[ICOM] 756 pro III or Ten Tec Orion

[Carl Moreschi]

Bill,

I was referring to the standard tentec filters (1.8, .5 and .25) when I said
the extra roofing filters filters provide every little improvement.  I have
the 600 hertz inrad filter in place of the 1000 hertz tentec filter.  This
one certainly helps.  But clearly the 500 and 250 hertz tentec filters do
not help and I am sure about the 1800 hertz filter.

Carl Moreschi N4PY
Franklinton, NC
----- Original Message ----- 
From: "Bill Tippett" <btippett at alum.mit.edu>
To: <icom at mailman.qth.net>
Sent: Friday, January 28, 2005 2:33 PM
Subject: [ICOM] 756 pro III or Ten Tec Orion


> 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
>
>
>
>
>
>
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