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
