Re: Retuning a 23cm duplexer, any hints please?


Alan Beard
 

Hi all,

Thomas Eddison 'tinkered' until the breakthrough...

The figure of 8 loop did the trick.


Where are the 'tinkerers' out there????

I've achieved a super steep slope on the high side of a pass, now
to see if I can get another super steep slope on the lower frequency 
side of the high pass. 

Come on guys, where's your imagination?

Alan VK2ZIW

On Tue, 6 Apr 2021 07:44:42 +1000, Alan Beard via groups.io wrote
> Hi all,
> Here are my mods to this 1800 MHz duplexer so far:
>
> > www.unixservice.com.au/hamradio/repeaters/duplexers/23CMpix/
> IMG_3809c.JPG
> Tuning is now much easier with the M3 screws further out, out from the 4mm ID tube.
>
> My next question is:
>
> Can the inter-digital filter be made BandPass and BandReject?
>
> (as we do for 2m repeaters) (photos, drawings please)
>
> Our 20 MHz split for 23cm repeaters is pretty tight.
>
> I see nothing on the web.
>
> Alan VK2ZIW
>
>

>
>

> On Sun, 4 Apr 2021 22:05:14 +0000 (UTC), KENT BRITAIN wrote
> > Interestingly the 3rd harmonic is not exactly 3X the 430 MHz frequency, but close.
> > Often easier to do the first tuning at the 430 MHz frequency,m then fine tune at the 23 cm frequency.
> >
> > Quite often we see the 450 MHz filters from commercial mobile radios surplus.  Most of those tune 23 cm as well.   Good luck with your project,  Kent WA5VJB/G8EMY
> >
> > On Sunday, April 4, 2021, 4:43:42 PM CDT, Alan Beard via groups.io <beardal@...> wrote:
> >
> > Thanks Kent,
> >

> > We have a "parrot" 23cm repeater over in the Wollongong area and changing it to Full duplex will require
> > cavity filters. I acquired this one, at a good price a few years ago. Perhaps spares never used.
> > Using 70cm cavities in 3rd overtone is a great idea. 
> >

>
> ---------------------------------------------------
> Alan VK2ZIW
> Before the Big Bang, God, Sela.
> OpenWebMail 2.53, nothing in the cloud.
>
>

---------------------------------------------------
Alan VK2ZIW
Before the Big Bang, God, Sela.
OpenWebMail 2.53, nothing in the cloud.

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