In this section we will look at some of the more common software, used for SSTV, RTTY, Etc. Programs like EasyPal, MMSSTV, MMTTY and possibly a few more. We will look at some of the common mistakes made when setting up these programs, And some tips to better your chances of receiving these types of signal.
Most of us just install the software and believe it will work for all of us all the time, This is not always the case when we are dealing with digital modes. These digital modes rely on timing to reproduce an image or text that is sent to us.
Are all sound cards created equal?
The simple answer is NO, There are many different manufacturers, And most sound cards are manufactured within tolerances. This means all sound cards are different even when from the same manufacturer.
What can I do about it?
Calibrate your software and soundcard using the tips on this blog. This will help get both sound cards on the same speed. This will for example maximise your chances of perfect image reproduction when receiving an SSTV signal.
Why Should I calibrate my soundcard ?
The problems with sound cards is that when you select for example 11025 kHz one soundcard maybe on 11024 kHz and the other sound card maybe on 11025 kHz, or 11023 kHz. As far as both parties are concerned the soundcard is selected (In software) to be 11025 kHz. We just assume that all sound cards are the same and calibrated to be exactly the same … And in reality they are not. This for example results in slanted images in SSTV reception, This is due to timing differences in both sound cards.
How can I calibrate my soundcard ?
Most software will have some form of calibration screen to calibrate our soundcard to the signal we listening to, This will maximise our chances of getting a perfect image the first time with no intervention from us.
What else can I do ?
Other problems are due to the way we set up the hardware. Make sure you both use the same sampling rate in the software you are using and calibrate it. I highly recommend you set up any software to use the stereo mixer, And disable any system sounds that are not required. This eliminates all other sounds that may disrupt the normal flow of audio to the software. It will take some experimentation with both pieces of software, But it is possible to operate that way.
In my next post …
Calibrating MMSSTV and MMTTY
Best Regards
Simon
Simon's Technology Corner 