FYI, ARRL used the optional Ten-Tec #2001
600 Hz filter for their tests per their normal policy of ordering
any optional filters closest to their 500 Hz measurement
bandwidth. Recall that ARRL did not use the TT #217 500 Hz
for the original Orion tests due to IMD problems. Eventually
this discovery led to the development of the Inrad #762 600 Hz,
which in turn led to the 4-pole filters / front end scheme used in
Orion II. Orion with an Inrad #762 is electrically quite similar to
Orion II with the TT #2001.
RSGB never orders optional filters for their
tests, so the stock 1000 Hz roofing filter was used in
both Orion and Orion II tests. However they apparently
had a bad 1000 Hz filter in their original Orion test since
close-in IMD results using the 2400 Hz filter were better.
The 2400 Hz results were the ones RSGB used in the
review summary. This time around the 1000 Hz filter had
better results for 1 kHz IMD spacing as expected.
Bottom line points to remember when comparing
these product reviews:
1. ARRL used the stock 1000 Hz for Orion.
2. ARRL used the optional 600 Hz filter for Orion II.
3. RSGB used the stock 2400 Hz filter for Orion.
4. RSGB used the stock 1000 Hz for Orion II.
5. Orion/762 should have equivalent IMD/BDR to #2.
6. Sherwood used the stock 1000 Hz for Orion.
7. Sherwood used the optional 600 Hz (for 2 kHz
spacing) and 300 Hz (for 1 kHz spacing) for Orion II.
8. Sherwood made some anecdotal comments about
Orion/762 but never published actual measurements.
9. The above are not completely consistent but track
well within a few dB of measurement/sample variation.
10. Think mid-90's IMD for Orion/762 and Orion II/2001
at 2 kHz spacings.
73, Bill W4ZV
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