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...
>

>

> 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.

Wanted: 10GHz SMA Isolators

Chris Bartram G4DGU <chris@...>

Hello All,

I'm looking for a couple of small 10GHz ferrite isolators for a new WG input LNA I'm working-on to replace my 2011 design. Does anyone have any they'd be prepared to sell me at a sensible price?

Chris

G4DGU

Re: A quick lashup 2.3 to 3.4 GHz horn

KENT BRITAIN

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...

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.

Re: A quick lashup 2.3 to 3.4 GHz horn

Alan Beard

Hi all,

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

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.

Re: QO-100

Andy G4JNT

Not sure I do either - in the traditional    2.D²/λ   sense
But when the transmitter is not a point source (not diffraction limited, I think, in optical terms)  there must be some name for it.
The sun is 0.6° wide, so any antenna beamwidth narrower than that gets 'interesting'

Andy

On Sat, 5 Jun 2021 at 20:17, Dave G8KHU <david@...> wrote:
<< ...in the sun's near field. >>

Not sure I completely agree with that Andy.

If the sun is a single source driving a sun diameter antenna, then yes indeed.

If you consider the sun to be an enormous array of coherent radiaters, then again yes.

However if the sun is considered as an enourmous array of non-coherent, independant small radiators then wouldn't the effective near/Fresnel/far field boundaries would be determined by the geometery of the individual radiator rather than the array geometry?

Dasve G8KHU

Re: dish positioning?

steve G1PPA

Hi Ben
That's what I use with simple switch to reverse polarity 12vdc set your the centre to 0deg then
You have equal throw either side , it was suggested to me by G8DMU and it works very well
Cheers steve
G1PPA

On Sat, 5 Jun 2021 at 20:47, militaryoperator via groups.io
<Military1944@...> wrote:
Thinking on what someone said I was trying to figure out how to nod the dish up and down to get the best signal. In my case it needs to be very light as its manually raised. I was trying to think about a spring-loaded arrangement and to simply have a cord over a pully coming down the mast which I simply pull on the nod dish dow, releasing it will nod dish back up due to spring.

or.... ebay 124219350197

The smallest one has 2inch movement which would be more than enough but can't see it it can be nudged in and out or its either fully in or fully out.

What do others use for nudging their dishes?

Ben
--------

ps:   This one, 124267700578 has a 1inch stoke which should be adequate? I'm assuming its a dc motor, reverse the polarity on leads to get in and out?

Re: dish positioning?

militaryoperator

Thinking on what someone said I was trying to figure out how to nod the dish up and down to get the best signal. In my case it needs to be very light as its manually raised. I was trying to think about a spring-loaded arrangement and to simply have a cord over a pully coming down the mast which I simply pull on the nod dish dow, releasing it will nod dish back up due to spring.

or.... ebay 124219350197

The smallest one has 2inch movement which would be more than enough but can't see it it can be nudged in and out or its either fully in or fully out.

What do others use for nudging their dishes?

Ben
--------

ps:   This one, 124267700578 has a 1inch stoke which should be adequate? I'm assuming its a dc motor, reverse the polarity on leads to get in and out?

dish positioning?

militaryoperator

Thinking on what someone said I was trying to figure out how to nod the dish up and down to get the best signal. In my case it needs to be very light as its manually raised. I was trying to think about a spring-loaded arrangement and to simply have a cord over a pully coming down the mast which I simply pull on the nod dish dow, releasing it will nod dish back up due to spring.

or.... ebay 124219350197

The smallest one has 2inch movement which would be more than enough but can't see it it can be nudged in and out or its either fully in or fully out.

What do others use for nudging their dishes?

Ben

Re: QO-100

Dave G8KHU

<< ...in the sun's near field. >>

Not sure I completely agree with that Andy.

If the sun is a single source driving a sun diameter antenna, then yes indeed.

If you consider the sun to be an enormous array of coherent radiaters, then again yes.

However if the sun is considered as an enourmous array of non-coherent, independant small radiators then wouldn't the effective near/Fresnel/far field boundaries would be determined by the geometery of the individual radiator rather than the array geometry?

Dasve G8KHU

Re: UK Microwave OPs - Digest #264

Andy G4JNT

Andy

On Sat, 5 Jun 2021 at 15:31, Chris Bartram G4DGU <chris@...> wrote:

Andy,

If it's the same as the one I have, and it looks suspiciously like it, I
have the manufacturer's data sheet on that horn ...

Let me know if you'd like it.

Chris

G4DGU

Re: UK Microwave OPs - Digest #264

Chris Bartram G4DGU <chris@...>

Andy,

If it's the same as the one I have, and it looks suspiciously like it, I have the manufacturer's data sheet on that horn ...

Let me know if you'd like it.

Chris

G4DGU

Re: QO-100

Andy G4JNT

An instinctive feeling is nagging me that the fraction of the sun in the antenna beamwidth doesn't matter when working things out this way.   But it's hard to quantify why, except that using a solar flux density and an antenna aperture assumes nothing about the source, and that it's ideally a point source

SO applicable to small antennas, but what about narrow ones which are , to all intents and purposes, in the sun's near field.
(I know that sounds a bit daft at first sight, but think about it)

Andy

On Sat, 5 Jun 2021 at 13:59, Andy Talbot <andy.g4jnt@...> wrote:
I'm also puzzled as to how that can work with arbitrary antenna beamwidth
If the beamwidth is much larger than the sun's disc diameter then only a portion of the solar flux is contributimg,  A very narrow beamwidth, ie << 0.6° will see all the  sun

I shall go and sit in the garden and either :

A) Try to work it all out from first principles   or
B)  Realise the grass needs cutting and really ought to be doing that instead

Andy

On Sat, 5 Jun 2021 at 13:02, Andy Talbot <andy.g4jnt@...> wrote:
I can't make that G/T equation work with your values.
What is  k   ?

And I assume it should read
G/T = 10 * log [ 4 π k (10^(N/10) - 1) / ( λ^2 S) ] . dB/K

Andy

On Sat, 5 Jun 2021 at 12:36, Mike Willis <willis.mj@...> wrote:
Forgot to add, if the transmitted noise power is roughly the same as the solar flux that gives a handle on the gain of the transponder once you do the link budget taking into account the distance, the G/T and the bandwidth.

--
Mike G0MJW

Re: QO-100

Andy G4JNT

Worked out the equation from first principles now, and it gives the same as Mike's example

k is Boltzman's constant, 1.38E-23
and S in the equation is the actual solar flux in Watts per m^2/Hz,  not the S(f)  from the first equation

Andy

On Sat, 5 Jun 2021 at 13:59, Andy Talbot <andy.g4jnt@...> wrote:
I'm also puzzled as to how that can work with arbitrary antenna beamwidth
If the beamwidth is much larger than the sun's disc diameter then only a portion of the solar flux is contributimg,  A very narrow beamwidth, ie << 0.6° will see all the  sun

I shall go and sit in the garden and either :

A) Try to work it all out from first principles   or
B)  Realise the grass needs cutting and really ought to be doing that instead

Andy

On Sat, 5 Jun 2021 at 13:02, Andy Talbot <andy.g4jnt@...> wrote:
I can't make that G/T equation work with your values.
What is  k   ?

And I assume it should read
G/T = 10 * log [ 4 π k (10^(N/10) - 1) / ( λ^2 S) ] . dB/K

Andy

On Sat, 5 Jun 2021 at 12:36, Mike Willis <willis.mj@...> wrote:
Forgot to add, if the transmitted noise power is roughly the same as the solar flux that gives a handle on the gain of the transponder once you do the link budget taking into account the distance, the G/T and the bandwidth.

--
Mike G0MJW

Re: QO-100

Andy G4JNT

I'm also puzzled as to how that can work with arbitrary antenna beamwidth
If the beamwidth is much larger than the sun's disc diameter then only a portion of the solar flux is contributimg,  A very narrow beamwidth, ie << 0.6° will see all the  sun

I shall go and sit in the garden and either :

A) Try to work it all out from first principles   or
B)  Realise the grass needs cutting and really ought to be doing that instead

Andy

On Sat, 5 Jun 2021 at 13:02, Andy Talbot <andy.g4jnt@...> wrote:
I can't make that G/T equation work with your values.
What is  k   ?

And I assume it should read
G/T = 10 * log [ 4 π k (10^(N/10) - 1) / ( λ^2 S) ] . dB/K

Andy

On Sat, 5 Jun 2021 at 12:36, Mike Willis <willis.mj@...> wrote:
Forgot to add, if the transmitted noise power is roughly the same as the solar flux that gives a handle on the gain of the transponder once you do the link budget taking into account the distance, the G/T and the bandwidth.

--
Mike G0MJW

Re: A quick lashup 2.3 to 3.4 GHz horn

Andy G4JNT

Looks a bit like that, but it's smaller
Mouth dimensions (internal)  104 x 69mm

Andy

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

Re: A quick lashup 2.3 to 3.4 GHz horn

SAM JEWELL

To which I add I have a number of the 1.5 -15GHz ones in stock.

Sam, G4DDK

On 5 Jun 2021, at 12:04, Murray Niman <g6jyb@...> wrote:

﻿
You may find that the central ridge/flair ideally needs to extend further to prevent 2.3 cutoff/dispersion and smooth out the impedance change

There is no reason why you cant start by taking one of Kents WA5VJBs flaired pcb vivalidis such as https://www.ebay.co.uk/itm/254170352417  (the hard bit) and then enclose it in a DIY horn surround built from metal or blank fr4 PCB to direct the radiation better

73

Murray G6JYB

Re: A quick lashup 2.3 to 3.4 GHz horn

Tim Hague M0AFJ <m0afj@...>

Looks like a 1-18GHz horn similar to the ETS Lindgren / Emco 3115.

Best Regards
Tim Hague

On 5 Jun 2021, at 12:36, Andy G4JNT <andy.g4jnt@...> wrote:

﻿
Would have helped if I'd attached some photos.

<Vhorn1.jpg>

<Vhorn2.jpg>

Andy

On Sat, 5 Jun 2021 at 12:32, Andy Talbot <andy.g4jnt@...> wrote:
I found this horn in my junk box.   It's been a bit bashed about, and there is no label, but I just tested it's match, and there is something li[ke -13dB RL at 2.4GHz and it changes if I wave my hand around in front, so appears to be working (ish)

Is it reasonable to estimate its gain from the front area, and if so, what sort of efficiency could I expect?
I'm after an antenna of accurately known gain, although it doesn't have to be too much gain,  at 2.4GHz for some QO100 measurements.

And trying to resist constructing one from tin plate.

Andy

On Sat, 5 Jun 2021 at 12:04, Murray Niman <g6jyb@...> wrote:

You may find that the central ridge/flair ideally needs to extend further to prevent 2.3 cutoff/dispersion and smooth out the impedance change

There is no reason why you cant start by taking one of Kents WA5VJBs flaired pcb vivalidis such as https://www.ebay.co.uk/itm/254170352417  (the hard bit) and then enclose it in a DIY horn surround built from metal or blank fr4 PCB to direct the radiation better

73

Murray G6JYB

Re: QO-100

Andy G4JNT

I can't make that G/T equation work with your values.
What is  k   ?

And I assume it should read
G/T = 10 * log [ 4 π k (10^(N/10) - 1) / ( λ^2 S) ] . dB/K

Andy

On Sat, 5 Jun 2021 at 12:36, Mike Willis <willis.mj@...> wrote:
Forgot to add, if the transmitted noise power is roughly the same as the solar flux that gives a handle on the gain of the transponder once you do the link budget taking into account the distance, the G/T and the bandwidth.

--
Mike G0MJW

Re: QO-100

Mike Willis

Forgot to add, if the transmitted noise power is roughly the same as the solar flux that gives a handle on the gain of the transponder once you do the link budget taking into account the distance, the G/T and the bandwidth.

--
Mike G0MJW

Re: A quick lashup 2.3 to 3.4 GHz horn

Andy G4JNT

Would have helped if I'd attached some photos.

Andy

On Sat, 5 Jun 2021 at 12:32, Andy Talbot <andy.g4jnt@...> wrote:
I found this horn in my junk box.   It's been a bit bashed about, and there is no label, but I just tested it's match, and there is something li[ke -13dB RL at 2.4GHz and it changes if I wave my hand around in front, so appears to be working (ish)

Is it reasonable to estimate its gain from the front area, and if so, what sort of efficiency could I expect?
I'm after an antenna of accurately known gain, although it doesn't have to be too much gain,  at 2.4GHz for some QO100 measurements.

And trying to resist constructing one from tin plate.

Andy

On Sat, 5 Jun 2021 at 12:04, Murray Niman <g6jyb@...> wrote:

You may find that the central ridge/flair ideally needs to extend further to prevent 2.3 cutoff/dispersion and smooth out the impedance change

There is no reason why you cant start by taking one of Kents WA5VJBs flaired pcb vivalidis such as https://www.ebay.co.uk/itm/254170352417  (the hard bit) and then enclose it in a DIY horn surround built from metal or blank fr4 PCB to direct the radiation better

73

Murray G6JYB

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