Frequency control

["Leif Åsbrink" <SMTP:LEIF.ASBRINK@xxxxxxxxxxxxxxxxxx>]

Hi All,
 
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You are supposed to have the 2.5, 10.7 and 70 MHz units.
(WSE RX2500, WSE RX10700 and WSE RX70)

The center frequencies to choose from are
0, 2.5, 10.675,10.700,10.725,10.750, 69.975.70.000,70.025,....
The arrows will (should) work within each frequency band
but to change band you have to enter a frequency value.

If you enter 10.7 the frequency scale at the center is 
0.0 (10.700000) The full frequency is shown in the 
afc window. The scale always has the same direction but 
the spectrum should invert assuming you did nothing to 
the hardware when the new value was entered into the box.

When the frequency in the box is changed, the nearest
center frequency compatible with the hardware is selected.
The hardware is defined in hwaredriver.c.
The center frequency is stored in fg.passband_center
and -1 or +1 is stored in fg.passband_direction
Then a series of hardware commands is issued to set
the hardware accordingly.

The current hwaredriver.c uses the parallel port to select
one out of 255 hardware units to which a serial control word
will be sent through a slow serial interface that uses two
of the control pins. A third pin is used to verify that the 
hardware responds properly.

It would be trivial to replace this routine by something else
that could use any hardware port that one can get permission to
write to under Linux. If you know Linux well enough to use
the drive routines for serial or parallel ports you can
make a far more clever solution than the onew I have put
into Linrad now.

I need this control interface for checking the new WSE units
but at the moment there is no reason for anyone else to bother 
about it unless you have some other hardware that could be 
computer controlled. The serial interface would fit the DDS 
synthetizer that was described in QST a few years ago but 
the performance (many spurs)does not make it very attractive. 
I guess many rigs can be controlled by the PC serial port 
so if you know the protocol it will be possible to set the 
frequency from Linrad by writing to the serial port..


73
Leif  /  SM5BSZ

LINRADDARNIL