Topics

Astro Spy - Signal Level Range

Jochen Richert
 

Dear Astro Spy Developers

I am using Astr Spy with my Airspy Mini on a 2m Dish and homemade Biquad for receiving and logging 1420 MHz HI signals. To have a better readability, would it be possible to make the signal level also pre selectable in 1 dBFS steps and not only 10 dBFS?
I already tried to change it from -65 to -70 but it will only show in 10dBFS steps. I would really like to have this feature, because my signal level sometimes falls just below -70 and so I loose about 9 dbFS os scaling factor, because I have to use -60 to -80.


Many thanks and greetings from Switzerland
HB9DRT, Jochen

prog
 

Are you aware you also have the actual RF gain to fit your signal within the desired range?

David Eckhardt
 

We had a 'somewhat' similar problem at LTO (Little Thompson Observatory:  <starkids.org>) in setting up our H1 receiver.  Our setup:
     1)  14-foot diameter off-center-fed dish
     2)  1 GHz HPF (to get rid of local RF noise)
     3)  LNA (nominal +22 dB gain, NF = 0.5 dB)
     4)  Bias tee
1 through 4 are at the feed which is a loop 1/4-wavelength in front of a splash plate.
     5)  75-feet 1/2-inch hardline
     6)  Another +20 dB LNA
     7)  bias tee
     8)  AirSpy
     9)  PC running Radio Sky Pipe (freeware at <http://radiosky.com/skypipeishere.html>)

We had to include the second LNA in the warm room (item 6) to have enough gain to get the 'signal' significantly out of the noise for RSP.  Suggest you add another gain stage in front of the AirSpy. 

Our system noise temp runs - measured - about 100 k.  We should do better, but the requirement of the 1 GHz HPF dictates that initial loss to get rid of RF dirt from a close-by cell tower. 

Dave - W0LEV
'

     8)  PC

On Sat, Aug 5, 2017 at 6:03 AM, Jochen Richert <jochen.richert@...> wrote:
Dear Astro Spy Developers

I am using Astr Spy with my Airspy Mini on a 2m Dish and homemade Biquad for receiving and logging 1420 MHz HI signals. To have a better readability, would it be possible to make the signal level also pre selectable in 1 dBFS steps and not only 10 dBFS?
I already tried to change it from -65 to -70 but it will only show in 10dBFS steps. I would really like to have this feature, because my signal level sometimes falls just below -70 and so I loose about 9 dbFS os scaling factor, because I have to use -60 to -80.


Many thanks and greetings from Switzerland
HB9DRT, Jochen




--
Dave - WØLEV
Just Let Darwin Work

prog
 

I have the impression his problem is more about the flexibility of the display than the actual quality of the signal, which seems good since it's not the problem he's complaining about.

Jochen Richert
 

Hi Dave

Thanks for your answer and the description of your setup. "prog" explained it right, I have not a problem with the signal strength, I would like to have the possibility to scale the signal strength in smaller steps than only 10 dbFS.
In the moment, I can also see the 1.5 dBFS lowered noise floor, due to the coronal hole facing to us. This is also the reason, why the level drops below -70 dbFS. You may have a look to my animation on youtube  https://youtu.be/4FC_6LQjpHA where you see the signal level over 24 hours.
My Setup is a 2 Meter Dish, a HB9BBD LNA with 40 dB gain and 0.19 dB NF. Than through 5 Meter low loss Koax Cable CS29 into my Airspy Mini. I agree, I do need a bit more gain but the next days, I will replace the Bi Quad by a Linear Horn or Septum Horn Feed.

So I hope, the developers could easily switch a bit and all is working ;-)

vy 73's de HB9DRT, Jochen

prog
 

The problem is that "bit" also affects SDR# and all the spectrum plugins, since it's based on the same reusable component.
The easiest trick is to increase/decrease the RF gain by 1 tick (3 dB) which will align your signal in the right region.

David Eckhardt
 

OK.  I understand.  Using my spectrum analyzers, there are many times I employ the 5 dB per major division, and, on occasion, even the 1 dB per major div.

While we're at it, using either the radio astronomy application aimed at the H1 line or the spectrum analyzer (SpectrumSpy), it would be extremely helpful if we had something as small as 10 kHz span and choice of resolution bandwidths.  Of course, there is always something more that would be 'absolutely' needed......

Personally, I have recommended the AirSpy to many customers (EMC and RFI) who do not have the resources to buy or rent  a full-up spectrum analyzer.  For the purpose of reducing radiated emissions, the AirSpy is just what is needed!  It's a wonderful piece of test gear if you don't have a spectrum analyzer (which I do).  But, this is getting off the subject.

Dave - W0LEV   



On Sat, Aug 5, 2017 at 10:36 AM, prog <info@...> wrote:
I have the impression his problem is more about the flexibility of the display than the actual quality of the signal, which seems good since it's not the problem he's complaining about.




--
Dave - WØLEV
Just Let Darwin Work

Marcus D. Leech <mleech@...>
 

On 08/05/2017 02:41 PM, David Eckhardt wrote:
OK.  I understand.  Using my spectrum analyzers, there are many times I employ the 5 dB per major division, and, on occasion, even the 1 dB per major div.

While we're at it, using either the radio astronomy application aimed at the H1 line or the spectrum analyzer (SpectrumSpy), it would be extremely helpful if we had something as small as 10 kHz span and choice of resolution bandwidths.  Of course, there is always something more that would be 'absolutely' needed......

Personally, I have recommended the AirSpy to many customers (EMC and RFI) who do not have the resources to buy or rent  a full-up spectrum analyzer.  For the purpose of reducing radiated emissions, the AirSpy is just what is needed!  It's a wonderful piece of test gear if you don't have a spectrum analyzer (which I do).  But, this is getting off the subject.

Dave - W0LEV   

Jumping right into the middle of this thread.

The H1 "line" is usually only a MAX of about 2dB above the surrounding continuum noise, which itself corresponds to a sky temp of perhaps 10-20K
  at 21cm.

I usually set my display on my own apps to about 0.5dB/div, but of course, I also log all the data, so I can later inspect and process it at whatever level
  of detail I might desire.


Jochen Richert
 

Yes, that is possibly and I also tried this already by changing the amplification, but that would only zoom 10 dbFS.
So I know now, that it is not an easy bit changing, changing the config file would not help and have to look further, into other possible solutions.

Many thanks for all the help and ideas around.

Jochen

jdow
 

Have you considered placing the second LNA in the middle of your 75' feed rather than at the input for the Airspy? It might purchase a few easy more degrees of noise temperature.

{^_^}

On 2017-08-05 07:53, David Eckhardt wrote:
We had a 'somewhat' similar problem at LTO (Little Thompson Observatory: <starkids.org <http://starkids.org>>) in setting up our H1 receiver. Our setup:
1) 14-foot diameter off-center-fed dish
2) 1 GHz HPF (to get rid of local RF noise)
3) LNA (nominal +22 dB gain, NF = 0.5 dB)
4) Bias tee
1 through 4 are at the feed which is a loop 1/4-wavelength in front of a splash plate.
5) 75-feet 1/2-inch hardline
6) Another +20 dB LNA
7) bias tee
8) AirSpy
9) PC running Radio Sky Pipe (freeware at <http://radiosky.com/skypipeishere.html>)
We had to include the second LNA in the warm room (item 6) to have enough gain to get the 'signal' significantly out of the noise for RSP. Suggest you add another gain stage in front of the AirSpy.
Our system noise temp runs - measured - about 100 k. We should do better, but the requirement of the 1 GHz HPF dictates that initial loss to get rid of RF dirt from a close-by cell tower.
Dave - W0LEV
'
8) PC
On Sat, Aug 5, 2017 at 6:03 AM, Jochen Richert <jochen.richert@... <mailto:jochen.richert@...>> wrote:
Dear Astro Spy Developers
I am using Astr Spy with my Airspy Mini on a 2m Dish and homemade Biquad for
receiving and logging 1420 MHz HI signals. To have a better readability,
would it be possible to make the signal level also pre selectable in 1 dBFS
steps and not only 10 dBFS?
I already tried to change it from -65 to -70 but it will only show in 10dBFS
steps. I would really like to have this feature, because my signal level
sometimes falls just below -70 and so I loose about 9 dbFS os scaling
factor, because I have to use -60 to -80.
Many thanks and greetings from Switzerland
HB9DRT, Jochen
--
*Dave - WØLEV
*
*/Just Let Darwin Work/*

Marcus D. Leech <mleech@...>
 

On 08/05/2017 10:53 AM, David Eckhardt wrote:
We had a 'somewhat' similar problem at LTO (Little Thompson Observatory:  <starkids.org>) in setting up our H1 receiver.  Our setup:
     1)  14-foot diameter off-center-fed dish
     2)  1 GHz HPF (to get rid of local RF noise)
     3)  LNA (nominal +22 dB gain, NF = 0.5 dB)
     4)  Bias tee
1 through 4 are at the feed which is a loop 1/4-wavelength in front of a splash plate.
     5)  75-feet 1/2-inch hardline
     6)  Another +20 dB LNA
     7)  bias tee
     8)  AirSpy
     9)  PC running Radio Sky Pipe (freeware at <http://radiosky.com/skypipeishere.html>)

We had to include the second LNA in the warm room (item 6) to have enough gain to get the 'signal' significantly out of the noise for RSP.  Suggest you add another gain stage in front of the AirSpy. 

Our system noise temp runs - measured - about 100 k.  We should do better, but the requirement of the 1 GHz HPF dictates that initial loss to get rid of RF dirt from a close-by cell tower. 

Dave - W0LEV

Our own setup for 21cm is:

0.85m offset dish-->circular-waveguide-feed-->20dB, 0.5dB NF LNA--->25m of RG6--->1400-1427MHz filter---->AirSpyMini

We produce live spectra every few minutes here:

http://www.ccera.ca/files/live_data/h1/live_spec.png

If I were going to be running more than 25m of RG6, I'd put a line-amplifier (doesn't need to be an LNA) in-line.  In fact, when we convert this to
  a "binocular" survey instrument, that's what we'll do, because those dishes are further away from our lab.


Daniel Fox
 

I would like to see the Astrospy software to be able to periodically log the averaged spectrum to a csv file.  A couple of other things on my wish list, but this would be a good start.

prog
 

This is the proverbial "when everything falls on your head at the same time."
Software wishlists will be processed when the HF+ is launched.

Jochen Richert
 

Dear Developers

As the HF+ is launched now, I would like to ask again, if there is the possibility to make AstroSpy able to periodically log data into a csv file and probably to store a printscreen of the graph.

Many thanks
Joe

prog
 

On Sat, Jan 6, 2018 at 07:18 am, Jochen Richert wrote:
Dear Developers

As the HF+ is launched now, I would like to ask again, if there is the possibility to make AstroSpy able to periodically log data into a csv file and probably to store a printscreen of the graph.

Many thanks
Joe
Should be doable... after the dust settles down :-)
It won't take long. Stay tuned.

Daniel Fox
 

I too have asked if Astrospy could be modified to do this.  Just the modification for logging to the csv file would be enough, a plot could be made from that.

 

Dan

 

From: main@airspy.groups.io [mailto:main@airspy.groups.io] On Behalf Of Jochen Richert
Sent: Saturday, January 06, 2018 10:19 AM
To: main@airspy.groups.io
Subject: Re: [airspy] Astro Spy - Signal Level Range

 

Dear Developers

As the HF+ is launched now, I would like to ask again, if there is the possibility to make AstroSpy able to periodically log data into a csv file and probably to store a printscreen of the graph.

Many thanks
Joe

Daniel Fox
 

Any chance there will be an update to Astro Spy that does periodic logging, or the possibility of making the source code public so others could work on an update?