Date   

Re: Best Gain Settings for 137 mhz reception

W0LEV
 

Here is the link to Chip's U310 (metal case) preamps.  The J-310 works as well.


On Sat, Sep 9, 2017 at 9:54 AM, jdow <jdow@...> wrote:
LNA4All has a lot of gain. In most situations 5 dB gain is enough to set system noise figure well enough. 10 dB might be needed if you have a long coax run. With 20 dB you almost certainly have too much gain involved. That causes IMD from digital saturation effects without improving reception particularly. For beset results you need to play with the individual gain settings on the R820T2 chip. It will still be a little problematic. So a specialized 162.500 MHz filter might be your way out of trouble. A gain setting around 10 would be WAY WAY too high, regardless. I have a 20 dB preamp here and have the expected problems with it. I need to use some subtle filtering to just make up the cable loss and about 6 or 7 dB of extra gain over the amplifier's useful range.

If GB is anything like the US pager transmitters are your likely source of problems. "Good luck" filtering them They are witnin band for anything other than SAW filters or very selective filters based on helical resonators. (The latter are fun to play with. But, the mechanical design for such filters is awkward.)

If you can find the major source of RF energy you can combine a selecting 162.5 MHz filter with a tuned coaxial stub to null the interference source. And for God's sake, reduce the AirSpy gain - a lot. (I use around minimum settings on R820T2 based RTLSDR dongles, which have even worse problems with overload.)

In the final analysis, the number of digitized bits is going to set your usable instantaneous dynamic range. If you improve noise figure 4 dB that means interfering sources that just barely cause overload before will be on the order of 7 dB into overload. (4 dB for NF improvement and 3 dB or more for the extra gain needed to "set" the noise figure below the R820T2 noise figure.)

Mumble mumble - where can I get a 10 dB attenuator that passes DC with no attenuation? That's a start....

{^_-}   Joanne

On 2017-09-09 07:28, David J Taylor via Groups.Io wrote:
From: Ruben Navarro Huedo (EA5BZ)

Hello friends:
I am trying my Airspy R2 receiving NOAA and Meteor M2 sats.
My setup is:
Wimo TA-1 Turnstile Antenna (http://www.wimo.com/scanner-antennas_s.html) --> LNA4ALL --> Around 10 meters Aircell 7 coax --> Airspy
I have been trying with Linearity and using a Gain value around 10.
If i use a higher gain value i start to have some intermittent BCFM interferences.
My question is:
Could i obtain better SNR values using Free Gain mode? What adjustment is the best?
How do you think i could obtain better SNR values? Using another LNA? Using a BCFM filter?

Thank's a lot for your help.
=======================================

Ruben,

Are you sure you need any extra gain?  I'm testing with Linearity, Gain: 14, Sample rate: 3 Msps, Decimation: 64, using an Airspy Mini.  Are you sure what's causing the interference?  I get pager transmissions on both 138 and 153 MHz which show up as bands - some with a near 1 minute repetition interval.

Ideally a filtered pre-amp, such as:

  https://store.uputronics.com/index.php?route=product/product&path=59&product_id=94

but unfortunately this is out of stock.  Therefore I would go for a broadcast FM reject filter.  I see that Amazon offer one from a Greek amateur - SV1AFN:

  https://www.amazon.co.uk/FM-Notch-88-108-reject-receivers/dp/B074S8JBBZ/

All being well the forthcoming Airspy HF+ will perform better.

73,
David GM8ARV






--
Dave - WØLEV
Just Let Darwin Work


Re: Best Gain Settings for 137 mhz reception

W0LEV
 

At those freqencies why not build yourself a common gate J-310 preamp.  Nominally 12 dB of gain, 1.5 dB NF, narrow band design.  IF and ONLY IF you MUST have a preamp, this is a good choice as the gain is not too great, NF is good, and the dynamic range is to die for.  Google:  N6CA preamps or something like that.  They are very simple to build and really difficult to "get it right". 

Dave - W0LEV

PS:  I'd still recommend an FM SBF in front of it all.  DON'T, DO NOT, use a wideband unfiltered "DC-to-Light" preamp!

On Sat, Sep 9, 2017 at 9:54 AM, jdow <jdow@...> wrote:
LNA4All has a lot of gain. In most situations 5 dB gain is enough to set system noise figure well enough. 10 dB might be needed if you have a long coax run. With 20 dB you almost certainly have too much gain involved. That causes IMD from digital saturation effects without improving reception particularly. For beset results you need to play with the individual gain settings on the R820T2 chip. It will still be a little problematic. So a specialized 162.500 MHz filter might be your way out of trouble. A gain setting around 10 would be WAY WAY too high, regardless. I have a 20 dB preamp here and have the expected problems with it. I need to use some subtle filtering to just make up the cable loss and about 6 or 7 dB of extra gain over the amplifier's useful range.

If GB is anything like the US pager transmitters are your likely source of problems. "Good luck" filtering them They are witnin band for anything other than SAW filters or very selective filters based on helical resonators. (The latter are fun to play with. But, the mechanical design for such filters is awkward.)

If you can find the major source of RF energy you can combine a selecting 162.5 MHz filter with a tuned coaxial stub to null the interference source. And for God's sake, reduce the AirSpy gain - a lot. (I use around minimum settings on R820T2 based RTLSDR dongles, which have even worse problems with overload.)

In the final analysis, the number of digitized bits is going to set your usable instantaneous dynamic range. If you improve noise figure 4 dB that means interfering sources that just barely cause overload before will be on the order of 7 dB into overload. (4 dB for NF improvement and 3 dB or more for the extra gain needed to "set" the noise figure below the R820T2 noise figure.)

Mumble mumble - where can I get a 10 dB attenuator that passes DC with no attenuation? That's a start....

{^_-}   Joanne

On 2017-09-09 07:28, David J Taylor via Groups.Io wrote:
From: Ruben Navarro Huedo (EA5BZ)

Hello friends:
I am trying my Airspy R2 receiving NOAA and Meteor M2 sats.
My setup is:
Wimo TA-1 Turnstile Antenna (http://www.wimo.com/scanner-antennas_s.html) --> LNA4ALL --> Around 10 meters Aircell 7 coax --> Airspy
I have been trying with Linearity and using a Gain value around 10.
If i use a higher gain value i start to have some intermittent BCFM interferences.
My question is:
Could i obtain better SNR values using Free Gain mode? What adjustment is the best?
How do you think i could obtain better SNR values? Using another LNA? Using a BCFM filter?

Thank's a lot for your help.
=======================================

Ruben,

Are you sure you need any extra gain?  I'm testing with Linearity, Gain: 14, Sample rate: 3 Msps, Decimation: 64, using an Airspy Mini.  Are you sure what's causing the interference?  I get pager transmissions on both 138 and 153 MHz which show up as bands - some with a near 1 minute repetition interval.

Ideally a filtered pre-amp, such as:

  https://store.uputronics.com/index.php?route=product/product&path=59&product_id=94

but unfortunately this is out of stock.  Therefore I would go for a broadcast FM reject filter.  I see that Amazon offer one from a Greek amateur - SV1AFN:

  https://www.amazon.co.uk/FM-Notch-88-108-reject-receivers/dp/B074S8JBBZ/

All being well the forthcoming Airspy HF+ will perform better.

73,
David GM8ARV






--
Dave - WØLEV
Just Let Darwin Work


Re: Best Gain Settings for 137 mhz reception

Ruben Navarro Huedo (EA5BZ)
 

Thank's Dave for your answer.

Yes... i have been playing with gain setting and (at this moment) best settings are using FREE with
IF 5
Mixer 15
LNA 7

I will wait for my BPF-AIR and continue testing.


Re: Best Gain Settings for 137 mhz reception

Ruben Navarro Huedo (EA5BZ)
 

Hello David:

A lot of thank's for your answer.
I am sure interference comes from BCFM when i am using high gain.

2 weeks ago i bought this filter:
http://eshop.ddamtek.cz/ddamtek-bpf-air
But i am still waiting for it.

Really i think i don't need more gain. What i need is better SNR.
And i think i can have better SNR using BPF or BCFM reject filter.


Re: Best Gain Settings for 137 mhz reception

jdow
 

LNA4All has a lot of gain. In most situations 5 dB gain is enough to set system noise figure well enough. 10 dB might be needed if you have a long coax run. With 20 dB you almost certainly have too much gain involved. That causes IMD from digital saturation effects without improving reception particularly. For beset results you need to play with the individual gain settings on the R820T2 chip. It will still be a little problematic. So a specialized 162.500 MHz filter might be your way out of trouble. A gain setting around 10 would be WAY WAY too high, regardless. I have a 20 dB preamp here and have the expected problems with it. I need to use some subtle filtering to just make up the cable loss and about 6 or 7 dB of extra gain over the amplifier's useful range.

If GB is anything like the US pager transmitters are your likely source of problems. "Good luck" filtering them They are witnin band for anything other than SAW filters or very selective filters based on helical resonators. (The latter are fun to play with. But, the mechanical design for such filters is awkward.)

If you can find the major source of RF energy you can combine a selecting 162.5 MHz filter with a tuned coaxial stub to null the interference source. And for God's sake, reduce the AirSpy gain - a lot. (I use around minimum settings on R820T2 based RTLSDR dongles, which have even worse problems with overload.)

In the final analysis, the number of digitized bits is going to set your usable instantaneous dynamic range. If you improve noise figure 4 dB that means interfering sources that just barely cause overload before will be on the order of 7 dB into overload. (4 dB for NF improvement and 3 dB or more for the extra gain needed to "set" the noise figure below the R820T2 noise figure.)

Mumble mumble - where can I get a 10 dB attenuator that passes DC with no attenuation? That's a start....

{^_-} Joanne

On 2017-09-09 07:28, David J Taylor via Groups.Io wrote:
From: Ruben Navarro Huedo (EA5BZ)
Hello friends:
I am trying my Airspy R2 receiving NOAA and Meteor M2 sats.
My setup is:
Wimo TA-1 Turnstile Antenna (http://www.wimo.com/scanner-antennas_s.html) --> LNA4ALL --> Around 10 meters Aircell 7 coax --> Airspy
I have been trying with Linearity and using a Gain value around 10.
If i use a higher gain value i start to have some intermittent BCFM interferences.
My question is:
Could i obtain better SNR values using Free Gain mode? What adjustment is the best?
How do you think i could obtain better SNR values? Using another LNA? Using a BCFM filter?
Thank's a lot for your help.
=======================================
Ruben,
Are you sure you need any extra gain?  I'm testing with Linearity, Gain: 14, Sample rate: 3 Msps, Decimation: 64, using an Airspy Mini.  Are you sure what's causing the interference?  I get pager transmissions on both 138 and 153 MHz which show up as bands - some with a near 1 minute repetition interval.
Ideally a filtered pre-amp, such as:
 https://store.uputronics.com/index.php?route=product/product&path=59&product_id=94
but unfortunately this is out of stock.  Therefore I would go for a broadcast FM reject filter.  I see that Amazon offer one from a Greek amateur - SV1AFN:
 https://www.amazon.co.uk/FM-Notch-88-108-reject-receivers/dp/B074S8JBBZ/
All being well the forthcoming Airspy HF+ will perform better.
73,
David GM8ARV


Re: Best Gain Settings for 137 mhz reception

W0LEV
 

The AirSpy needs an FM SBF.  This should be placed in front of the preamp if at all possible.  Yes, you will suffer the insertion loss of the filter, but that's better than being limited by FM BC noise.

Also, without going into a long dissertation on gain, NF, and dynamic range, use the "Sensitivity" setting in your SW.   In SDR#, the settings are: 1)  Sensitivity, 2) Linearity, and 3) Free (where you can set RF, IF, and mixer gains individually).  "Best Setting" is different for each application depending on antenna gain, close-by RF sources, LNA gain, LNA passband, feedline loss, . . . .   However, best reception will be had by setting parameters for best [(S + N) / N] ratio which can be seen on the spectrum at the top of the waterfall (in SDR#, at least).

Dave -W0LEV      

On Sat, Sep 9, 2017 at 8:01 AM, Ruben Navarro Huedo (EA5BZ) <runahue@...> wrote:
Hello friends:
I am trying my Airspy R2 receiving NOAA and Meteor M2 sats.
My setup is:
Wimo TA-1 Turnstile Antenna (http://www.wimo.com/scanner-antennas_s.html) --> LNA4ALL --> Around 10 meters Aircell 7 coax --> Airspy
I have been trying with Linearity and using a Gain value around 10.
If i use a higher gain value i start to have some intermittent BCFM interferences.
My question is:
Could i obtain better SNR values using Free Gain mode? What adjustment is the best?
How do you think i could obtain better SNR values? Using another LNA? Using a BCFM filter?

Thank's a lot for your help.




--
Dave - WØLEV
Just Let Darwin Work


Re: Best Gain Settings for 137 mhz reception

David J Taylor
 

From: Ruben Navarro Huedo (EA5BZ)

Hello friends:
I am trying my Airspy R2 receiving NOAA and Meteor M2 sats.
My setup is:
Wimo TA-1 Turnstile Antenna (http://www.wimo.com/scanner-antennas_s.html) --> LNA4ALL --> Around 10 meters Aircell 7 coax --> Airspy
I have been trying with Linearity and using a Gain value around 10.
If i use a higher gain value i start to have some intermittent BCFM interferences.
My question is:
Could i obtain better SNR values using Free Gain mode? What adjustment is the best?
How do you think i could obtain better SNR values? Using another LNA? Using a BCFM filter?

Thank's a lot for your help.
=======================================

Ruben,

Are you sure you need any extra gain? I'm testing with Linearity, Gain: 14, Sample rate: 3 Msps, Decimation: 64, using an Airspy Mini. Are you sure what's causing the interference? I get pager transmissions on both 138 and 153 MHz which show up as bands - some with a near 1 minute repetition interval.

Ideally a filtered pre-amp, such as:

https://store.uputronics.com/index.php?route=product/product&path=59&product_id=94

but unfortunately this is out of stock. Therefore I would go for a broadcast FM reject filter. I see that Amazon offer one from a Greek amateur - SV1AFN:

https://www.amazon.co.uk/FM-Notch-88-108-reject-receivers/dp/B074S8JBBZ/

All being well the forthcoming Airspy HF+ will perform better.

73,
David GM8ARV
--
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-taylor@blueyonder.co.uk
Twitter: @gm8arv


.


Best Gain Settings for 137 mhz reception

Ruben Navarro Huedo (EA5BZ)
 

Hello friends:
I am trying my Airspy R2 receiving NOAA and Meteor M2 sats.
My setup is:
Wimo TA-1 Turnstile Antenna (http://www.wimo.com/scanner-antennas_s.html) --> LNA4ALL --> Around 10 meters Aircell 7 coax --> Airspy
I have been trying with Linearity and using a Gain value around 10.
If i use a higher gain value i start to have some intermittent BCFM interferences.
My question is:
Could i obtain better SNR values using Free Gain mode? What adjustment is the best?
How do you think i could obtain better SNR values? Using another LNA? Using a BCFM filter?

Thank's a lot for your help.


Re: Spy Server on the ASUS Tinkerboard

mike@...
 


The reduced bandwidth mode puts more loading on the server (Tinkerboard) and I was losing data when the FFT frame rate was set to the default 20 fps. Changing to 10 fps solved the problem and left a very occasional glitch, which is why I said that it just manages to cope. If you're having good results with Linaro, that's good news, because it's probably a better match  to the Tinkerboard hardware. I moved-on to other distros because there were reports of the early Linaro being unstable and poorly supported.

Regards,


Mike - G4WNC


Re: Interest List for HF+ ? #airspyhfplus

wb6la@...
 

Thanks very much! A few GMail filters and fireworks will go off to mark the initiation of preorders.

Cheers, 


Re: Recommended ARM SoC board for Spy Server

Martin Smith
 

The Odroid HC1 might be interesting, I've not used it but I do like the look of the heatsink. 8 cores (4xA15-Cortex+4xA7-Cortex), gigabit, SATA3, but only one USB 2.0 HS port (which is better than the RPi which has a 5 port hub hardwired into it's one and only USB 2.0 HS port shared by the 10/100 NIC and anything else that is connected).
http://www.hardkernel.com/main/products/prdt_info.php?g_code=G150229074080

It is basically a stripped down XU4, with one USB 3.0 port hardwired into a USB3-to-gigabit bridge chip (Realtek RTL8153 ~112MB/sec) and the other USB 3 port hardwired into a USB3-to-SATA3 bridge chip (JMicron JMS578 ~300MB/sec). Well the LAN is 10/100/1000 so the throughput would be ~1.12MB/sec or ~11.2MB/sec or ~112MB/sec depending on the network it is connected.


Re: Recommended ARM SoC board for Spy Server

jdow
 

On 2017-09-07 07:58, prog wrote:
The Tinkerboard is connected via Ethernet but the SDR# is connected via WiFi.
Try reproducing with ethernet first.
That's a real good point. I've noticed that at least in the US WiFi hates active wireless phones (not cellphones) which share the same spectrum.

{^_^} Joanne


Re: Recommended ARM SoC board for Spy Server

prog
 

The Tinkerboard is connected via Ethernet but the SDR# is connected via WiFi.
Try reproducing with ethernet first.


Re: Recommended ARM SoC board for Spy Server

KF7IJZ
 

On Wed, Sep 6, 2017 at 01:31 pm, prog wrote:
On Wed, Sep 6, 2017 at 01:27 pm, KF7IJZ wrote:
I only have one odd behavior, but I don't think it's the TInkerboard.
I think it's related to your local network. Trying ping'ing the board when it happens again.

 When it happens I am actively Connected to the board via SSH and rebooting the board does not fix the behavior.  I will try this and maybe some packet captures to see what happens. I see in the console out from SpyServer that it continues to respond to tuning commands even though SDR# plays no audio and the waterfall is "frozen". 

The Tinkerboard is connected via Ethernet but the SDR# is connected via WiFi. Other troubleshooting suggestions are appreciated!


Re: Recommended ARM SoC board for Spy Server

Gymnae
 

@KF7IJZ: Have you tried armbian as an alternative to Asus' linaro release? On other SoCs I had good results with Armbian, maybe it will broaden the appeal of the tinkerboard for other parallel uses.


Re: Spy Server on the ASUS Tinkerboard

KF7IJZ
 

When you say "It only just manages to cope with the reduced bandwidth mode and I've had to drop the FFT frame rate in the Spy Server config file to 10fps." do you mean having Spyserver do the FFT processing and audio streaming?  I am running the latest Linaro from Asus and have had no problems with my TInkerboard decoding FFT/streaming audio.


Re: Recommended ARM SoC board for Spy Server

prog
 

On Wed, Sep 6, 2017 at 01:27 pm, KF7IJZ wrote:
I only have one odd behavior, but I don't think it's the TInkerboard.
I think it's related to your local network. Trying ping'ing the board when it happens again.


Re: Recommended ARM SoC board for Spy Server

KF7IJZ
 

I am currently running a Tinker Board as a host for both an Airspy R2 and an Airspy Mini.  In my tests using airspy_rx, I was able to get roughly a total of 12msps between the two interfaces.  I have the R2 hooked up for VHF/UHF duties and the Mini connected to a Spyverter R2 for HF duties.  I am still launching Spyserver manually and have two config files.  I assume that I could run two instances configured for different ports simultaneously and everything would be fine, I just haven't had time to play with that.

Running the R2 at full bandwidth (8msps) and decoding narrow FM, the Spyserver is using ~ 165% CPU and very little RAM.  You will want active cooling on the Tinkerboard though.  With no fan in a room that's 74degF, it quickly climbs to 70degC in no time.  With a USB fan, it stays around 40.

Finally, I only have one odd behavior, but I don't think it's the TInkerboard.  Occasionally, I have to reboot my PC running SDR# when connecting to one of my remote Airspy nodes.  The FFT will start to come across with no audio for ~ 3 seconds and then SDR# acts like it freezes - the last line of FFT data just repeats and there is no audio.  I'm able to hit the "stop" button and the application responds to clicks but no connection.  Even after closing the app and starting again.  What's odd is that when this happens rebooting the tinkerboard or stopping and starting Spyserver does nothing - I actually have to reboot my computer to make it work again.

Good luck!  This has been the only good application I've found for the Tinkerboard thus far.  Sad thing is that the USB is still run through an onboard hub rather than directly to the SoC, but it's still fast enough for Spyserver.


Re: SpectrumSpy compatibility with other SDR HW?

David J Taylor
 

Ok, so when the hf+ starts selling, maybe.

Is there other software that does the same job, reasonably well, for the cheaper dongles?


Hans J. Albertsson
==========================================

You could try searching Google......or buy an Airspy Mini.

Cheers,
David
--
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-taylor@blueyonder.co.uk
Twitter: @gm8arv


Re: SpectrumSpy compatibility with other SDR HW?

prog
 

You need to find reasonably competent cheap programmers for that to happen.

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