HRPT - optimizations and great images!
I made some changes to my HRPT setup and was able to get very good images from NOAA19 for example. Take a look at my Video about the changes below:
BIAS-T on the SPF5189z
To power a SPF5189z LNA over Bias-T, for example from the SDR directly, you just solder a 10uH coil from the middle ( signal ) pin at the output of the LNA to the +5v pad. As far as i know you can also use different values, but the inductance should be quite high (at least something in the uH range) to filter out the signal.
The new Feed
I tried different version of my Feed in the past weeks and months. Fist i used a 3 turn helix with 40mm spacing, after that a 7 turn one with 20cm spacing that was recommended to me for an offset dish. Now i found that some people had luck with a 8 turn helix and a spacing of 12mm. I also adapted the mathcing method with a copper strip, that is often used, to my 3D printed support. Overall that version of the feed gave me the best results so far and seems to be quite good.
Images I received
Here are some of the images i was able to get in the past weeks. They are all handtracked as useal because i don't have an automatic tracker yet. I also post them on Twitter each time i receive one: Twitter @tysonpower
NOAA19 from the 1st of january 2018 - very low 23° max elv pass
NOAA19 from the 14th of january 2018
NOAA19 from the 24th of january 2018