A VHF 50-ohm Dummy Load is a basic test and measurement tool for developing high frequency radio transmitters, feedlines and antennas. Not all resistors are created equal and high frequency parasitic inductance and capacitance can distort your RF measurements. Build an inexpensive VHF 50-ohm Dummy Load from a BeO (BerylliumOxide) resistor and some scrap shop materials.
The “front panel” is formed from a rectangle of printed circuit board (PCB) material and a SO-239 UHF radio connector.
I purchased this BeO resistor for $6 at my local surplus electronics recycler. It is mounted on a salvaged heatsink. In practice, power dissipation is only limited to heatsinking ability. I’ve tested 100W, at least intermittently, for 15 sec.
My poor soldering technique lead to an abrupt impedance discontinuity at the VHF connector. Nevertheless, S11 performance for frequencies up to 300 MHz is tolerable.
From 1MHz to 300Mhz, S11 insertion loss (reflection) is minimal (~1.2)
Conclusion
50-ohm Beryllium Oxide resistors are rated for up to 30GHz frequency bandwidth. Using a different resistor form factor (surface mount) and better soldering technique you can build a high performance 50-ohm dummy load for almost any radio frequency situation.