Ecco le info di Patrick F6CTE su questo nuovo modo:
Lentus can be a QSO mode (as JT65) or a beacon mode (as WSPR). By default, the normal mode is the QSO mode. However, if you push one of the three buttons relative to the Beacon mode, you transmit as a beacon (with three possibilities).
Here is the condensate:
Here is a new Multipsk test version about Lentus:
http://f6cte.free.fr/MULTIPSK_TEST_27_01_2012.ZIP
Paste this adress in your Internet Explorer or equivalent. Download the file.
Create a temporary folder (C:\TEST, for example), unzip the file in it and start C:\TEST\Multipsk.exe (the auxiliary files will be created automatically).
Important:
· PC time accuracy
The transmission of a LENTUS frame must begin theoritically at the fourth second of the minutes 0, 5, 10,…,50, 55 with a tolerance of +/-0.1 sec on the PC clock. So it will be necessary before beginning to do LENTUS, to set your PC clock to the right time through Internet.
For this, it must be used 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 ms. The use of the “AboutTime” freeware is widely encouraged as the PC time error is determined by the soft, simply by setting time twice, the second time (and the followings) will give the PC time error.
The time service nist1-ny.ustiming.org works well (to add in the page “Time Host”, function “Add”).
It is recommended to, automatically, set time each 30 minutes (page “Options”, check “Set time at” 30 minutes intervals
· HF frequency accuracy
Due to the very low S/N ratio, it is possible neither to hear the Lentus signal nor to see it on the waterfall. So the transceiver must be very precisely tuned, to be sure to be on the right frequency. For this:
o first make work the transceiver (in reception) at least one half an hour, for temperature stabilization,
o then the transceiver must be tuned in USB, on a fixed WWV carrier at 2.5, 5, 10 or 15 MHz, to determine the offset.
For example, with an AF frequency of 1000 Hz on the waterfall, tune the transceiver to 4999.0 KHz. The WWV trace must be at 1000 Hz on the waterfall. The difference between the WWV trace on the waterfall and 1000 Hz will be equal to the offset (AF observed-1000). For example, if the trace is at 990 Hz, the offset will be equal to 990-1000=-10 Hz (= -0,01 KHz) and this means that the real reception frequency is equal to 4999 - (-0,01 KHz)=4999.01 KHz.
o to tune to the true HF frequency, this offset will be added to the HF frequency (to compensate). In the previous example the transceiver would be tuned to 4999 + (-0,01 KHz)=4998,99 KHz to have a WWV trace at 1000 Hz on the waterfall.
Note: the offset being linear with the HF frequency, if the measured offset is worth dF (10 Hz for example) at 5 MHz, it will be equal to 2*dF (20 Hz in the example) at 10 MHz .
The recommended frequencies are the following (with an AF frequency of 1000 Hz, in USB): 134.8, 1837.0, 3589.0, 7037.5, 10141.5, 14074.0 KHz. In all cases, the frequencies chosen (HF+AF) must coincide with a 100 Hz division. For example, if the transceiver is precisely tuned to the HF frequency 14074.0 KHz, the AF possible frequencies will be 300, 400,…,2100, 2200 Hz. So if the signal cannot be heard or seen, it will be enough to be precisely tuned to a Lentus frequency to decode Lentus transmissions.
· Drift and maximum HF frequency
There is a risk of slow drift. This one is supposed inferior or equal to 1 Hz/minute. Consequently, for common transceivers, it is recommended:
· to make work the transceiver (in reception) at least one half an hour, for temperature stabilization, before beginning Lentus,
· to use frequencies inferior to 14.35 MHz, to limit drift (this one being proportional to the frequency).
The transceiver HF frequency is, thus, supposed to be quite stable.
The “Drift test” button (see “General panel”) permits to determine, once a minute, the drift of the transceiver in Hz/mn.
· RX/TX sampling frequencies
The LENTUS mode requires that the RX/TX sampling frequencies be precisely determined (thanks to the “Determination of the RX and TX sound card sampling frequencies” option of the “Adjustments” menu). For details, see Determination of the sound card RX/TX sampling frequencies.
It is strongly recommended to use the 48 KHz frequency (“Sound card 48 KHz” button) and, consequently to execute steps 1 and 2 (but not the others).
Selection of a received transmission for the automatic decoding
· As long as the reception has not begun (“RX” non displayed), it can be selected, on the waterfall, any given bandwidth by clicking on the synchronization frequency with the left button of the mouse. Any transmission between the blues dashes will be automatically decoded. The blue dashes correspond to the transmission bandwidth. The yellow dashes correspond to the decoding channel (140 Hz). The small white dash represents the current central frequency.
· Once the reception has begun (“RX” displayed), the frequency can be changed only inside the decoding channel (yellow dashes). Changing the frequency can have an interest only at the very beginning of the reception, if it is observed that the carrier is not located between the blue dashes. After the first 20 seconds of the first minute of reception, any modification of frequency will lead to a decoding failure.
Note: the synchronization phase lasts all the first minute. This one permits to determine the central frequency and the drift.
73
Patrick
Eccoci con il secondo articolo della sezione Tecnica operativa, questa volta proposto da Mauro HB9FBG.
Nemmeno la prima neve del 2012 ha fermato i visitatori della prima edizione di Computerfest & Radioamatore di questo nuovo anno, che ci ha visto condividere lo stand con il
