Message-ID: <001301c3d88e$844a66d0$ee9bfea9@oben>
From: "dj9dw" <dj9dw@t-online.de>
To: rsgb_lf_group@blacksheep.org
References: <5047BBB4.205C80C5.0000CE2C@aol.com>
Date: Sun, 11 Jan 2004 23:01:50 +0100
Subject: Re: LF: T2-ringing
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the choke is the only device, that I did not change. All the other methods
were tried and invain. However, I did not dare connecting D to S for the
reasons, you mentioned. I even thought of the PSU, which is stabilized by 5
times 3055. Is that cazy? That's what a problem can make out of me, hi.
Running on 32Volts by 8 Amps - still ringing. If I aproximate a t37-core to
T2, frequency decreases...shure. C-R-combination on drain makes heat, only.
50 Ohm dirct at T2 still ringing. LPF was hooked on network: PERFECT!. Will
try the coke one of these days.
Tks so far es 73, Peter, dj9dw.
----- Original Message -----
From: <G0MRF@aol.com>
To: <rsgb_lf_group@blacksheep.org>
Sent: Sunday, January 11, 2004 7:14 PM
Subject: Re: LF: T2-ringing


> In a message dated 1/11/2004 12:30:03 PM Eastern Standard Time,
dj9dw@t-online.de writes:
>
> > nonconducting side. Eather a steady current and heat on the
> > FET's or by
> > adding a cap from D to G.
>
> This may be a mistake, but please remember you may have peaks to 200V on
the drains and a limit of 20V (ish) on the gates. Any capacitor as suggested
will destroy the devices in an instant.
> I have seen a few 'mods' including a zobel network i.e. a capacitor and
resistor in series between drain and ground. This does de-Q the circuit
quite well. Changes in value of the normal drain to ground 10nF will have
some effect but it's likely to change any resonant frequency without
reducing the Q or the total peak voltage. Bob G8RW ran his unit at over 300W
and had installed 'transorbs' that conducted just below the max drain limit
of the FETs. However, Bob's just had a single peak at the switch on / off
points and not the 'ringing' described here. It may be worth looking at the
T94-2 core / decoupling caps as well if ringing is at 1MHz+
>
> 73
>
> David  G0MRF
>
>