Using the spectrum analyser as a dipmeter
For a long time I never had the need to have a dipmeter for HF and VHF. This changed in recent years with my activity on the lower bands.To see the resonance frequency of a LC or a coaxial trap I borrowed the dipmeter of my friend Jack PE1KXH. It did his job but in a way that resonances were not clearly visible. The “dips” were rather small. Jack remembered a way to use the spectrum analyser and the sweeper as a dipmeter. It was rather simple!
First one had to make a few coils on a BNC connector.
If the frequency coverage is OK you can use the same spectrum analyser / sweeper set-up. If you couple the inductors then you get a more or less straight line:
If you couple these inductors to a LC combination you get the following result: On the photo a LC parallel resonant on 7 MHz.
Resulting in the following picture on the analyser
The same but now for a coaxtrap for 80M made out of PTFE coax:
The result is much more precise than the rather old fashioned dipmeter.