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
