Topband: Collins R390 and 75A4 on 160m

[Bill Tippett]

        The referenced page from Sherwood Engineering has 
comparisons of several vintage receivers including the R390
but unfortunately not the 75A4.  Since the R390 was a 
military receiver and the 75A4 was strictly amateur, it 
would not surprise me that the R390 might be the better of
the two but I've seen no test data to support that.  The
most important measurement in the Sherwood table is the next
to last column (Dynamic Range Narrow Spaced) with the last
column being the actual spacing of 2 kHz.  Let's compare 
this to recent ARRL measurements at 5 kHz (which might be a 
little dangerous since test conditions were probably not 
identical):

Rig                           IMDDR3 (@ 5 kHz) BDR

Ten-Tec Orion                  101 (claimed)    ?
Elecraft K2                     88             126 
Ten-Tec Omni 6+                 86             119
Yaesu FT-1000MP                 83             111
ICOM IC-756 Pro                 80             104
Collins R-390A                  79 (@ 2 kHz)    ?
Yaesu FT-1000MP Mark V          78             106
ICOM IC-775DSP                  77             104
ICOM IC-706 MkII G              74              86
Yaesu FT-1000MP Field           73             107
Kenwood TS-570D                 72              87
ICOM IC-756                     67              98

ARRL Test Data:  http://www.elecraft.com/K2_perf.htm and
http://www.arrl.org/members-only/prodrev/pdf/pr0208.pdf  which
adds the FT-1000MP Field to the summary on the Elecraft page.

Sherwood Test Data:  http://www.sherweng.com/table.html

                                        73,  Bill  W4ZV