Hi Paul,
For VLF i use a protection circuit that monitors the antenna current. If
it suddenly or slowly drops, the transmission is interrupted. This help
to prevent smoking coils. In principle you just need an RX that converts
to audio and ten feed this into SpecLab. There you directly calibrate
the level into Ampere and produce a nice antenna current plot. You will
see which drift and changes are normal and then you can decide at which
level you interprete it as a fault. My circuit needs just 1 second to
stop transmitting after the level has been crossed.
Maybe worth to consider?
73, Stefan
PS: Another technique may be without software: Measure the current of
the PA (DC, input) and the antenna current. Then, compare these two
voltages. If a certain ratio is lost, then stop TXing. There you don't
even need a receiver and complex measurements.
Am 15.01.2019 22:56, schrieb N1BUG:
Eventually I will rebuild it perfect... although I would prefer to
start over with a new coil as this one requires too much
maintenance. Right now I don't have the luxury of time for any of
that. It's solar minimum and I need this thing working. :)
I don't trust the inner coil form for HV now, too much carbon:
http://www.n1bug.com/vario-fail-2-1200.jpg
So that'll have to get replaced. I will make the connections
differently this time!
73,
Paul
On 1/15/19 10:42 AM, Chris Wilson wrote:
Hello N1BUG,
I too have had issues with bolted connections to the variometer. Not
an expensive fix so long as you don't mind a few battle scars, but
knowing you, you probably want it cosmetically perfect again ;) LF
without smoke is QRP...
Tuesday, January 15, 2019, 2:50:18 PM, you wrote:
Thanks to all who monitored and provided reports on this latest test
of slow JT9 modes.
The test ended suddenly around dawn this morning. Here is the reason:
http://www.n1bug.com/vario-fail-1-1200.jpg
It's the inner coil from the 2200m loading coil / variometer:
http://www.n1bug.com/vario-fail-0-1200.jpg
I had hoped to be on looking for QSOs tonight, but obviously that is
not going to be possible. I do not know when I will be QRV again.
I have a very busy day today, so the final report on the JT9 test
might not be ready until tomorrow.
73,
Paul N1BUG
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