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Re: LF: For today the FETs survived... and are working!

To: [email protected]
Subject: Re: LF: For today the FETs survived... and are working!
From: Markus Vester <[email protected]>
Date: Sun, 4 Jun 2017 05:20:01 -0400
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> The gates now are switched with a square wave (a bit smoothed in the rising side) swinging from + 20 to -10 V with respect to ground.

Why are these so unsymmetrical? With 50% duty cycle and DC-free output from the transformer, the two polarities should have the same amplitude.


> Unfortunately I cannot rise the supply continously from 50V to the final 180V.. so will let it to be used to eat 50V and later give 180V

Oh man, that's going to be a tense moment! Take care, and be sure to protect yourself against bits flying around!

Best 73,
Markus

-----Ursprüngliche Mitteilung-----
Von: marcocadeddu <[email protected]>
An: rsgb_lf_group <[email protected]>
Verschickt: So, 4. Jun 2017 11:11
Betreff: LF: For today the FETs survived... and are working!

Good morning LF &VLF :-)

I had not a big choice among available cores for the driver xfmr.. and
finally I choose a BN43-202 with a lower AL but higher cross section.
Now the driver xfmr is wound 10T primary and 22T+22T of sec (it had to
be 20T but the cutted wire allowed a couple of turns more ;-) )
Now have provided much confortable test points for the gates too.
So I wired everything and replaced the original 150µH coil with
4x2200pF in the output tank and have again available(but not yet
connected) the 25T for the guard circuit.

the gates now are switched with a square wave (a bit smoothed in the
rising side) swinging from + 20 to -10 V with respect to ground.

The tx is running since about half an hour at 50Vdc and only the dummy
load is warming a bit.
With 7T/19T xfmr on the output it is puring 35Wout with 45W input

Unfortunately I cannot rise the supply continously from 50V to the
final 180V.. so will let it to be used to eat 50V and later give 180V

Cross your fingers!

Marco IK1HSS

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