broad that mostly we are
dealing with transmitted splash rather than rx overload products. In the wide
spaced dynamic range measurements the K3 is the clear leader (104dB to 99dB).
The K3 tests far superior to the Perseus in Ultimate Filter rejection (105dB vs
95dB), but can someone explain to me what this measurement means in a direct
digital conversion receiver, since there is no IF filter to leak around?
The Perseus is the clear leader in Local Oscillator phase noise at -147dBc @
10kHz compared to the K3 at -138dBc.
Again the K3 is a clear leader in sensitivity -138dBm cf -125dBm, but this
differential can be eliminated with the addition of third party high performance
preamps eg DXE and Kiwa, as most of us do.
Ditto in respect of blocking dynamic range K3 140dB vs Perseus 125dB, but I need
to read up the ARRL lanual on the 3Hz bandwidth blocking measurement footnoted
against the K3 but not the Perseus.
Many thanks to Rob for making the measurements available to us all, Guy for
blogging it and John Plimmer for spotting it first.
73s GD DX DE Sam Dellit VK1DXA Canberra, Australia
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