[Amps] 160m mosfet linear amplifier problem with ferrite cores

[sasas asasas]

what do you mean with the phrase: <<The device substitution has possibly reduced the amplifier's gain and efficiency.>> .
thank you

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--- On Sat, 4/17/10, Ron Youvan <ka4inm at tampabay.rr.com> wrote:

From: Ron Youvan <ka4inm at tampabay.rr.com>
Subject: Re: [Amps] 160m mosfet linear amplifier problem with ferrite cores
To: "amps" <amps at 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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