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From: "Ken Wright" <ken.h.wright@btinternet.com>
To: <rsgb_lf_group@blacksheep.org>
References: <001201c83be4$79fff920$0401a8c0@ken> <001f01c83be6$6978cb20$0900a8c0@Lark>
Date: Tue, 11 Dec 2007 11:23:46 -0000
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Subject: LF: RE: Re: IRF530N in 500kHz PA
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Hi Alan, Thanks for the reply, I am trying to run it in pseudo class C, driv=
ing it from a xtal controlled osc, 10mW output into a buffer/driver amp.

 73 Ken M0KHW

-----Original Message-----
From: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksh=
eep.org] On Behalf Of Alan Melia
Sent: 11 December 2007 11:10
To: rsgb_lf_group@blacksheep.org
Subject: LF: Re: IRF530N in 500kHz PA

Hi Ken I suggest you are probably not driving it hard enough. Many of these
switching FETs require more than 6 volts to swich on hard and they have a
very high gate capacity so you need some current drive capability as well.
We have used a pnp-npn totem pole driver on 12v to good effect. I think
there may be troubles if you are trying to get it linear. If you are trying
to go ClassD/ E then you should not be tuning for max output but for the
correct drain wave form. I cant comment on Class A /B performance.

http://www.alan.melia.btinternet.co.uk/classepa.htm

Cheers de Alan G3NYK


----- Original Message -----
From: "Ken Wright" <ken.h.wright@btinternet.com>
To: <rsgb_lf_group@blacksheep.org>
Sent: Tuesday, December 11, 2007 10:56 AM
Subject: LF: IRF530N in 500kHz PA


Has anyone experienced problems using an IRF530N in a 500kHz PA?. I am using
an IRF530N into an L =E2=80=93 C =E2=80=93 L  output network the design para=
meters for the
network are input:10 ohms, output 50 ohms, centre frequency 502.5 kHz, Q=20=
=3D
12, giving, L1  38=C2=B5H, C1 3.7nF, L2  84=C2=B5H, C1 consists of a 3.3nF f=
ixed
capacitor plus a 2 gang 500pF variable, 3mH inductor in the drain. I have
tried driving the MOSFET with a 5v positive peak signal, and with a 3v rms
signal sitting on a +ve bias, I have managed to obtain 5w into a Marconi
TF1152A/1 (50=CE=A9) power meter about three times, but when 12v is removed=20=
from
the PA and reconnected there is no output, C1 is adjusted for maximum power
output, but is never the same position twice, and there seems to be a very
critical adjustment of the drive to obtain, a) an output, b) anything that
looks like a sine wave, although when I have got it right there is a very
good sine wave. Any ideas anyone as to what may be going wrong?



My direct e-mail is  ken.h.wright@btinternet.com





73   Ken Wright   M0KHW    IO91TV