N4PY wrote:
>You will notice that when using SSB and using a 2400 hertz filter or any
filter in that approximate range, the Orion filters are much sharper.
Interesting data Carl. Doesn't the IC-7800 have a way to vary
filter shape factors (like Orion's DSP tap settings)? I believe
the 756 PRO II has this and would be surprised if the 7800 did not.
Were your measurements with maximum DSP selectivity enabled? It
also appears there could be a software glitch for the 1000 Hz DSP
filter, unless there is some reason its shape factor should be so
wide there. Ten-Tec also clearly opted for their CW filters to be
broader at narrow settings, probably to minimize ringing.
On a different but related note, I was looking over the data on
Sherwood Engineering's website here,
http://www.sherweng.com/presentation.html
and noticed an important point I had previously overlooked. Using
ONLY the 20 kHz roofing filter, Orion still has the best 2 kHz IMD
performance of any current radio, 1 dB better than the IC-7800 using
its 6 kHz roofing filter, and only 4 dB worse than an R-4C using a
600 Hz roofing filter. This is truly astounding performance, and
attests to the fact that Orion's IF chain, even excluding the narrow
roofing filters, is extremely robust compared to other receivers.
73, Bill W4ZV
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