Re: A quick lashup 2.3 to 3.4 GHz horn


KENT BRITAIN
 

Hi Alan

Most of these horns are used on my antenna range and have Network Analyzer S11 and Gain tables laminated on them.   Yes, they work nicely in 50 Ohm systems.

Traditionally on an exponentiation Slot or Vivaldi antenna the feed point was 1/4 wave in front of a short.
Later is was learned that replacing the 1/4 wave slot with a circle greatly broadened the frequency response of the antenna.     As for the ridges themselves.   The size of the opening determines the lowest frequency they will work at. How close you can position the slots determines the highest frequency.   Basically it's the structure behind the feedpoint that is helping to set the impedance.

Kent

PS  I like to think to the Vivaldi antennas as a ridged horn without the horn! hihi

On Sunday, June 6, 2021, 04:32:47 AM CDT, Alan Beard <beardal@...> wrote:


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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