Mini Dish Build/Setup/Takedown Video Playlist

[Jason Burnfield]

Hi All,

I've made a playlist of videos documenting the build, setup, use, and teardown of my new mini-dish.

Enjoy!

https://youtu.be/3I0rMmoj8CE?si=GJuEWDMHCwg6taJH

[Jason Burnfield]

Also, here are the results of a ground, sky, sun test and both milky way transits today (GL72 and GL174).

[fasleitung3]

Thanks, Jason

I was wondering why your spectrum goes "up" rather than down at the edges as one would normally expect due to a filter.

Wolfgang

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[Jason Burnfield]

Hi Wolfgang,

I’m not sure. The raw uncorrected spectrum looks as expected. The background is corrected with a 50 ohm load calibration so maybe there is a drift down after correction?

I’ve seen it move up or down after correction in the past.

I don’t use the background correction if I’m drift scanning galaxies because I use the pre and post transit data for background correction. But I do use it for Milky Way scans.

Jason Burnfield
405-615-3924

“Six pints of bitter, …And quickly please, the world’s about to end.” - The Hitchhiker’s Guide to the Galaxy

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[Stephen Arbogast]

All,

 I have noticed  this   too.   I am using  an AirSpy   with Discovery  Dish   and   feed.  If   I shutdown  for  only a  moment  and  then  restart the  total detected  power  starts high but  returns lower again within  several minutes.  Could  the  thermal  changes   take  place that  quickly or ?????

[Stephen Arbogast]

Also, just for  kicks  I thought  I would run  some  simulations of the   QPL9547  chip  used in Discovery Dish feed   for   H1. I found   the  footprint  in KiCad but  I  have not found the  .model file  for  simulation... any ideas?

[Jason Burnfield]

I really believe the background correction causes the inversion of the slope if the magnitude of the shape is slightly higher than the actual spectrum being captured afterwards. I think it is always a fine balance. I’ve actually seen it become a sideways “s” shape if one side is slightly higher and the other slightly lower than the live spectrum.

Jason Burnfield
405-615-3924

“Six pints of bitter, …And quickly please, the world’s about to end.” - The Hitchhiker’s Guide to the Galaxy

To view this discussion visit https://groups.google.com/d/msgid/sara-list/7c028b08-83bd-4924-9091-507309395860n%40googlegroups.com.

[Stephen Arbogast]

Yes,   back ground  correction can   cause  problems..  I have   experienced this.    I have  some   graphs where back  ground   correction  was  way  off.

[Eduard Mol]

Hi Jason, great work as always! Looks a lot quicker and easier to set up than my 3-metre dish (1+ hours…)!

My Airspy mini is also very sensitive to temperature changes. 

I suspect using a 50ohm load may not be a very good method. Usually for “strong” galactic HI I don’t even make background spectra at all, instead I fit the background around the HI line with a 3rd order curve. 

It would be interesting to compare different methods. 

Op za 4 apr 2026 om 08:03 schreef 'Stephen Arbogast' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>

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[Stephen Arbogast]

My   Air Spy  is  SDR  is  working  fine....       I  agree   with   Edward  Mol..  we need   better   software  models.

[Jason Burnfield]

My main design parameter for the new dish has been thoroughly tested and that is the ability to stand up to severe wind! 😃👍

Jason Burnfield
405-615-3924

“Six pints of bitter, …And quickly please, the world’s about to end.” - The Hitchhiker’s Guide to the Galaxy

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