BH2RCG 1:1 Choke Balun on the VNA

I recently purchased a 1:1 choke balun from Aliexpress. Voltage-mode 1:1 baluns are very common on the site, and it is quite hard to find a current-mode balun (choke). I managed to find a current-mode balun. The pictures and description in the listing described it as a current mode balun and also watertight. I've put it on the VNA to measure its common mode attenuation.

 

 

Before putting it on the VNA, I opened the enclosure and took a look inside. It appeared as per the listing on Aliexpress.

 

 

It has coax wired cross-over style around the toroid core. For chokes that don't have to deal with high voltages (i.e. for dipole antennas, not for doublet antennas), I'm a big fan of winding coax around the core, as it preserves the 50Ω characteristic impedance of the system.

The enclosure is also partially filled with an epoxy resin as a waterproofing measure. The resin is very hard, and concentrated around the connector and terminal ends.

For measuring the common mode attenuation, I used my usual VNA setup. 

 

 

The insertion loss, resistance, and reactance curves look quite different to the 2643251002-based choke.

 

  

The resonance up around the 80 MHz region (not pictured). At the high end, the resistance is greater than the reactance at around 20 MHz of 873Ω.

 

 

At the 40m band, common mode attenuation is 27dB, and the resistance is 1.6kΩ. The curve of the traces indicate better performance down to 1MHz.

The measurements indicate performance not as good as the 2643251002-based choke, however my opinion is that it has good enough performance for 40m and below, but is also well built and watertight.

 

If you'd like to purchase one yourself, here is the Aliexpress store I bought it from: https://www.aliexpress.com/item/32815205477.