Hello I never meant to come
across as acrimonious, just insistent.
The plot is from a Rohde
and Swartz FSUP signal source analyser in this
case.
https://scdn.rohde-schwarz.com/ur/pws/dl_downloads/dl_common_library/dl_brochures_and_datasheets/pdf_1/FSUP_bro_en.pdf
The LO I used is from Kuhne
electronics and is known as the XO1, it was
intended as a 116MHz LO for use with 144 MHz
transverters. It is not a custom product. It
is simple Xtal oscillator with a narrow band
PLL. The plot shows its performance when
locked to a Leo Bodnar GPSDO at 10MHz.
It is normalised to 1Hz so
in an SSB BW you can add 68dB to this plot
assuming 2400Hz BW for SSB. I do not agree
that this performance levels are only
obtainable by special equipment. In fact older
equipment like the IC-202 used to fair better.
New equipment is making a pigs ear of this and
transmitters are getting worse. A K3S and a
transverter is all you need, or indeed a FDM
Duo, Hermes, Flex or ANAN SDR.
These radios are all
capable of meeting the code of conduct which
in practice does have a positive effect. Not
perfect but its existence is useful.
Now that we have such
excellent receivers maybe we should pay
attention to the TX chain?
This thread was about the
Hermes, I apologise for hijacking it.
Regards
Conrad
Um, I am not sure I
understand that picture. That is the
analyzer's specification or something very
custom you have put together? I'm answering
both emails here.
If that is the noise level you are insisting
everybody meet I suspect you are going to be a
very frustrated gentleman for the rest of your
life. (Some old rigs never die. They simply
make more noise.) The IC7300 might be capable
of being tamed with a reference oscillator
replacement. But I bet more bits in the D/A
are required for that design than exist in
reasonably priced D/A converters. Regardless
"state of the art" only appears in hand
tweaked radios or VERY expensive military or
scientific equipment where there is a
perceived need. (And codes of conduct are not
worth the bits they fill on an exabyte storage
array. Cats and humans cannot be herded.)
Even if 7300s are not "clean" as you would
have it are they cleaner than their peers on
the commercial market? From your complaints I
suspect they are not. But it is a point worth
asking. I ignored the argument until it got
acrimonious.
{^_^}
On 20220225 04:03:42,
Conrad, PA5Y wrote:
Hi, no it is actually 5
different IC7300s tested by 3 different
people, including Rob Sherwood. if you have
time you can see the plots and some other
data that I posted earlier just do a search.
I’m in my lunch break or I would do it for
you.
Yes my TX IS that good
but it is easier for me because I use 0dBm
transverter drives at 28Mhz and transverters
with high quality Xtal local oscillators.
The 0dBm from either my K3S or TS-890S is
very good indeed. IMD3 from both is better
than -50dBc.
On 144 MHz, PN noise at
1kHz separation is -144dBc/Hz and close to
156dBc/Hz at 10kHz. This is with the LO PLL
active, free running it is a little better.
Composite noise is the same as in this case
it is PN dominated. IM3 is -38dBc but more
importantly the 7th and 9th
orders are better than -80dBc. This is
achieved by using tetrode finals on all
bands.
432 and 1296 are of
course worse as the LOs are multiplied from
Xtals in the VHF region. However my TX is
some 40dB better than an IC-9700 at 1.3GHz
at 10kHz separation.
Only 50MHz is a little
worse due to my TS-890S PA linearity but
with the noise on 6m being higher it is
acceptable. When I am on FT8 where linearity
does not matter it is superb. But who cares
we are all on the same ‘channel’.
73
Conrad PA5Y
I suspect your
specification is still beyond the state of
the art. Is your transmitter that good?
It sounds like the 7300 is cleaner than
average close in but has some issues fairly
far out. That is a little surprising. I
wonder if the "IP+" technology is simply RF
feedback to linearize the transmitter stages
such as is seen in the old Collins kW SSB
amplifiers. I can see that having an issue
that depends on the charteristics of the
feedback loop. But those are strange
characteristics.
I take it the noise peaks are broadband,
right? Do they depend on the transmit
frequency in any way? It sounds very much
like there is a defect in a specific radio
near you. Is that the case or are hams
measuring this in general? If this affects
all the 7300s then the FPGA code will
probably have to be reworked to fix the bug.
I kinda wish I had one and a nice lab with
lots of pertinent test equipment. I doubt
Keysight and ICOM would set me up to do it.
(It'd be better for them to set up a tiger
team of their engineers with the equipment
needed to suppress this possible bug.)
{^_^}
On 20220225 01:55:45,
Conrad, PA5Y wrote:
By clean I mean - can I
hear anything of sufficient magnitude to
disturb the noise floor anywhere in band,
and hence inhibit my ability to receive
signals close to the noise floor. The
noise floor in a semi-rural location on
28, 50 and 70MHz is not particularly low
so I do not feel that this is
unreasonable. The biggest problem with the
IC7300 is the AM noise bump at 20kHz and
130kHz which is only 60dB down on the
carrier when running at 30W on 28MHz. This
power level is typical when driving an
amplifier. When modulated with an SSB
signal this occupies a considerable amount
of bandwidth. The close in PN -s only
-120dBc/Hz at 1kHz and -130dBc/Hz at
10kHz. The composite noise is -115kHz at
10kHz, this is not what I would consider
clean, even close in. The K3S( and a few
others) is far better in this respect
although the PA has quite poor linearity,
especially on 6m.
The Hermes will do a
much better job with any decent PA, even
without pure signal. There are some spurs
@ -65dBc which improve with a higher
sample rate. I have not checked these
with the V2 firmware but I will do
immediately I receive my Hermes from
Apache.
I do not think that a
transceiver at the IC-7300 price point has
fixed pre-distortion. As you quite
correctly say keeping it under control
over temperature and voltage variation
would be difficult. Also Icom would almost
certainly have mentioned it in their
advertising. What the IC7300 does well is
manage audio overshoots by using a ‘look
ahead’ algorithm. This is maybe where the
impression of it having a clean TX comes
from.
I think that the
problem here is that so many transceivers
are quite bad, so I can just about accept
that the IC-7300 is less bad.
73
Conrad PA5Y
OK, please refresh my
mind what you mean by "clean". It
certainly appears to be sending something
much closer to pure signal concentrated
within its intended bandwidth than most
other transmitters. I also understand that
it is not as good as it can be with full
active predistortion. Both might generate
increased noise at some significant
separation from the intended signal
frequency. I am not sure of the mechanism
by which this would take place.
As an ornery critter there is nothing I
would sit down and declare "clean" without
a definition of "clean". I guess I am
asking for your definition of the term or
even of the term "clean enough".
{O.O}
On 20220225 01:13:11,
Conrad, PA5Y wrote:
I KNOW for a fact
that the IC7300 is not clean. Please
provide me some evidence to the
contrary. I have measurements with a
R&S FSWP Signal analyser out to a
1MHz BW. You guys are looking in an SSB
BW which is fine unless you happen to be
130kHz away, then you will hear plenty
of splatter from the IC7300. I tested
the IC-7300 as a result of hearing this
on 50MHz. In other words the lab tests
were driven by on air experience.
You are spreading
misleading and incorrect information.
73
Conrad PA5Y
On Wed, Feb 23, 2022
at 12:24 PM, Max wrote:
I just think if we
follow good design and signal chain
management that superb, clean signals
can also be generated without the need
for PS, that's all.
Max,
I disagree. My signal is my signature.
Audio clarity is admittedly important
but what matters most to me is a
splatter-free signal, and in that regard
nothing comes close to what PS can
produce. As I stated earlier, even the
best Class A amplifiers only have -40dB
splatter. PS starts
at -60db and often pushes -70dB. That
means that PS reduces splatter to less
than 1% (and at times only 1/10 of 1%)
of what even the best traditional
equipment can produce.
I also agree with Simon that the 7300
(and also the 7610 for that matter)
produces an extremely sharp-edged signal
with unarguably less splatter than is
achievable with any other non-ANAN
radio. It was explained to me by Ray
N5LAX that the reason those radios are
so clean splatter-wise is because ICOM
embedded an algorithm into the
firmware that functions very similarly
to PS in the sense that it corrects for
non-linearity in the PA, but it is a
fixed-value (i.e., static) correction
only, not a real-time self-adjusting
correction value such as is employed by
PS. NOTE: I have not been able to verify
that info, but that is what was told to
me over-the-air by Ray when I commented
that I had no idea how the 7300 could
produce such a clean, sharp-edged
signal. So I'm repeating it here.
IMO it's unwise and short-sighted to
summarily dismiss the game-changing
value that PS brings to the hobby. Its
benefits are so unarguable that I (and
Rob Sherwood) often wonder why the
big-name radios don't offer it as a
standard feature. It's free, so utilize
it for goodness sake!
73,
Mark
