Hi Dave and Stefan,
Thank-you for the very helpful information. I hope to get started
on the new QRO TX soon.
73
Joe VO1NA
On Fri, 28 Mar 2014, Dave G3WCB. wrote:
Joe,
Polypropylene caps are recommended for LF work. WIMA MKP types work well.
FKPs are even better, if you can find them. It's the current through them
that seems to be the killer, so it's best to make up the desired value with
parallel combinations.
73, Dave G3WCB IO91RM
-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Stefan Schäfer
Sent: 28 March 2014 10:09
To: [email protected]
Subject: Re: LF: VO1NA_OK2BVG
Hi Joe,
Class E is fascinating and can be high efficient, 98% or so. However the
output impedance has to be quite exactly 50 Ohm +-j0! A SWR of 1.5 can
reduce the efficiency significantly so that all the advantages of the
class E design are lost.
Thus, i'm using class-D designs. I have 2 PAs for 630m. A small one
running at 12 VDC,
https://dl.dropboxusercontent.com/u/19882028/MF/100W-475KHZ-PA.png and
https://dl.dropboxusercontent.com/u/19882028/MF/DK7FC%20472%20kHz%20PA%2015W
%2B100W.JPG
and a large one giving 0...1.2 kW, running as a H bridge, switching
directly at 320V DC.
The efficiency can easily reach more than 90% too.
For you, i assume a normal class D using 2 (or 2x2) FETs against ground,
using a ferrite output transformer may be the best choice. This design
is used by many active MF stns, i know.
What power range do you inted to realise?
73, Stefan/DK7FC
Am 28.03.2014 00:24, schrieb [email protected]:
Hi Stefan,
I have some IRFP140BPF hexfets. Using Alan's G3NYK Class E
design spreadsheet for 200 watts at 13.8 Vdd gives 144 and 119 nf
for C1 and C2 and 1.14 uH for L. I have used silver mica for C1 and C2
but these are expensive. What do you use? I remember mentioned your
class e experiments.
73
Joe
On Wed, 26 Mar 2014, Stefan Schäfer wrote:
Am 26.03.2014 19:36, schrieb [email protected]:
Perhaps some day I will QRO!
Joe
Yes, please :-)
73, Stefan
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