I'm currently working on a home-brew HF transmitter. I have everything working like I want, but before I take it OTA, I want to measure the spurious products that it generates. I don't have a (real) spectrum scope or any real LMR-grade bench gear. So I'm looking for a way to make sure the transmitter is within Part 97 specs for spurs. My first thought was to use an SDR, and measure the carrier level shown in the waterfall, then move to each of the spurs and measure them similarly. The SDR software I'm using (GQRX) shows the waterfall in dB, so this seemed like a good (if slow) way to do a quick verification. So I tied the SDR to the transmitter through a "T" connector and a big attenuator; the other end of the "T" is a 50-ohm load resistor. This setup allowed me to use the SDR to watch the transmitter output without smoking the receiver. But even with the SDR in a completely metal case, it is picking up energy from pathways other than just the antenna cable. I'm guessing through the USB wires and just general proximity to the transmitter. So I don't completely trust the signal levels I'm reading to be an accurate representation of what will actually make it to the antenna if I take it OTA. Do any of you have words of wisdom on how to measure the carrier level and each of the spurs, without having to find somebody with an HP spectrum scope?