[ICOM] 756 pro III or Ten Tec Orion

[Bill Tippett]

N4PY wrote:
 >The extra roofing filters in the Orion provide very little benefit.

         Carl I strongly disagree.  Inrad's 600 Hz #762 significantly
improves Orion's already outstanding IMD at close spacings.
Sherwood Engineering's summary:

"At 5, 10 and 20 kHz, there is no significant (IMD) difference
between the stock 1.0 kHz Ten-Tec filter and the Inrad filter.
At 2 kHz spacing, the improvement is on the order of 6 to 7 dB.
At 1 kHz spacing the improvement is closer to 10 dB."

         Since Orion's IMD performance is already at the top of
ARRL, RSGB, Sherwood Engineering, and W8JI rankings using
only its stock 1000 Hz filter, the #762 puts it ahead by
even more.  For example, at 1 kHz spacings, which is not
unusual in a contest or large pileup, Orion's IMD is about
30 dB better than a PRO at this spacing.  This means it
will tolerate a 30 dB stronger signal before blocking (BDR)
or IMD products become a problem.

         Look at the summary of ARRL measurements below:

http://www.elecraft.com/K2_perf.htm#5%20kHz%20numbers
(Includes the PRO III Product Review from March 2005 QST).

In the critical areas of 5 kHz spacing IMD and BDR, the PRO III
provides only a 1 dB improvement over the PRO II, and actually
neither is as good as the original PRO although you would likely
never notice the difference except in a laboratory test.  The
point is that the PRO III does not offer any substantial
improvement over the PRO II or PRO as far as strong signal
handling at close spacings.

         Back to N4PY's comments about Orion roofing filters,
I agree that TT's 500 Hz and 250 Hz are not recommended due to
degraded IMD performance versus the stock 1000 Hz.  But the
600 Hz is a HUGE improvement which takes Orion's strong signal
performance up another l0 dB at 1 kHz spacings (and this plug
in filter only costs $80).

         Back to W4TEY's original question, Ed for your casual
operating, I consider a closeout PRO II a much better value.
For much less money, you get nearly the same performance as
the PRO III.  Orion would be vast overkill for someone who
is not a serious contester or low-band DX'er.

                                         73,  Bill  W4ZV