I'm trying to learn about PLC (I know the risks), so I want to start with the simplest circuit specified in the LM1893 datasheet to use on 220v AC powerline.
The transformer there doesn't have any specs, how can I choose a suitable transformer for that purpose?
Electronic – What are suitable transformer specs to use with LM1893 PLC modem
power line communicationtransformer
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Look for something called a Line Impedance Stabilisation Network, or LISN. You'll find a circuit diagram for it in MIL-STD-461.
It's essentially a diplexer, a high pass filter for signals above a few kHz, and a low pass for the mains current at 50/60 Hz.
The Stabilisation part of it is that it isolates the circuit under test from the (presumably very low, and unknown) impedance of the mains supply.
In your case you'd turn it around and use it to isolate the load, and feed the RF into the mains.
I don't think the LISN goes as high as 500 MHz, but up there the mains impedance is irrelevant. You can just disconnect the power and test it directly with your equipment. To be thorough, try a few different power extension leads on the power strip, to get an idea of the range of values you can expect in practice.
I assume that the applied voltage must be somewhere near the 50/60 Hz rated voltage. That means that the maximum flux density Bmax will be a lot less than rated. This is a toroid transformer that is described as "low loss." The leakage inductance should be low because of the toroid construction.
Here are some notes re: losses:
Best Answer
fig.7 on p.9 in the datasheet shows recommended transformers.
Notice also that LM1893 itself is obsolete (watermark in the datasheet).