that pulses every 6ms(I looked at it on my scope).
I'd recheck the scope time base. 6 ms sounds to fast for the frame rate of any transmitter. Maybe it is the time for the sync pulse, as they were in the 4-8 ms range.
There were also two different modes that systems operated with. One was a fixed frame rate, while the other had a variable frame rate. Both systems had advantages and disadvantages. Here are a few:
Fixed frame rate systems gave better servo performance. This was because the pulse stretcher circuit in the servo could be optimized for an exact frame rate. However, the receiver had to contend with a variable width sync pulse, and if all the channels were giving the minimum pulse outputs, this could be quite a long time (especially with more than 4 channels) or a very short time with maximum pulse widths. A large part of the problem is getting the time constants correct so the receiver can properly reset.
Variable frame rate systems always had the same length of sync pulse, so the receivers were more stable. If minimum pulses were send out, then the frame rate was quite short, and servos might start to buzz a bit because the pulse stretcher inside the servo would not have time to completely discharge before the next control pulse reached it. This caused high current drain (shades of digital servos). If the pulse stretcher was configured to avoid this one condition (all minimum pulse widths), then the servos tended to be very slugish when the frame rate slowed down (all maximum width pulses).
Ah, the joys of system engineering in the ANALOG WORLD.
I'd start at the decoder and work backward (especially if it has a simple IC decoder).