Hello VLF,

I un-wound the defective stack of the large coil which was used for 2970 Hz. It took about 4 hours to carefully unwound about 1000 turns, or about 1 km of wire. The wire will be used for new coils which are already planned.

Now, the remaining 4 stacks should hold at least 15 kV. I connected the coil to the antenna and found the resonance close to 4470 Hz.
Now i'm running (since 12 UTC) a carrier transmission on 4470.005 Hz. The antenna current is just 150 mA. That's an ERP of about 3 uW. A first signal on the 67 km band from here :-)
Let's see how long it holds until there is the next fault :-/

Reports/Spectrograms welcome...

As usual there is a monitoring of the signal in 3.5 km distance from my tree grabber: http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html

73, Stefan

Am 13.08.2017 22:17, schrieb DK7FC:

The repetition of yesterdays message failed. At 15:38 UTC the safety function tripped. I've just been on the roof, when re-starting the transmission i can see a spark in the center of one of the stacks. So now there is another one which has a flash over! :-(
It must be replaced, which is a lot of work. So the tranmissions on 3675 Hz will stopp for some time. At least we have some carrier detections and even EbNaut decodes.

I need to think about a different coil concept.... More current, more voltage, more power, more more more!