Section One - Introduction
Welcome all builders to the homebrew Hfpacker-Amp
V4 R6 Project. This project parts and your efforts will
eventually provide you with a compact 5 watt input to 30-35
watt output linear amplifier for use with QRP SSB/CW
transmitters on the amateur bands 160 through 10 meters and
which can be powered from a 12 volt DC supply. In this
section, you are introduced to the building of the HF Packer
Amp. The design is a good balance between output power,
physical size and battery power consumption. The completed
amplifier will reward the builder with a clean, more powerful
output signal for a QRP rig when radio conditions become
marginal.
This project is not a beginner's project and requires a
medium skill level to complete it successfully. You can take
advantage of some fabricated options available to you.
•
Fabricated Coil Set
•
Fabricated Cable Set
•
Fabricate and install Amp circuit board
Inductors
Builders require soldering, hand tool, basic electronics
and component identification skills. This project manual is not
included with the kit in order to keep kit costs to a minimum. All
builders will receive the construction manual in a pdf format.
You can also download from the hfprojects site:
http://groups.yahoo.com/group/hfprojects/
The manual is produced in landscape format to allow more
readable text per screen. This manual provides all you will
need to successfully complete the amplifier project, however,
some additional PDF files are provided at the above website
for those interested in seeing more pictures of the project at
various stages of construction.
The genesis of the basic amp circuit is fully described
in the 2001 ARRL Handbook and in reprint articles from the
ARRL. If you are an ARRL member, you can view the amplifier
articles on-line. Full amplifier circuit design credit is given to
Mike Kossor, WA2EBY. The amplifier module is mounted to
the inside bottom of the chassis box and its MOSFETs are
attached to a heat sink. The power supply unit is an integral
part of the amplifier module while the filter board is mounted
above the amplifier module.
Circuit Details
The amplifier module is a push-pull design, biased for
Class AB linear operation and uses low-cost power MOSFETs
in its output stage. Maximum efficiency is at 10 MHz and
develops over 50 watts output. QRP transmitter RF input is
first sensed, which trips a relay, feeding RF through an RF
attenuator pad. The signal is then applied to the primary of T3
via an input impedance-matching network consisting of L2. T3
is a 1:1 balun that splits the RF signal into two outputs 180
degrees out of phase. One of these signals is applied by C3 to
Q1's gate. The other signal is routed via C7 to Q2's gate. The
drains of Q1 and Q2 are connected to the primary of output
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