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LF: G4HUP aerial current meter/ hazards

To: [email protected]
Subject: LF: G4HUP aerial current meter/ hazards
From: "Dr. Wolf Ostwald" <[email protected]>
Date: Sat, 5 Aug 2017 07:38:38 +0200
In-reply-to: <3D9A092BFA65418DBEE13188A4C58580@gnat>
References: <0883B95D3F4D417F975C59A900E1A838@gnat> <[email protected]> <3D9A092BFA65418DBEE13188A4C58580@gnat>
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good morning !
a current transformer with ferrites of unknown origin and virtues is a very risky thing.
As these cores are widely available on swapmeets its a lure to use them.
But they can be tested. I blew a few of them by just putting them on with a single primary turn and with power less than a hundred watts they got hot and broke.
The losses can be extremely high.
It does not help to measure their magnetic constant. As that has not much to do with frequency dependent losses. a way to find out is to use a 50 ohm load and measure the RF voltage across the terminals. Then u just put the toroid over the "hot" side of the resistor terminals. If the measured RF voltage drops heavily, the core is useless. You dont want it to block, u want to derive some RF for measuring purposes. The above core would go into pieces and additionally as it poses a high inductance to ur feedline, the amplifier stage may go south, depending on the safety factor involved with ur construction .

73 de wolf   df2py

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