Hi Simon,
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Mabe it's possible with later generation analysers that have a greater dynamic range, but most stuff available to hobby users isn't going to cut it.
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I have a HP8563E, but it hardly gets turned on, as apart from the frequency coverage to 26GHz, it's not that much use for everyday stuff.
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My tone sources are two crystal oscillators followed PA's and then by attenuators, individual absorptive band pass filters, a high power combiner and yet another attenuator, all built into a standalone box. I start off with 5w of RF and end up with 100mW at the output. The mini-Circuits combiners that are normally specified start to generate their own IP's at around +10dBm, and standard band pass filters don't present a 50 ohm match outside their passband, which can affect the generation of IMD products.
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Even with this, and a decent set of notch filters, I have difficulty making repeatable IMD measurements, mainly because of leakage and minor phase shifts that affect the generation of IMD. It's hard enough at HF frequencies, and having in the past measured passive IMD, produced in cellular antennas, I know how much more difficult that can be.
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You read the application notes from folks like Aligent / Keysight, and they make the test setup it looks easy, but at least for me, in a home workshop, it wasn't that straight forward.
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However, I'm prepared to accept that your mileage may vary...
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Regards,
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Martin
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On Mon, Oct 14, 2024 at 06:29 PM, rfsam wrote:
One just need a good "Big Box" Spectrum Analyzer (HP/Agilent/Keysight) with good LowPIM attenuator in front of it.
