[Elecraft] RF Hash from IBM Laptop

[Bob Tellefsen]

Hi don
I have two laptops here, and both can be run from an external battery
source.
HOWEVER, I need to run them through a small inverter to bring the
voltage up to around 13.8v.  I checked this with my variable
voltage bench power supply to find out where the laptop switched
from external power to internal.  It is usually above normal
battery voltage by 1-2 volts, hence the small inverter.

I built the one from Sam Ulbing, N4UAU.  It was written up in QST
as "My All-Purpose Voltage Booster".  He sells the kit for a very
reasonable price.  You can find him on the web under his call.

 I used mine on Field Day, and it was extremely quiet.  Not a trace of hash
anywhere.  A side benefit in running on batteries in the field is that the
converter is regulated.  As the input voltage drops, the output stays
pretty near constant.

This would not be a problem in the shack with a fixed supply.  I suggest
you check your laptop using a variable voltage power supply and find
out how low you can go before it switches over to the internal battery.

Good luck and 73
Bob N6WG