[ICOM] Truth in advertising

[Bill Tippett]

KD7EFQ (KT0DD) wrote:
 >Just compared the T.O.I. numbers of the pro III to the TT Orion and was
disappointed. The Pro III T.O.I. is fairly close to Orion at 20khz spacing, 
but
falls way behind Orion at 5khz spacing. The industry needs to get 
standardized on
it's method of measuring receiver performance. It is quite misleading to just
throw out a number without any parameters.

         Part of this may be due to ARRL historically only testing
down to wide (20 kHz) spacings.  Since 1998 and perhaps earlier, they
began testing to 1 kHz but the numbers are somewhat buried in their
Expanded Test Reports.  Kudos to ARRL for beginning to report 5 kHz
results in their QST articles and hopefully they will begin reporting
1 and 2 kHz performance there.  I noticed they included measurements
in tabular form for IMD and BDR to 1 kHz for the 7800's ETR, which is
much easier to read than interpolating the swept graphs used in
previous reports.  I suspect we will see the same in the PROIII's ETR
when published.  FYI, here is the 7800 data from the ETR:

http://www2.arrl.org/members-only/prodrev/reports.html

Spacing BDR     IMD
20              137     104
5               115     89
2               97*     80*
1               96*     67*

* phase noise limited measurement

As you can see, BDR/IMD performance degrades significantly at 1 kHz
spacing, although the measurement was limited by phase noise (yet
another area for improvement!)  1 kHz spacings are not unusual for
contests and big pileups on CW.  In fact this weekend it was more
like 3-500 Hz between stations in the CQ 160 CW Contest!

 >The same thing happened with the 7800. When all was said and done the 
7800 is
about equal to Orion on T.O.I.  for only $7500. more in cost. I was looking
at the Pro III, but now It's back to Ten Tec. 73.

         It is only close at 5 kHz.  At 1 kHz, Orion's BDR is 118 dB
and IMD is 84 dB (which can be improved ~10 dB by adding an $80
Inrad #762 filter).  TOI is a calculated number with IMD as
one of the inputs, so I expect the 7800's TOI would degrade
another ~22 dB at 1 kHz based on ARRL's data above.

         The good news about all the discussion of roofing filters,
IMD, BDR, etc is that manufacturers ARE taking notice, just as
some did about key clicks.  If this were not happening, you
would not see both Icom and Yaesu scrambling to provide narrow
roofing filters in their high end offerings.  Thanks to Joel W1ZR
and Mike KC1SX for the ARRL Reports which are one of our best
sources of objective data.  They (and competition) do seem to be
positively influencing manufacturers to produce better products.

                                         73,  Bill  W4ZV