The way Wilkinson combiner works is very intriguing. It basically uses quarter wave transformer with a 100 ohm resistor across the port 1 and 2. It works in both even and odd modes (180 degrees out of phase) so that the two parallel transmission lines are balanced with zero potential across the two input ports and hence it achieves good isolation, it is a narrow band device with low loss:
https://rickettslab.org/bits2waves/d...ry-and-design/
I am looking into building the IF stages for the 6-gang tuner. Having seen Nelson Jones article in WW 1971, I am toying with the idea of having the design using three crystals and a 5-pole Cherbysher 10.7MHz LC filter (see attached block diagram).
The CA3035 is an early form of IC having the gain of about 20db. It can be used either in cascode or long tailed push-pull configurations as IF amp. The main advantage is that they have less feedback capacitance enabling it to be stable with good gain. In the IF amp with simple BJT and transformer, there is a tendency to oscillate and some form of neutralization is needed when it happens.
I prefer 280khz wide band crystal for the best MPX fidelity. Looking at the Murata datasheet, it has 330ohms I/O impedance. So I built a simple test jig using LC reactive matching pads using 3/6db attenuators on both ends. I did the sweep the Nanovna V4 plus 4. It hits the center of the Smith charter at the centre exactly at 10.7MHz. It shows that LC matching pad is a narrow band device only works at a specific frequency.
According to the manufacturer web site, we cannot use the NanonVNA V2 plus 4 to measure crystals. So i dont know how much it affects my measurement attached. When i connect the output of the V4 plus 2 to my scope, it shows pulsating waveforms which indicates rapid switching on and off to generate higher harmonics? My NaonVNA F V2 has started to malfunction unfortunately.
It generates continuous waveforms that is more suitable for crystal measurements. I think the cheapest original version of the NanoVNA is more suitbale for crystal measurements as well.