WiFi dish + DD feed + HackRF setup in a very-high-RFI environment

[Ayushman Tripathi]

Hi,

Here's the data I got yesterday from my new smaller setup, WiFi 1m dish and DD feed on my new Alt-Az mount, using a HackRF One SDR. Peak relative to cold sky is +0.63 dB.

I also received the OCXO clock reference for the HackRF, which I'll set up this week, it's an oven-controlled 10 MHz reference, much more stable than the stock TCXO, so that should fix the HackRF's drift issues.

Since this setup is in a very urban, RFI-intensive area, my observation time is limited to local 3 AM to 6 AM. After that, some unknown device turns on that makes the H-line disappear into the noise floor and raises the NF. I'm trying to locate it using a portable SDR setup I made with an RTL-SDR and an Android phone.

I'll also try optimizing the performance this week and share the results.

Thanks

[Ayushman Tripathi]

Hi! I managed to push the HI line another +0.18 dB (now peaking at +0.81 dB above cold sky) just by adding more mesh to the back of the dish, in a high-RFI setup.

Will keep trying more optimizations to see how much further it can go.

[Stephen Arbogast]

Very  cool!

Here is  an idea  for  control of a  small  light  weight  dish...    I implemented  this  a  year   ago   but  lately   the  baro  pressure  sensor was  reporting  zero......    After  debugging    software the   solution  was to apply  a  vacuum  cleaner to  the hole  in  top  of SP06   IC...   now it  is  working...       Here  is  the Extended Kalman  Filter ...   

https://www.google.com/search?q=extended+kalman+filter+phil%27slab&client=ubuntu-sn&hs=y0p&sca_esv=cbcb3eaaead68c4b&channel=fs&sxsrf=APpeQnvhN5_I03FvKOAr7ka6YZmbOnL_3Q%3A1781920635502&ei=e_M1auWmHojZ0PEP7Ku4sQU&biw=1769&bih=798&oq=extended++&gs_lp=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&sclient=gws-wiz-serp#fpstate=ive&vld=cid:e6221956,vid:7HVPjkWOrLE,st:0

[andrew....@googlemail.com]

That is a really nice plot.

Andy

 

From: sara...@googlegroups.com <sara...@googlegroups.com> On Behalf Of Ayushman Tripathi
Sent: 20 June 2026 02:22
To: Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Subject: [SARA] Re: WiFi dish + DD feed + HackRF setup in a very-high-RFI environment

 

Hi! I managed to push the HI line another +0.18 dB (now peaking at +0.81 dB above cold sky) just by adding more mesh to the back of the dish, in a high-RFI setup.

Will keep trying more optimizations to see how much further it can go.

On Tuesday, June 16, 2026 at 7:30:19 PM UTC-4 Ayushman Tripathi wrote:

Hi,

Here's the data I got yesterday from my new smaller setup, WiFi 1m dish and DD feed on my new Alt-Az mount, using a HackRF One SDR. Peak relative to cold sky is +0.63 dB.

I also received the OCXO clock reference for the HackRF, which I'll set up this week, it's an oven-controlled 10 MHz reference, much more stable than the stock TCXO, so that should fix the HackRF's drift issues.

Since this setup is in a very urban, RFI-intensive area, my observation time is limited to local 3 AM to 6 AM. After that, some unknown device turns on that makes the H-line disappear into the noise floor and raises the NF. I'm trying to locate it using a portable SDR setup I made with an RTL-SDR and an Android phone.

I'll also try optimizing the performance this week and share the results.

Thanks

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[Stephen Arbogast]

I use    an  OCXO with my   AirSpy  ...  no  difference .      

Here  is shot of  my baro   presssure  monitor   using   Serial  Studio......    I have   three channels     but  can see  only  channel  two....   What is    best  to    use for   displaying   data  from  my usb  port?

[Stephen Arbogast]

It  drifts    but  you  get the  idea.

[Stephen Arbogast]

Very  cool....   stuff....    

https://www.youtube.com/watch?v=hQUkiC5o0JI

[Ayushman Tripathi]

Hi Stephen, really nice setup!

Yes, I think your AirSpy already has a better TCXO, I read somewhere that HackRF's built-in TCXO drifts a lot over time, which is why I picked up an OCXO for my home setup. For the bigger dish I use an AirSpy Mini, which doesn't have a CLOCK IN port anyway :) For the HackRF, once I sort out the RFI issues here, I can do a comparison drift scan with and without the external OCXO.

One thing I'm still figuring out though, HackRF wants a 3.3 V square wave at 10 MHz (per its docs: "expects 3.3 V square wave at 10 MHz"), but this OCXO I got from Banggood outputs 5 V on its TTL output. I tried a 10 dB attenuator, and it dropped the level to 1.6 V, which is below the 3.3 V threshold. I'll try it anyway or get a ~5 dB attenuator instead.

Otherwise, I'll need to figure out how to put a resistor divider between the HackRF's CLK IN and the OCXO's TTL OUT. This OCXO's 2nd output which is sine, goes down to −1 V, but the HackRF doc says not to go below 0 V and not sure even if it accepts sine anyway.

Thanks!

[Stephen Arbogast]

Here is a handy Python program for plotting data from usb, /dev/ttyACM0 on Linux.

[Cathal O'Donghaile]

Ayushman, are you running SDR++ from a phone?

[Ayushman Tripathi]

Hi Cathal,

Yes, I'm using SDR++ and SDRangel on an Android phone as a portable setup for hunting RFI sources. Both SDR++ and SDRangel (along with its Radio Astronomy plugin) run directly off the RTL-SDR over USB on Android phones, tablets, etc. Unfortunately, the iPhone doesn't support these, as iOS doesn't give apps access to 3rd party USB devices :)

Attached are some pics of SDRangel and SDR++ running on an Android phone.

[Cathal O'Donghaile]

Thanks for that,  Ayushman . Outside of my radio astronomy pursuits, I'm also making a SW radio. It'll make life easier that I can run it from a tablet or phone.

[Stephen Arbogast]

Since I have a GPSDO  I connected it to my AirSpy and makes no difference in my Hydrogen Line plots.  It does greatly improve frequency stability of my signal generator.

On Saturday, June 20, 2026 at 10:20:11 PM UTC-6 Ayushman Tripathi wrote: