> Can a spark gap tesla be modulated by cw (Morse key)? Not too cause interference or actually transmit rf but just to play with.
Sure, but you'd need a relay between the key and the power circuits -as well as placing yourself a safe distance from the coil!
> Back in early days of radio this was done with a spark gap transmitter. But I don't think they actually had high voltage on the key itself? If I broke the 120v with the key powering the nst wouldn't it weld the contacts eventually?
Some of the early rigs had lots of juice across the key, and the op's made sure to keep well away from the contacts! The contacts would tend to be eroded by the sparking, rather than being welded shut.
> I think I could do it using a 12v relay but not sure about the lag between key closure and relay activation.
The delay should be only a few tens of mSec with a fast relay.
> Has anyone heard of this or has messed with spark gap transmitters?
Dunno' about a true Tesla Coil, but here's a real low-power spark TX that was put on the air legally:
http://W5JGV.com/375 Meter Spark Transmitter/index.htm
Best DX & 73,
Ralph W5JGV - WD2XSH/7
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