Hydrogen line setup + interest in narrowband SETI candidate search

[Ayushman Tripathi]

Hello, I’m setting up a small radio telescope in my personal research time.

Hardware so far:

• 1.2m dish

• Discovery Dish hydrogen line feed

• L-band signal chain: Feed → LNA1 → BPF → LNA2 → BPF → SDR
  (QPL9547 LNAs, ~1420 MHz SAW filters)

• SDRs: HackRF One, Nooelec NESDR w/ 0.5 ppm TCXO (planning Airspy and a larger dish later)

• Processing: i9-14900KS, running Ubuntu Server

My long-term personal goal is to perform systematic monitoring in the 1420 MHz band to search for narrowband candidates (e.g. WOW-class events) with proper time/frequency integration and statistics.

If anyone here is interested in collaborating on the software / data processing algorithm side (search strategies, waterfall integration, automated candidate detection + RFI rejection), I would like to connect. Thanks

[Marcus D. Leech]

--

I admire you enthusiasm.  However, the "Big Ear" that captured the WOW signal had an aperture almost 2000 times your proposed 1.2m dish.  The probability of actually
  detecting SETI signals with your tiny dish approaches zero.   However, as an intellectual exercise, I'm sure you'll learn a lot of things....

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[Ayushman Tripathi]

Hi Marcus,

Thanks for your reply. Yes, I am planning to upgrade to a larger dish in the future—possibly via surplus auction or scrapyard. The main engineering challenge will be wind loading and mechanical stabilization.

Realistically I agree: reaching anywhere near a Big Ear-class aperture is not practical for me.

My thinking is this: if a narrowband signal happens to be strong enough, and I am pointed at it, then even a small instrument can detect it if the SNR is above threshold. Of course the probability is much lower than with large instruments (50-100m class), but my hope is to compensate partly by long dwell time, I intend to automate 24/7 observing and continuous candidate scoring.

Most large facilities have very limited SETI allocation time compared to all the other radio astronomy science they do, so there is still parameter space where continuous small-instrument monitoring can contribute unique temporal coverage.

I’m starting with the 1.2 m system as a development platform, improving sensitivity and pipeline automation, and will gradually upgrade aperture as opportunities arise.

Only roughly a dozen major radio telescopes have ever run dedicated or commensal SETI in 60 years (Big Ear, Green Bank, Arecibo, Parkes, Lovell, ATA, MeerKAT, FAST, etc.). And according to the “Cosmic Haystack” analysis (Wright et al. 2018), the fraction of the total sky–frequency–time search volume that has been completed so far is on the order of 10⁻¹⁸ — essentially a hot-tub out of an ocean.

https://arxiv.org/abs/1809.07252

So there is still an enormous unexamined search space.

Thanks.

[Shaik Samad Pasha]

Hi ayushman,

I am Shaik and happy to collaborate with you, I started radio astronomy recently, I am from Hyderabad, India.

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Shaik Samad Pasha

[Alex P]

Hello  Ayushman,

Please Read This and equate it to the theoretical capability of a  1.2m dish  Without even considering Local RFI.

Nikolova 2025
Lecture 7: Antenna Noise Temperature and System Signal-to-Noise Ratio
(Noise temperature. Antenna noise temperature. System noise temperature.
Minimum detectable temperature. System signal-to-noise ratio.)

https://www.ece.mcmaster.ca/faculty/nikolova/antenna_dload/current_lectures/L07_Noise.pdf

Regards,

Alex Pettit

[Ayushman Tripathi]

Hi Shaik, Sure, thanks. 

[Ayushman Tripathi]

Hi Alex!

Thanks, Yes, I attempted to calculate it for my 1.2 m dish and a potential upgrade to a 2-4 m dish in the future. Here are the results: (Though there can be a few mistakes)

1.2 m Grid Dish + QPL9547 Dual-LNA (Narrowband SETI)

(Assumptions: 1 Hz bins, single polarization, 1 hour coherent integration, SNR ≥ 5, G_tx = 50 dBi ET beacon, λ = 21 cm)

1. Antenna Gain: 23.48 dBi, 0.79 m² effective area | G = (4π × A_eff) / λ²

2. Receiver Noise: 24.5 K (QPL9547 dual-LNA, 33 dB gain) | T_R = T₁ + T₂/G₁ + T₃/(G₁G₂) + T₄/(G₁G₂G₃) (Friis)

3. System Noise: 50 K total (Sky: 15K, Feed losses: 10K, Receiver: 25K) | T_sys = T_sky + T_feed + T_R/(e_feed)

4. Sensitivity (1-hour): 2,910 Jy @ 1Hz | 2,060 Jy @ 2Hz | 1,300 Jy @ 5Hz | ΔT_min = T_sys / √(Δf × τ) then S = (2k × ΔT_min) / A_eff

5. ET Detection: Interstellar narrowband beacons (1 Hz bins) would require ET transmitter power of ~164 MW at 10 ly, rising to ~16.4 GW at 100 ly (assuming a 50 dBi transmitting array, 1 hour integration, SNR≥5, T_sys≈50 K). Accidental leakage is below detectability at these ranges.

Alternative with Pessimistic System (T_sys = 183.5 K):

3. System Noise: 183.5 K total (Sky: 15K, Antenna losses: 124K, Line: 8.5K, Receiver: 35.7K) | T_sys = T_A + T_P(1/e_A - 1) + (1/e_A)T_LP(1/e_L - 1) + (1/(e_A×e_L))T_R

4. Sensitivity (1-hour): 10,680 Jy @ 1Hz | 7,550 Jy @ 2Hz | 4,780 Jy @ 5Hz

5. ET Detection (pessimistic): Interstellar narrowband beacons (1 Hz bins) would require ET transmitter power of ~601 MW at 10 ly, rising to ~60.1 GW at 100 ly (assuming a 50 dBi transmitting array, 1 hour integration, SNR≥5, T_sys≈183 K).

Similarly, for a 4-meter dish:

ET Detection (realistic, Tₛᵧₛ ≈ 50 K): Interstellar narrowband beacons would require ~14.8 MW at 10 ly, rising to ~1.48 GW at 100 ly (50 dBi transmitter, 1 h, 1 Hz).

ET Detection (pessimistic, Tₛᵧₛ ≈ 183.5 K): Interstellar narrowband beacons would require ~54 MW at 10 ly, rising to ~5.41 GW at 100 ly (50 dBi transmitter, 1 h, 1 Hz).

So, it seems it'll be worth the upgrade from a 1-meter dish to a 3 or 4-meter one. I found some nice deals on Alibaba; the issue currently for me is where to mount it, as I installed my 1.2-meter grid on my balcony, and it's impossible to get anything larger than 1.8 m there. Though I've a potential place near a forest, there's very little RFI there, but setting it up there means first installing something like Starlink there for 24×7 internet and also EcoFlow etc. for power, but it'll be more like a remote setup, as I can't be there, and then I'll need to set up a remote rotator also. But for sure it's a future project.

Was looking at the inflatable reflectors also; it seems they're more expensive currently.

Anyway, I'm hoping if the ET transmitter is strong enough, then even a smaller dish can see it, as I plan to automate this and continue this for many years. For sure will get at least a 2-meter dish soon.

https://www.alibaba.com/trade/search?spm=a2700.product_home_newuser.home_new_user_first_screen_fy23_pc_search_bar.keydown__Enter&tab=all&SearchText=3m+satellite+dish+l+band&has4Tab=true&from=pcHomeContent

Thanks.

[andrew....@googlemail.com]

Ayushman,

 

Why don’t you join our H-Line group and we can then support you in this process. You would be able to periodically present your progress with larger time slot on the main group – of course, it does not stop you accessing support via the main groups and mailing lists as well.

 

If you interested in taking part in these monthly Zoom/Teams meetings, then contact me on the contact me page on www.astronomy.me.uk and I will send you a link.

 

Andy

 

Dr Andrew Thornett

Lichfield Radio Observatory

www.astronomy.me.uk

 

NB If you can’t get to sleep, then you can while away a lot of hours looking through the content of the website – currently just under 300GB of incredibly geeky stuff, designed to make anyone snore aloud!

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[Ayushman Tripathi]

Hi Andrew,

Sure — I'll join and share the progress and any relevant findings.

Thanks

[andrew....@googlemail.com]

Hi Ayushman,

You’ll need to send me your email address via the contact me page on astronomy.me.uk

Andy

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[Ayushman Tripathi]

Okay, done. Thank you.

[Ayushman Tripathi]

Hi, I recently completed my setup for Hydrogen Line and some initial SETI-style attempts, and I’m looking for advice on improving the sensitivity and overall performance.

I tried pointing the dish toward Cassiopeia for about 2 hours today. It was low on the horizon during the session, and this is the result I obtained. Next step I'll be doing the calibration, but before doing that, I’d like feedback on whether the system setup looks reasonable and what improvements would be most effective.

I tested both the HackRF One and the NESDR SMArtEE. The NESDR seems better in terms of noise baseline stability, but I may not have found the optimal settings for the HackRF yet.

Front-end chain:

For RTL-SDR (NESDR SMArtEE):
Dish Antenna → LNA1 (QPL9547) → Filter1 → LNA2 (QPL9547) → Filter2 → NESDR SMArtEE

For HackRF:
Dish Antenna → LNA1 (QPL9547) → Filter1 → LNA2 (QPL9547) → Filter2 → External Bias Tee → HackRF One

Software used:
Virgo and DSPIRA Spectrometer for hydrogen observations.
Also, I set up TurboSETI for narrowband SETI-style searches.

virgo -da "rtl=0,dc_offset_mode=1" -f 1420200000 -b 2400000 -c 4096 -t 1.0 -d 3600 -rf 3 -db -n 3 -m 3 -S x.csv -p x.png

RF gain = 3 dB seems to be the most stable for the NESDR.

I’d appreciate recommendations on improving sensitivity, baseline stability, feed optimization, calibration steps, or better methods/software for Ubuntu that can help refine this setup further.

*For context, the device wrapped in aluminum foil in the photo is my HackRF One, which I shielded to reduce RFI, this seemed to help slightly.

Thank you.

[b alex pettit jr]

Hello Ayushman,

Please Review This ...

Your Comment :  " RF gain = 3 dB seems to be the most stable for the NESDR " 

 Reply : In every case I've tested, the   SDR Gain should be @ Maximum   42 dB  

You probably have large out of band RFI issues being so close to your building.

Use This Chart to find the bright regions in the Milky Way

( Best : RA 06:15 Hrs Dec + 20 Dg     and    RA 20:30 Hrs  Dec + 40 Dg )

Ideas 

My Presentation for the SARA Conference July 2022

https://www.youtube.com/watch?v=C6NCefVxNL8

Here is data from my extended WiFi dish system 

Alternate Software,.

Project HLine3D

https://github.com/AP-HLine-3D/HLine3D

      Regards,

      Alex Pettit

      Proj HL3D

===========================================================

[b alex pettit jr]

A more appropriate FFT size is 512 points, not 4096 

This plot show No H Line Data

[Ayushman Tripathi]

Hi Alex, sure — thanks a lot! I used the settings you recommended and ran a 30-minute test, and this is what I got. It seems stable. I’ll run some proper observations later today once Cassiopeia moves into my dish’s view. Thanks again.

Regarding the RFI, I’ll turn off my EcoFlow and other equipment running in the nearby room to reduce interference. I always get the same baseline shape whenever the front end is powered, so I tried doing a band sweep around the H I line using both the HackRF and RTL-SDR, but didn’t find any significant RFI. It’s possible the dual LNAs are amplifying some noise they pick up, or the curve I’m seeing might also be coming from the band-pass filters themselves.

The above SDR++ screen is of RTL connected with the frontend chain.

And the below screen is of the HackRF One connected with a simple TG.46.8113 Dipole Terminal Antenna 450MHz - 6GHz.

[b alex pettit jr]

Hello Ayushaman,

Rather than "Cassiopeia"

Take data scan sets through one of these regions

[Ayushman Tripathi]

Hi, Alex.

Sure, I will try today.

Thanks.

[Lester Veenstra]

Current units look like this

 

 

Lester B Veenstra  K1YCM  MØYCM  W8YCM   6Y6Y W8YCM/6Y 6Y8LV (Reformed USNSG CTM1)

les...@veenstras.com

 

452 Stable Ln

Keyser WV 26726 USA

 

GPS: 39.336826 N  78.982287 W (Google)

GPS: 39.33682 N  78.9823741 W (GPSDO)

 

 

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[Ayushman Tripathi]

Hi, I collected new data tonight—I'll analyze it soon.
Also, I'm buying this 2.5 meter mesh parabolic dish, and it should arrive next week. It’s a professional-grade broadcast dish with a deep parabolic profile and solid steel support arms, which should give me better gain and sensitivity.

I’ll be installing it at a remote rural location and connecting it to a Raspberry Pi 500 running a server by end of November or early next month.