Hi Christian,
-------- Originalnachricht --------
Betreff: Re: LF: MF PA
Von: "C. Groeger"<[email protected]>
An: [email protected]
Cc:
Hi Stefan,
Thanks for these infos!
This is always helpful because I'm not a really good technican. Everything I
built was a mixtiure of my ideas and stuff from the net...
Output power is 100 w, measured with a 100 w bulb, matched to 50 ohms via
transformer. Thus efficiency is ok, I think.
The overall setup is:
Vxo/xo 10 mc/10.24 mc, mixer, Fd,
PreDriver 2n2219, Driver irf640, pa 2 x irf 540.
I have attached a foto...
73, df5qg
There is no photo attached. Note that attachments on this reflector must
not exceed 400 kB (or so). Otherwiese the email is rejected. Better use
a dropbox link for large attachments, so people can decide if they want
to have a look at it before downloading all the stuff.
Well, 100W out at 120W in is 83% efficiency. And 20W losses can't be a
problem for 2 TO-220 FETs as long as you use a suitable heat sink and
reasonable thermal coupling.
But i'm not sure how you measure 100W RF power with a 100W bulb. Is
there no reactive component of the impedance of that bulb when running
at 475 kHz?
Take a look to the gate voltage, be sure that it is a real rectangular
wave. Also run the PA in CW-key-down without connecting a load or a low
pass filter and check if the output transformer becomes warm or hot.
Maybe the core material is not suitable or the number of primary turns
is to low? I don't expect overvoltage problems from a 100V FET at 12V
DC supply voltage. Just some ideas...
73, Stefan/DK7FC
|
