I got a comment that recommended this RF BRIDGE 0.1 – 3000 MHz from http://www.transverters-store.com/rf_bridge/rf_bridge.html. It looked really interesting as I was planning to build something similar myself. The price was very reasonable ($10) so I had to test out it. Did the ordering, and quite quickly I received a letter from Ukraine that contained this:
Here is the device:
Here is circuit diagram from the product page:
Here are two pictures: First is output terminated to 50 ohms and second with 450 MHz antenna connected to RF bridge output
Those measurements show that this RF bridge can be used successfully for antenna measurements. It gives quite similar performance than my previous measurements with directional coupler. The advantage of this bridge is that this can be used to measure matching other impedance than just 50 ohms – just use a suitable reference against which you want to compare matching (it can be 75 ohms resistor or something mote complicated). Based on this tests the RF BRIDGE 0.1 – 3000 MHz from http://www.transverters-store.com/rf_bridge/rf_bridge.html seems to deliver what it promises.
Here are some measurements on RF bridge with Rigol spectrum analyzer tracking generator up to 1.5 GHz. Those small grey adapters on the SMA connectors you see on the pictures are 10dB and 20dB 50 ohms attenuators that I use as close to 50 ohm terminator in this quick measurement…