John Portune, W6NBC, on Cavity Duplexers

John Portune, W6NBC, spoke to W6SD about how Cavity Duplexers are used in ham radio repeaters, along with the details of how they work, how they are tuned, and the physics behind these vitally important but often unfamiliar devices.

[@rubidiotesla4458]

Such a complex subject for lay people like me, but master Jhon Portune, with his mastery, managed to convey the content in a simple and motivating way.

[@rubidiotesla4458]

I lack words to thank the attention that Mr. Jhon Portune gave me when I sent him some questions by email. I want to say that it was through his book that my interest in understanding the operation of a duplex filter was awakened.

[@bobcat_the_Lion]

Thanks for the explanation John. I always wondered how they could have a transmitter and a receiver with only 600 kHz separation on the same antenna. Yes, they told me that they used cavity duplexers, but somehow it was a mystery to me how they worked.
73 de Johan, PA3BVB

[@PowderMill]

Thanks again… it’s been close to 2 years since I originally discovered this great video.
Even during Covid.1.0, I still managed to get a few repeaters completed and installed for friends running GMRS and HAM repeaters.
This video is my “go to” when trying to explain the function of the duplexer.
So.. thank you again.

[@rubidiotesla4458]

Hello,
What would "L & C" be used in the presentation, around 17:30 by the master, Jhon Portune?

[@PowderMill]

@@rubidiotesla4458 I’m pretty sure he’s referencing “Inductance” and “Capacitance”.

[@mikesradiorepair]

Excellent presentation. The only thing I would recommend is not using those cheap little VNA's to tune a duplexer. They do not have enough dynamic range to accurately tune a duplexer. You will loose 30dB or more in performance due to the poor dynamic range of those little Chinese VNA's. If you plan on tuning a lot of duplexers or building your own save up and get a relatively cheap spectrum analyzer with a tracking generator. The Chinese made (Siglent and Rigol for example) SA's have adequate dynamic range for the job.

[@PowderMill]

Hi. Ike…
I really miss your videos and channel!
I hope all is well…
Thanks for years of knowledge.

[@sureshv8823]

Excellent from a practical genius 🎉! Thanks 🙏 a lot sir

[@rubidiotesla4458]

Are the cavities the tubes, in this case, four were used?

[@rubidiotesla4458]

Cavity is a part of the duplexer?