If I go to VLF I am going to add to my existing inductance outside. I plan to make a box using "plexiglass" quarter inch thick with glued seams so is weather proof. It will be clear [no color] and is very good dielectric. I was going to ask you how much clearance I need and 30 cm is about 1 foot or 12 inches clearance around the coil. Leave air gap around bottom so air can circulate so you don't build up moisture. Small muffin fan with shroud to pull fresh air up and around coil and out.
Could even use clear vinyl material .025 thick and a clear vinyl box over a plastic pipe frame would be cheaper. Clear vinyl used for side curtains on boats-etc.
I am in sewing business [make boat and truck covers] so could make you cover and you build the frame-I ship clear vinyl cover UPS to you or you could have local canvas company make it. Use "RTV" over stitches to make water tight-Bob
Date: Thu, 26 Dec 2013 18:32:43 +0100
From:
[email protected]To:
[email protected]Subject: Re: VLF: 8969.99
Hi Bob,
Of course, if the coil is protected against rain, then it is no
problem. But the coil is quite large and due to the high voltage, the
housing should ideally have a distance of 30cm or more to the coil. So
the housing must be quite large, even more. And that makes it dangerous
because of wind blasts on the to of the building in 35m AGL...
Anyway it would be nice and i also thought about using a simple foil
across the coil, without additional distance.
However on LF, there are partial discharges on the top of the coil
which burns holes into the protecting foil. And the VLF winding is
2000m long. It is a lot of effort to repair it after a short cut
between some turns due to arcing. So it is a high risk.
I think i will make a test in the near future and see if 9 kHz partial
discharges are as agressive as 137 kHz partial discharges :-)
73, Stefan/DK7FC
Am 26.12.2013 16:32, schrieb Bob Raide:
Stefan;
Even if you have your coils in weather proof housing rain is no good to
transmit on 9 kHz? Bob
Date: Thu, 26 Dec 2013 13:55:11 +0100
From:
[email protected]
To:
[email protected]
Subject: Re: VLF: 8969.99
Hi Uwe, Tom, VLF,
Best signal ever from Tom, capture attached. Is it due to the
propagation or did it improve your signal?
What about some tests in OPDS32 or maybe JT9-30? Unfortunately there is
permanent rain here so i have to wait some days longer.
73, Stefan/DK7FC
