On Feb 4, 2005, at 1:12 AM, Paolo Cravero as2594 wrote:
I'd like to remind you a simple study I made on two
100ohm 5W resistors found in a PC monitor PSU.
See (part
of the page is in Italian, ROS=SWR in tables)
Basically those "inductive" resistors can be used to form cheap QRP *HF*
dummy loads, with SWR <1.3:1 at 30MHz.
I installed my RF voltage probe on that load, and that is the way I
measure (ehm, estimate) my circuits' output power.
A wonderful idea!
I suspect that if you wired the resistors in parallel on a 50-ohm stripline PC board with the connectors X-ed on opposite sides of the board, you could cancel out a lot of the inductance. It would also be theoretically possible to add a variable capacitor to cancel out the inductive reactance and get a higher usable frequency at lower SWRs, at the penalty of making the load frequency-dependent.
An indexed dial for the variable capacitor would fix that. If it were a fixed-frequency load. tune it once and forget it.
Jim N6OTQ
