Has anyone tried a phased array for H line monitoring?

[JERRY TAYLOR]

Just curious if anyone has tried using multiple antennas as a phased array for H line observations?  I am thinking about trying it myself but thought I'd see if anyone else has done it and see what their results were and maybe get some tips before I try it.

Jerry Taylor

[Marcus D. Leech]

On 2025-08-29 10:23, JERRY TAYLOR wrote:

Just curious if anyone has tried using multiple antennas as a phased array for H line observations?  I am thinking about trying it myself but thought I'd see if anyone else has done it and see what their results were and maybe get some tips before I try it.

Jerry Taylor

I did this back in the day with a pair of loop yagis.   Worked OK, but a dish is way more convenient, and cheaper, TBH.

Dishes were invented precisely because building large arrays of individual antennas at UHF and above frequencies is decidedly tricky--they're
  very sensitive to phasing issues.

 

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[JERRY TAYLOR]

Thanks Marcus.  I have very limited space so I will need to use yagis like the Pettit designed patch yagi.  

Am I correct in assuming that with 2 yagis my beam width will decrease and thus the total signal may not change vs a single yagi but the resolution will increase?  

Can theoretical numbers be put to a 2 yagi array vs a single yagi?

Jerry

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[Marcus D Leech]

A two yagi array will give you a smaller beam width by something less than 1.414. 

Sent from my iPhone

On Aug 29, 2025, at 12:45 PM, JERRY TAYLOR <gfaj...@gmail.com> wrote:



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[Marcus D Leech]

It’s a 5/8”

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On Aug 29, 2025, at 12:45 PM, JERRY TAYLOR <gfaj...@gmail.com> wrote:



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[tedcl...@gmail.com]

I have not explored a proper multiplying interferometer (with a fancier SDR), as Wolfgang detailed,
      RTOP Oct 2023
      https://www.youtube.com/watch?v=PYzJ-8d1s1w&t=1169s

But I explored using two 1420 MHz antennas together with a cheap SDR.
Wolfgang kindly called it an adding interferometer, but it is simply an antenna array,
      RTOP Oct 2023
      https://www.youtube.com/watch?v=PYzJ-8d1s1w&t=1650s
And then with 3 antennas,
      Drakes Lounge: October 2023
      https://www.youtube.com/watch?v=wS67xbMVwVk&t=1289s

I introduced that inexpensive PZT antenna at the Aug-2023 SARA Eastern Conference,
      ezRA - PZT Antenna Tests
      https://www.youtube.com/watch?v=VZrd2-VFiPE
The construction dimensions are in the YouTube notes.

My goal is to repeat this exploration with the smaller disk Yagi antennas.
The location of my first try (picture attached) had too much RFI.


And there are Rich's notes,
      Radio Astronomy Formulas: Lesson 17 - Interferometry Fringe Spacing
      https://www.youtube.com/watch?v=rYhUKFn7IWg

---
Ted Cline
TedClineGit at gmail.com

[tedcl...@gmail.com]

I have not explored a proper multiplying interferometer (with a fancy SDR), as Wolfgang detailed,

[Marcus D Leech]

Oh lord. I replied to the wrong email. Sorry about that. 

Sent from my iPhone

On Aug 29, 2025, at 3:25 PM, tedcl...@gmail.com <tedcl...@gmail.com> wrote:

I have not explored a proper multiplying interferometer (with a fancy SDR), as Wolfgang detailed,

To view this discussion visit https://groups.google.com/d/msgid/sara-list/337102dd-19a9-4e3d-8add-b14f3ba0034an%40googlegroups.com.

<IMG_20240915_190027267.jpg>

[James Abshier]

What you get from a 2 yagi array will depend on the spacing between the antennas. If the spacing is, say, one wavelength, you should get about twice the signal power compared with a single antenna. If the antennas are spaced far apart, you will essentially have an interferometer with many grating lobes in the primary antenna beam. For an extended source such as a hydrogen cloud, only about 1/2 of the power will get through the grating screen.  You could adjust the antenna spacing so that the first grating lobe falls on the first null of the antenna primary pattern. That should give you the best resolution that you could achieve (with an extended source). You might get some loss in signal that way, but I suspect the loss would be small.

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[James Abshier]

Clarification: In a previous post I stated that an array of 2 antennas spaced one wavelength apart would provide twice the power of a single antenna. While this is true for point sources, it is not in general true for extended sources. The reason for this is that the beam pattern of the 2 antenna array is smaller than that of the single antenna. For an extended source that completely fills the beam of the single antenna, the additional aperture size of the 2 antenna array is offset by the fact that the narrower beam width intercepts a smaller portion of the extended source. So the relative amounts of power received would likely be about the same. If the extended source was completely contained in the smaller array beam width, then it would be more like a point source and an increase in received power with the 2 antenna array would be expected.

Jim Abshier

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[Jon Abel]

I am building a condensed array of loop antennas using patent 512,340 - and the 1700 loops include wirelength resonances that run from 300 Mhz to 15 Ghz.    It is a novel type of radio telescope and may give you what you are looking for.    I am in the process of writing SDR python code for it now (with the help of AI).    Might give you some ideas.

[Stephen Arbogast]

What the  hell  is a condensed   array of loop antennas?  Quoting  patents    does not help.  Why not use  GNU  Radio?

[Stephen Arbogast]

So   far  I have tried    three approaches   to  using  GNU  Radio  to  come  up  my own  approach to over come  the  limitations of   Python ...    Having   problems  with  all of them...    like   Marcus   Leech  said     ..  "    takes  a   lot  of time   and  patience to learn GNU  Radio" ... 

1.   BAA_Seminar  was not  written  for   simple  single  stream    for   beginners.

2.  I have  tried my own  version  by  copying and modifying   his  stuff...   not  working!  I have  not  solved  my  errors  yet.

3.  I have  tried some   experimental  software   from  Ted  Cline....    very  good...     but  finding   as per  previous  suggestions   I need  to  run  it stand  alone

I  will  continue  to  explore .....

So  far  I  find    BAA_Seminar  to be be very  reliable  and  gives  consistent   results but    would   like   ezRA   software capability   such  as the    option to   delete  spurs   from my  raw data files  with the   option  that   ezRA provides............   delete   from  raw  data file

Yes  I know    I want perfection.....

Stephen

[Douglas Decker]

I am running EZRA and SDR# on same pc with no major issues. It can be done and it works.

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[Stephen Arbogast]

Why    are you  doing this?

[Stephen Arbogast]

Maybe   you  are using   a  super    pc?   I  think  all modern  computing   platforms  today  run multitasking.....   I have had  problems    when I demand  a sample  rate   of  10 M/sec...  

Please  provide more  details...

[Stephen Arbogast]

What sample rates for each SDR? 

[Stephen Arbogast]

what  clock speed  for your  pc io?

[Mike Otte]

You can run Baa_Seminar for a collector and EZRA has a converter to change the data and then present it.

To view this discussion visit https://groups.google.com/d/msgid/sara-list/46c2d930-be0a-4464-ae7f-1c41c16898f6n%40googlegroups.com.

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Mike Otte W9YS

[Stephen Arbogast]

Yes  ....  guess  I am lazy...  I would  like to have  one program to  run.....to  collect  data, assure me that my  data is  valid   and  produce   beautiful   results  but  Science   does not work  this  way...   some   work   is required to  filter out  the outliers........  I have  managed to use  ezRA   tools to filter    my  raw   data  and  get some  very  good     heat plots...

Maybe use   AI   in  the   future  will  do  this  for me?????

Stephen

[Douglas Decker]

Ezra for “HL” reception and SDR# for meteorite detection using msk144. Just commenting that multiple apps both using different Sdr’S. No problems. Ps being doing Linux and Windows \ Os2 since mid 70’s. I mostly do just windows now it is simpler.

Sent from my iPhone

On Sep 6, 2025, at 10:37 PM, 'Stephen Arbogast' via Society of Amateur Radio Astronomers <sara...@googlegroups.com> wrote:



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[Jon Abel]

Rhetorical questions are rude.  It's something novel to try.