SSTV Slant Adjustment Help
Are your images slanted?
MMSSTV has a very cool and easy way to adjust your slant or sound
card crystal frequency. In some cases, the offset numbers can be used
in other SSTV applications such as ChromaPix.
First things first.
Turn off any and all auto slant features. The Auto slant features
works only for receiving images and will have no effect on your transmitted
images. It is best never to use "Auto slant" or any
feature like it ever.
My opinion on Autoslant
First Adjust slant for received images
- In the menu bar at the top of the main window , Select "Option"
and then "Setup MMSSTV"
- Select the "RX" tab and remove the check from the "Auto
- Select the "Misc" tab and set the "TX offset"
to zero (0.00) and click the "OK" button. to save that
- Most of the following information is available in the help file
- If you want to calibrate your soundcard accurately, listen to
radio. These stations can be found on 5, 10 or 15 MHz
- Go to "Option" and then "MMSSTV Setup"
- Select the "Misc" tab and push "Adj" button
near the bottom left
- Next you can select full screen for best resolution. The
screen should be mostly all black to start..
- Right clicking the screen anywhere near the white line
will position green to help with the alignment .
- See the example screen with the diagonal "slanted"
Example of straight line below.
- You should receive the WWV signal that says "At the
tone, ?? hours ?? minutes coordinated universal time" for a
little while Full screen will get you the highest resolution.
This may take a few minutes.
- You should start seeing a reasonably straight white line but
it may be on an angle.
- Single click on the very bottom of the line and then again at
the very top of the line. The dialog box should close and a new
clock number will be set. You may need to repeat this operation
a couple time to get the hang of it
- If you get a line with a lot of slant, you may need to do this
procedure a few times. The more vertical the line gets after
each adjustment, capturing more of the line will get you the highest
accuracy. (points further apart from each other will get the highest
accuracy) Full screen dialog box with a full length line from the
top of your monitor to the bottom will get you the best results.
- Right click on the screen to get the green positioned near the
white line to check vertical alignment for best results.
- Once the line is as vertical as you can get it, you have now
corrected your sound card crystal frequency. Your receive crystal
is now corrected. Note Receive only and in most cases, transmit
too. You should not ever need to change this number again
as long as you use this computer or sound card.
Adjust slant for transmitting images
- In most cases after adjusting your receive slant, your transmitted
images will be good. In most cases this is true. Most
sound cards are using one or the same crystal for data in as for
the data out however there are sound cards using separate crystals
for data-in then for data-out.
- To adjust the transmitted slant, you will be changing only the "TX
offset" shown below. Do not adjust the receive "Clock".
your receive is good now at this point.
- You can check your TX offset at some of the
cams but be carful, some SSTV cams are using "Auto slant"
and this will not help.
My SSTV cam "Auto
slant" is disabled and will help you if it hears you.
- Sometimes it may be easier to find a SSTV friend on the air
and have them help you with the TX offset. Most hams using MMSSTV
will be able to give you an exact the number to put in your TX offset
after receiving your picture if needed.