[Elecraft] OT: HF Packer Amplifier

[eric norris]

Dear Fellow Elecrafters:

Over the past few years I have received a number of great recommendations for 
non-Elecraft equipment on this list--everything from military surplus hard cases 
to headphones and cable Y-adapters.  I now own a lot of this stuff.

In that spirit I would like to pass along a recommendation for the HF Packer 
Amplifier kit offered by Virgil Stamps.  I have now built two of these.  They 
operate from 160m to 10m, and will RF detect or use a PTT input.  Output is 
about 30 watts on the low bands, less on the high bands.  Input is selectable at 
build time.  I used 2.5w input.  This gives me the ability to use my amps with 
my K1, KX1, or FT-817.  I've even used it with a Rockmite and DCxx rig.  There 
are two versions available, one with a fan and one with a higher mass heatsink 
and no fan.  The fan version is good for digital modes or high duty-cycle CW, 
like calling CQ contest style at full power.  


The design is really cool.  There are two boards, one has the amplifier itself 
and the power supply.  The other is an LPF board.  Unlike the THP HL-45 amp, 
there are not a lot of protection circuits, but there is one.  In case a MOSFET 
blows, that circuit shunts the PS output to prevent the shorted MOSFETS from 
taking out the PS.  The PS is a switcher design providing 29.5 volts for the PA 
MOSFETS.  This means the amplifier will operate down to nearly 8V at full 
power--great for battery use.  Power draw for my amps is between 4.5 and 7 amps 
depending on band/power at 13.2v input.    


MOSFETs are IRF-510s that are extremely cheap ($1 or so)  and easy to replace.  
I blew a pair during high-power testing and had them replaced in about 20 
minutes.  


Virgil has made the difficulty of the build selectable as well.  You can get a 
full set of toroids from Virgil or from thetoroidguy at earthlink.net, and you can 
also get all the cables pre-made.  Buying all of the cables and toroids makes it 
an easy kit.  Doing it all yourself makes it an intermediate level kit.  There 
is one surface-mount IC that is already installed on the board.  The boards are 
high quality.  The case is provided and is very rugged.  It's a cool kit and a 
great amp for when you don't want to be QRP.  


I have no relationship with this company whatsoever.  I just like this kit!    

The amp page is at 

http://www.hfprojectsyahoo.com/hf-packeramp.html

there is a yahoo group at

hfprojects at yahoogroups.com


Virgil provides excellent customer support, very impressive.  He is constantly 
tweaking improvements especially with the manual and builders tips.  Sound 
familiar? 

73

Eric WD6DBM   .