Looks like he clearly had a bad 500 Hz filter. It does not match our
measurements here or Sherwood's. We'll make sure the customer gets a
replacement.
We were not contacted prior to publication so we were unable to replace
it ahead of time.
Also, their TX tests were incorrectly run at 120W instead of at our spec
limit of 100w. TX IMD will degrade at least 5 dB at 120W. That's there
for the CW guys ;-)
73, Eric WA6HHQ
----
AD6XY - Mike wrote:
So... to your figures. The 500Hz filter is 8 dB worse than the 2.7 kHz
filter out of band but at close spacings. According to the review it suffers
non-linearites not noted in the 2.7kHz stock filter nor the 8 pole INRAD the
400Hz filter. These showed odd properties with tone spacing that makes me
think it was the DSP responding to the wider skirts of the 5 pole 500Hz
filter but maybe that particular filter had a fault, it happens with
crystals. Even so 88 dB dynamic range at 2kHz is not at all bad.
I am sure the experts can explain this behaviour but for now I think it
might be better to order an 8 pole 400Hz filter than a 5 pole 500Hz one -
you will be able to sleep better.
Mike
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