After I noticed an add on ebay from some person who was selling HAM use dummyloads made from a SO239 connector and a ceramic 10W wirewound 47 Ohm resistor soldered to it using 4 extra wires. As if they are not inductive enough yet
But I was curious how they would hold for HAM use. So I made some dummies to test.
I hooked them on my VNA and did some sweeps. I made a |Z| sweep, that is the total impedance the transmitter sees, Z split up in R and jX called real Z and im Z, phase, return loss (a better alternativecfor VSWR, around 25 dB is good) and a smith chart. Because scales vary, I made markers for several shortwave HAM bands.
A 50.04 Ohm Ohmite resistor, I have no clue what type it is. Could be wirewound, carbon composite is most times capacitive. Only usable for 160 meters. For the rest it is worthless. Very inductive and as you see down here, it is not the one wire making it inductive.
Three good quality chip resistors, 150 Ohm and 50W a piece. Very usable for HF dummyload. You see on the picture it has rather long wires but you see, that the resistor is more important then the wire attatched.
Although the lightbulb was just for fun they are very usable in real live. Hook a 100W to a tuner and you have a handy visual tuning aid. Above is the reason for this test, a ceramic wirewound resistor. I had no 47 Ohm here so I used a 30 Ohm. A 50 Ohm is probably even more inductive. This is total not usable. It is 29.51 Ohm DC, and allready at 160 meters it is 35 Ohm, that is 18,6% off. It is a bit like the Ohmite one
Two 1% metalfilm resistors. Very usable.