Very cool and thank you...your scope shots are always so informative
I see yours is running at a similar 1.8MHz.
Ah no, the cap is a 0.022uF a '223' as written on an orange ceramic.
I tried all sorts and arrived at the cap value through trial and error, for the most output from least current - those being the primary reasons for building this setup.
Tests this evening have been to do with coil geometries. The pills bottle winding has been based on a few years now of induction coil builds for Tesla towers and other projects....diameter to wire gauge etc bench stuff.
So what would happen with vastly different set ups ?
The first pic shows a 24+24 turn pills bottle sized transmitter coil and a 24 turn coil of the same 23AWG gauge wrapped around a reel of adhesive packing tape. The reel is below the coil.
By adjusting the variable pot value, for the Positive rail to Base resistance to 390ohms, the red LED fired up quite well. The induction range is 2", but, the current used was quite a hefty 8mA.
The second pic shows a different arrangement. A 36+36 transmitter coil was used. With the pot now at 35K the large receiving coil and the small regular coil both lit. Amperage fell right down to 1mA, which I was very happy about.
A transmitter coil was tried, wound on the packing tape reel of 24+24 turns. It ran ok and gave a reading of 2mA but so incredibly intriguingly showed a mere whiff of meter needle movement when the Base and Collector wires were reversed.
Y'see, a coil will run better with the wires one way than the other....the 2 ends affect the running amperage and I can only guess that's because both won't be exactly the same resistance. When hardly the blip of current was seen, it didn't do anything with any receiving coil tried...but I want to get that running and see what happens.
It's also interesting to find that a higher wind coil doesn't necessarily translate to lower running amperage and that loading a transmitter down with extra receiving coils can actually reduce the current used !
That Base resistance pot is becoming ever more useful. It's a 50K by the way.