Hello Adam,
From reading of your NPR chart, could I understand that apart from IC7851, the
K3 (with new KSYN3A installed) is the second best in terms of NPR test?
73
Johnny VR2XMC
寄件人︰ Adam Farson <far...@shaw.ca>
收件人︰ Elecraft List <elecraft@mailman.qth.net>
傳送日期︰ 2015年09月14日 (週一) 2:51 PM
主題︰ Re: [Elecraft] K3 to IC-7800 Comparison?
For Jim K9YC:
Hi Jim,
Many thanks for the post on my presentations at the club meeting on Saturday
September 5.
To quote:
"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."
The instrumentation I use for NPR testing is re-purposed telecom test
equipment, as described in my Web article and also in my article in QEX for
March/April 2015. I rely on the surplus market for the test sets, and also
for the filter pairs (bandstop and bandpass). The bandstop filters typically
have 95 dB stopband attenuation and ~ 3 kHz stopband width.
A number of these filters are on (or near) amateur bands, e.g. 1940, 3886,
5340, 7600 and 11700 kHz. The first filter pair I acquired was on 5340 kHz,
so all the test data in my web article are on this frequency (which is in
the 60m band). The Flex-6700 does not have a preselector for this band, so
the noise loading will hit the front end and the ADC harder. This will
degrade the NPR reading by a few dB, but it will show how the receiver
behaves if heavily loaded on a band for which no preselector is fitted.
As I picked up additional filters, the number of frequencies on which I run
the test has steadily increased. Links to multi-frequency NPR data for
various radios (including the K3 with KSYN3A) are on my website:
http://www.ab4oj.com/test/main.html#NPR
It was a pleasure meeting you guys over the Labour Day weekend.
73, Adam VA7OJ/AB4OJ
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