Thanks Everyone!
It worked!
The answer was a pull down resistor. It got rid of that slope. I tried a few, and worked out that 4.7K was the highest value I could use. That gave me a final voltage about 4.2V which should be fine.
Then I had to play with the frequency I specified to get exactly 38 pulses in 1mS. Even though the scope's measurement function still reports it as 38.46KHz - I told you it was a cheap scope!
Here are two images of what I have now.
Thanks again!
Andy
Attachment 8114
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