Cool, I removed the trace and green wired and the nosie is 99.99% gone. Just a tiny 10mV ripple now which doesn't overly effect the function. Out of interest I took a look back at some of my previous posts and all the boards where I was having the 8Mhz noise, and 52kHz noise etc... were all boards where the input lines came close to the output lines, and the ones that didn't don't have the noise. So I MUST remember this for the next boards it is probably the source of all the little noises.
With the noise gone I reprogrammed the PIC to its usual function and took some scopes.
Here is the transducer being driven (using x10 scope). It starts at approx 90V and falls to as low as 40V by the end of the drive, and then self-resonates. A little interesting, perhaps my smoothing capacitor on the transistor is not big enough and running out of energy or causing anti-oscillation?
And here is the amp output using the ProWave sensor from about 50cm away:
At first I thought "oh great its no different than when it was driven at 5V"... so I took back at a look at the old scope of when I was driving it at 5V and using 7,500x amplification (this one is currently using 1,500x) and the scope was only 30cm away and at 2V drive. This one is almost twice the distance away and only at 1,500x amplification so I would say it is an improvement.
And here is the amp output using the sensor I have no details on, that is an outdoor sensor (presumably the same ProWave I just used) inside a rubber housing:
The noise is definately dampened so it looks really nice and smooth, however so is the recieved signal. It never got rail-to-rail no matter how close I got, but at least I could see the signal this time and couldn't before.
I am surprised that driving it at 90V would improve the signal a lot and would not need any more than 1,500x amplification, but it looks like it still does. I will solder the other res and caps on so it is 7,500x amplification and hopefully fingers crossed that will be enough... finally.
Failing that if it still isn't enough I will try to drive both legs instead of one and get 150V or more drive, but it definately looks like it is getting there now as I am seeing signals back from the outdoor sensors from half a meter. With another good amplification boost I'm hoping I will get rail to rail from a good 5 meters or so.
Out of interest I put the indoor sensor on this circuit and driving it at 90V was so powerful for it that I could actually hear the sensor pulsing the ultrasound it was quite cool.