Date: Mon, 9 Apr 2018 17:20:57 +0100
From: Chris Wilson <dead.fets@gmail.com>
Message-ID: <1647806154.20180409172057@gmail.com>
To: N1BUG <rsgb_lf_group@blacksheep.org>
In-Reply-To: <1b882ae9-fede-3ec4-256e-9b068d3acf99@n1bug.com>
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Subject: Re: LF: W1VD amp help - more waveforms
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Hello again Paul

What's   the   vertical   board  in  the  end of the case? If it's the
multiplier  I  am  not qualified to say what having in the same box as
all that RF might be, but i would have some concerns.

I would mount the driver board, shortened if necessary, vertically
right by the FET mounting screws and shorten the gate wires. If Jay
hasn't got a board I can send detailed photos of my boards that work
OK, they aren't PCB's, as Jay had run out. My "Jay board" got ratty
after a lot of fiddling and soldering and I wanted to remove surplus
to my needs stuff, so I made my own. They are a special UK board with
separately insulated squares on one side and full copper the other,
you link the squares with solder tracks and drill point the ground
plain where leads stick through that are not to be grounded. I can
even send you a ready drill pointed board and the link photos. My
output transformer is a bit tighter wound as the 180 odd strand
speaker wire is malleable and winds quite tight. I didn't have any
real problems soldering it. But I can't really say it's *THAT* much
"better". I can send you some of that if you want? I can check what
ceramic caps I used for the stack. RS Components or Farnell would have
been the source, high ESR ones, quite expensive I remember thinking.

I'd be tempted to apply full voltage and see what happens, I see a max
of about 160V on the drain spikes at 55V input. What I have noticed is
if the antenna is suspect current draw increases substantially as do
the spikes on the drain waveforms. Into a dummy load the ringing is a
*BIT* less than into the antenna, but not a *LOT* different. If the
aerial is not perfectly resonant or to a lesser extent, the matching
is wrong then the waveforms go to pot.

Monday, April 9, 2018, 4:34:17 PM, you wrote:

> Yep, voltage breakdown of the FETs was my worry. However I may be
> making a false assumption. I assumed the voltage spikes in the
> ringing would vary linearly with applied drain voltage? Perhaps that
> isn't necessarily so?

> With 13V on the drains the first spike here is 'about' 64V.

> Efficiency seems fine. I wouldn't try to put an exact figure to it
> what with measurement accuracy in three places (voltage, current, RF
> power) but it 'appears' to be in the mid 90s.

> Paul


-- 
Best regards,
 Chris                            mailto:dead.fets@gmail.com