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I have a non-functioning transmitter for a radar I've built. When I was checking for shorts using a multimeter, I noticed that the resistance measurements between RFin and GND and RFout and GND of my power amplifier (SE5004L) were practically 0 (about 0.8ohm). The datasheet specifies that these ports are matched to 50ohm. I thought I might have damaged the device during soldering so I performed the same measurement on a brand new SE5004L and got the same result. Moreover there is no short between the voltage supply pin and GND (confirmed when hooked up to 5V as well). Am I faced with two bad chips, or is the measurement I'm performing flawed, or does this result somehow make sense?

If the chips are bad, how do I prevent this sort of thing (especially considering one of the chips is fresh out of the packaging)?

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enter image description here

From the datasheet.

Figure 1 suggests that there is a low impedance path to ground on both the input and output. Have a look at the PCB and see if there is an inductor close to the input and output ports. You may be able to trace the path from the connectors to verify that this is the cause of your low DC resistance "problem".

The inductors will present a high impedance to high frequencies and so will not affect RF.

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  • \$\begingroup\$ There aren't any external inductors hooked up, could they be internal? \$\endgroup\$ – MattHusz Feb 23 at 0:29
  • \$\begingroup\$ I am not familiar with the device and assumed that it is a ready-built module. If it is just a chip then there will not be inductors inside as these can't be integrated on the chip. I recommend that you un-accept my answer for a day or two to encourage other more insightful answers. Then pick the one that best answers your question. \$\endgroup\$ – Transistor Feb 23 at 9:09

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