[G0HZU_JMR]

Good work! My TR4172 also suffered a microstrip failure in the attenuator section.

If you do experiment with the impedance mode, turn down the CRT brightness first. Otherwise, it can draw a pin sharp stationary dot on the smith chart that can be frighteningly bright. However, I've not burnt the CRT on mine so maybe it is fairly immune to burn. The calibration process for the impedance mode is quite clunky and time consuming but on the few occasions I tried to use it, the performance was much better than I was expecting. However, I think a modern nanovna is going to be easier to use and will usually give much better performance for impedance measurements.

I spent many years using this TR4172 at work, so I grew quite fond of it. When the chance came to save it from disposal, I bought it from the company for the cost of a small charitable donation. The strongest points of the TR4172 were the second harmonic intercept and the LO phase noise at 100kHz offset. The mixer IP3 was impressive too at about 21dBm across HF and into VHF.

I mainly used it for VHF and UHF synthesiser design back in the early 1990s and also for distortion measurements. The KE5FX plotter software can work with it via GPIB but it is very fiddly to set up on a TR4172 that has the options that mine has. It's not an issue with the KE5FX SW, I think it depends if the TR4172 has the enhanced GPIB capability fitted. No-one at work could ever get this TR4172 to plot with an old school HP plotter but it isn't faulty as such.