Re: 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>

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