Re: A quick lashup 2.3 to 3.4 GHz horn


Alan Beard
 

Thanks Kent,

Can you do a Return Loss plot to determine if the feed impedance is 50 ohms?

I can readily get the gap to between 1 to 2 mm witch surely is close enough for the 4GHz 
or so maximum frequency I intend to use with my HackRF One.

It's a practical thing. I can cut with tin-snips a smooth curve. But to fold metal to simulate
a thicker piece, I cannot achieve a curve, only a straight edge as you see in my image
in the previous email.
From:
https://www.slideshare.net/mariasheebap/ridge-guide
 
My thought, using a very thin ridge puts the  a2/a1 down at 0.01 where the graph becomes obscure.
And the impedances get high.

If the ridge were 1/5th the waveguide broadface width and the  gap was 1/20 the waveguide narrowface,
the impedance would be around 50 ohms. (for their 0.7 a/b waveguide)


And, looking at a Return Loss plot of a 1 - 18 GHz, it was not that good, around 10 to 15db.
With those results, I'm putting my horn on my antenna pole and giving it a go.

Alan VK2ZIW
 


On Sat, 5 Jun 2021 23:05:42 +0000 (UTC), KENT BRITAIN wrote
> I have perhaps a dozen Ridged horns of different sub-species.
>
> Most have a ridge several millimeters wide.
>
> But my 1-18 GHz one has the ridge ground to a fine edge along the top.
>
> I think the fine edge helps the upper frequency limit.   How close you can make the 
> gap between the top and bottom ridges has a major effect on the upper frequency limit of the antenna.
> Kent.
>
> On Saturday, June 5, 2021, 05:13:38 PM CDT, Alan Beard <beardal@...> wrote:
>
> Hi all,
>

> Thanks guys for the pictures of commercial wide band horns but...
>

> Can somebody answer the question please?
>

> The ridge thickness, can it be thin, one sheet of sheet metal, say 1mm ?
>

> (Just like the Vivaldi)
>

> Does this affect the feed impedance?
>

> Here is my SAAV2 scan.
>

> Alan VK2ZIW
>

>

> On Sat, 5 Jun 2021 13:31:05 +0100, Andy G4JNT wrote
> Looks a bit like that, but it's smaller
> Mouth dimensions (internal)  104 x 69mm
>
> Andy
> www.g4jnt.com
>
> On Sat, 5 Jun 2021 at 13:16, Tim Hague M0AFJ via groups.io <m0afj=yahoo.co.uk@groups.io> wrote:
>

> Looks like a 1-18GHz horn similar to the ETS Lindgren / Emco 3115.
>
> Best Regards
> Tim Hague
>
>


---------------------------------------------------
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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