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
