Hi David
No possibility with an antenna change hi.
What confused the issue with 9.2.2 is the table of modems says;
¡°+¡± means enable multiple slicers.
¡°-¡° means single slicer.
but one creates multiple demodulators using a "single slicer" B-
5@30 (etc)
I expect that "slicers" is another name for "demodulators", but
by looking at the log display (eg ___||||__) it suggests something
like 9@30 that is probably not number/spacing set and/or is
automatic/dynamic. This all contras though when one has to use B-
to set that manually. The table should probably read "- means
manually setting quantity and spacing of demodulators, the default
being 1".
So is there any practical advantage running B+ over B- when (say)
multiple demodulators are employed?
My question about audio input level is really not about clipping
as that is kind of obvious. It's about as a signal gets weaker and
the bit width narrows. eg assume it was weak enough to fall to
(say) 6 bits rather than 16. Does that affect decoding maths
reliability. I have found when using fldigi for example the RF
preamp can help that.
As it is I was reliably decoding a host of US stations this
morning up around 70-80%, but my 50W wasn't getting back.
Cheers Bob
On 17/12/24 08:31, David Ranch via
groups.io wrote:
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Hello Bob,
Have been going through the docs on this and now decoding
quite weak/noisy signals, quite interesting. Want to make sure
I have covered everything else that "may not be documented".
Most of the 14105 chatter here is marginal. Using latest 1.8.
Your #1 best way to improve 300bps AFSK packet is a better antenna
on your side.? I do completely understand that this is the hardest
thing to do though.? Ultimately, the 300bps AFSK mode without
addons like FX.25 is not very robust and this is one of the many
reasons other HF digital modes have tried to replace it.? I would
argue the most popular of these in modern times is VARA though I
pray the revitalized ARDOP-CF mode might make a comeback here.
I haven't found an understandable explanation on the term
"slicers" yet. I am using the older format;
MODEM 300 1600:1800 B- 5@30 /1
ie what are the merits of using (say) B+ or even A+ instead. I
see 9 "modems" on the log display with that (eg ___||||__).
Has there been new modem development since 1.7? Might be nice
to see a list of current modems (and summary) available.
The modem section is described in the Direwolf User Guide section
9.2.2 but each slicer is trying to simultaneously decode the
signal with different frequency offsets to hopefully decode
slightly off frequency stations (very common HF)? The downside on
running more slicers is CPU load but it's really not much of a
burden even on low power systems so I recommend you enable it.
FX25 and "FIX_BITS 1 AX25" also works well. Seeing quite a
few recoveries. Am TXing 16.
These are both good things to have enabled and FX.25 will help a
lot but only to those remote stations that offer it.
Am wondering how important audio input level setting (and
even sampling division rate) is in regard to quantisation
errors and dynamic range. If so is there a debug option that
shows the occupied bit width, or is this what "audio level"
actually logs?
The ideal audio level? is just to ensure you're getting some
signal in while not clipping and Direwolf is very flexible here.?
The sampling divisors are again a CPU saving thing if you really
need it but it's been mentioned before that 300bps is a VERY slow
mode so even using a /3 divisor won't hurt decoding much.
--David
KI6ZHD
