Australian Ham Radio Discussion Forum ( AHRDF )

Hi all,
We're all 'Jack Of All Trades" right, and duplexers, particularly for 2m are a problem....
Here is a surplus UHF set from a VK5 site, yes 3/4 wave @ 70cm, perfect for 2m


Using commercial surplus gear is "our speciality".
Coupling loop progress:
Higher freq pass

[b]Lower freq pass[/b]
TNC connectors because two N connectors won't fit in the cavity access hole.
I can only get 32db notch depth with a single N and the series loop and cap design.
The above do 35db or so. (measured by my Wiltron 640)
See: http://www.repeater-builder.com/projects...earch.html
===== Now here's the tricky bit ==============
Notice my coupling loops have a Large Area and a two & half turn loop.

"Why is it so?"  -- Julius Sumner-Miller

It makes it so so much easier to adjust the pass-to-notch spacing.
[b]Where is this discussed anywhere else?[/b]
Yes, I'd like to know.
All this "trade secret" stuff was done th the 60s and held tightly in company libraries.
I had a Decibel Products UHF cavity set, I want to see the innards!!
Alan VK2ZIW

At the WIA AGM in the Gold Coast, a presentation on Duplexers was made.

I was not there. It highlights the need for REAL expertise.

I've been working on a web page of "Basics". Yes, there are different types of cavities
and within the BandPass AND notch cavity group, there are different methods.
What do WE need to know in using them?
http://www.unixservice.com.au/hamradio/r...asics.html
Alan VK2ZIW

Some more progress on use of Magnetic Coupling

Pass then Notch, 2x 195mm x 2mm wire 14mm ID coil
and a scan


============ swap the pass and notch ============

Notch then Pass 2x 205mm 2mm wire 14mm ID coil (AA battery)

Another build, is it repeatable...

What about a wider view to see attenuation of local signals...

And Phase to guage line lengths to antenna Tee...

HOWZAT - Alan VK2ZIW