hi
Forget about pseudoscience and subjective evaluation. That guy discredits himself with those crazy writings.
For my 75 ferrite bars, 1 feet diameter, giant super ferrite sleeve, I made the costly mistake of using 3mm thick 500 strands of 0.1mm Litz which is optimised for below 200kHz. I got Q near and over 2000 at 100kHz with the DER DE-5000. I will replace the 500 0.1mm Litz by 660/46 in spaced windings. At the moment the Q is poor for MW frequencies., I did measurement using a Q-meter developed by a Chinese Ham Mr Gao. It reads Q=200 at 1.2MHz. I have got the 660/46 Litz from Ming (a crystal radio builder in the USA who also owns an ebay store). Mr Gao's Q meter gives readings are consistent with the De-5000 at similar frequencies. Gao's meter is based on the simple method of ring-down technique that can be done using a scope and a synch square pulse wavelength trigger...you count the number of damped cycles on the scope and work out the Q indirectly. Mr Gao Q meter makes it automatic and is accurate for high Q measurements.
It is very difficult to Q measurement when Q is over 1000. Most cheaper Q-metesr cannot measure Q over 500. I tested the air variable capacitor of my Heathkit Q-meter, it uses aluminium plates and has low Q. The moment you attach a high Q coil to a normal variable air capacitor, the Q drops by 50%. A surefire Q-killer. I am looking for untarnished, silver-plated air variable capacitor for Q measurement.
I will also replace the blue foam core by 2.5 litre HDPE water bottle. The tangent loss of HDPE is lower than high-density blue foam used in aqua dumbells. White PVC pipe has higher tangent losses than HDPE.
In addition, I also got some "magic" R40C12 toroids and bars from Ming. Now this is very impressive. I got the Q reading of over 1200 for two 38mm diameter R40C1 stacked toroids with 270/46 Litz. They got Q over 1400 at different frequencies and winding techniques. I have been playing with different winding configurations; "contra-winding" and space-winding to optimise the Q.
I am waiting to buy the NanoVNA v2 Plus 4 :-*which has a dynamic range of 90db. It is out of stock. I have the NanoVNA V2, its dynamic range is not good enough for Q VNA measurement (using loosely -coupled sniffer coil). The dip is too small for 3db Q measurement method.