#270: Tune a Duplexer with a Spectrum Analyzer + Tracking Gen or VNA

This video shows how to tune a notch-type duplexer using a spectrum analyzer with a tracking generator, as well as with a vector network analyzer (VNA). It also discusses the basics of what a duplexer is, and a quick review of the most popular types. Notes from the video can be found here:

[waylonk]

Wow, I learned quite a bit from watching this video. The follow-along visual representation was super helpful in understanding what's going on inside a duplexer. I'm grateful to knowledgeable amateurs like yourself for posting videos on complex topics for other HAMs to learn from.

[marcdowns]

I sure wish I had found your channel sooner. I found it while searching for duplexer tuning but then skimmed your channel' s other titles. I'll be spending a great deal of time here. Thanks for all of the great content! KD9PDE

[legionaire]

Thanks for this video, I had hoped to see you prepare both your spectrum and vn anaylyzers to make these measurement (i.e. normalize and set a reference) and also view the traces with different spans. I know a portion of your audience may find this tedious but I'm sure I'm not alone here in my desire to see you explain these processes and narrate the changes to the measurements on the screen. I'm looking forward to your next video, keep up the great work!

[HansVanIngelgom]

I just discovered that they have a 6GHz VNA at my new job, which I now pet and talk sweet words to every morning.
It has one feature that I thought was really cool: just like modern scopes have a fft function that allows you to see a frequency spectrum, that VNA has a inverse fft function that converts your measurement to the time domain. This allows you to see where reflections happen, eg. To me that was mind blowing but it makes perfect sense when you think about it. It has phase and frequency information, all it needs for a transform!

[sneakysnake]

Substantial difference between the two methods. Have never used or seen it done with a VNA. Thanks for the video.

[jnlfd]

I was looking for information because fiplex does not present tuning instructions. It was helpful. Thanks.

[kbsvj]

I wish I had somebody like you who would make me their apprentice. Nice video. 73

[Radiowild]

Great video! I'm sure lots of folks will benefit with you showing us how to tune that filter!

[budokai]

EXCELLENT explanation sir! Thank you. I am assembling a GMRS repeater, and you answered some questions I had.
Rick

[derrick_builds]

Thanks for the video. Just got a VNA last week. This helps a lot.

[billmoran]

Always enjoy your videos! Years ago a Spectrum Analyzer was unobtanium for me at least because of the cost. I guess my bank account just doesn't keep pace with the state of the art. I'd love a VNA, but they are too new to be affordable. I guess I'll live with -90 db. It's still nice to see why the new gear costs big bucks!

[towerman]

Good video, and informative. Keep up the good work.

[stevenwilliams]

Thanks for a succinct and informative video. I would like a list of equipment for reference. I know these videos take time to make as does annotation. Very nice work!

[CamiloMendivelso]

greetings from Colombia!, thanks for the video, well explained!

[californiakayaker]

Wow, excellent. My cheaper VNAs probably do not have that noise floor but I will check. Only have one cavity now, and old, tight, GE blue can.

[TheRadioShop]

Big thumbs up Alan, Nice explanation. Looks like a VNA is my next bit of gear I need to get. As always thanks for sharing your knowledge.

[TheRangerDale]

Nice Video Alan very well explain and having the visuals makes it even better . Thats why I enjoying watching the videos and learning . wish Santa drop off one of those Spectrum Anaylers thats what need to complete the Test bench. 73's Alan

[perdidoanonimo]

Hi Alan, very nice and didactic video, many thanks!. I have an old Spectrum Analyzer (without Tracking Generator) and a Vector-Network Analyzer (the VNWA from DG8SAQ), and it would be great to see an example or learn from you how to combine them both so that the VNA acts as TG for the Spectrum Analyzer... I have found this topic also in several forums, but never found a proper tutorial or explanation on how-to. Again, many thanks for your videos! I am learning a lot.

[nicochio]

Great video, congratulations. I have just a quick question about the improved dynamic range you got with the VNA. It is because your VNA has a higher dyn. range than the spectrum analyser, or is it because the VNA is "intrinsically" better at discriminating low signals?
I am asking because the architecture of a spectrum analyser and of a VNA both appear to me as quite similar, so I'd expect that the dynamic range of the VNA is due to some better performance of its internal components, for instance : more bits in the ADC, lower noise, improved LNA.

[saintfather]

I connect HIGH and LOW with VNA and tune the HIGH part for max attenuation. I have to make sure that transmitter signal(from LOW) has max attenuation, coming to the receiver(connector HIGH). When I tune transmitter I connect ANT and LOW and tune it for min attenuation. Because power of tranmitting signal is more inportant than isolation between ANT and LOW on receiving frequency. Doesn't matter if receiving signal -30 and lower dBm comes to the transmitter. So when I did my last duplexer I tuned attenuation between LOW and ANT just 10 dB, but I got the max output power. What do you think?