How does this POTY antenna work??


Chris Wilson
 

Hello John,

Wednesday, May 19, 2021

Thank you John, Colin and Paul for the explanations of this set up, much appreciated, I now see how it works and understand much better. As a bit of technical eye candy it scores highly, too, in my book :)


Best regards,
Chris 2E0ILY mailto:chris@chriswilson.tv


JF> Chris,
JF> The pic shows a circular patch feed for 2.4GHz , similar to the
JF> POTY type .The N elbow feeds 2.4GHz RF to the patch element .
JF> His site says he uses a 20W PA , so depending on the attenuation
JF> along the TX cable , he should put in a reasonable signal .


JF> My system outputs 1.5W via a 5m run of LDF450 Heliax via an 80cm
JF> offset - that puts my signal at -5dB relative to the Beacons on QO100.


JF> The SMA lead will connect a probe inside the round waveguide to
JF> the downconverter behind the assembly. An LNB is a downconverter ,
JF> in this case a block + antenna .The N elbow plug will carry
JF> downconverted RF and DC to the shack end unit that will supply the
JF> required output RF for the radio in use.


JF> What is interesting to see is the conical horn and rear choke
JF> flange (?) . I would be interested to know what interactions
JF> /pattern distortion occur on 2.4GHz .
JF> Certainly the feed will be more efficient than open ended waveguide at 10GHz .


JF> 73
JF> John
JF> G0API
JF> On Wed, 19 May 2021 at 10:32, Chris Wilson <chris@chriswilson.tv> wrote:


JF>
JF> 19/05/2021 10:19
JF>
JF> I am slowly getting into amateur satellite work and runa 1.8
JF> meter prime focus dish with a POTY antenna for 2.4GHz TX and a
JF> coaxial LNB for circa 10.5GHz reception. I know the LNB down
JF> converts to around 940 MHz using an intermediate frequency.
JF>
JF> I heard a very nice signal from a chap who appeared to know a
JF> lot about the hardware used, so looked him up on qrz.com He was
JF> using a POTY antenna the like of which I have not seen before. It
JF> has a feed horn and appears to feed the RX side without an LNB
JF> directly to a Kuhne down converter. How might that work, I thought
JF> down converters expected a lot of gain from the LNB and an already
JF> down converted signal, to some extent, done within the LNB?
JF>
JF>
JF> I placed a photo of this nicely looking engineered device here:
JF>
JF> http://www.chriswilson.tv/DJ8EI.JPG
JF>
JF> It appears there's no LNB but the RX antenna is inside the POTY tube itself.
JF>
JF>
JF> Thanks for any insight to this newbie!
JF>
JF> --
JF> Best Regards,
JF> Chris Wilson.
JF> mailto: chris@chriswilson.tv
JF>
JF>
JF>
JF>
JF>
JF>
JF>
JF>


Paul Randall G3NJV
 

Beautifully engineered indeed. However that coaxial link from the waveguide to the Kuhne box will introduce loss and thus degrade the rx noise figure compared to what you might get with the more direct connection found inside a typical LNB.

Perhaps someone has done comparative measurements on these two approaches?



Sent from my Galaxy



-------- Original message --------
From: Colin G4EML <colin@...>
Date: 19/05/2021 10:48 (GMT+00:00)
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] How does this POTY antenna work??

The Kuhne down converter does exactly the same job as a regular LNB. It just has a coax input instead of having an integral antenna. That arrangement simply connects an external antenna to it.

It is not really correct to call that a POTY antenna. The POTY is the name of a specific design, not a generic term.

Colin G4EML



On 19 May 2021, at 10:32, Chris Wilson <chris@...> wrote:



 19/05/2021 10:19

I am slowly getting into amateur satellite work and runa 1.8 meter prime focus dish with a POTY antenna for 2.4GHz TX and a coaxial LNB for circa 10.5GHz reception. I know the LNB down converts to around 940 MHz using an intermediate frequency.

I heard a very nice signal from a chap who appeared to know a lot about the hardware used, so looked him up on qrz.com  He was using a POTY antenna the like of which I have not seen before. It has a feed horn and appears to feed the RX side without an LNB directly to a Kuhne down converter. How might that work, I thought down converters expected a lot of gain from the LNB and an already down converted signal, to some extent, done within the LNB?


I placed a photo of this nicely looking engineered device here:

http://www.chriswilson.tv/DJ8EI.JPG

It appears there's no LNB but the RX antenna is inside the POTY tube itself.


Thanks for any insight to this newbie!

--
      Best Regards,
                  Chris Wilson.
mailto: chris@...













John Fell
 

Chris,
The pic shows a circular patch feed for 2.4GHz , similar to the POTY type .The N elbow feeds 2.4GHz RF to the patch element .
His site says he uses a 20W PA , so depending on the attenuation along the TX cable , he should put in a reasonable signal .

My system outputs 1.5W via a 5m run of LDF450 Heliax via an 80cm offset - that puts my signal at -5dB relative to the Beacons on QO100.

The SMA lead will connect a probe inside the round waveguide to the downconverter behind the assembly. An LNB is a downconverter , in this case a block + antenna .The N elbow plug will carry downconverted RF and DC to the shack end unit that will supply the required output RF for the radio in use.

What is interesting to see is the conical horn and rear choke flange (?) . I would be interested to know what interactions /pattern distortion occur on 2.4GHz .
Certainly the feed will be more efficient than open ended waveguide at 10GHz .

73
John
G0API

On Wed, 19 May 2021 at 10:32, Chris Wilson <chris@...> wrote:


  19/05/2021 10:19

I am slowly getting into amateur satellite work and runa 1.8 meter prime focus dish with a POTY antenna for 2.4GHz TX and a coaxial LNB for circa 10.5GHz reception. I know the LNB down converts to around 940 MHz using an intermediate frequency.

I heard a very nice signal from a chap who appeared to know a lot about the hardware used, so looked him up on qrz.com  He was using a POTY antenna the like of which I have not seen before. It has a feed horn and appears to feed the RX side without an LNB directly to a Kuhne down converter. How might that work, I thought down converters expected a lot of gain from the LNB and an already down converted signal, to some extent, done within the LNB?


I placed a photo of this nicely looking engineered device here:

http://www.chriswilson.tv/DJ8EI.JPG

It appears there's no LNB but the RX antenna is inside the POTY tube itself.


Thanks for any insight to this newbie!

--
       Best Regards,
                   Chris Wilson.
mailto: chris@...







Colin G4EML
 

The Kuhne down converter does exactly the same job as a regular LNB. It just has a coax input instead of having an integral antenna. That arrangement simply connects an external antenna to it.

It is not really correct to call that a POTY antenna. The POTY is the name of a specific design, not a generic term.

Colin G4EML

On 19 May 2021, at 10:32, Chris Wilson <chris@chriswilson.tv> wrote:



19/05/2021 10:19

I am slowly getting into amateur satellite work and runa 1.8 meter prime focus dish with a POTY antenna for 2.4GHz TX and a coaxial LNB for circa 10.5GHz reception. I know the LNB down converts to around 940 MHz using an intermediate frequency.

I heard a very nice signal from a chap who appeared to know a lot about the hardware used, so looked him up on qrz.com He was using a POTY antenna the like of which I have not seen before. It has a feed horn and appears to feed the RX side without an LNB directly to a Kuhne down converter. How might that work, I thought down converters expected a lot of gain from the LNB and an already down converted signal, to some extent, done within the LNB?


I placed a photo of this nicely looking engineered device here:

http://www.chriswilson.tv/DJ8EI.JPG

It appears there's no LNB but the RX antenna is inside the POTY tube itself.


Thanks for any insight to this newbie!

--
Best Regards,
Chris Wilson.
mailto: chris@chriswilson.tv


Chris Wilson
 

19/05/2021 10:19

I am slowly getting into amateur satellite work and runa 1.8 meter prime focus dish with a POTY antenna for 2.4GHz TX and a coaxial LNB for circa 10.5GHz reception. I know the LNB down converts to around 940 MHz using an intermediate frequency.

I heard a very nice signal from a chap who appeared to know a lot about the hardware used, so looked him up on qrz.com He was using a POTY antenna the like of which I have not seen before. It has a feed horn and appears to feed the RX side without an LNB directly to a Kuhne down converter. How might that work, I thought down converters expected a lot of gain from the LNB and an already down converted signal, to some extent, done within the LNB?


I placed a photo of this nicely looking engineered device here:

http://www.chriswilson.tv/DJ8EI.JPG

It appears there's no LNB but the RX antenna is inside the POTY tube itself.


Thanks for any insight to this newbie!

--
Best Regards,
Chris Wilson.
mailto: chris@chriswilson.tv