Cream of the Crop 20/Cream of the Crop 20 (Terry Blount) (1996).iso/os2/rafax11.zip/RADIOFAX.HLP

OS/2 Help File | 1996-06-12 | 28KB | 658 lines

ΓòÉΓòÉΓòÉ 1. Introduction ΓòÉΓòÉΓòÉ

This program receives weather faxes and other radio faxes from a High Frequency
(Short Wave) radio. The radio requires Single Side Band (SSB) or a Beat
Frequency Oscillator (BFO).

The computer requires OS/2 MMPM/2 and a supported sound card.

To get started browse the following sections :

     Physical configuration
     Tuning the radio
     Tuning the computer
     Possible problems


ΓòÉΓòÉΓòÉ 2. Getting Started ΓòÉΓòÉΓòÉ

This program is designed for novice users. Jargon is kept to a minimum. The
following sections should get you started in receiving the standard weather
faxes.


ΓòÉΓòÉΓòÉ 2.1. Physical configuration ΓòÉΓòÉΓòÉ

Use either a microphone :

Or an inline connection :

to the microphone or inline socket of the sound card.

When you first start this program a Set Initial Parameters dialogue should be
displayed. If not then on the menu line, select Options, then select Set
Initial Parameters. The Set Initial Parameters dialogue is displayed. Click on
the appropriate Audio Input radio button. Click on OK


ΓòÉΓòÉΓòÉ 2.2. Tuning the radio ΓòÉΓòÉΓòÉ

Tune the radio to a weather fax frequency. Choose a single side band, usually
upper, or tune the beat frequency oscillator, usually negative. You should hear
a sound like crickets.

     What radio fax sounds like


ΓòÉΓòÉΓòÉ 2.3. Tuning the computer ΓòÉΓòÉΓòÉ

On the menu line, select Window.  Select Show spectrum.

A small window will appear. This window displays the audio frequency spectrum
of the incoming fax.

Select Record.  Select Start now. After a few seconds black lines appear in the
spectrum window. The red line is the division between black and white parts of
the incoming weather fax. There may be two peaks on the black lines if a fax is
being received on the radio, one for black and the other for white. If a
greyscale picture (an audio frequency between the black and white extremes
represents a shade of grey) is being received, the black lines look like a blob
shaped by the particular picture.

Adjust the volume on the radio so that the VOL bar at the top of the spectrum
window is about a third of the way across. This volume bar indicates the
amplitude of the audio. Almost no bar indicates insufficient audio from the
radio. A near full bar indicates too much audio and likely signal distortion.
You may need an OS/2 mixer applet for your specific sound card to increase the
Microphone or linein gain sufficiently.

The aim of the next exercise is to position the red line between the two peaks
(or somewhere within the blob for greyscale). If you have a BFO you can tune it
to reposition the peaks around the red line. Or you can use the + and - keys to
move the red line up and down. Note that the spectrum window only refreshes
after every few seconds. If you want faster update select Record/Fast update.
The best results may be got tuning the BFO so that the white peak is at 2300
Hz, the black at 1500 Hz and the red line at 1900 Hz.

With the red line positioned between the two peaks, a picture should be
unfolding in the main window. For a black and white picture, the foreground is
usually black and the background white. If this is not the case the radio is
tuned to the oposite side band. Select  Record/Negative or Positive to correct
the colours.

The two peaks of the spectrum may be hard to see if there is some high
frequency interference or computer generated noise. Move the red line up and
down until you get the best picture;

When you want to stop receiving, select Record then select Stop.

Also refer to :

     Alignment/Align
     Record/Start on sync
     Record/Auto sync and save


ΓòÉΓòÉΓòÉ 2.4. Possible problems ΓòÉΓòÉΓòÉ

Gaps between individual lines in the spectrum.

The audio volume from the radio is too low. You may need an OS/2 mixer
application, for your particular sound card, to set the input gain level.
Adjust the gain and radio volume so that the volume bar in the Spectrum window
is about one third the way across the window.

Many peaks in the spectrum.

The audio volume from the radio may be too high and clipping the signal. Adjust
the input gain (mixer) and radio volume so that the volume bar in the Spectrum
window is about one third the way across the window.

Picture jumps horizontally.

Buffers from the sound card occasionally disappear. I have seen this on Sound
Blaster cards recording 8 bit samples. If you have a 16 bit Sound Blaster card
set Bits per sample (Options menu) to 16.

Picture looks noisy.

Check that the input gain and radio volume is adjusted so that the volume bar
in the Spectrum window is about one third the way across the window. Try
selecting 64 greys in case the picture is grey scale. If the picture still
looks noisy, listen to the monitor then compare to What radio fax sounds like.

Noise could come from the computer, monitor, other appliance or atmospheric
conditions. You should use an outside antenna and the lead connecting it to the
receiver should be shielded.

Message - Program not keeping up with Fax input.

This message occurs when half the allocated memory for the transfer of sound
information from the sound card to the program is used up. Try to reduces
processor load and swapping activity from other applications.

Try only using the spectrum when tuning, reducing the dots per line, reducing
the sampling rate, reducing the grey scale or using black and white when grey
scale pictures are not being transmitted.

Radiofax fails while Grey definition is set to 16

Some VGA drivers have a problem processing 4 bit bitmaps (16 greyscale). Use 64
greyscales instead or try and obtain a recent video driver.

Picture is skewed.

The sound card and driver may not be sampling exactly as specified. Use
Alignment/Skew to slope the picture back to the left or right while a picture
is being received.


ΓòÉΓòÉΓòÉ 3. Menu items ΓòÉΓòÉΓòÉ

Only valid menu items will be enabled at a particular time. A few items, for
which facilities is not yet written, are permanently disabled.


ΓòÉΓòÉΓòÉ 3.1. File/New ΓòÉΓòÉΓòÉ

Clears the current picture without saving it. The Record menu items will then
be enabled.


ΓòÉΓòÉΓòÉ 3.2. File/Create viewing window ΓòÉΓòÉΓòÉ

Creates a new window titled "View Faxes" for the purpose of displaying saved
faxes while a fax is being received in the primary window. Any number of these
windows can be created.


ΓòÉΓòÉΓòÉ 3.2.1. View Faxes Window ΓòÉΓòÉΓòÉ

This window was created by the File/Create viewing window menu item. It is used
primarily to display a saved fax (use File/Open) while the primary window is
busy receiving a new fax. If you want to compare a number of pictures, create a
number of View Faxes windows.


ΓòÉΓòÉΓòÉ 3.3. File/Open ΓòÉΓòÉΓòÉ

Displays a dialogue from which you can select one or more saved faxes from a
list. The selected faxes will then be displayed in progression.

If the disk is formatted with FAT then each list entry displays the long file
name from the Extended Attribute followed by the FAT file name.

Refer to Open Radio Faxes Dialogue.


ΓòÉΓòÉΓòÉ 3.4. File/Save ΓòÉΓòÉΓòÉ

Saves the fax, currently displayed in this window, on the hard drive. The file
path from the current directory will be \RFAXES\FAX on 1995-01-25 at 02-30.BMP
where :

     1995 is the year
     01 is the month, January
     25 is the day of month
     02-30 is the Coordinated Universal Time in hours(24) and minutes.

 This is the date and time the fax started. The date format enables the files
 to be listed cronologically when sorted in alphabetic order.

 This is an OS/2 HPFS long file name. If the disk is formatted with FAT then a
 file name FAXnnnnn.BMP is generated and the long name is stored in the
 extended attributes.


ΓòÉΓòÉΓòÉ 3.5. File/Save as ΓòÉΓòÉΓòÉ

Saves the fax, currently displayed in this window, on the hard drive. You