Hi everyone.  Let me comment on test data on my web site for the TS-590SG.

First there are new features, and I haven’t had any time to even look at them yet.  I also haven’t yet used the SG on the air, but simply ran it through the lab yesterday afternoon in about four hours.  I have a long form report available, but I cannot give any “user” feedback yet.  I did run the original TS-590S in a 160 meter CW contest in either 2010 or 2011, doing a “shoot out” between it and the T-T Eagle.  The Kenwood was easier to use, but both handled the QRM well.

All the radios in my web table have been ranked by one number, close-in (2 kHz) dynamic range.  This is an important number, particularly on CW.  It should not be considered the only important data point.  That would be like choosing a sports car that had the biggest engine, but disregarding how it handled on curvy roads!  Lots of aspects of a radio’s performance are important, and close-in dynamic range (DR3) is certainly one of them.

The dynamic range, and in this case the RMDR, is modestly better for the SG version compared to the S version.  RMDR stands for “reciprocal mixing dynamic range” as per the ARRL definition.  (April 2012 QST, sidebar Bob Allison Lab Engineer)  I used to call this “phase noise limited”.  It is the same thing. Since day one (1977) I always ranked my chart (table) as to how the measured dynamic range could be the performance limit in a CW pile-up (DX or contest).

Another thing that I feel is a problem when we are all in the search of “the holy grail” of receiver performance is the question of “what is good enough”.  When I was visiting Flex Radio this year, Steve Hicks said he felt that he could draw a line at some point in my performance chart and say everything above that line “is good enough” from the standpoint of dynamic range (be it third-order dynamic range [DR3] or RMDR).  I agree with that statement.  So does Tom Rauch, W8JI.  Tom and I have said for years that 80 dB is usually good enough. Since it would be rare to be able to operate a radio at its perfect optimum, maybe you want a bit higher number.  In the past couple years, as radios have improved, I have said I want 85 dB or more. How about 90 dB so there is a bit of a safety factor.

For this one data point, the TS-590S came in at 88 dB for the down-conversion bands, and 76 dB for the up-conversion bands.  The TS-590SG comes in at 92 dB for the down-conversion bands and 79 dB for the up-conversion bands.  Kenwood has clearly said in their advertising material that the SG has a cleaner local oscillator (LO).  The first mixer is also discussed, but I don’t know what might have changed there.  The wide-spaced (20 kHz) DR3 of both units measured the same at 104 dB.

I don’t get excited about blocking numbers since they are 30 to 40 dB above DR3 (or RMDR) values.  The League tests blocking with a 1-Hz audio spectrum analyzer so that phase noise is virtually eliminated from the measurement.  It is a valid measurement for the design engineer since it tells him when to quit spending money on the mixer and when to focus on the synthesizer (LO).  For the amateur I don’t think the 1-Hz number  is a useful, since none of us use a 1-Hz CW filter on the air.  Likewise the ARRL DR3 number since 2007 has also used this same phase noise elimination testing method.  I briefly tested a few radios for blocking with their method, and my blocking numbers with an “S” footnote were done in that way.  I later decided this was meaningless data, so I don’t measure with a 1-Hz filter anymore.  Thus it looks like the 590S has a higher blocking value than the 590SG.  That isn’t the case since the two radios were tested in different ways.  I never tested DR3 with a 1-Hz filter since I always thought that measurement was misleading.  If the RMDR of a radio is 80 dB, and the DR3 measured with a 1-Hz filter is 100 dB, the real limit of that radio is 80 dB.  (Read the QST sidebar for a better understanding of this issue.)

For the last few months the TS-590S has been selling at a truly bargain price of about $1250.  If a ham could only budget that much for a radio, I would recommend buying one of the few remaining TS-590S radios.  If $1750 is in the budget, I would buy the new one.  It is great that Kenwood continues to improve on a fine radio.  It was a great radio when it came out four years ago, and it is even better today.

73, Rob Sherwood, NC0B