Tom
Thanks for your analysis. One thing that is different
for the SDR-1000 on 160 compared to 80M is that the
filter on the front end is low pass on 160 instead of
band pass so the RX can be used down below 100khz.
This does effect RX performance on 160 since it does
open the front end to more RF than would otherwise be
the case. Also in my experience is that there is a
significant difference in the strong signal handling
capability between the 192 khz sampling rate and 48khz
sampling rate on different sound card. With a D-44
sound card at 48khz sample I can DX on 80M CW, copying
s-3 signals while running 1500W of SSB up around 3770.
The antennas for each radio in this exercise are full
size verticals 120ft apart and I have measured +23dBm
on the RX antenna while transmitting. I have not been
able to achieve anything like this level of strong
signal handling with the FA-66 sound card at 192khz,
so even though the FA-66 is one of the recommended
sound cards there may be hardware variations that
produce significant differences in outcome. I haven't
tried the FA-66 at 48khz so it may be more related to
the sample rate than the actual piece of hardware, but
suffice it to say there are multiple variables that
may give a better or worse operating experience using
the SDR-1000 in various environments.
Part of the "problem" in how the SDR works is that all
the power in the sampling bandwidth is given equal
consideration. In other words as the signal is
converted to the base band and progresses to the sound
card there is no discrimination regarding the band
width except for the bandwidth inherent to the QSD.
So your conclusion that it doesn't work like a roofing
filter kind of radio actually understates the the
nature of the radio. It is a radio that is designed
to not work like a roofing filter radio, but instead
is a radio that is designed to look at a wide chunk
(192 khz for example) of spectrum (more like a
spectrum analyzer) and I think it would be fair to
point this out explicitly. You can't really expect a
radio that is designed to look at 192khz of spectrum
to act like an Orion II which is designed to look at
as low as a 300hz of spectrum. The radio's behavior
therefore is not so much of a "problem" as it is a
consequence of the design philosophy. Also I might
point out that with a Drake or a Yaesu, you don't
"see" anything, and even with an Orion what you "see"
is far more crude and rudimentary that what you
actually do "see" with the SDR, so these are part of
the design trade offs. The only way you are going to
know the nature of packet pileup with a Yaesu is to
constantly tune and aurally analyze the nature of the
pileup. The SDR actually does a very good job of
allowing you to "see" a pileup. A full blown fuel
dragster goes real good in a straight line because
that is what it is designed to do. Try running it on
a formula one course and it turns to crap.
My experience using the SDR-1000 as a main RX on a
recent 160M contest made me draw a little different
conclusion. I spent part of the contest trying to
find the worst case operating situation I could. I
found 2 DX stations in different parts of the world,
one in Europe and the other in the Caribbean. The
stations were 40 hz apart and both were about S1 to S3
varying with QSB. They were both being called by US
and European hams, with strong signals. With the SDR
I was able to tease out and work each station as a
single signal while they were being called by 6 to 10
strong US stations. I tried this experiment with my
Orion with the 600hz roofing filter and 100hz DSP
bandwidth and was unable to achieve anything like the
same degree of signal discrimination. This was in a
true contest situation, although not in a quasi
"multi" or SO2R kind of situation. So there are some
good things and some bad things and some mediocre
things with any design.
I'm not a member of the reflector which is why I am
posting this to you directly instead of on that venue.
Thanks again for your review
73
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