We could speed up the convergence, making it act faster in the case of QSO's
and not broadcaster's.
It was my own bias and ignorance which led me to set it long for broadcast
dx'ers.
This could be a possible enhancement. I will toss it in the ring as an add
on to possibly the dsp tab and if we get past that possibly one of the
buttons, settings in the context sensitive control panel but all of this has
to be added to the "list".
Bob
Sent from my Verizon Wireless 4G LTE Phone
-----Original message-----
From: ke...@3950.net
To: flexradio@flex-radio.biz
Sent: Sun, Dec 18, 2011 18:09:29 GMT+00:00
Subject: Re: [Flexradio] FlexRadio Digest, Vol 80, Issue 17
On 12/18/2011 12:33 PM, Bob McGwier wrote:
Absolutely NOTHING. That is the REASON for having the (synchronous AM)
SAM
detector. Maybe we should not have included the AM detector at all
[...]
I am glad it is included. Some AM QSOs, especially those involving
antique gear, have participants separated by many hundreds of Hz,
and it's nice in such cases not to hear the 'swoop' of the
regenerated carrier locking in when the stations are breaking back
and forth quickly. When everyone's very close to zero beat, of
course, SAM is much to be preferred.
Let me thank you right now for all the great work you have done with
the Flex hardware and software. As I said in another venue recently
"...doing all the filtering and demodulation with perfect
mathematical accuracy in software not only gives you tremendous
dynamic range and filtering capability, but it makes the recovered
audio almost supernaturally clean-sounding. Listening to a Flex into
a good sound system for the first time is like discovering that
pillows had been strapped to your speakers, and gravel had been
stuck to your voice coil, for all these years -- and finally
removing them."
I wonder if Flex, or anyone with the ability to do the coding, ever
considered these four enhancements that definitely interest me:
1. Costas loop detection for receiving pure DSB with suppressed
carrier. No transmitted carrier is required for a Costas loop sync
detector. It depends on the audio null in the Q channel for phase
lock. It makes DSBSC practical and supposedly does better than a
carrier lock sync detector when propagation is turbulent, even on AM.
2. Provision for transmission and phase-locked reception of SSB with
a pilot carrier down 20 dB or so. This was used by TMC for HF SSB
broadcast relay gear and gave SSB a clarity, with perfectly aligned
harmonics, that current ESSB techniques cannot (though they can come
close with rubidium or GPS frequency standards).
3. Use of "selectable sideband sync detection" using the phasing
technique to cancel the interference in either the upper or lower
sideband of an AM signal. (Since there is no significant desired
audio in the Q channel, the desired audio is _not_ cancelled from
either sideband.) This gives a 6 dB s/n advantage over the "drag the
filter edge" technique of chopping off one sideband when it is
interfered with. This would also lend itself to a fantastically
effective kind of binaural reception on AM: LSB interference in the
left headphone channel; USB interference in the right channel;
desired AM audio -- and _nothing but_ desired AM audio -- in the
center. I have experienced this and it allows the brain to process
the signal in a way that allows _much_ better intelligibility.
4. Adding the ability to see the modulated RF (really IF) on the
receiver scope, instead of just the demodulated audio. This tells
you a lot about the received signal, especially on AM, and would be
a very valuable tool.
With best Yule wishes,
Kevin, WB4AIO.
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