RE: [CQ-Contest] several contesting questions

[Bill Tippett <btippett@alum.mit.edu>]

K0HB wrote:
>In a contest radio, you look first for a bullet proof receiver (or as close
as you can get to bullet proof).  The two key things which will make or
break a good contest radio are a good noise floor (MDS) and adjacent
channel blocking (BDR).  ARRL has a spot someplace on their web with all
the results from their lab tests.  If you see a "good deal" on a certain
radio, go there and check out the numbers.  In my experience, the CQ
magazine reviews are mostly fluff without good technical support.

        Steve, I generally agree with Hans but would also consider IMD 
Dynamic Range
with 5 kHz interfering signal spacing as a good measure of how very close 
strong
signals may affect what you hear in your passband.  IMHO, this is more 
important
than MDS, since most current radios have nearly equivalent MDS 
performance.  MDS
becomes even less important if your noise floor is raised by adjacent 
station QRM.
Here is a good summary by Elecraft of ARRL measurements for recent radios.  BDR
and IMDDR3 measurements at 5 kHz (4th and 6th columns from the left) are 
what you
should look at.  The IC-746Pro is not listed but is likely similar to the 
756Pro2,
since I believe they have similar front-ends.

http://www.elecraft.com/K2_perf.htm (see first Table on this page)

If you are looking at older radios, here is another good summary, although 
these
measurements were by Sherwood Engineering, not ARRL.  Here I would look 
primarily
at the second column from the right which is IMDDR3 at (mostly) 2 kHz spacings.
BDR is probably NOT meaningful here because interfering signals are at 100 kHz:

http://www.sherweng.com/table.html

Here's yet another comparison table by W8JI:

http://www.w8ji.com/receiver_tests.htm

                                                        73,  Bill  W4ZV
P.S.  Unfortunately some very popular contest radios, like the TS-850 are not
included in these summaries.

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