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Greetings,
I have started work on a new amplifier (80 - 10 meters) utilising the =
popular grounded grid design but with a slight difference than the norm =
as I use four valves in parallel, of the AMPEREX 4-250 type. The main =
reason is I have ample supply of 4-250's (as compared to the usual 4-400 =
or 4-500 one reads about in designs). I still would like to break the 1 =
KW barrier on output.
I have a similar working one I build in 1999 but although it is working =
it is not very efficient and prone to destroying chokes and by-pass =
capacitors. Power output is also way below what I expected .. and not =
breaking the 1KW barrier.
I run the valves with +/- 3,400 Volts on the plate and the filaments =
have two transformers connected in parallel giving the 5 Volts at +/- 15 =
Amps.
I need advice on how to improve performance and limit component =
failures.
I know I have to look at the capacitance of the four valves in parallel =
as this will impact on efficiency especially at 10 meters. I AM JUST =
NOT SURE WHAT I AM SUPPOSED TO BE LOOKING AT.
My plate choke will also have to be properly designed, as previously I =
took it out of a YAESU 2100Z and just transferred it to the homebuild =
version. It works but surely is partly the cause of the lower than =
expected power output.
I also now want to add a tuned input circuit as previously I just put a =
ATU beween the rig and amp input.=20
Any advice, especially on the use of the four valves in parallel be it =
practical or an indication that I should use two valves will be =
appreciated.
Wynand van Wyk
ZS6ARF
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<META content=3D"text/html; charset=3Diso-8859-1" =
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<BODY bgColor=3D#ffffff>
<DIV><FONT face=3DArial size=3D2>Greetings,</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>I have started work on a new amplifier =
(80 - 10=20
meters) utilising the popular <FONT color=3D#000080><EM>grounded grid=20
</EM></FONT>design but with a slight difference than the norm as I use =
four=20
valves in parallel, of the AMPEREX 4-250 type. The main reason is I =
have=20
ample supply of 4-250's (as compared to the usual 4-400 or 4-500 one =
reads about=20
in designs). I still would like to break the 1 KW =
barrier=20
on output.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>I have a similar working one I build in =
1999 but=20
although it is working it is not very efficient and prone to destroying =
chokes=20
and by-pass capacitors. Power output is also way below what I =
expected ..=20
and not breaking the 1KW barrier.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>I run the valves with +/- 3,400 Volts =
on the plate=20
and the filaments have two transformers connected in parallel giving the =
5 Volts=20
at +/- 15 Amps.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>I need advice on how to improve =
performance and=20
limit component failures.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>I know I have to look at the =
capacitance of the=20
four valves in parallel as this will impact on efficiency especially at =
10=20
meters<FONT color=3D#ff0000>. I AM JUST NOT SURE WHAT I AM =
SUPPOSED TO BE=20
LOOKING AT.</FONT></FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>My plate choke will also have to be =
properly=20
designed, as previously I took it out of a YAESU 2100Z and just =
transferred it=20
to the homebuild version. It works but surely is partly the cause =
of the=20
lower than expected power output.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>I also now want to add a tuned input =
circuit as=20
previously I just put a ATU beween the rig and amp input. </FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>Any advice, especially on the use of =
the four=20
valves in parallel be it practical or an indication that I =
should use two=20
valves will be appreciated.</FONT></DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>Wynand van Wyk</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>ZS6ARF</FONT></DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV> </DIV></BODY></HTML>
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