Different readings from barebones and cased Sawbird H1

[Cathal O'Donghaile]

Hi Everyone

I'm hoping someone can help me. I've been testing both a barebones H1 and cased H1 filter from Sawbird with AirSpy and I'm getting very different readouts. Most notably, I'm getting a faint hydrogen reading from the barebones and nothing from the cased one. Attached are screenshots:

So 3 things stand out:

• Hydrogen bump on Barebones
• The difference in profile between the 2 devices
• The cased H1 signal is louder sitting above the 50Db line whereas the barebones signal is slight quieter below the 50Db line
  
  Anyone any ideas what might be wrong? Is it possible the cased one isn't picking up the signal from the probe. Just a note I have a copper probe attached.

Would appreciate the help, thank you

Cathal

[Cathal O'Donghaile]

Attached pics once again. Not sure if they are displaying above.

[Alex P]

I can't comment on the differing plots BUT, in either case your settings need to be changed.

use a 512 FFT 

9 million averages requires ~ 50 Minutes of Time .. try  Intermediate Avg 100 & a total of 300K = 100 seconds

only that tiny shift looks like H data

Disable Offset Tuning

[edhar...@gmail.com]

Obvious questions:

 

How are you powering the cased Sawbird?  (Is the LED lit?)

Are you powering via the USB connector or via the RF line/SDR?  (Does your SDR actually support power?)

(As it’s too easy to do… I’ve done it… :o) Are you sure you’ve got the antenna on the input side and SDR on the output side?

 

Ed

 

From: sara...@googlegroups.com <sara...@googlegroups.com> On Behalf Of Cathal O'Donghaile
Sent: Monday, May 11, 2026 10:17 AM
To: Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Subject: [SARA] Re: Different readings from barebones and cased Sawbird H1

 

Attached pics once again. Not sure if they are displaying above.

On Monday, 11 May 2026 at 15:09:09 UTC+1 Cathal O'Donghaile wrote:

Hi Everyone

 

I'm hoping someone can help me. I've been testing both a barebones H1 and cased H1 filter from Sawbird with AirSpy and I'm getting very different readouts. Most notably, I'm getting a faint hydrogen reading from the barebones and nothing from the cased one. Attached are screenshots:

 

 

So 3 things stand out:

 

• Hydrogen bump on Barebones
• The difference in profile between the 2 devices
• The cased H1 signal is louder sitting above the 50Db line whereas the barebones signal is slight quieter below the 50Db line
  
  Anyone any ideas what might be wrong? Is it possible the cased one isn't picking up the signal from the probe. Just a note I have a copper probe attached.

Would appreciate the help, thank you

 

Cathal

--
--
You received this message because you are subscribed to the Google
Groups "Society of Amateur Radio Astronomers" group.
To post to this group, send email to sara...@googlegroups.com
To unsubscribe from this group, send email to
sara-list-...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/sara-list?hl=en
---
You received this message because you are subscribed to the Google Groups "Society of Amateur Radio Astronomers" group.
To unsubscribe from this group and stop receiving emails from it, send an email to sara-list+...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/sara-list/b65f3e71-3d83-48e5-ae8d-71bb76f8ede1n%40googlegroups.com.

[b alex pettit jr]

Use a 50 Ohm Terminator on the LNA input for Background Correction acquisition

It will give you a  flat line across the IFavg Spectrum & data files

[Cathal O'Donghaile]

For Ed:

Yes, the LED is lit up on both the cased and barebones. I'm providing power via the coaxial between the SDR and LNA. It's the NooElec Smartee V3.  I've also made the mistake of wiring the wrong way around, but this time no lol.

Alex:

Thanks for those settings and the suggestion of 50 Ohm terminator. I'll re-run tests. 

[b alex pettit jr]

Cathal,

Your current settings requires 50 mins to capture a Background Correction frame.

THEN, when you begin to capture Real Data, IFaverage tosses the first frame before recording a file...

meaning you may be waiting 1 1/2 hrs or more to capture One File

[b alex pettit jr]

I should have added : it takes at least 50% of the frame time for the spectrum to begin to stabilize & show the final value.

Meaning, you need to wait at least 1/2 hr before really 'seeing' any data with your current setting ....  so go with much

shorter  time frames during eval.

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

[Cathal O'Donghaile]

Thanks, Alex. I've recalibrated the background and set the IF Average parameters per your guidance. The background is now completely flat. 

I'll be taking new readings in the morning. See how it goes.

[b alex pettit jr]

OoooooK !