rudder jerk with other PC

[Buhmann]

Hello

I use FMS with an old FM 4014 with SmartPropoPlus.

It works fine on my main computer but on the computer from my son the rudders jerk.

On the other computer the channel assignment is not the same as on the first computer. Maybe one sound card inverts the signal.


Does anybody knows how to kill the jerking?

My son wants to fly


Thanks for help...

[shaul_eiz]

Buhmann,
I suspect a few things:
1. Do you use a stereo plug? You may want to try a mono plug.
2. Use Winscope to compare the signals on both of the computers. Do you see a significant difference? What is it?
3. Do you use the same input on both (e.g. Microphone). My guess, the problematic one is Line-in.
4. When you say that the "channel assignment is not the same" - do you mean that the channels actually all shifted by one?

Please let us know. It will be great if you manage to post the Winscope picture of both computers.
Inverting the signal is not a problem. SmartPropoPlus deals with both positive & negative shift, detecting the correct one automatically.

Best Regards
Shaul Eizikovich

[Buhmann]

Hello shaul_eiz

1. Yes I'm using a stereo plug. I can test it with a monoplug but I have to buy some first.
What do you mean is the electrical different between stereo and mono plug?
I think that the second channel is simply unused.


2. I used "visual Analyzer" to show the signal on my PC.
On both the signal seems to be the same. There is only one different I see. The signal is inverted between the both computers. On one it is positiv modulated and on the other it is negative modulated.

On the first computer it works very fine with the simpel cable. Because the rudder jerking I test to reduce the amplitude of the signal. I build a voltage divider with to resistances. I tested a 1:10 and 1:100 divider. The signal amplitudes is now reduced extremly but the behavior is the same on both computers.

3. Yes I use the same input. I use Line-In because first I didn't use a voltage divider and I thought that the microphone input is more voltage sensitive.
After it have not worked fine on the second PC I have tested it on the microfon input but the jerking is the same.

4. Yes. The channelassignment is shifted by one.


I try to give you a picture of the signal later. Now I cannot access the computer. I hope it works because I have sometimes some problems to trigger the signal so that the signal is runnning on the screen.

Thanks for help...

[shaul_eiz]

Hi Buhmann,

Let me explain what I think is happening.
When you plug a mono jack into a stereo socket, the data is transmitted to the left stereo channel while the right stereo channel is grounded.
However, when you use a stereo jack, the right stereo channel is electrically floating. A floating lead located next to a lead carrying data may inject into your sound card a signal which is a derivative of the original signal.
Some sound cards will successfully ignore this signal. Some won't.
SmartPropoPlus, when reading a derivative of a PPM signal misinterprets the signal as a PPM signal, starting with the second channel.

(Reference: http://en.wikipedia.org/wiki/Image:Jack_plug.png)

Having said all that, the solution seems to be straightforward: ground the right stereo channel of your jack.

Shaul

[Buhmann]

Hi shaul_eiz

I understand that voltage is inducted in open wires but I do not understand how it can affect the other channel which is read by SmartPropo Plus. Or does Smartpropplus exploit both chanels?


However. I will ground the right chanel from the computer side plug.


I made some screenshots. I will attach the if I can

First the shot from my first computer where it works fine:





And now the other computer with the jerking:




I found a different between the two soundcards. On the first computer I can visualize a grater range of voltage. On the second computer the sensitive ist much graeter.

The big overspeaking from one to the other chanel ist worrying.




Now I have grounded the right chanel. Now the scope shows a flat line as I like it.
But the jerking ist unfortunately still there.


I have another idea. My computer is a modern A64 with 2x2GHz.
The computer from my son works with 1x1100MHz. Is it possible, that the computer is to slow?


cu