This dry dummy load has been designed to provide constant 50 Ω impedance to a radio transmitter to allow off-air tests and experiments.
The coaxial construction creates a load that presents a more stable resistance to the transmitter output over a wider range of frequencies, testing has shown the following SWR measurements using a nanoVNA, +/-:
3.8 MHz – 1.01:1
7 MHz – 1.02:1
30 MHz – 1.05:1
50 MHz – 1.12:1
70 MHz – 1.22:1
145 MHz – 1.50:1
433 MHz – 1.70:1
Constructed from high quality PCB material and using 20 x 1 KΩ 2 Watt Metal Film or Carbon Film resistors (see photos) the dummy load while air cooled is capable of absorbing RF energy of 40-50 Watts continuously for 1 minute, and up to 100 Watts for several seconds. The load can also be mounted in a can with oil for longer use at 100 watts.
Connection to the dummy load is via a high quality SO-239 UHF Connector mounted on the PCB.
Overall dimension is: 50 mm diameter.
Weight: 100g
Cost: 15USD
