dynamic range bandwidth

[William Carver]

ARRL, RSGB (RadCom), W8JI and Sherwood always use 500 Hz or
the "Closest Available to 500 Hz" (per ARRL Test
Procedure).  Sherwood is the only tester who sometimes uses
additional bandwidths but they are always footnoted.

73,  Bill  W4ZV


I understand that, because I pore over others test data to compare my
own receiver work with the professionals. And I know the difference in
dynamic range between 400 Hz and 500 Hz is very, very small.

But in a comparison of different receivers the test bandwidth "should",
in my opinion, be included in the comparative data to nail it down. If I
was giving a talk at my local ham club, I could measure the K3 MDS with
the DSP bandwidth at 50 Hz and make the K3 sensitivity and dynamic range
look even better. But...of course that would be a little deceitful, eh?

IMHO the viewer should not have to go to the Sherwood test and the ARRL
test to verify the dynamic range is for the same bandwidth. All it takes
is a statement of the bandwidth and the basis for the data is fully
defined without having to go back to original sources and figuring it
out for yourself: a significant level of trust is instantly established
in the data. No games need to be played for the K3 to look good and I'd
hedge my position by explicitly stating the comparative bandwidths.

Bill - W7AAZ



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[Bill W4ZV]

W7AAZ:

 > I understand that, because I pore over others test data to compare my
own receiver work with the professionals. And I know the difference in
dynamic range between 400 Hz and 500 Hz is very, very small.

         About 1 dB from Elecraft's own measurements if I recall correctly.

 > But in a comparison of different receivers the test bandwidth "should",
in my opinion, be included in the comparative data to nail it down. If I
was giving a talk at my local ham club, I could measure the K3 MDS with
the DSP bandwidth at 50 Hz and make the K3 sensitivity and dynamic range
look even better. But...of course that would be a little deceitful, eh?

         Why?  Most testers have adopted ARRL's methodology of 500 Hz
BW (or closest filter to that) at 2 kHz spacings.  What's deceitful
about that?

 > IMHO the viewer should not have to go to the Sherwood test and the ARRL
test to verify the dynamic range is for the same bandwidth. All it takes
is a statement of the bandwidth and the basis for the data is fully
defined without having to go back to original sources and figuring it
out for yourself: a significant level of trust is instantly established
in the data. No games need to be played for the K3 to look good and I'd
hedge my position by explicitly stating the comparative bandwidths.

         Elecraft used published ARRL measurements at 5 kHz spacings
for their Power Point comparison table and ARRL always uses 500 Hz
filters (or closest thereto).  I don't see any basis for saying games
were being played.  If the tests were using significantly different
BWs (e.g. 200 Hz vs 500 Hz) you would be correct.

         If you want to see games being played, check out Icom's and
Yaesu's claims of "3 kHz" roofing filters that are actually 5-6 kHz,
or "6 kHz" filters that are actually 10 kHz.  Elecraft doesn't do
stuff like that.

                                         73,  Bill  W4ZV

P.S.  Re your comment about the K3 having high power consumption in
RX mode a week or so back.  The K3 is one of the most power efficient
rigs available, especially for a 100W class radio.  See the far right
column below:

http://www.elecraft.com/K2_perf.htm#Main%20RX%20Table

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