Re: HRIT and LRIT Low-Cost System
Posted: Sun Aug 12, 2018 4:15 pm
Rob,
Some additional information for you to consider. The grid antenna choice was made for this post with careful research and a considerable amount of effort went into testing, modification, and seeing what worked well. The 1 meter diameter grid parabolic antennas, regardless of brand, typically employ a quarter-wave to half-wave dipole as the receiving element. So it is not too difficult to modify one to set it to the exact frequency desired. What was found in testing the Premiertek ANT-GRID-24DBI antenna was that the biggest increase in gain in the 1.69GHz frequency range came from simply flipping over the existing secondary reflector as described in the post. Alternate secondary reflectors and optimizing the dipole for 1.69 GHz were also tested. The results were only marginally better, not enough to propose going through all the trouble to make extensive antenna changes, when you can obtain similar results without modifying the dipole and by simply flipping over the existing secondary reflector.
Here are some numbers from testing using the RSP2, the SAWBird GOES LNA, and the ANT-GRID-24DBI antenna:
1) Premiertek ANT-GRID-24DBI out of the box constructed as instructed by Premiertek operating at 1.69 GHz on GOES 16: Signal Quality 69.7 Viterbi Corrects 455
2) Premiertek ANT-GRID-24DBI with secondary reflector flipped over at 1.69GHz on GOES 16: Signal Quality 95.7 Viterbi Corrects 65
3) Premiertek ANT-GRID-24DBI with dipole modification for 1.69 GHz and optimized secondary reflector for 1.69 GHz: Signal Quality: 98.0 Viterbi Corrects 30
As mentioned, given that the greatest positive change for operation of the ANT-GRID-24DBI at 1.69 GHz was made simply by flipping over the secondary reflector as described in the post, other modifications were not described. This also makes setup easier and does not void the warranty on the antenna.
*** Update: If you are reading this, jump to the June 23, 2019 post for more advanced modification and further improvement.
Some additional information for you to consider. The grid antenna choice was made for this post with careful research and a considerable amount of effort went into testing, modification, and seeing what worked well. The 1 meter diameter grid parabolic antennas, regardless of brand, typically employ a quarter-wave to half-wave dipole as the receiving element. So it is not too difficult to modify one to set it to the exact frequency desired. What was found in testing the Premiertek ANT-GRID-24DBI antenna was that the biggest increase in gain in the 1.69GHz frequency range came from simply flipping over the existing secondary reflector as described in the post. Alternate secondary reflectors and optimizing the dipole for 1.69 GHz were also tested. The results were only marginally better, not enough to propose going through all the trouble to make extensive antenna changes, when you can obtain similar results without modifying the dipole and by simply flipping over the existing secondary reflector.
Here are some numbers from testing using the RSP2, the SAWBird GOES LNA, and the ANT-GRID-24DBI antenna:
1) Premiertek ANT-GRID-24DBI out of the box constructed as instructed by Premiertek operating at 1.69 GHz on GOES 16: Signal Quality 69.7 Viterbi Corrects 455
2) Premiertek ANT-GRID-24DBI with secondary reflector flipped over at 1.69GHz on GOES 16: Signal Quality 95.7 Viterbi Corrects 65
3) Premiertek ANT-GRID-24DBI with dipole modification for 1.69 GHz and optimized secondary reflector for 1.69 GHz: Signal Quality: 98.0 Viterbi Corrects 30
As mentioned, given that the greatest positive change for operation of the ANT-GRID-24DBI at 1.69 GHz was made simply by flipping over the secondary reflector as described in the post, other modifications were not described. This also makes setup easier and does not void the warranty on the antenna.
*** Update: If you are reading this, jump to the June 23, 2019 post for more advanced modification and further improvement.