Hi Chen and others.
I could empirically confirm conclusion from what you wrote Chen.
I owned some ICOM transceiver, a flex 3000, and now a small batch of
K3. Not anyway thinking to move on K3s.
The TX side of those transceivers is the different slice of the same cake.
The way as other stations pitched on my same QRG when in Contesti
RUNning is the empirical metering. That's is a variable value, not
only checking how much peoples are coming too much near by. There are
side effects regarding common parts of the pursued paths, i.e. N-to-W,
and relative positions on the world map.
PA wen't unchanged as a ACOM 2000 and a OM-3500. Well lowered to
operate with heavy duty cycle 24/48 hours. MS/2 or SO2R.
ICOM AFSK is poor, awfully large, with MMTTY and its standard DSP
filters for tone generating.
Peoples went far away from me.
ICOM FSK is a little bit better curing the audio baseband harmonics
but still having its set of added conversion harmonics.
Peoples went far away from me. That's the same with older and newest
transceivers.
FLEX-RADIO 3000, AFSK only. Nice shaping TX channel with user
modifiable TX filter. With the 170 Hz shift I'd used 400/450 HZ tight
TX filter. Harmonics and tones stayed well within a respectable mask.
I could move people away from may QRG - the RX filer of 400/500 Hz
bandwidth - simply enlarging the TX filter side from where thay had
effectively jumping on me.
Peoples start jumping on me, but I had somewhat a cure for the more
easy case. I mean a cure for cases when someone was coming +/- 500 Hz
from my tones. And, of course the interfering signal wasn't to large
or degraded.
Peoples went someway away from me.
K3 first FSK microcode. FSK almost as for ICOM in TX, the same
proximity effect when in RUN. But there was no cure shaping the TX
filer, nor real time, nor offline.
Peoples went not so away from me.
K3 latest FSK microcode. Well reputed tone generating shaper into
their audio DSP, i.e. predistortion. AFAIK was no cure shaping the TX
filer, nor real time, nor offline.
Peples are constatly coming on my signal. I have had to adopt antenna
patterns and choice as to maintain Northern and Eastern EU into my TX
path patterns. I.E. stacking verticals a or Yagi when doing NA and SA
with Yagi pointed those directions. I have to made clear for EU that I
am there when having US RUNs. It's more easy when having JA RUNs. Path
patterns are fringing North EU and just over Eastern EU.
I am now on K3 latest firmware DSP tone generation. Incidentally this
firmware add some other features (bugs cures but formally dressed :-)
that are welcomed.
Now there are more and more way to combine application and technology cahnges:
2Tone TX base shaping for AFSK, that's is better tan standard MMTTY
tone shaping;
2Tone other FSK manipulation metods;
2Tone specific hardware addon;
MMTTY TX tones shaping with modern multi-core CPU.
But still all the people there hook their radio with any kind of
"garbage" and there is no response when cracklings from more than one
KHz away. there is no way to mitigate that problem, when someone that
doesn't listen me due to path and his effective local RX filtering
jumps that near or more ... with standard poor and blurred tones. I
just change my QRG to keep my old tennis ball.
That's anyway a good exercise. I am pretty sure that each one of us is
doing something wrong and something better, I couldn't not cast the
first stone.
It's just an empirical view.
73 de iw1ayd
>
> ------------------------------
>
> Message: 5
> Date: Tue, 16 Feb 2016 16:46:22 -0800
> From: Kok Chen <rtty@w7ay.net>
> To: RTTY Reflector <RTTY@contesting.com>
> Subject: Re: [RTTY] Flex RTTY AFSK Only
> Message-ID: <A768625D-4C53-4865-9D44-28EB05B7E44E@w7ay.net>
> Content-Type: text/plain; charset=us-ascii
>
>
> On Feb 16, 2016, at 3:02 PM, post@lb3re.com wrote:
>
>> asked Flex about FSK few years ago, and it was not in their plans
>
> "AFSK" and "FSK" can mean different things to different people.
>
> FM AFSK has a very different meaning for example, where the "AFSK" is
> modulating an FM carrier. This was the original meaning of "AFSK."
>
> Later, amateurs use an audio tone pair to modulate an SSB transmitter, and
> this was also called AFSK I.e., the tone pair is modulated to RF as (SSB
> suppressed carrier-fM) and (SSB suppressed carrier-fS) where fM is 2125 Hz
> and fS is 2295 Hz if the transmitter is using LSB and you are using the
> 2125/2295 tone pair. This is why Mark is the higher of the two states on RF.
>
> Even later, when I/Q modulators appeared (as in SDRs), a baseband (DC, or
> zero frequency centered) tone pair consists of Mark at +85 Hz and Space at
> -85 Hz. I/Q modulators can tell the difference between positive and negative
> frequencies (depends on whether Q leads I or Q lags I in phase). This has
> also been called AFSK.
>
> Direct conversion SDRs like the SDR-1000, Flex 5000 and the KX3 still need
> use an offset like 2125 and 2295 Hz to avoid "images" of the Mark and Space
> from bleeding through. You have to send 2125/2295 audio ("AFSK") to these
> transmitters. In that sense, you need to apply the same care when you use
> these "SDR" rigs just as you do with superhet transmitters.
>
> Fortunately, except for QRP folks tinkering with SoftRocks, these direct
> conversion "SDR" have gone the way of buffaloes.
>
> Modern SDRs like the Flex 6xxx and HPSDR use Digital Up Convert (DUC)
> modulators to generate RF directly, with D/A converters running at over 100
> mega samples per second. The only thing between the D/A converter and the
> antenna is the PA and matching networks.
>
> With the DUC transmitters, modulation is done in arithmetic (in an FPGA,
> usually) and as such, you can send baseband I/Q Mark and Space (+85 Hz and
> -85 Hz) to these transmitters directly, and any spurs that are caused by the
> output D/A converter are usually below -80 dBc.
>
> I do not know if Flex implements FSK using I/Q into its DUC, or if they took
> the lazy way out and just pass an AFSK input to the SSB transmitter.
>
> I do know that the regular HPSDR desktop software which 99.9% of HPSDR owners
> use, still generates RTTY by passing AFSK (e.g., 2125/2295) through the SSB
> mode.
>
> However, those who writes their own software can use an HPSDR rig (like
> Hermes, Angelia, ANAN-100, etc) in the I/Q mode to generate super clean FSK
> signals. The transmit PA non-linearity is the only source of distortion.
>
> The interesting thing is that math-based software modems like 2Tone actually
> start out as equations which describe a baseband I/Q signal; cocoaModem did
> that back in 2005 or so. Unfortunately, to modulate an SSB transmitter, that
> internal I/Q signal (which only exists as numbers in memory) has to be
> converted to a scalar audio tone pair to modulate the early-21st century
> transmitters.
>
> Interestingly, the K3 "FSK mode" is really not FSK (i.e., there is no
> oscillator being slewed between Mark and Space carriers) but its "FSK" signal
> starts out also as an abstract I/Q signal. Now you know why it can put out
> cleaner RTTY signals than other superhet transmitters.
>
> The K3 is still nowhere near as clean as a properly waveshaped baseband I/Q
> waveform that directly modulates a DUC transmitter (for example, write your
> own software for HPSDR) since the K3's I/Q signal is still going through
> analog mixers, etc before it reaches the antenna. However, the K3's "FSK"
> mode is usually cleaner than first generating I/Q in 2Tone and cocoaModem,
> convert the I/Q to an audio signal, and then passing that audio signal to an
> SSB transmitter.
>
> 73
> Chen, W7AY
>
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