Date   

Re: Airspy mini and rtl_fm

prog
 

On Wed, Jan 17, 2018 at 10:27 am, Brian Machesney wrote:
Thanks, but this doesn't seem to agree with the block diagram of the Airspy HF+ on the web site. For example, where is the polyphase mixer/filter? I see no mention of it in the datasheets.
I probably read your message too fast. This thread is about the Airspy Mini, not the HF+. Different architectures.


Re: Airspy mini and rtl_fm

Dave GW4GTE
 

Google STA709 and you've pretty much got it.


Re: Airspy mini and rtl_fm

Brian Machesney <nekvtster@...>
 

Thanks, but this doesn't seem to agree with the block diagram of the Airspy HF+ on the web site. For example, where is the polyphase mixer/filter? I see no mention of it in the datasheets.

On Wed, Jan 17, 2018 at 11:51 AM, prog <info@...> wrote:
On Wed, Jan 17, 2018 at 08:50 am, Brian Machesney wrote:
Can someone please tell me the lineup of chips in the Airspy HF+?
This: https://www.nxp.com/products/processors-and-microcontrollers/arm-based-processors-and-mcus/lpc-cortex-m-mcus/lpc4300-cortex-m4-m0/32-bit-arm-cortex-m4-plus-2-x-m0-mcu-282-kb-sram-ethernet-two-hs-usbs-80-msps-12-bit-adc-configurable-peripherals:LPC4370FET100

And an R820T2 tuner from Rafael Micro.



Re: Airspy mini and rtl_fm

prog
 


Re: Airspy mini and rtl_fm

Brian Machesney <nekvtster@...>
 

"There's no RTL chip in Airspies."

Can someone please tell me the lineup of chips in the Airspy HF+?

On Wed, Jan 17, 2018 at 4:57 AM, prog <info@...> wrote:
On Tue, Jan 16, 2018 at 11:32 pm, Ronneil Camara wrote:
I might receive my mini this weekend or next week and I'm so excited. Has anyone used rtl_fm with it?
There's no RTL chip in Airspies. So, everything that starts with rtl_* is excluded.
Here's the alternative: https://github.com/rxseger/rx_tools



Re: squelch debate

w9ran <w9ran@...>
 

On 1/17/2018 7:20 AM, Siegfried Jackstien wrote:
and i am guessing nearly all voice activity squelch and noise surpression work like this
Most military and commercial radios have incorporated voice or "syllabic" squelch for decades, and thus they are the only ones I use for long-time monitoring.    They have been implemented in both hardware and software as well, and the circuits/algorithms are described in documentation from Stephens Engineering Associates, Harris, Codan, and others.    Voice squelch on SSB channels is essential for those who monitor particular frequencies for activity - I built my first one back in the 1970s and have no idea why the ham manufacturers have ignored such a useful feature.

73, Bob W9RAN


Re: squelch debate

Siegfried Jackstien
 

and it is inside the fimware of mchf :-)

sound almost like my icom when i connect the jps nir 10 to its output (audio noise reduction in a box connected between speaker and rig)

a clever voice "squelch" splits the channel (audio passband) in many small segments and checks if there is voice or not .... and only the voice gets towards speaker

the "sprachextractor lingua" also does it this way

and i am guessing nearly all voice activity squelch and noise surpression work like this

if it is doable in a small stm32f4 (in mchf) then it is easy to do in a powerfull pc :-)

dg9bfc sigi


Re: Airspy mini and rtl_fm

Ronneil Camara <ronneilcamara@...>
 

I'll check out the github. Thank you so much prog!

On Wed, Jan 17, 2018 at 3:57 AM, prog <info@...> wrote:
On Tue, Jan 16, 2018 at 11:32 pm, Ronneil Camara wrote:
I might receive my mini this weekend or next week and I'm so excited. Has anyone used rtl_fm with it?
There's no RTL chip in Airspies. So, everything that starts with rtl_* is excluded.
Here's the alternative: https://github.com/rxseger/rx_tools



Re: Airspy mini and rtl_fm

prog
 

On Tue, Jan 16, 2018 at 11:32 pm, Ronneil Camara wrote:
I might receive my mini this weekend or next week and I'm so excited. Has anyone used rtl_fm with it?
There's no RTL chip in Airspies. So, everything that starts with rtl_* is excluded.
Here's the alternative: https://github.com/rxseger/rx_tools


Re: HF+ superb overload resilience

prog
 

On Tue, Jan 16, 2018 at 11:34 pm, jdow wrote:
And at HF don't forget that the first 10 dB to 30 dB (or more?) of noise figure degradation comes free, no cost to weak signal detection. One exception here might be daytime LF and low MF DXing. D layer absorption leaves the noise levels very low and signal levels very low. But, I don't remember ever seeing word of people trying to do weak signal work on 75 meters or 160 meters in the daytime. When the bands are open they are open to noise as well as signals. And the noise always swamps the sensitive receiver's noise with efficient antennas.

That's why people get away with selling clever whip antennas with variable resistors across the antenna base to ground. They sound good and quiet on receive. They radiate like a dummy load on transmit. Yet people get away with selling such trash.

{^_-} Joanne
Indeed. Leif measured about 34 dB of NF margin with his antenna. I measured about 38 dB with Adam using his 80m skyloop antenna (remotely), so this confirms the observations.
I think we can reduce the threshold of the AGC by 6 dB (one step) without degrading sensitivity on HF, but it will help the IMD performance quite significantly. A "Cheap" optimization.
I will communicate the test firmware privately to people who can/are willing to do some measurements. The public release will follow when all is good.


Re: Airspy mini and rtl_fm

jdow
 

The mini is not an rtl dongle. So, of course not. For FM reception at the rtl_fm level a plain old super cheap RTL dongle, not even one of the good ones from RTL-SDR.com or NooElec. Plain old Hong Kong Chinesium is good enough.

{^_^}

On 2018-01-16 19:40, Ronneil Camara wrote:
I might receive my mini this weekend or next week and I'm so excited. Has anyone used rtl_fm with it?


Re: HF+ superb overload resilience

jdow
 

On 2018-01-16 04:17, prog wrote:
On Tue, Jan 16, 2018 at 03:23 am, jdow wrote:
You are also probably running afoul of the transmitter noise figure effect.
What is the off channel noise floor power from the transmitters. Usually it
is rather high, partly because they are starting at fairly low power,
milliwatts, and amplifying it to its final transmitter power. So if they
have a 100 kW transmitter (+50 dBW) starting at 1 mW (-30 dBW) with a 10 dB
"noise figure" at this lowest level stage that noise power gets amplified by
80 dB just as the signal is amplified. That's just GOTTA do something to the
off channel noise levels you have on your site, too. Your site is not a good
site for somebody into QRP.
{O.O}
Doing QRP in these conditions is insane, but not uncommon. There are enough crazy people who will attempt it :-) The receiver is well optimized for regular use cases, but it also offers the necessary assets (High DR at Low NF) to fight against extreme band condition, if necessary.
Here are the options:
1) One can sacrifice some of the NF to move the DR to a more comfortable region. The AGC does that already, though it may need more software optimizations to be perfect (ie. smarter than most of us). When we launched the Airspy One, it took almost 2 years to extract the full potential of the R820T(2). The Taiwanese Rafael Micro were not very helpful, but we could crack the IF/RF filtering problem by more experimentation. In the end, everybody using that tuner benefited from that work, including the cheap RTL-SDRs. Now the situation is different. ST Micro are more than helpful and willing to develop patches that enhance the dynamic performance for our niche market, despite it being a bit off their marketing chart. So, many thanks to ST Micro to let us have a free ride in the first place, and helping us improve the design as a bonus. The upcoming firmware updates look very promising :-)
2) Sacrifice some of that NF by using sharp (and probably lossy) filters and rely on the good in-band performance with the hope that the transmitters nearby are clean enough and do not kill your weak signal with splatter. Leif SM5BSZ could demonstrate that some light filtering can improve the dynamic performance quite significantly. We will see to what extent we can build the newer versions on top of this alien tuner and the experience we are building.
And at HF don't forget that the first 10 dB to 30 dB (or more?) of noise figure degradation comes free, no cost to weak signal detection. One exception here might be daytime LF and low MF DXing. D layer absorption leaves the noise levels very low and signal levels very low. But, I don't remember ever seeing word of people trying to do weak signal work on 75 meters or 160 meters in the daytime. When the bands are open they are open to noise as well as signals. And the noise always swamps the sensitive receiver's noise with efficient antennas.

That's why people get away with selling clever whip antennas with variable resistors across the antenna base to ground. They sound good and quiet on receive. They radiate like a dummy load on transmit. Yet people get away with selling such trash.

{^_-} Joanne


Airspy mini and rtl_fm

Ronneil Camara <ronneilcamara@...>
 

I might receive my mini this weekend or next week and I'm so excited. Has anyone used rtl_fm with it?


Re: squelch debate

Simon Brown
 

So,

 

Any noise such as a static crash, click or dit will open the squelch. Real SSB squelch uses VAD – voice activity detection, not easy in a noisy environment but doable – you have this on your mobile phone.

 

 

From: main@airspy.groups.io [mailto:main@airspy.groups.io] On Behalf Of Buford T. Justice
Sent: 17 January 2018 00:13
To: main@airspy.groups.io
Subject: Re: [airspy] squelch debate

 

Not what I meant.  I meant having a squelch based solely on SNR.  You have SDR# on and go to a frequency that has no activity.  The noise floor may be -82.5dBFS and the SNR might be 3.5dB.  A signal above that (or whatever the listener chooses) should unmute the squelch.  The squelch should be based on what dB signal level the listener wants to hear.

I just wish LSB and USB had squelch.  The suggested use of "IF Noise Reduction" can effect stuff a listener wants to hear.

BTJustice

 


Subject: Re: [airspy] squelch debate
Sent: Tue. 1/16/2018 3:12:18 PM CST -0600
From: doug <dmcgarrett@...>
To: main <main@airspy.groups.io>

You should be able to dig out a CW signal less than 7.6 dB above the average noise level, by ear, so you would want the squelch to be either adjustable or switchable.  (BTW, a tangential signal is 8 dB

above the noise, not 7.6, if that's what you had in mind.)

--doug, WA2SAY.


Re: Online - London SpyServer

Blogger <blogger@...>
 

Hello John,


That's the one. 

Many thanks for all the other suggestions as well.

There is a 2s delay between the spyserver and the internet output.

https://tunein.com/radio/Spectrum-558am-s10088/?utm_source=tiEmbed&utm_medium=referral&utm_content=s10088


Tuesday, January 16, 2018, 1:39:16 PM, you wrote:


> Spectrum apparently has Arabic programming as well, which a bit more

> realistic from London.


> On Jan 16, 2018 16:36, "John Patterson" <hakuro.jp@...> wrote:


>> A simple search reveals SBC Al-Quran al-Karim transmits on this frequency

>> from Saudi Arabia, that was about the only Arabic language station that I

>> could see on that frequency, but you can see them all online.


>> On Jan 16, 2018 16:26, <blogger@...> wrote:


>>> Indeed.

>>> Then Anyone knows what is the station on 558kHz?

>>> One hour Arabic music then one hour Arabic talk.

>>> Thanks








Best regards,



Re: >> ( Want your radio to be listed here? Contact us.) #spyserver

Tilman D Thulesius <sm0jzt@...>
 

Hi there

Yes this radio is permanent. I have a dedicated server running it. I might have multiple HF+ running of it in the future. This to open up multiple segments.
I might also swap for a better antenna to cater for the multi-HF+ radio:s

Im struggling a bit with understanding the different settings in the config-file. 

If i set the start frequency to 7.1 MHz and remove client control   ( =0), having multiple user access . Does that mean I have a band limitation to 40 meters ??
What happens if I give control ?? Does that mean the first user can move the segment for the users coming in at the same time ??

/ Tilman


Re: Just what is a "Polyphase harmonic rejection mixer "

jdow
 

Use this URL http://icd.ewi.utwente.nl/publications/get_file.php?pub_id=563

The site creates a temporary copy of the file for viewing. It goes away when you disconnect. So you have to use the real URL to get there.

{^_^}

On 2018-01-16 09:00, doug wrote:
On 01/16/2018 07:29 AM, prog wrote:
On Sun, Jan 14, 2018 at 10:41 pm, drew231955 wrote:

The main break through with the HF+ is the Polyphase harmonic rejection
mixer. As best I can work out, when converting to base-band, it is an
effective filter for the desired signal and rejects even strong signals
close by with virtually no filtering ahead of the mixer.

It uses multiple phases of the local oscillator to use phasing to reject
its harmonics, but at the same time, and because it is to a 200 kHz
base-band, it rejects everything else too.

The big advantage is not needing a large number of band pass filters like
a direct sampling SDR; the IC-7300 has 15!

The best explanation I have found is a slide show;
http://icd.ewi.utwente.nl/temp_files/158b39412cff88a4181bfec0f4449c24.pdf.
It is also subject to patent;
https://www.google.ch/patents/US20110298521?hl=de. One of the authors
wrote the slide show.
There is something wrong with this url. I think it's the second / What should the character be?
--doug


Presumably the mixer is a CMOS device, but I have not found one. And the
RF cover on the HF+ is too hard to remove!

Any thoughts on this very novel approach?

Regards Drew VK4ZXI

You can see it as a "super Tayloe mixer". The problem with the original Tayloe Mixer is the harmonic responses at multiples of the LO frequency. The fix is to mathematically suppress these responses by adding more phases. The LO will no longer look like a square wave, but rather like a quantized sine wave. Basically, the more phases you add, the more harmonics you cancel.
This method is combined with narrow band filtering at the mixer itself. There is a switched-capacitor N-Path filter built into the mixer that is tuned using the same LO phases, which provides additional selectivity.
When you see it, all the ingredients required to implement this architecture can be implemented using CMOS silicon, and have a very good "horizontal" and "vertical" scalability: Horizontal with more phases (hence, less harmonics); Vertical with better fab processes (better linearity and NF).

The icing on the cake: This same technology can also work for TX.

The future looks bright!


Re: squelch debate

Buford T. Justice <BTJustice@...>
 

Not what I meant.  I meant having a squelch based solely on SNR.  You have SDR# on and go to a frequency that has no activity.  The noise floor may be -82.5dBFS and the SNR might be 3.5dB.  A signal above that (or whatever the listener chooses) should unmute the squelch.  The squelch should be based on what dB signal level the listener wants to hear.

I just wish LSB and USB had squelch.  The suggested use of "IF Noise Reduction" can effect stuff a listener wants to hear.

BTJustice


Subject: Re: [airspy] squelch debate
Sent: Tue. 1/16/2018 3:12:18 PM CST -0600
From: doug <dmcgarrett@...>
To: main <main@airspy.groups.io>
You should be able to dig out a CW signal less than 7.6 dB above the average noise level, by ear, so you would want the squelch to be either adjustable or switchable.  (BTW, a tangential signal is 8 dB

above the noise, not 7.6, if that's what you had in mind.)

--doug, WA2SAY.


Re: Online - London SpyServer

Marco Melandri
 

On Tue, Jan 16, 2018 at 01:49 pm, prog wrote:
On Tue, Jan 16, 2018 at 01:36 pm, prog wrote:
http://www.spectrumradio.net/programmes/arabicspectrum
Sounds best with these settings:

Same LondonHF server, another station, in DRM mode.
The performance of your SpyServer is simply great as well as G7KUF's setup.
https://youtu.be/VCs0pCzwOxs


Re: Online - London SpyServer

prog
 

On Tue, Jan 16, 2018 at 01:36 pm, prog wrote:
http://www.spectrumradio.net/programmes/arabicspectrum
Sounds best with these settings:

13061 - 13080 of 39999