On 9/13/2015 2:10 AM, Jim Brown wrote:
He seems quite genuine, no horses in the race, his objectives seem to
be the same as Rob Sherwood and my own -- to put mfrs feet to the
fire to improve the receive performance and signal quality of the
stuff they sell us. :)
Adam is an out an out Icom evangelist - not exactly unbiased.
An example is in the footnote for the Flex-6700, which has no
preselector for the range where he had to do his measurements, which
may have caused that radio to measure worse than it would on the ham
bands.
On the other hand Adam limits noise power for direct sampling SDR
designs to a lower level than used with traditional up/down conversion
transceivers. The lower noise power input gives the direct sampling
designs an unfair advantage be ignoring strong signal environments.
73,
... Joe, W4TV
On 9/13/2015 2:10 AM, Jim Brown wrote:
On Sat,9/12/2015 2:12 PM, Skip Cameron wrote:
If anyone has done a K3 to IC-7800 comparison,
Here's another VERY interesting set of RX measurements. The Noise Power
Ratio (NPR), is essentially a measure of how broadband noise and QRM
outside the passband show up inside the passband. It combines the
effects of phase noise and various forms of non-linearity in the RX
system. First study the methodology, then the data. Big numbers are
better. :)
http://www.ab4oj.com/test/docs/npr_test.pdf
The guy who did this work is Adam Farson, VA7OJ, AB4OJ, an EE retired
from a career in telecom, now living in Vancouver, BC. He spoke to our
local ham club last weekend, and his presentation was quite interesting.
Several of us had dinner with him. He seems quite genuine, no horses in
the race, his objectives seem to be the same as Rob Sherwood and my own
-- to put mfrs feet to the fire to improve the receive performance and
signal quality of the stuff they sell us. :)
There's an important caveat to his work. The NPR measurements require
very sophisticated band-stop filters in his instrumentation setup, and
based on the filters he has been able to source, that limits the
frequency range where he can do his measurements. An example is in the
footnote for the Flex-6700, which has no preselector for the range where
he had to do his measurements, which may have caused that radio to
measure worse than it would on the ham bands.
73, Jim K9YC
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