Hi
Clemens,
Oh, OK. But anyway it was a very good hint to mention the
JUMA 500 TX since it leads me to the CMCD design and this paper which nicely
describes the problem of the VMCD desgin which i am trying in my first
tests.
The output C of the FETs is the problem. Since i want to have a
relatively high power (100W) at 12V DC, the primary impedance is very low. So
i have to use FETs with a very low on-resistance, ideally as low as possible
of course. To find them is no problem (e.g.
IRFP4368),
but the output C is much to high then. I tried a IRZF48N (2 of them of course)
as a compromise between RDSon and Cout but am just getting 60% efficiency at
70W in the first attempt. That's not acceptable for a /p PA that has to stay
compact, i.e. without a big heat sink and/or a fan...
The basics are
well explained in this paper, makes fun to read :-)
73,
Stefan/DK7FC
Am 31.05.2012 13:08, schrieb Clemens Paul:
It costs 300 Euro which is not to much.
Unfortunately you have to add 23%VAT tax within EU and
shipping costs
which I estimate to 30-40 Euro.
So we end up
somewhere around 400 Euro.
Interesting kit,though.
73
Clemens
DL4RAJ
