[hpsdr] Clean RF linear amplifier for <100mW to 100W

[h-hartfuss at t-online.de]

Tom, 
I am using behind Penelope a CCI kit with two MRF433 as a driver stage
to maximal 8 W in class A (bias current 3 A) with IMD3 better than -50
dB
overall at 7 MHz. 
I am just measuring in detail a next stage following
with two MRF429 (50 V), that's a CCI kit as well (AN-758). 
If run in class A with 8 A quiescent current it delivers up to 100 W
with IMD3 a little less than 50 dB
below one of the test tones (clearly better than 50 dB at your envisaged
30 W). 

Since 400 W of steady state power must be dissipated in
this mode of operation I have water cooled the transistors by using a
computer processor cooling system.

I am just busy measuring all specifications in detail, that's IMD3 as
function of power at all bands. 
I will send a paper on it to Stan for publication in the next PSR, the
TAPR quarterly newsletter.

Best 73, Hans, DL2MDQ.




-----Original Message-----
Date: Sun, 20 Feb 2011 19:59:21 +0100
Subject: [hpsdr] Clean RF linear amplifier for <100mW to 100W
From: "Tom Cathey" <k1jj at comcast.net>
To: <hpsdr at lists.openhpsdr.org>

***** High Performance Software Defined Radio Discussion List *****

 Hi All,

Since getting the basic HPSDR system up and running (with help from the
guys
here) I have been searching and testing many RF linear amplifiers
looking
for one that will amplify <100mW to 100W.   I've tried TMC tube
versions, PA
units from HF transceivers, the CCI amps, etc.  

None have been satisfactory, even in class A1. The CCI kit amps I tested
(MRF-150 kits) were lacking, perhaps due to core design, I don't know.
The
tube amps did OK, but require tuning.  The particular solid state amps
I've
tested were not clean enough to complement Penny's nice -55db++ 3rd
order
output.

* I am looking for at least -45db third IMD specs with final amplifier
voltage of greater than 28 volts. (No 13.8 V amplifiers)   I need about
30W
to drive my tube linear final amp, thus a 100W amp, backed down to 30W
for
cleanliness, would be nice.


Can anyone suggest a reasonably priced SS amplifier kit, board or unit
that
is available with these specs?   I'm not looking to reinvent the wheel
or do
R&D here... :-)   There seems to be a void for an amp like this because
the
commercial use of HF is so low.  There was a German ham who talked of a
SS
linear with similar specs, but haven't heard anything since.

* A linear amp like this would be a popular addition to the HPSDR line. 
The
Pennywhistle, being a 13V amplifier, has IMD in the -30's and is only
16W
out, so I am looking further.

Thanks for any suggestions.

Tom, K1JJ

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