i mesured the r.f power with digital power/swr meter and it was only 190 W at
106VDC (6A current). The manufacter claims that at 500w output r.f power, at
110vdc, the current is 13A. So, the efficiency is below 50%.
---------------------------------------------------------------------
http://tzitzikas.site90.net (tzitzikas site)
http://forum.tzitzikas.site90.net (tzitzikas forum)
---------------------------------------------------------------------
--- On Sat, 4/17/10, Ron Youvan <ka4inm@tampabay.rr.com> wrote:
From: Ron Youvan <ka4inm@tampabay.rr.com>
Subject: Re: [Amps] 160m mosfet linear amplifier problem with ferrite cores
To: "amps" <amps@contesting.com>
Date: Saturday, April 17, 2010, 6:24 AM
HI sasas asasas:
> Hi, I have constructed this linear amplifier 500w rms (2 kW pep) (50 Ohms)
> with 12 mosfet irfp360, http://tzitzikas.webs.com/linear500w.jpg for 160m
> band.
> When I gave 3 Watts of driving power, it gave to output only 190 W at 106VDC
> (6A current). Two radio amateurs who have construct this linear claim tha it
> gives 500w
> r.f power at 110vdc.
I have been looking at this schematic all week. I don't get the "500w rms -
2 kW PEP" thing,
that doesn't make sense to me. RMS isn't that different from average and 2 kW
PEP is about the same
as average.
Also, 106 V. X 6 Amps. = 636 Watts at 50% efficiency TPO = 318 Watts is all you
should be looking
for. (at this drive level)
The device substitution has possibly reduced the amplifier's gain and
efficiency.
> But when I tried to give 4 watts of driving r.f power the ferrite Cores (43
> material)
> of transformer T3 broken! Which do you think is the problem??
First, type 43 is correct for the HF HAM bands, but I am not sure about the
top band.
You need to replace the broken core and test it "just for gain" (no more than 2
Watts of drive) at 7
MHz then compare the gain on 160 m.
> http://tzitzikas.webs.com/linear20a.JPG
> http://tzitzikas.webs.com/ferrite_broken1.JPG
> http://tzitzikas.webs.com/ferrite_broken2.JPG
Yup, broke.
--
Ron KA4INM - The next election, I know what is going to happen, I'm going
to help.
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