Re: [casper] Solar Spectrometer Channeliser

[Tavi B]

Hi,

Thank you for your reply!

I would consider LimeSDR or maybe XTRX, it have a GPS onboard and PCI-ex
interface.

Best regards,

Tavi


În mar., 11 feb. 2020 la 08:05, Mugundhan vijayaraghavan <
v.vaishnav151...@gmail.com> a scris:

> Hello Tavi,
>
> There are implementations of red pitaya as a SDR by Pavel Demin, but the
> max. bandwidth (that he has implemented) is about 2.5 MHz and also is
> limited in tuning range.
>
> Yes, using SDRs is another option. LimeSDR is a possible candidate which
> gives tunability and max. instantaneous bandwidth of ~ 60 MHz. It also has
> an Intel (Altera) FPGA, which people have tried to program to do some DSP
> as well.
>
> So this is a good suggestion.
>
> Sincerely,
>
> Mugundhan
>
>
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> 
> .
>

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Re: [casper] Solar Spectrometer Channeliser

[Tavi B]

Hello,

Reading this topic I've understand that Red Pitaya cannot tune to any
frequency band like a SDR does. From my point of view is not adequate to
use as a wide band solar bursts spectrograph.

I would use SDR(s) instead, with the radio front end already made. The
speed of sweeps is a concern and you should use large bandwidth high end
ones. The good news is there are some available on the market, is not very
expensive and if you want more speed you can use many of these in parallel,
each tuned on a channel of the ADC width. What do you think?

Octavian Blagoi.
www.astro.ro

În mar., 11 feb. 2020 la 04:42, Mugundhan vijayaraghavan <
v.vaishnav151...@gmail.com> a scris:

> Hi Ross,
>
> I agree with what you say.
>
> At this point, if one is interested in only a single channel, then Dan's
> idea of quadrature mixing can be tried out.
> If one has to use mixers, rather than 60 MHz, depending on the filter's
> roll off, one may have to settle for slightly smaller bandwidth.
>
> Thanks,
>
> Mugundhan
>
> On Tue, Feb 11, 2020 at 7:37 AM Ross Martin  wrote:
>
>> Hi Mugundhan,
>>
>> If you have a single stage mixer with an LO at 80MHz, it has the problem
>> that the effective mixer signal may not be just a sine wave, but instead a
>> sine wave with a tiny DC offset.
>>
>> If you have a DC offset that's X dB down from the sine wave amplitude, it
>> will pass the original signal through at a level X dB down.  You need to be
>> very careful that X is enough to provide the performance you desire,
>> because the original signal is on top of your output signal and will
>> interfere with it if it's not adequately attenuated.
>>
>> The mixer will also have distortion. That distortion will cause 2nd, 3rd,
>> and higher-order effects, that need to be considered regarding what their
>> amplitudes might be and in what frequency ranges they are.
>>
>> With more widely separated input and output frequencies for the mixer,
>> it's easier to arrange that all these undesired mixer outputs are at
>> frequencies that don't matter and can be rejected with lowpass or bandpass
>> filters. In your case, a lot of these error terms will be right on top of
>> your signal, and thus can't be rejected with a filter. That's probably not
>> a problem if you only need 10dB, but if you want quality signals it should
>> be analyzed carefully based on the specs of your mixer and your desired
>> performance.  It may be that available mixers are really, really good, but
>> it's something that should be checked carefully.
>>
>> Another issue with what you've proposed is that your output band goes all
>> the way down to 0 Hertz. Mixers may produce a lot of noise near 0 Hertz,
>> from squaring and quadratic distortion terms that effectively perform an AM
>> detection on your entire input signal. Because of this noise, you probably
>> don't want your signal going all the way down to zero Hertz, but instead
>> have it bounded away from zero by some small amount with at least a DC
>> rejection filter.  I'm not sure offhand how much separation might be
>> enough.  This problem will also affect multi-stage mixers.  It may be that
>> the mixer quality is good enough that this effect is small, but it should
>> be checked carefully.
>>
>> Another issue you need to consider is that signals cannot cut off
>> instantly in the frequency domain.  They must have tails that fade off
>> gradually. And if you've got a sine wave at 1Hz, it's tails are most likely
>> not going to fade off below desired levels by 0Hz.  Almost no analog
>> filters are that good. Instead the tails will go past 0Hz into negative
>> frequencies.  For real signals, negative frequencies fold back into
>> positive frequencies and cause interference.  For this reason also, I
>> believe your signal must be strictly bounded away from 0Hz.
>>
>> Regards,
>>
>> Ross
>>
>>
>> On Mon, Feb 10, 2020, 8:26 AM Mugundhan vijayaraghavan <
>> v.vaishnav151...@gmail.com> wrote:
>>
>>> Hi Ross,
>>>
>>> Just to add, we can also have the lo at 80mhz, and use the lower side
>>> band. 80 will be at 0, 20 will be at 60. But the band can be flipped
>>> offline.  We can have a strong lpf at 60mhz, which can  cut the lo off
>>> before downstream processing.
>>>
>>> Mugundhan
>>>
>>> On Mon, 10 Feb 2020, 15:18 Mugundhan vijayaraghavan, <
>>> v.vaishnav151...@gmail.com> wrote:
>>>
 Hi Ross,

 I'm not working with Colm on this. So I don't know about the resources
 available to him.

 What you're saying is true. Doing it with a single stage may be
 problematic as with 20 MHz LO, the there will be overlap of the side bands.
 So, minimally, we need to have two stages. where the 20-80 MHz can be
 up-converted to outside the band and then down-converted into the base band
 of 0-60 MHz.

 Sorry for not being clear earlier.

 But anyway, for the RedPitaya, due to the sampling restrictions, 20-80
 MHz band has to be got into 0-60 MHz for getting the full band with 

Re: [casper] heliospectroscope

[Tavi B]

Hello, Jishnu,

Thank you very much for your reply. I will try your suggestion when I'll
arrive at home, maybe next week.
I think your reply is very helpful and is OK regarding this mailing list.

Best regards
Octavian

În mar., 19 nov. 2019 la 11:23, Jishnu Nambissan T  a
scris:

> Hi Tavi,
>
> It would be best to use an SDR or a board like Redpitaya or SNAP that can
> sample the entire band, but if you have got an RTLSDR, I can suggest a
> small trick that might work (no harm in trying). GQRX might be an overkill
> as you don't need the demodulation part.
> I have written a small python code that uses pyrtlsdr to read some samples
> and FFT them. The centre frequency is changed and the process is repeated.
> The spectra are then stitched together. The code snippet is not the best
> and the logic has got some bugs. Nonetheless, you can start from that and
> develop. It is available at https://github.com/VU3VWB/rtlsdr_spec_analyser ;
> try rtl_spec_analyser_fft_scan_3.py
>
> NB: This is my first time replying to a mailing list, please let me know
> if there is some silly mistake (reply, reply to all etc.)
>
> Regards,
> Jishnu
>
> --
> *From: *"Tavi B" 
> *To: *casper@lists.berkeley.edu
> *Sent: *Thursday, 14 November, 2019 08:17:31
> *Subject: *Re: [casper] heliospectroscope
>
> Hello, Dan,
>
> Thank you very much for your detailed answer. I will read the details of
> suggested boards.
>
> So far I've try RTL-SDR, Airspy2+Spywerter and bladeRF x40+XB200 with
> gqrx. But the gqrx cannot sweep and record full bandwidth at needed sample
> rate. The main concern is the time of stabilization of the frequency tuned,
> that's why a large simultaneous bandwidth is desired. The bladeRF 2.0 is
> faster and have a large bandwidth (56MHz) and have affordable price. It is
> an integrated radio with TX and filters but we would not pay for features
> that we don't need. RedPitaya sounds better.
>
> Best regards,
> Octavian
>
> marți, 12 noiembrie 2019, 16:13:51 UTC+2, danseti a scris:
>>
>>
>> hi octavian,
>> i don't know much about solar radio spectroscopy,
>> but i think in some solar applications, the SNR is very high,
>> and the time variability is slow enough that you could use a spectrometer
>> with a small instantaneous bandwidth,
>> perhaps 10 or 20 MHz bandwidth, and then sweep this spectrometer across
>> your 800 MHz band.
>> if that's the case,  the spectrometer could be very inexpensive because
>> you could use a GNUradio system.
>>
>> if you need more instantaneous bandwidth, the red pitaya fpga board has
>> two 125 Msps ADC's,
>> and casper has a spectrometer tutorial for this board.  you might be able
>> to use the spectrometer tutorial design directly,
>> or modify the design for your application.  the red pitaya boards cost a
>> few hundred dollars.
>> https://www.redpitaya.com/f130/STEMlab-board
>>
>> the next step up would be to use a snap fpga board, which costs about
>> $3000, and has four 950 Msps ADC's.
>> casper has a spectrometer tutorial for the snap board as well.
>>
>>
>> for even higher instantaneous bandwidth, there are several casper ADC
>> boards you could plug into the snap board.
>> eg: single 2 Gsps ADC board, a dual 2.5 Gsps ADC board
>>
>> information on the snap board, adc boards and tutorials are on the casper
>> wiki pages.
>>
>>
>> best wishes,
>>
>> dan
>>
>>
>>
>>
>> Dan Werthimer
>> Marilyn and Watson Alberts Chair
>> Astronomy Dept and Space Sciences Lab
>> University of California, Berkeley
>>
>>
>> On Tue, Nov 12, 2019 at 1:27 AM Tavi B  wrote:
>>
>>> Hello,
>>>
>>> I'm new in this research, in Romania there is no scientific radio
>>> telescope yet. I'm working at the Solar Group of Astronomical Institute of
>>> Romanian Academy and this is the reason I would start with a solar radio
>>> spectroscope, CALLISTO like station. I searched an inexpensive SDR to
>>> emulate the callisto analog receiver but with fairly large bandwidth and
>>> speed. The high end ones are too expensive and have many features that we
>>> don't need like DAC, TX, filters and so on.
>>>
>>> I've learned that a 12bit ADC with high Mbsp and a FPGA can do the job,
>>> we don't need to decode or demodulate a signal, just record the noise level
>>> coming from the Sun (or other radio astronomy objects). In this search I've
>>> found your group and I wonder if you can help me to find a really cheap
>>> solution because we don

Re: [casper] heliospectroscope

[Tavi B]

Hello, Dan,

Thank you very much for your detailed answer. I will read the details of 
suggested boards. 

So far I've try RTL-SDR, Airspy2+Spywerter and bladeRF x40+XB200 with gqrx. 
But the gqrx cannot sweep and record full bandwidth at needed sample rate. 
The main concern is the time of stabilization of the frequency tuned, 
that's why a large simultaneous bandwidth is desired. The bladeRF 2.0 is 
faster and have a large bandwidth (56MHz) and have affordable price. It is 
an integrated radio with TX and filters but we would not pay for features 
that we don't need. RedPitaya sounds better.

Best regards,
Octavian

marți, 12 noiembrie 2019, 16:13:51 UTC+2, danseti a scris:
>
>
> hi octavian,
>
> i don't know much about solar radio spectroscopy, 
> but i think in some solar applications, the SNR is very high, 
> and the time variability is slow enough that you could use a spectrometer 
> with a small instantaneous bandwidth, 
> perhaps 10 or 20 MHz bandwidth, and then sweep this spectrometer across  
> your 800 MHz band.   
> if that's the case,  the spectrometer could be very inexpensive because 
> you could use a GNUradio system.
>
> if you need more instantaneous bandwidth, the red pitaya fpga board has 
> two 125 Msps ADC's,
> and casper has a spectrometer tutorial for this board.  you might be able 
> to use the spectrometer tutorial design directly, 
> or modify the design for your application.  the red pitaya boards cost a 
> few hundred dollars.  
> https://www.redpitaya.com/f130/STEMlab-board  
>
> the next step up would be to use a snap fpga board, which costs about 
> $3000, and has four 950 Msps ADC's. 
> casper has a spectrometer tutorial for the snap board as well. 
>
>
> for even higher instantaneous bandwidth, there are several casper ADC 
> boards you could plug into the snap board. 
> eg: single 2 Gsps ADC board, a dual 2.5 Gsps ADC board
>
> information on the snap board, adc boards and tutorials are on the casper 
> wiki pages. 
>
>
> best wishes,
>
> dan
>
>
>
>
> Dan Werthimer
> Marilyn and Watson Alberts Chair
> Astronomy Dept and Space Sciences Lab
> University of California, Berkeley
>
>
> On Tue, Nov 12, 2019 at 1:27 AM Tavi B > 
> wrote:
>
>> Hello,
>>
>> I'm new in this research, in Romania there is no scientific radio 
>> telescope yet. I'm working at the Solar Group of Astronomical Institute of 
>> Romanian Academy and this is the reason I would start with a solar radio 
>> spectroscope, CALLISTO like station. I searched an inexpensive SDR to 
>> emulate the callisto analog receiver but with fairly large bandwidth and 
>> speed. The high end ones are too expensive and have many features that we 
>> don't need like DAC, TX, filters and so on. 
>>
>> I've learned that a 12bit ADC with high Mbsp and a FPGA can do the job, 
>> we don't need to decode or demodulate a signal, just record the noise level 
>> coming from the Sun (or other radio astronomy objects). In this search I've 
>> found your group and I wonder if you can help me to find a really cheap 
>> solution because we don't have a budget for this project right now. 
>>
>> What modules I can buy or build myself (I have basic skills on 
>> electronics, microcontrollers and radio) to get a spectrogram of 400 MHz 
>> wide with a better than 0.1s time resolution? The Sun radio burst can be 
>> received between 10-1500MHz but with different antennas, so I would start 
>> with a log periodic dipole wide band antenna, from 120 to 800MHz. 
>>
>> Thank you and best regards,
>> Octavian Blagoi
>> researcher
>> AIRA www.astro.ro
>>
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>> <https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/68ef8ced-7318-436d-b1fd-a96db187122f%40lists.berkeley.edu?utm_medium=email_source=footer>
>> .
>>
>

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[casper] heliospectroscope

[Tavi B]

Hello,

I'm new in this research, in Romania there is no scientific radio telescope 
yet. I'm working at the Solar Group of Astronomical Institute of Romanian 
Academy and this is the reason I would start with a solar radio 
spectroscope, CALLISTO like station. I searched an inexpensive SDR to 
emulate the callisto analog receiver but with fairly large bandwidth and 
speed. The high end ones are too expensive and have many features that we 
don't need like DAC, TX, filters and so on. 

I've learned that a 12bit ADC with high Mbsp and a FPGA can do the job, we 
don't need to decode or demodulate a signal, just record the noise level 
coming from the Sun (or other radio astronomy objects). In this search I've 
found your group and I wonder if you can help me to find a really cheap 
solution because we don't have a budget for this project right now. 

What modules I can buy or build myself (I have basic skills on electronics, 
microcontrollers and radio) to get a spectrogram of 400 MHz wide with a 
better than 0.1s time resolution? The Sun radio burst can be received 
between 10-1500MHz but with different antennas, so I would start with a log 
periodic dipole wide band antenna, from 120 to 800MHz. 

Thank you and best regards,
Octavian Blagoi
researcher
AIRA www.astro.ro

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