So I have had some success since my last post.
I have turned up the volume slider in my Windows machine used for Winlink to drive the audio higher. This was triggering the VOX PTT on my MiniProSC interface, but I remembered that the PTT line is driven by one audio channel and the actual data is sent over the other (L&R, can't remember which does which) but by adjusting the balance, I could fine tune the data audio level and the PTT level independently.
The TX-500 does seem to need to be driven quite hard in terms of the audio, but it works really well when it is. I have been running off a 3S 18650 Li-Ion battery pack and for sustained digiops at 10W I was averaging around 400mAh used per 1 hour session. I recharge the packs from a AGM battery which in turn is charged by Solar panels.
Hope this may help someone.
