Comment on my BFM spectrum please... #ettusb210 #uhd #sdrconsolev3


Erik. M0MWF
 

Hi,

As you can see from the attached picture, I have 3 large 'humps' in the BFM range, with stations appearing out of the top of each (for the most part). You do not see any noise floor inbetween these three groups, like you do at the top end of the spectrum.

Why is this?

I can only guess; are these groups of stations each coming from a common wide-band amplifier?

Thanks in advance for your thoughts.


Simon Brown
 

Get a 88-108MHz bandpass filter.

 

Simon Brown, G4ELI
www.sdr-radio.com

 

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of erik@...
Sent: 21 May 2019 06:40
To: main@SDR-Radio.groups.io
Subject: [SDR-Radio] Comment on my BFM spectrum please... #sdrconsolev3 #uhd #ettusb210

 

Hi,

As you can see from the attached picture, I have 3 large 'humps' in the BFM range, with stations appearing out of the top of each (for the most part). You do not see any noise floor inbetween these three groups, like you do at the top end of the spectrum.

Why is this?

I can only guess; are these groups of stations each coming from a common wide-band amplifier?

Thanks in advance for your thoughts.


Jim Smith G0OFE
 

Looks like some sort of RFI from somewhere. I have a similar problem in the lower few Mhz of the band when beaming south. When I tune in on one (in BFM mode),  I have this ugly 50hz hum.

================================
Jim, Bournemouth, Dorset. IO90BR.
Elad FDM-S2, Airspy HF+, SDRPlay and Funcube Dongle SDR Recievers
8-element OP-DES for Band 2, 8-element LFA for 2m, 3-element LFA for 6m, 20m Windom for HF,. Wellbrook 1530 Loop for LF


On 21/05/2019 05:40, erik@... wrote:
Hi,

As you can see from the attached picture, I have 3 large 'humps' in the BFM range, with stations appearing out of the top of each (for the most part). You do not see any noise floor inbetween these three groups, like you do at the top end of the spectrum.

Why is this?

I can only guess; are these groups of stations each coming from a common wide-band amplifier?

Thanks in advance for your thoughts.

Virus-free. www.avast.com


Erik. M0MWF
 

Thanks gents. I'll get a filter.

As an aside, have you seen the 3D spectrum on this radio?

https://www.youtube.com/watch?time_continue=1331&v=avS51gRJ71s

Might be an idea for SDR Console...

Thanks.


Ray Lyford
 

You could use the Spectrum Lab software it does a 3D display quite well.

Ray


From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> on behalf of erik@... <erik@...>
Sent: 21 May 2019 06:59
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] Comment on my BFM spectrum please... #sdrconsolev3 #uhd #ettusb210
 
Thanks gents. I'll get a filter.

As an aside, have you seen the 3D spectrum on this radio?

https://www.youtube.com/watch?time_continue=1331&v=avS51gRJ71s

Might be an idea for SDR Console...

Thanks.


Allan Isaacs
 

Most SDRs are wide open to signals across the whole radio spectrum.

If you have an SDR Play you can see an effect of this here in the UK by looking at the broadcast FM band.

The SDR Play allows adjustment of the Local Oscillator and with this set to 144MHz I can see very strong signals from 88.5 to 108 MHz perfectly duplicated in the range 376.5 to 396MHz. These are images and are much the same strength as the proper signals.

Jim in Bournemouth might like to check this and we can compare notes?

 

Your interference appears to have blocks around 4MHz wide so tune your receiver until you see these on their correct frequency.

For example the digital radio band here uses well defined blocks of about 1.5MHz in the 220MHz band.

By tuning around you’ll see several instances of these (digital) blocks and no doubt there’s a mast close by that’s transmitting your interference, maybe a mobile phone mast, TV or whatever. Sometimes a smaller mast is designed to look like a tree so may not be too obvious.

Your best option is to use a filter tuned to attenuate the interfering signals or, if you wish to mainly listen to the FM band, use a bandpass filter for that band or both filters.

Unless you attenuate your interfering signal it will mess up most of your reception, not just BFM, perhaps by raising the noise floor even if those blocks are not obvious.

Allan G3PIY

 


From: main@SDR-Radio.groups.io [mailto:main@SDR-Radio.groups.io] On Behalf Of erik@...
Sent: 21 May 2019 06:40
To: main@SDR-Radio.groups.io
Subject: [SDR-Radio] Comment on my BFM spectrum please... #sdrconsolev3 #uhd #ettusb210

 

Hi,

As you can see from the attached picture, I have 3 large 'humps' in the BFM range, with stations appearing out of the top of each (for the most part). You do not see any noise floor inbetween these three groups, like you do at the top end of the spectrum.

Why is this?

I can only guess; are these groups of stations each coming from a common wide-band amplifier?

Thanks in advance for your thoughts.

_._,_._,_

 


Jim Smith G0OFE
 

I'll have a look at this when I get time, but first the OP needs to have a listen on a frequency within a block, but no other signal, and in BFM mode, and let us know if he hears anything (a horrid-sounding hum) to (probably) rule out an emc issue or otherwise.

================================
Jim, Bournemouth, Dorset. IO90BR.
Elad FDM-S2, Airspy HF+, SDRPlay and Funcube Dongle SDR Recievers
8-element OP-DES for Band 2, 8-element LFA for 2m, 3-element LFA for 6m, 20m Windom for HF,. Wellbrook 1530 Loop for LF


On 21/05/2019 08:32, Allan Isaacs wrote:

Most SDRs are wide open to signals across the whole radio spectrum.

If you have an SDR Play you can see an effect of this here in the UK by looking at the broadcast FM band.

The SDR Play allows adjustment of the Local Oscillator and with this set to 144MHz I can see very strong signals from 88.5 to 108 MHz perfectly duplicated in the range 376.5 to 396MHz. These are images and are much the same strength as the proper signals.

Jim in Bournemouth might like to check this and we can compare notes?

 

Your interference appears to have blocks around 4MHz wide so tune your receiver until you see these on their correct frequency.

For example the digital radio band here uses well defined blocks of about 1.5MHz in the 220MHz band.

By tuning around you’ll see several instances of these (digital) blocks and no doubt there’s a mast close by that’s transmitting your interference, maybe a mobile phone mast, TV or whatever. Sometimes a smaller mast is designed to look like a tree so may not be too obvious.

Your best option is to use a filter tuned to attenuate the interfering signals or, if you wish to mainly listen to the FM band, use a bandpass filter for that band or both filters.

Unless you attenuate your interfering signal it will mess up most of your reception, not just BFM, perhaps by raising the noise floor even if those blocks are not obvious.

Allan G3PIY

 


From: main@SDR-Radio.groups.io [mailto:main@SDR-Radio.groups.io] On Behalf Of erik@...
Sent: 21 May 2019 06:40
To: main@SDR-Radio.groups.io
Subject: [SDR-Radio] Comment on my BFM spectrum please... #sdrconsolev3 #uhd #ettusb210

 

Hi,

As you can see from the attached picture, I have 3 large 'humps' in the BFM range, with stations appearing out of the top of each (for the most part). You do not see any noise floor inbetween these three groups, like you do at the top end of the spectrum.

Why is this?

I can only guess; are these groups of stations each coming from a common wide-band amplifier?

Thanks in advance for your thoughts.


Virus-free. www.avast.com


Joe Puma
 

He’s on 102mhz which suggests he wants broadcast band.  

Those humps look like cellular or maybe HD tv?, you might be getting major IMD from a cell tower. Maybe browse around around cellular frequencies 700mhz, 800 and 900. 



On May 21, 2019, at 1:50 AM, Simon Brown <simon@...> wrote:

Get a 88-108MHz bandpass filter.

 

Simon Brown, G4ELI
www.sdr-radio.com

 

 

From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io> On Behalf Of erik@...
Sent: 21 May 2019 06:40
To: main@SDR-Radio.groups.io
Subject: [SDR-Radio] Comment on my BFM spectrum please... #sdrconsolev3 #uhd #ettusb210

 

Hi,

As you can see from the attached picture, I have 3 large 'humps' in the BFM range, with stations appearing out of the top of each (for the most part). You do not see any noise floor inbetween these three groups, like you do at the top end of the spectrum.

Why is this?

I can only guess; are these groups of stations each coming from a common wide-band amplifier?

Thanks in advance for your thoughts.


Erik. M0MWF
 

I know what you mean about duplicates.

I can perfectly hear 2m conversations around 30MHz. It often drives me mad as I'm scanning around the frequencies.


Erik. M0MWF
 

Hi,
 
The location is Phuket, Thailand. I can listen to those Thai stations within the blocks if desired (but why would you, terrible stations), without any noise at all. Indeed the strongers government stations acheive full quieting too.

Phuket FM (one of the harder stations to receive well) has the odd 'crackling' from time to time, but still comes in stereo, and I enjoy it much with my wireless headphones. Typical strength is ~ -97dBm. They have an agreement with the BBC, and I get 2hrs of house music a couple nights / week. Lovely. Expensive radio, I know, and not audiophile quality too. But very listenable.

I can often hear Air Traffic all around the the place too. "One thirty decimal nine" BOOMS out perfect at around 70MHz. Have to back off the gain (normally 45dB), and if using my ZX60-P103LN+ mini circuits LNA, I have to have as little as < 20dB of gain, or the ADC is oversaturated.

HDSDR has the humps too, but last time I checked it had only TWO! That confused the hell out of me. I believe it uses a newer UHD version, but don't know much of any other differences.