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
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