Topics

Newbie material on HF+

Pete Smith
 

Please pardon the extreme newbie questions - I bought an Airspy HF+ recently, intending to use it on the IF of my K3 for spectrum display.  Of course, the K3 is off at Watsonville, so I've been experimenting, comparing the Airspy with a Red Pitaya and a QS1R.

From what I've seen I like SDR# a lot.  Is there anywhere an SDR# manual specifically for the HF+?  I keep running into things in the Quick Start that are not germane to my HF+, running the latest firmware.

Also, can anyone point me toward an explanation of the dBFS scale used for signal strength with the Airspy HF+?  I've established that my Elecraft XG-3's S-9 signal equates to 20 dBFS on SDR#, and its -33 dBM (equivalent to 40 over 9) more than "pins the meter" on SDR#.  Is this normal?  

-- 

73, Pete N4ZR
Check out the Reverse Beacon Network 
at <http://reversebeacon.net>, now 
spotting RTTY activity worldwide. 
For spots, please use your favorite 
"retail" DX cluster.

David Eckhardt
 

If you have an S-9 signal which is -73 dBm and you have set dBFS to 0 dBm, the dBFS should read -73 dBm.  If you have set full scale to -20 dBm, the dBFS should read -53 dBFS.  Likewise, if you set the dBFS to -73 dBFS, the dBFS should read 0 dBFS. 

Dave - WØLEV

Virus-free. www.avast.com

On Thu, Apr 5, 2018 at 8:23 PM, Pete Smith <n4zr@...> wrote:

Please pardon the extreme newbie questions - I bought an Airspy HF+ recently, intending to use it on the IF of my K3 for spectrum display.  Of course, the K3 is off at Watsonville, so I've been experimenting, comparing the Airspy with a Red Pitaya and a QS1R.

From what I've seen I like SDR# a lot.  Is there anywhere an SDR# manual specifically for the HF+?  I keep running into things in the Quick Start that are not germane to my HF+, running the latest firmware.

Also, can anyone point me toward an explanation of the dBFS scale used for signal strength with the Airspy HF+?  I've established that my Elecraft XG-3's S-9 signal equates to 20 dBFS on SDR#, and its -33 dBM (equivalent to 40 over 9) more than "pins the meter" on SDR#.  Is this normal?  

-- 

73, Pete N4ZR
Check out the Reverse Beacon Network 
at <http://reversebeacon.net>, now 
spotting RTTY activity worldwide. 
For spots, please use your favorite 
"retail" DX cluster.




--
Dave - WØLEV
Just Let Darwin Work

Pete Smith
 

But how do you "set" full scale?  Clearly right now it is not correct. I'm looking for a measurement scale for my noise level and signal strengths that is comparable with other SDRs and hardware radios.

73, Pete N4ZR
Check out the Reverse Beacon Network 
at <http://reversebeacon.net>, now 
spotting RTTY activity worldwide. 
For spots, please use your favorite 
"retail" DX cluster.
On 4/5/2018 7:10 PM, David Eckhardt wrote:

If you have an S-9 signal which is -73 dBm and you have set dBFS to 0 dBm, the dBFS should read -73 dBm.  If you have set full scale to -20 dBm, the dBFS should read -53 dBFS.  Likewise, if you set the dBFS to -73 dBFS, the dBFS should read 0 dBFS. 

Dave - WØLEV

Virus-free. www.avast.com

On Thu, Apr 5, 2018 at 8:23 PM, Pete Smith <n4zr@...> wrote:

Please pardon the extreme newbie questions - I bought an Airspy HF+ recently, intending to use it on the IF of my K3 for spectrum display.  Of course, the K3 is off at Watsonville, so I've been experimenting, comparing the Airspy with a Red Pitaya and a QS1R.

From what I've seen I like SDR# a lot.  Is there anywhere an SDR# manual specifically for the HF+?  I keep running into things in the Quick Start that are not germane to my HF+, running the latest firmware.

Also, can anyone point me toward an explanation of the dBFS scale used for signal strength with the Airspy HF+?  I've established that my Elecraft XG-3's S-9 signal equates to 20 dBFS on SDR#, and its -33 dBM (equivalent to 40 over 9) more than "pins the meter" on SDR#.  Is this normal?  

-- 

73, Pete N4ZR
Check out the Reverse Beacon Network 
at <http://reversebeacon.net>, now 
spotting RTTY activity worldwide. 
For spots, please use your favorite 
"retail" DX cluster.



--
Dave - WØLEV
Just Let Darwin Work

jdow
 

You don't - from the GUI. Full scale means the magnitude of the sample coming out of the USB data stream for a sample is 1.00000.

If you are adventuresome you can edit the SDRSharp.exe.config file to change this line:
<add key="fftOffset" value="-40.0" />

{^_^}

On 20180405 18:15, Pete Smith wrote:
But how do you "set" full scale? Clearly right now it is not correct. I'm looking for a measurement scale for my noise level and signal strengths that is comparable with other SDRs and hardware radios.
73, Pete N4ZR
Check out the Reverse Beacon Network
at<http://reversebeacon.net>, now
spotting RTTY activity worldwide.
For spots, please use your favorite
"retail" DX cluster.
On 4/5/2018 7:10 PM, David Eckhardt wrote:
If you have an S-9 signal which is -73 dBm and you have set dBFS to 0 dBm, the dBFS should read -73 dBm.  If you have set full scale to -20 dBm, the dBFS should read -53 dBFS.  Likewise, if you set the dBFS to -73 dBFS, the dBFS should read 0 dBFS.

Dave - WØLEV

<https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=icon> Virus-free. www.avast.com <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=link>


On Thu, Apr 5, 2018 at 8:23 PM, Pete Smith <n4zr@... <mailto:n4zr@...>> wrote:

Please pardon the extreme newbie questions - I bought an Airspy HF+
recently, intending to use it on the IF of my K3 for spectrum display.  Of
course, the K3 is off at Watsonville, so I've been experimenting,
comparing the Airspy with a Red Pitaya and a QS1R.

From what I've seen I like SDR# a lot.  Is there anywhere an SDR#manual
specifically for the HF+?  I keep running into things in the Quick Start
that are not germane to my HF+, running the latest firmware.

Also, can anyone point me toward an explanation of the dBFS scale used for
signal strength with the Airspy HF+? I've established that my Elecraft
XG-3's S-9 signal equates to 20 dBFS on SDR#, and its -33 dBM (equivalent
to 40 over 9) more than "pins the meter" on SDR#.  Is this normal?

--

73, Pete N4ZR
Check out the Reverse Beacon Network
at<http://reversebeacon.net> <http://reversebeacon.net>, now
spotting RTTY activity worldwide.
For spots, please use your favorite
"retail" DX cluster.




--
*Dave - WØLEV
*
*/Just Let Darwin Work/*

Pete Smith
 

Is there no way of adjusting the overall system gain?  Right now, on the GUI's graphical and numeric displays, my -73 dBM reference reads about -53 DbFS, where FS=0 db  Sure, I can mentally subtract 20 dB from every displayed signal strength, but ...

What is the advantage of dBFS over dBM, from the operator's perspective?

73, Pete N4ZR
Check out the Reverse Beacon Network 
at <http://reversebeacon.net>, now 
spotting RTTY activity worldwide. 
For spots, please use your favorite 
"retail" DX cluster.
On 4/5/2018 10:17 PM, jdow wrote:

You don't - from the GUI. Full scale means the magnitude of the sample coming out of the USB data stream for a sample is 1.00000.

If you are adventuresome you can edit the SDRSharp.exe.config file to change this line:
<add key="fftOffset" value="-40.0" />

{^_^}

On 20180405 18:15, Pete Smith wrote:
But how do you "set" full scale? Clearly right now it is not correct. I'm looking for a measurement scale for my noise level and signal strengths that is comparable with other SDRs and hardware radios.

73, Pete N4ZR
Check out the Reverse Beacon Network
at<http://reversebeacon.net>, now
spotting RTTY activity worldwide.
For spots, please use your favorite
"retail" DX cluster.

On 4/5/2018 7:10 PM, David Eckhardt wrote:
If you have an S-9 signal which is -73 dBm and you have set dBFS to 0 dBm, the dBFS should read -73 dBm.  If you have set full scale to -20 dBm, the dBFS should read -53 dBFS.  Likewise, if you set the dBFS to -73 dBFS, the dBFS should read 0 dBFS.

Dave - WØLEV

<https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=icon>     Virus-free. www.avast.com <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=link>


On Thu, Apr 5, 2018 at 8:23 PM, Pete Smith <n4zr@... <mailto:n4zr@...>> wrote:

    Please pardon the extreme newbie questions - I bought an Airspy HF+
    recently, intending to use it on the IF of my K3 for spectrum display.  Of
    course, the K3 is off at Watsonville, so I've been experimenting,
    comparing the Airspy with a Red Pitaya and a QS1R.

    From what I've seen I like SDR# a lot.  Is there anywhere an SDR#manual
    specifically for the HF+?  I keep running into things in the Quick Start
    that are not germane to my HF+, running the latest firmware.

    Also, can anyone point me toward an explanation of the dBFS scale used for
    signal strength with the Airspy HF+? I've established that my Elecraft
    XG-3's S-9 signal equates to 20 dBFS on SDR#, and its -33 dBM (equivalent
    to 40 over 9) more than "pins the meter" on SDR#.  Is this normal?

    --
    73, Pete N4ZR
    Check out the Reverse Beacon Network
    at<http://reversebeacon.net> <http://reversebeacon.net>, now
    spotting RTTY activity worldwide.
    For spots, please use your favorite
    "retail" DX cluster.




-- 
*Dave - WØLEV
*
*/Just Let Darwin Work/*







David Eckhardt
 

dBFS in the modern SDR is set with regard to the digital dynamic range.  That is set by the number of bits in the DAC's, ADC's, and the processor with or without decimation, be it a PC-like CPU or an FPGA like the Icom 7300.  FPGA = Field Programmable Gate Array.  dBFS is set such that all but (possibly) the most significant bit (the 'top' bit) is used in establishing the digital information.  Once all bits are utilized, the digital end of things goes into saturation.  This is not 'graceful' saturation as is so prevalent in the older superhetrodyne receiver designs, but is a hard stop.  When all bits in the digital process are utilized, there is no more information in the bit stream.  Once the top or most significant bit is utilized in an SDR system, the game is over.  Total nonsense in the digital world results and all information becomes garbage.  Therefore, the use of dBFS is used.  At that level, the supplier assures that the absolute strongest signal that could possibly enter the antenna port (without damage) will not cause digital saturation.  dB down  from that level involves the lower and lower significant bits in the digital treatment of the signal.  However, if there is not enough dynamic range in 'bit space', you will no be able to detect the noise floor.  It's a matter of placing the available digital dynamic range 'window' properly to avoid digital saturation.  Some modern SDR's, for that reason, provide options of internally switching in attenuators and filters to additionally handle this problem.   

Yesterday, I set up an SDRPlay 01 (RSP01) on 160-meters. With my 300-foot doublet connected directly, the system was in analog saturation.  I was receiving the AM BC band everywhere, no matter where I tuned the RSP01.  However, I was not yet in digital saturation.  The original design had neglected the analog overload problems in preference to the digital end of things (proper allocation of gain distribution throughout the system).  It took a 25 dB attenuator at the antenna input to more-or-less render the problem manageable (that's a LOT of attenuation up front!).  In designing the RSP1A which has recently been introduced (I have one coming), the problem has (mostly) been addressed.   

Dave - WØLEV   

Virus-free. www.avast.com

On Fri, Apr 6, 2018 at 11:15 AM, Pete Smith <n4zr@...> wrote:

Is there no way of adjusting the overall system gain?  Right now, on the GUI's graphical and numeric displays, my -73 dBM reference reads about -53 DbFS, where FS=0 db  Sure, I can mentally subtract 20 dB from every displayed signal strength, but ...

What is the advantage of dBFS over dBM, from the operator's perspective?

73, Pete N4ZR
Check out the Reverse Beacon Network 
at <http://reversebeacon.net>, now 
spotting RTTY activity worldwide. 
For spots, please use your favorite 
"retail" DX cluster.
On 4/5/2018 10:17 PM, jdow wrote:
You don't - from the GUI. Full scale means the magnitude of the sample coming out of the USB data stream for a sample is 1.00000.

If you are adventuresome you can edit the SDRSharp.exe.config file to change this line:
<add key="fftOffset" value="-40.0" />

{^_^}

On 20180405 18:15, Pete Smith wrote:
But how do you "set" full scale? Clearly right now it is not correct. I'm looking for a measurement scale for my noise level and signal strengths that is comparable with other SDRs and hardware radios.

73, Pete N4ZR
Check out the Reverse Beacon Network
at<http://reversebeacon.net>, now
spotting RTTY activity worldwide.
For spots, please use your favorite
"retail" DX cluster.

On 4/5/2018 7:10 PM, David Eckhardt wrote:
If you have an S-9 signal which is -73 dBm and you have set dBFS to 0 dBm, the dBFS should read -73 dBm.  If you have set full scale to -20 dBm, the dBFS should read -53 dBFS.  Likewise, if you set the dBFS to -73 dBFS, the dBFS should read 0 dBFS.

Dave - WØLEV

<https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=icon>     Virus-free. www.avast.com <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=link>


On Thu, Apr 5, 2018 at 8:23 PM, Pete Smith <n4zr@... <mailto:n4zr@...>> wrote:

    Please pardon the extreme newbie questions - I bought an Airspy HF+
    recently, intending to use it on the IF of my K3 for spectrum display.  Of
    course, the K3 is off at Watsonville, so I've been experimenting,
    comparing the Airspy with a Red Pitaya and a QS1R.

    From what I've seen I like SDR# a lot.  Is there anywhere an SDR#manual
    specifically for the HF+?  I keep running into things in the Quick Start
    that are not germane to my HF+, running the latest firmware.

    Also, can anyone point me toward an explanation of the dBFS scale used for
    signal strength with the Airspy HF+? I've established that my Elecraft
    XG-3's S-9 signal equates to 20 dBFS on SDR#, and its -33 dBM (equivalent
    to 40 over 9) more than "pins the meter" on SDR#.  Is this normal?

    --
    73, Pete N4ZR
    Check out the Reverse Beacon Network
    at<http://reversebeacon.net> <http://reversebeacon.net>, now
    spotting RTTY activity worldwide.
    For spots, please use your favorite
    "retail" DX cluster.




-- 
*Dave - WØLEV
*
*/Just Let Darwin Work/*










--
Dave - WØLEV
Just Let Darwin Work

jdow
 

None that I can think of. Although it does remind you that this thing is not calibrated, something the typical ham gear does not do even though it is generally extremely mal-calibrated. You can take that key value in the config file I pointed out below and avoid the mental calibration. It will then, at least on one frequency and one set of conditions, report the accurate value you want.

That noted HF+ has an AGC in it. So that, right off the bat, limits your achievable accuracy. The AGC optimizes the dynamic range of the HF+ for the conditions it is facing. Twin signal generators can show you the AGC action. I don't know the SDRSharp and SDR Console avail themselves of any AGC setting which may exist to "correct" readings. So you may be forced into either operating with the AGC suppressed, which will impose some additional limits, or resorting to the old Sn, with n - 0..9, meanings for reports. Hams who expect calibrated readings are not as well educated as they might like to be, IMAO.

{^_^} Joanne

On 20180406 04:15, Pete Smith wrote:
Is there no way of adjusting the overall system gain?  Right now, on the GUI's graphical and numeric displays, my -73 dBM reference reads about -53 DbFS, where FS=0 db  Sure, I can mentally subtract 20 dB from every displayed signal strength, but ...
What is the advantage of dBFS over dBM, from the operator's perspective?
73, Pete N4ZR
Check out the Reverse Beacon Network
at<http://reversebeacon.net>, now
spotting RTTY activity worldwide.
For spots, please use your favorite
"retail" DX cluster.
On 4/5/2018 10:17 PM, jdow wrote:
You don't - from the GUI. Full scale means the magnitude of the sample coming out of the USB data stream for a sample is 1.00000.

If you are adventuresome you can edit the SDRSharp.exe.config file to change this line:
<add key="fftOffset" value="-40.0" />

{^_^}

On 20180405 18:15, Pete Smith wrote:
But how do you "set" full scale? Clearly right now it is not correct. I'm looking for a measurement scale for my noise level and signal strengths that is comparable with other SDRs and hardware radios.

73, Pete N4ZR
Check out the Reverse Beacon Network
at<http://reversebeacon.net>, now
spotting RTTY activity worldwide.
For spots, please use your favorite
"retail" DX cluster.

On 4/5/2018 7:10 PM, David Eckhardt wrote:
If you have an S-9 signal which is -73 dBm and you have set dBFS to 0 dBm, the dBFS should read -73 dBm.  If you have set full scale to -20 dBm, the dBFS should read -53 dBFS.  Likewise, if you set the dBFS to -73 dBFS, the dBFS should read 0 dBFS.

Dave - WØLEV

<https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=icon>     Virus-free. www.avast.com <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=link>


On Thu, Apr 5, 2018 at 8:23 PM, Pete Smith <n4zr@... <mailto:n4zr@...>> wrote:

    Please pardon the extreme newbie questions - I bought an Airspy HF+
    recently, intending to use it on the IF of my K3 for spectrum display.  Of
    course, the K3 is off at Watsonville, so I've been experimenting,
    comparing the Airspy with a Red Pitaya and a QS1R.

    From what I've seen I like SDR# a lot.  Is there anywhere an SDR#manual
    specifically for the HF+?  I keep running into things in the Quick Start
    that are not germane to my HF+, running the latest firmware.

    Also, can anyone point me toward an explanation of the dBFS scale used for
    signal strength with the Airspy HF+? I've established that my Elecraft
    XG-3's S-9 signal equates to 20 dBFS on SDR#, and its -33 dBM (equivalent
    to 40 over 9) more than "pins the meter" on SDR#.  Is this normal?

    --
    73, Pete N4ZR
    Check out the Reverse Beacon Network
    at<http://reversebeacon.net> <http://reversebeacon.net>, now
    spotting RTTY activity worldwide.
    For spots, please use your favorite
    "retail" DX cluster.




--
*Dave - WØLEV
*
*/Just Let Darwin Work/*