#334

This video shows how to tune a 1.2GHz repeater duplexer using a NanoVNA V2plus4. A TX/RX Systems Vari-Notch duplexer is used in this video. One interesting question - does the NanoVNA V2plus4 have enough dynamic range to accurately tune the filters - particularly the notch / band-reject filter sections? I check the results using a more professional VNA - the Tektronix TTR506A. A brief description of the function of the duplexer is given, followed by the setup and calibration of the VNA, and then the tuning process.

SPOILER ALERT:
The NanoVNA V2plus4 seems to have enough dynamic range to properly tune the duplexer if you take your time to optimize everything. Based on this, I would say that the original NanoVNA (-H, and -H4) would not have a low enough noise floor in the S21 measurement to properly align the notch filter sections.

Table of Contents:
00:00 - Introduction - what is a Duplexer
01:27 - What are we going to show?
01:55 - NanoVNA setup and calibration
04:59 - Hooking the VNA to the Duplexer
05:52 - Transmit / high-side initial results
06:35 - Receive / low-side initial results
07:37 - What is our new target for tuning?
08:11 - The general tuning process for this Vari-Notch duplexer
09:00 - Getting started on the tuning - moving the low-freq bandpass filters
11:02 - Tuning the Notch filters on the transmit side
12:13 - Return to receive side and tune the notch filters there
13:10 - Checking the results on the TTR506 VNA
14:55 - Summary