Thanks Al,
Yes, I like the idea of an interrupter circuit, the 813 isn't a great fan of excessive plate colour.
Plumbing some rough figures into a calculator gives me a tank frequency of around 400Khz on that design, not a million miles from where I want to be
I will look at the secondary coil in a little more detail when my brain is more switched on - Parallel LC circuits are easy to calculate, need to refresh my memory on series tuned stuff, especially when the streamers add a variable to the calculation.
I'm planning to use a 68mm former for my secondary, and was hoping for 110mm for the primary, but am quickly realising that I may need to go somewhat larger to maintain a decent loose coupling, and reduce the risks of flashover.
Lots of work to do - will start digging parts out over the weekend - think I will be shopping for doorknob caps - most of mine are more suited to VHF stuff
