Rebuilding dipole on a 2.4 GHz grid antenna for 1.7 GHz GOES reception - A few questions:

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jjstechino
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Joined: Tue Sep 29, 2020 12:59 pm

Rebuilding dipole on a 2.4 GHz grid antenna for 1.7 GHz GOES reception - A few questions:

Post by jjstechino » Wed Sep 30, 2020 11:48 am

I am trying to optimize reception of GOES 16 satellite. I tried all the tricks I read on the web on how to adapt the usual 2.4 gHz 100cm 24db Grid antenna, like reversing the concavity of the reflector, extending the distance from the dipole by 2.5 cm, flattening the reflector. Af all these only increasing the distance yielded some positive changes and brought viterbi from around 900 to mid 500 allowing reception of packets with a clear sky. where I live GOES 16 is quite high in the sky (49 deg) so I should be able to get a better reception. I decided to try to optimize this antenna a bit, see viewtopic.php?f=6&t=6119.
I am in the process of rebuilding the feed element.

My question here relates to placement of the dipole and I would love to have the opinion of more experienced people.
The antenna in its original form has the focal point at 33cm. The dipole is placed at 30cm and the reflector is placed at 35cm.

I am redesigning the dipole enclosure to be 3d printed and it would be fairly easy to readjust and optimize the above measures.

Should I extend the stem of the enclosure to place the dipole exactly at the focal point and maybe get rid of the reflector?

Or should I keep the original design and extend the support for the reflector by 2.5 cm?

In the hands of who has already tinkered with this type of antenna, what would be the better mod?

Thanks

rtlsdrblog
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Re: Rebuilding dipole on a 2.4 GHz grid antenna for 1.7 GHz GOES reception - A few questions:

Post by rtlsdrblog » Wed Sep 30, 2020 11:46 pm

In my experience even with a tuned dipole for 1.7 GHz, the reflector does still help increase the SNR, so i'd advise keeping it.

jjstechino
Posts: 3
Joined: Tue Sep 29, 2020 12:59 pm

Re: Rebuilding dipole on a 2.4 GHz grid antenna for 1.7 GHz GOES reception - A few questions:

Post by jjstechino » Wed Sep 30, 2020 11:49 pm

Would you place the dipole at the same distance (30 cm) as the original 2.4 GHz antenna or move it to the focal distance of 33 cm? Then I still can place the reflector and see if it helps further.

rtlsdrblog
Site Admin
Posts: 2773
Joined: Mon Nov 19, 2012 11:54 pm

Re: Rebuilding dipole on a 2.4 GHz grid antenna for 1.7 GHz GOES reception - A few questions:

Post by rtlsdrblog » Wed Sep 30, 2020 11:55 pm

I only tested with the same focal point as the original antenna design which is the same as yours, so not sure if moving it back would help.

I do recall that actually using the default concavity of the reflector worked best for me with the modified dipole, after moving the reflector back a little.

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