Date   

Re: Best Gain Settings for 137 mhz reception

David J Taylor
 

From: 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.
================================

Ruben,

The company you mention used to produce an FM stop filter (the HPN-30118) but I don't see it listed any more. I tested that here:

http://www.satsignal.eu/Radio/ddamtek-filters.html#HPN-30118

but you can see the response of the filter you have on order on that page too.

I also have the type of pager interference which Joanne mentioned, and it's a real killer on 2m for me. I managed to reduce it significantly using a repeater filter from China, where instead of using the filter in its normal mode (antenna to centre, RX and TX to each end), I use the filter end-to-end (nothing connected to the centre), so that each notch is in the path, producing the desired two notches at 137 and 153 MHz. I get 50-60 dB rejection. I wrote that up here:

http://www.satsignal.eu/Radio/2m-filter.html

The pager kills APT 137 MHz reception, but I did build a simple helical notch filter, where the aim was to produce a limited amount of attenuation so as not to reduce the wanted signal too much:

http://www.satsignal.eu/wxsat/filters/HelicalNotch.htm

I have that in front of the (now unobtainable) HAB pre-amp, a four-way splitter (helps reduce the gain, too), feeding an Airspy Mini.

You might also search eBay with: "FM Trap filter"

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


.


Re: Best Gain Settings for 137 mhz reception

jdow
 

The U310 is my favorite goto RF JFET. Properly used it can perform WONDERFULLY. Common gate push-pull has very nice IMD properties, especially for even order IMD which is naturally fairly high in JFETs as they are square law devices.

{^_^}

On 2017-09-09 09:19, David Eckhardt wrote:
Here is the link to Chip's U310 (metal case) preamps.  The J-310 works as well.
http://www.ham-radio.com/n6ca/50MHz/50appnotes/U310.html
On Sat, Sep 9, 2017 at 9:54 AM, jdow <jdow@earthlink.net <mailto:jdow@earthlink.net>> 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
<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
<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/
<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

Anders J. Ørts
 

Hi Ruben,
 
Rather than giving firm DO's or DO NOT's, I would like to tell you what works for me.
 
Here is my current setup and settings. 
Signal chain:
Antenna: Turnstile, old school type with a large screen, approx. 2.5m above the ground
LNA: Uputronics wideband (at the antenna)
Coax: ~15m RF240
Filter: RTL-SDR.com FM Broadcast Notch/Band stop filter
SDR: Airspy Mini
 
Here is my SDR# settings:


That gives me a noise floor of around -80dB.
When the MeteorMN2 is close, I see a SNR of 25-28 dB (with NOAA APT 40-45 dB SNR)
Most of the time I can decode signals from MeteorMN2, when the elvation is 2-3 degrees above the horizon.
 
I live in the country side and I think it's a quite RF-friendly environment. I have had problems with interference, but when I finally tracked it down, it turned out that it came from  components in my own off-grid solar system and an electronic mole scare!
 
All the best
Anders


Re: Best Gain Settings for 137 mhz reception

Ruben Navarro Huedo (EA5BZ)
 

David (GM8ARV) :

What do you think about BPF-AIR?
You have a test in your web site: http://www.satsignal.eu/Radio/ddamtek-filters.html
Will it help with my BCFM problem?

Tnx a lot.


New client app for the spyserver in development #airspyhfplus

prog
 

The DSP will be done in a RPi or similar running the a new version of the SpyServer. The FFT data and audio will be streamed over the network.

http://airspy.com/downloads/tablet-sdr.mp4


http://airspy.com/downloads/watch-sdr.mp4


Re: Best Gain Settings for 137 mhz reception

W0LEV
 

"Free" gain setting allows the user to set the RF, IF, and mixer gains independently. 

I am now on my third AirSpy.  The first two, AirSpy Ones, are laid to ruin by close-by lightning strikes (front end damage and USB loss).  So far......  ALL have (and do) need an FM Stopband filter before feeding RF to the input SMA connector.  The strongest FM signal here at my location is -35 dBm on the antenna I use for 20.1 MHz solar and Jupiter emissions.  That isn't 'too' strong as signals go, but its enough with the other stations in the FM band, all less than -35 dBm, to cause several intermod products to show up in a frequency slice from 18 through 26 MHz from the AirSpy.  The filter I use is -40 dB throughout the FM band.  With that, I have no problems with FM broadcast.

Here is another solution from AirSpy.US:


These preamps are filtered for the band of interest and will reduce the problem with the FM BC band while still giving  you better S/N (nower NF).  From my measurements, the AirSpy typically runs with a NF around 4 to 5 dB.  They claim better with the versioin 2, but I have not measured mine.  The NF is also pretty constant over the advertised frequency range.  This is more than adequate for HF, but at and above 50 MHz, you can gain better S/N by using a filtered, 'reasonable' gain preamp.  Spend the $53 from AirSpy America and cure all your problems.  Personally, I'd design and build what I need, but not everyone has the test equipment to assure what they build is what was intended in the final product.   

BTW:  The FM SBF filters from Amazon have a rather marginal track record.  Some work, others don't, loose components, bad solder - typical Chinese start-ups.

Dave - WØLEV

 

On Sat, Sep 9, 2017 at 1:40 PM, doug <dmcgarrett@...> wrote:

On 09/09/2017 09:01 AM, Ruben Navarro Huedo (EA5BZ) 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.
A filter will not improve SNR unless your SNR is being limited by interference--i.e., overload by local FM stations. If the FM is not overloading your receiver, your SNR is
being determined by the noise figure of the front end. You haven't mentioned whether you're using a preamp now. If so, the SNR is determined by the NF of the
preamp AND its gain. If you add a preamp and the FM interference goes up to the point of receiver overload, then put a filter AFTER the preamp. Of course, the
preamp itself must not overload on out-of-band signals like FM, aircraft radio, etc. You need a preamp with a high compression point.
I don't know what free gain mode is. What I have told you is general knowledge of receiver performance that applies to any receiving system.
--Doug, WA2SAY, retired RF engineer.





--
Dave - WØLEV
Just Let Darwin Work


Re: Best Gain Settings for 137 mhz reception

doug
 


On 09/09/2017 09:01 AM, Ruben Navarro Huedo (EA5BZ) 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.
A filter will not improve SNR unless your SNR is being limited by interference--i.e., overload by local FM stations. If the FM is not overloading your receiver, your SNR is
being determined by the noise figure of the front end. You haven't mentioned whether you're using a preamp now. If so, the SNR is determined by the NF of the
preamp AND its gain. If you add a preamp and the FM interference goes up to the point of receiver overload, then put a filter AFTER the preamp. Of course, the
preamp itself must not overload on out-of-band signals like FM, aircraft radio, etc. You need a preamp with a high compression point.
I don't know what free gain mode is. What I have told you is general knowledge of receiver performance that applies to any receiving system.
--Doug, WA2SAY, retired RF engineer.



Re: Best Gain Settings for 137 mhz reception

Ruben Navarro Huedo (EA5BZ)
 

Thank's David.

I go to study it.


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

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