The Keysite picture was showing the spurs
from a Hermes at 28.4 MHz with a 192kHz sample rate using
the V1 firmware. it has nothing to do with the IC7300.
I have spare time now so I will repost
the image of the IC-7300.
IC-7300 is at 30W output on 28.2 MHz with
offsets from 10Hz to 1MHz, Blue trace is PN, Black trace is
AM noise, Green trace is composite noise. This uses the FSWP
which can measure AM noise and PN simultaneously.
Then I will go away for a while.
Looking at the Keysight picture you
posted it's hard to tell the characteristics of the peaks
that appear beside the (was it?) 28.4 MHz signal. (The
screen notation of 390 kHz is confusing. That is the
marker's offset?)
It appears like the 7300 is using a digital frequency
synthesizer with way too few bits to make a good signal. If
I got a rig that bad I think I'd have some stern words with
ICOM about it. While it might be marginally legal it is
unethical to sell something that bad. (And at 100W I thought
the limit was -70 dB in the US.
{^_^}
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
