Date: Mon, 09 Apr 2012 13:18:03 +0200
From: Steinar Aanesland <saanes@broadpark.no>
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Subject: LF: New release (4.21) of MULTIPSK
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Hi all of you that like to try LENTUS on LF.

The beta testing is over . Here is the latest multipsk release with t=
he
new mode Lentus is included.

http://f6cte.free.fr

This mode is used for QRP transmissions  (down to a minimum S/N ratio=
 of
-34 dB) either in LF, MF and HF (14 MHz maximum) but not beyond.

The recommended frequencies (on the XCVR) are the following (with an =
AF
frequency of 1000 Hz, in USB): 136.3, 1837.0, 3589.0, 7037.5, 10138.7=
,
14074.0, 14095.6 KHz.


*LENTUS*

LENTUS means " Slow " (but also indolent, nonchalant, quiet=85) in la=
tin.
_Created by_: Patrick Lindecker (F6CTE) in 2012

*Description :*

_Baud rate_: 0.1465 (4800/32768) or 6.827 seconds by 5 bits symbol

_Messages_: a message of 293.5 seconds duration (43 symbols) begins a=
t
t=3D4 sec of the UTC minute 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50,=
 or
55 (it is necessary that the PC may be synchronized on a =93Standard=
=94 clock).

_Note_ : in manual transmission, it can also start at 4+6.827=3D10.82=
7 sec
(42 symbols sent) or 10.827+6.827=3D17.654 sec (41 symbols sent) or
17.654+6.827=3D24.481 sec (40 symbols sent), to =AB pardon =BB the Ha=
m
operator for a delay to answer, but with reception probability a bit =
weaker.

The message is normally composed of 43 symbols (but can be reduced to=
 40
symbols, see above), each one with a length of 32768 audio samples (o=
r
or 6.827 seconds). The 9 first symbols carry a tone allowing the
determination of the transmission central frequency. The 31 following=
 "5
bits symbols" carry the message (allowing the Reed-Solomon coding of =
75
bits). The last three symbols are transmission central frequency carr=
iers.

Messages can be either plain text (13 characters, preceded by a bit =
=93CQ
de=94 and a bit =93Beacon=94) or formatted text according to differen=
t
possibilities, listed below:

=B7    _A standard CQ call_composed of a bit =93CQ=94 + a bit =93Beac=
on=94 +
complete call (with 3 characters max in the mantissa, as for example
=93AZ2/FL5XYZ/MM=94) + optionally, a 6 characters Locator (accuracy +=
/-2.31
km in latitude and +/- 4.63 km in longitude).
Note: without the =93CQ=94, it is an information transmitted by the H=
am
answering to the CQ call,

=B7    _A =93Station description=94  type CQ call _composed of a bit =
=93CQ=94 + a
bit =93Beacon=94, a 6 characters call + suffix (as for example =93FL5=
XYZ/MM=94),
a =936 characters Locator=94 + Power level + =93mW/W=94 bit + relativ=
e gain of
HF antenna + directivity of the antenna.
Note: without the =93CQ=94, it is an information transmitted by the H=
am
answering to the CQ call,

=B7    _A =93Meteorological=94  type CQ call _composed of a bit =93CQ=
=94 + a bit
=93Beacon=94, a 6 characters call (as for example =93FL5XYZ=94), a =
=936 characters
Locator=94 + Temperature + Wind force + Type of weather + Humidity.
Note: without the =93CQ=94, it is information transmitted by the Ham
answering to the CQ call,

=B7    _A CQ call with precise geographical position_composed of a bi=
t
=93CQ=94 + a bit =93Beacon=94, a 6 characters call + a geographical p=
osition
(latitude + longitude) in =B0 =91 and 2 figures decimal (as for examp=
le
=9348-49.83N 002-22.02E=94). The accuracy is equal to 9 m in latitude=
 and in
longitude (about 60000 times more precise than a Locator position).
Note: without the =93CQ=94, it is an information transmitted by the H=
am
answering to the CQ call,

=B7    _An answer to a CQ with Locator 4 characters _composed of a 6
characters Call 1 ( as for example =93FL5XYZ=94) + 6 characters Call =
2 (as
for example =93FL5XYZ=94) + Locator 4 characters  (accuracy +/-55 km =
in
latitude and +/- 111 km in longitude), in answer of Call 1 to a CQ do=
ne
by Call 2,

=B7    _An answer to a CQ with S/N ratio and drift _composed of a 6
characters Call1 (as for example =93FL5XYZ=94) + 6 characters Call 2 =
+
Suffix (as for example =93FL5XYZ/MM=94) + S/N ratio (12 to -37 dB) + =
drift
(-4 to 4 by step of  0.1 Hz/mn), in answer of Call 1 to a CQ done by =
Call 2,

=B7    _An answer to finish a QSO_composed of a 6 characters Call 1 (=
as
for example =93FL5XYZ=94) + 6 characters Call 2 + Suffix (as for exam=
ple
=93FL5XYZ/MM=94) + =9373 GB SK=94.

_Moments of decoding :_

_Reception start_: the reception normally begins at t=3D4 sec and las=
ts 40
or 43 symbols (see below). In case of failure of the operator, the
reception can also begin at t=3D24.481 sec and lasts 37 or 40 symbols
(it=92s a degraded working).

_Decoding start_: the main decoding takes place after reception of 40
symbols (i.e. 273 seconds), which normally leaves about 25 seconds to
answer. However, there is still a margin of 20 seconds (to reach
25+20=3D45 sec), the message being, in that case, truncated but being=
 able
to be decoded.

In case of failure of the main decoding, other decoding attempts are
done after 41 symbols (280 seconds), 42 symbols (287 seconds) and 43
symbols (294 seconds). In this last case, it remains 6 seconds to
answer. However, there is still a margin of 20 seconds (to reach 6+20=
=3D26
sec), the message being, in that case, truncated but being able to be
decoded.

_Mode of transmission_: Lentus can be used to do QSO (two_way
communication) or as a beacon. In that last case, no answer is requir=
ed:

=B7    a beacon transmission  could be done at minutes 0, 5, 10, 15, =
20,
25, 30, 35, 40, 45, 50, or 55.

=B7    for a QSO, by mutual agreement , the Ham calling CQ will trans=
mit
at minutes 0, 10, 20, 30, 40, 50 and the Ham answering to the CQ call
will transmit at minutes 5, 15, 25, 35, 45, 55.

_Repeater_: Lentus can also be used, for very specific use, as a
repeater. As a repeater, it simply transmits  what it is received so =
as
to forward the message to other stations or to broadcast a message (w=
ith
several repeaters).

_Speed_ : 75 bits (or 13 characters maximum in plain text) by 5  minu=
tes
period (with only one message by period) or 0,43 wpm

_Modulation_ : MFSK 32 tones (for 5 bits) with a shift between tones =
of
0.7325 Hz (5 x baud rate).

The synchronization tone transmitted during the 9 first symbols
corresponds to the central frequency of the transmission bandwidth. I=
t
permits to determine this frequency (with a precision of about +/- 0.=
1
Hz) and the drift speed (up to 3 Hz/mn). The 32 possible 10^th symbol
(first data) frequencies will be estimated from these two pieces of
information. The synchronization frequency search bandwidth tolerance=
 is
variable from +/- 20 Hz to +/-80 Hz, counted from the frequency click=
ed,
by the user, on the waterfall.

_Receive mode_: USB. Each transmitting or receive period of 300 sec m=
ust
start at t=3D4 sec of the UTC minute 0, 5, 10, 15, 20, 25, 30, 35, 40=
, 45,
50, or 55 with a maximum tolerance of +/-0.1 sec of the PC clock. A
margin of 20 seconds is given as indicated in =93Messages=94 above.

It is possible to introduce an advance (from 0 to 0.1 second by 10 ms=
ec
steps) to compensate from a possible transmission delay (due to a big
distance to the zone to target or a delay due to a Wifi link, for
example). Symmetrically, in reception, this advance will be taken int=
o
account as a delay to start decoding.

The time to switch the transceiver is supposed to be very short
(definitely less than to 100 ms).

_Characters set_(46) : ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789 <SPACE> /=
 +
- . ? ! @ % $

_Shape of pulse_ : rectangular

_Bandwidth_: 23 Hz

_Synchronization:_using the very accurate time from an Internet Time
Service as the NSIT, through a SNTP or NTP protocol (but not through =
the
RFC-868 Time Protocol) so to have an accuracy widely better than 50 m=
s.
The use of the =93AboutTime=94 freeware is widely encouraged as the P=
C time
error is determined by the soft, simply by setting time twice, the
second time (and the followings) will give the PC time error.

_Coding code_: Reed Solomon (31, 15) or 31 symbols of 5 bits for 15
symbols of 5 information bits (so a yield of 0.48). The irreducible
polynomial P(x) is equal to X^5+X^2+1.
The generator polynomial G(x) is equal to a product of (X+alpha^i) wi=
th
i minimum=3D1.

_Convolution code_: no

_Interleaving_ : no interleaving nor Gray coding is used.

_Scrambling_ : each of the 31 Reed-Solomon symbols (which value is
between V=3D0 and V=3D31), which order is defined by O=3D0 for the fi=
rst
transmitted symbol until O=3D30 for the last transmitted symbol, is
associated with a XOR f(O). In other words, for each symbol, it is do=
ne
the operation V =3D V XOR f(O). This is done to avoid that a carrier
produces a suite of same symbols (suite which could be interpretable =
by
the Reed Solomon coding as a correct code). At reception, the V initi=
al
is found again by doing Vinitial =3D Vreceived XOR f(O). The f(O) fun=
ction
is random.

_Pmean/Ppeak_: 1

_Drift tolerance_ : 2 Hz/mn (note that the performance in S/N ratio t=
erm
is degrading with drift)

_Lowest S/N_: -34 dB (without any drift, for more than 90 % of the
frames), however  some frames are decoded at -36.5 dB. At -37 dB and
below, no frames are decoded.

Specifications of this mode will be found in the document
"Specifications 1.0 of the Lentus mode"  written the 10th of March 20=
12
("Specifications" on my WEB site: http://f6cte.free.fr/).



----------------


73 and good LENTUSING from LA5VNA Steinar