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Re: TinySA on an ArduinoDUE

 

I know, but I have display and box for the SA.
/Niels, oz9ny
Re: A caution about an ebay vendor

 

A lot of hackers take small amounts from lots of people hoping people won¡¯t notice or care.

Chris

On Tue, Feb 18, 2020 at 6:46 PM Jim Strohm <jim.strohm@...> wrote:
This vendor:

???

told me that "hackers got his account" and he wasn't able to ship my order.

It's pretty stupid, because he's into me for about USD$2.50.

That's right, two and a half bucks.

I'm going to work it for full recompensation, but it's almost beyond comprehension how a hacker could steal three bucks or some offshore ebay spooger could try to rip me off for three bucks.

I plan to ensure that his pain point ends at about USD$5000.?

Have a nice evening, all.

73
Jim N6OTQ
Re: Do attenuators around the mixer improve the performance of the tinySA

 

That noise on 10mhz is not seen when probing the GPIO2 pin.


On Wed, Feb 19, 2020 at 09:09 AM, Jerry Gaffke wrote:
I didn't chase it, but when I looked at my 10mhz reference with a scope
and set the trigger a little bit high, I saw some occasional disruption in the 10mhz.
Could be that the Si4432 doesn't do a clean divide-by-3 of the 30mhz reference,
as it is attempting to create a 50% duty cycle square wave.
And that setting up register 0x0A for 15mhz instead of 10mhz will be much cleaner.

Or I could have just been seeing trash due to layout issues.

Jerry, KE7ER
Re: A tinySA, packed in like sardines

 

Erik,

Good to know a bit more about SGIN.
SiLabs documentation is not terribly concise.

And curious that attenuators around the mixer do not seem to help.
Perhaps more trouble shows up with a complex incoming spectrum?

I have considered copper tape over properly sized wire/insulation.
My longest wire is the LO into the mixer at 4cm, still down around
a tenth of our minimum wavelenght at (434+250)mhz.?
Impedance on that wire is not critical, especially if there's a 6dB attenuator at the mixer.

If fabbing a board, I think I'd go with raw Si4431/Si4432 parts.
Much smaller, can better control noise, don't need the RF switch ...
Though would have to put them down using solder paste and a toaster oven.

With Si4431/Si4432 chips, SAW filters, and mixers all coming in at a dollar or so on eBay,
could stamp this thing out very cheaply.??
Building a prototype with such small parts is a significant challenge.

I've used those DB style connectors for nearly half a century now,
still my go-to connector for prototypes.
Can fab a board that solders in place between the solder pot pins.
If a board is small enough it can hide inside the DB9's plastic shroud.?

Still curious if we can ever approach the 120dB of dynamic range in any measurement
however contrived, as suggested by the RSSI curve in fig 31 of the Si4432 datasheet.
I think we now know that the detector itself is not capable of 120dB range at constant gain,
will need the 20+24=44 dB of additional range provided by the PGA and LNA control bits.

Jerry, KE7ER
Re: A tinySA, packed in like sardines

 

Looks beautiful!!
Some time ago I did measure the impact of the copper tape covering the long wires and you get indeed about 50 ohm impedance. Very cheap and very flexible coax replacement.
Strongly suggest to at least test enabling the AGC incl the SGIN (0x60)
The SGIN increases the signal gain quickly after a strong signal disappeared. Without this your AGC reduces amplification and keeps the amplification low too long and thus increases the noise floor unneeded.
--
HBTE Files section:?/g/HBTE/files
Erik, PD0EK
Re: TinySA on an ArduinoDUE

 

Niels,

The latest tinySA.ino SW on github contains a full graphical touch UI.

--
HBTE Files section:?/g/HBTE/files
Erik, PD0EK
Re: Panadapter #tinysa

 

Perhaps that's what JohnP was suggesting.
But I assumed he was talking about some other IF,
as the 434mhz IF on the tinySA is definitely not below 50mhz.

As Erik says, an 8 bit A2D has a dismal dynamic range.
So results won't be great, but could be at least "interesting".

Jerry, KE7ER


On Wed, Feb 19, 2020 at 07:20 AM, Jerry Gaffke wrote:
Might be interesting to put a DVB-T SDR dongle on the tinySA's 433.92mhz IF,
you could listen in as the tinySA slowly sweeps through a ham band.
The inverse of that panadapter idea.

Jerry, KE7ER

?
Hide quoted text

?

On Wed, Feb 19, 2020 at 07:07 AM, John P wrote:
On Sun, Feb 16, 2020 at 09:42 PM, jafinch78 . wrote:
Great call, I've been thinking about this recently (along with coupling to prevent adverse signal effect) and also wondering about the other way around for tapping the signal to perform demodulation as a receiver project.?
If you want to demodulate signals, a better approach might be to use an SDR on the IF; you'll most likely need an attenuator and maybe an up-converter as the SDR dongles don't work below 50MHz without some trickery. There are any number of SDR control programs out there (HDSDR, SDR#, etc.)?that will give you a waterfall?display as well as the spectrum as well as the ability to listen to any type of modulation.
?--
John P.
WA2FZW
Re: Do attenuators around the mixer improve the performance of the tinySA

 

Erik,

I didn't chase it, but when I looked at my 10mhz reference with a scope
and set the trigger a little bit high, I saw some occasional disruption in the 10mhz.
Could be that the Si4432 doesn't do a clean divide-by-3 of the 30mhz reference,
as it is attempting to create a 50% duty cycle square wave.
And that setting up register 0x0A for 15mhz instead of 10mhz will be much cleaner.

Or I could have just been seeing trash due to layout issues.

Jerry, KE7ER



On Wed, Feb 19, 2020 at 08:08 AM, <erik@...> wrote:
My guess is the spurs I'm seeing are caused by harmonics of the power calibration signal directly getting into the signal path after the mixer.
TinySA on an ArduinoDUE

 

My TinySA is taking form. I haven't yet removed the filters from the Si4432 modules because I wanted to see how they fit on the board.
I will combine Erik's TinySA software with this to have a standalone SA. I'm not sure I will implement the PC-communication, time will show.
/Niels

IMG_2146.JPG

A tinySA, packed in like sardines

 

My tinySA is starting to work, built ugly/manhatten style on a 2.25"x4.0" (55mm x 100mm)
copper clad board, sized to be the lid of a Seasons brand sardine tin.
??

Photo here, will be removed in a few weeks once it becomes outdated:
? ??/g/HBTE/files/KE7ER/DSC_6884.JPG

The DB9 connector at the top of the photo and the SMA connector down and to the right
are the only connections out of the tinySA.
SMA will eventually go through the board, once I'm sure placement is final.
I'll probably want to add the attenuator chip.

A big 3.3v LT1585 regulator rides on top of the DB9 (will be LM1117's), converting from 5v.
SPI signals from the DB9 go though a 200 ohm resistor, then a 0.001uF cap to ground,
hoping that might keep processor hash out of the tinySA.
This stuff around the DB9 will have to change when I add shielding.

RX Si4432 is on the left, going down from there are two B3790 SAW filters
(different pinout that most, quite narrow with a very deep stopband)
and an ADE-1 mixer at the bottom.
Room is left near the ADE-1 for possibly adding attenuators and an MMIC.
The 250mhz LPF is to the right of the ADE-1.
A wire with 10mhz from the TX SI4432 GPIO2 goes to the SMA for initial testing.

The wire used is 30 gauge (10 mil diameter, a 5 mil thick coating of PVC insulation).
Should be close to 50 ohms if the wire is taped flat to the copper plane:? ?
? ?
Final version will likely use miniature 50 ohm coax to reduce interference.

Board is laid out for shielding.
The ideal would be to have it all in one long row, unfortunately I had to?
turn a corner before implementing the 250mhz LPF and the SMA.
Shielding can be 0.25" high (6.36mm) strips of PCB board material.
One strip down the middle from the DB9 to below the mixer,
another along the left side, then three short strips between them placed
at the obvious gaps plus two more for the top and bottom ends.?
Note that one of those strips will divide the two SAW filters.
The 250mhz LPF would have to be treated separately with this layout,
and can also have a shielding strip between the two halves of the filter.
Note that adjacent 250mhz LPF inductors are at right angles (but awfully close).

Will then solder some copper braid across the top of all the shields,
and bolt a copper clad FR4 board across the top for a cover.

If you look closely at the TX Si4432, you can see that I am tapped into the?
bottom of the "LC" inductor that feeds power to the Si4432 final amplifier.
I have removed the tiny "C0" cap just below it to remove connection to
the output LPF and harmonic trap and RX/TX switch on the Si4432 module.
Much easier than removing all those LPF filter components.
That tap must have a series cap to prevent power from the "LC" inductor
from burning out our mixer, I have a 0.001uF cap placed near the mixer.

I have also removed the "CO" cap from my RX Si4432 module,
as this module is only used to receive and I don't plan to have it transmit
for signal generator mode.? Don't want to risk having 20dBm of RF going
out into my 5dBm absolute max SAW filters.

The Si4432 schematic shown on page 2 of Erik's build instructions does not
quite agree with my Electrodragon Si4432 module.? Mine has 3 inductors
in the 434mhz LPF, where as that schematic shows two at "LM" and "L0".

Board standoffs were made using a sheet metal punch on CEM board material
as per K7QO's suggestion here:??/g/qrp-tech/message/13590
I'm using the 3/32" punch from this Neiko set:
? ?

It takes a really hot iron to solder something like that SMA to a ground plane,
would be very frustrating with the wrong iron.
The SAW filters also took an awful lot of heat, the ground pins are directly connected?
to the top cover.? Since I have that SAW filter sitting directly on the ground plane,
the ground pins lose a lot of heat when trying to solder to them.

Just got my first more-or-less successful scan of the the 10mhz reference last night,
using the Nano (converted to 3.3v) shown in the photo and Arduino's Serial plotter.
Serial plotter left a lot to be desired, definitely ready to move to pyplot on the RPi.
Am using my tinySArpi.c code, will need some work before I'm ready to post it.
Code drives the ADE-1 at 8dBm (not 20dBm), has AGC off.
Not keen to find a MSWindows machine to run tinySA.exe on.

Will park this for awhile, need to spend time on other stuff.

Jerry, KE7ER
Re: Panadapter #tinysa

 

An RTL-SDR dongle has a terrible dynamic range due to its 8 bit ADC
Anything loud that comes through the BPF will deafen the RTL-SDR
I tested this in my 2GHz SA where I used an RSP1 on the 10.7Mhz IF.
Even the RSP1 has substantial less dynamic range compared to a good log detector.
But of course it shines when doing realtime FFT in narrow scans (e.g. as a panadaptor on a IF)
What does work well is using a last IF at 40kHz and a 24bit audio ADC but the 30kHz effective bandwidth (40kHz +/- 15kHz) is a rather limited and yes, I could have used I/Q audio input but then you still have the zero Hertz problem that limits the dynamic range.
There is often a difference between (simplified) theory and actual practice.
--
HBTE Files section:?/g/HBTE/files
Erik, PD0EK
Do attenuators around the mixer improve the performance of the tinySA

 

There has been some debate on having attenuators around the mixer, it is even suggested it may reduce spurs.
So I did test.
First picture is a scan of the 15MHz power calibration signal with 6dB attenuators between LO and mixer and mixer and BPF

?

Second picture without any attenuator



Signal improved with a bit more then 6dB and noise a bit less so the attenuators are NOT improving the noise level.
The spurs reduced both in absolute level and even more compared to the 15MHz signal (keep in mind the levels indicated are relative to the strongest peak, in this case 15MHz)

My guess is the spurs I'm seeing are caused by harmonics of the power calibration signal directly getting into the signal path after the mixer.

--
HBTE Files section:?/g/HBTE/files
Erik, PD0EK
Re: Panadapter #tinysa

 

Might be interesting to put a DVB-T SDR dongle on the tinySA's 433.92mhz IF,
you could listen in as the tinySA slowly sweeps through a ham band.
The inverse of that panadapter idea.

Jerry, KE7ER

?

On Wed, Feb 19, 2020 at 07:07 AM, John P wrote:
On Sun, Feb 16, 2020 at 09:42 PM, jafinch78 . wrote:
Great call, I've been thinking about this recently (along with coupling to prevent adverse signal effect) and also wondering about the other way around for tapping the signal to perform demodulation as a receiver project.?
If you want to demodulate signals, a better approach might be to use an SDR on the IF; you'll most likely need an attenuator and maybe an up-converter as the SDR dongles don't work below 50MHz without some trickery. There are any number of SDR control programs out there (HDSDR, SDR#, etc.)?that will give you a waterfall?display as well as the spectrum as well as the ability to listen to any type of modulation.
?--
John P.
WA2FZW
Re: Panadapter #tinysa

 

On Sun, Feb 16, 2020 at 09:42 PM, jafinch78 . wrote:
Great call, I've been thinking about this recently (along with coupling to prevent adverse signal effect) and also wondering about the other way around for tapping the signal to perform demodulation as a receiver project.?
If you want to demodulate signals, a better approach might be to use an SDR on the IF; you'll most likely need an attenuator and maybe an up-converter as the SDR dongles don't work below 50MHz without some trickery. There are any number of SDR control programs out there (HDSDR, SDR#, etc.)?that will give you a waterfall?display as well as the spectrum as well as the ability to listen to any type of modulation.
?--
John P.
WA2FZW
Re: TinySA.ino GUI testing #tinysa

 

Certainly plan to make any code available, but at the moment am working away from home (retirment is still a way off unfortunately) and cannot access the files.? Perhaps at the weekend, maybe best after making the touch menus work, agree ideally with encoder input as option.

But would be great even if there are different software options to agree on a standard pin-out for each processor type.

73

Dave M0WID
Re: SI4432 AGC #tinysa

 

Not naive.
Sometimes measurement accuracy can be more important than dynamic range.
But not always.
AGC could be a menu option if it works well enough.

Jerry, KE7ER


On Tue, Feb 18, 2020 at 06:38 PM, Joshua Blanton wrote:
So perhaps this is a naive perspective, but I would think that having AGC enabled in a spectrum analyzer would always be sub-optimal during measurement sweeps - because the changing gain/attenuation adds yet more variables to the calibration between samples within a single sweep.? Having the ability to do a "pre-sweep" of sorts to define the maximum/optimum gain settings for a given input could be valuable (along the lines of an "Auto" button for the analyzer, to pre-set gain balance), but throughout a single sweep I would expect the most consistent results to come from a fixed gain setting.
?
Obviously a fixed gain setting throughout the sweep may result in a lower overall dynamic range, but that seems like a tradeoff that makes sense.? Of course, all of my spectrum analyzer experience is with older units that are happy to have 70-80dB of dynamic range under ideal conditions!
?
Re: TinySA.ino GUI testing #tinysa

 

On Tue, Feb 18, 2020 at 02:32 PM, m0wid wrote:
I have the TinySA working with the ESP32 and the excellent TFT-eSPI library, but with an older version of the software without the touch features, but not yet had chance to convert the latest version to ESP32.

Hi Dave et.al. using the ESP32/ESP8266, any plans to upload to the HBTE groupsio Files section?? The code(s) would be great to review if you can as I was thinking about using an ESP32.?

?
Re: SI4432 AGC #tinysa

 

So perhaps this is a naive perspective, but I would think that having AGC enabled in a spectrum analyzer would always be sub-optimal during measurement sweeps - because the changing gain/attenuation adds yet more variables to the calibration between samples within a single sweep.? Having the ability to do a "pre-sweep" of sorts to define the maximum/optimum gain settings for a given input could be valuable (along the lines of an "Auto" button for the analyzer, to pre-set gain balance), but throughout a single sweep I would expect the most consistent results to come from a fixed gain setting.

Obviously a fixed gain setting throughout the sweep may result in a lower overall dynamic range, but that seems like a tradeoff that makes sense.? Of course, all of my spectrum analyzer experience is with older units that are happy to have 70-80dB of dynamic range under ideal conditions!


Josh, KB8NYP


On Tue, Feb 18, 2020 at 6:15 PM Jerry Gaffke via Groups.Io <jgaffke=[email protected]> wrote:
I don't yet have working hardware, so can't verify your results.?

I assume the blue line represents both PGA and LNA gain.
And that the single step down and back up near the middle represents the LNA gain.

The PGA gain initially staircases down in 8 steps over a period of roughly half
a horizontal division as the four bits of PGA gain are reduced from max gain of 24dB
to min gain of 0dB.? (From page 50 of SiLabs AN440)

Your artifact is also roughly half a horizontal division, somewhat delayed from that
reduction in PGA gain.? I think it's just that the PGA gain register and the RSSI register
are not in any way synchronized.? A quirk of the Si4432 design.

I think the solution is to leave the AGC off.
Each time the RSSI register is read, check the value to see if it is getting close to
either the upper or lower limits.? If it is, then adjust the PGA and/or LNA gain manually,
wait for a millisecond or two, and then re-read the RSSI register
before advancing to the next frequency of the scan.

A couple curiosities I don't really have an answer for:

1)? Why is the 20dB of LNA gain shifting showing up as only about a third
of the scale of the 24dB of PGA gain shifting in the blue trace???

2)? If PGA gain changes are not synchronized with the RSSI register,
how is it that changing the LNA gain bit is synchronized with the RSSI register?
The LNA is positioned before the PGA in the Si4432 receiver architecture,
the RSSI is way back toward the end of the receive process.

Jerry, KE7ER?


On Tue, Feb 18, 2020 at 02:15 PM, m0wid wrote:
I have been away, and will be the rest of the week, so no time to play, however last night I did add back in the matching components for the SAW filter.? It eventually dawned on me that a highly selective SAW filter at the IF was not ideal when doing a pass with wider RBW.? Apologies for being stupid.
This is the trace now - still the artifacts from agc changes.? Is this unique to my module, perhaps I have a dodgy one?? The artifacts do not appear, or change position, with different signal levels, and do not appear if the gain value is fixed.
Re: SI4432 AGC #tinysa

 

Dave,

One other thing, that sgin bit in register 0x69.
Not totally obvious to me exactly what the devil it does.
If you have it set, I suggest you clear it.

Jerry, KE7ER


On Tue, Feb 18, 2020 at 03:15 PM, Jerry Gaffke wrote:
I don't yet have working hardware, so can't verify your results.?

I assume the blue line represents both PGA and LNA gain.
And that the single step down and back up near the middle represents the LNA gain.

The PGA gain initially staircases down in 8 steps over a period of roughly half
a horizontal division as the four bits of PGA gain are reduced from max gain of 24dB
to min gain of 0dB.? (From page 50 of SiLabs AN440)

Your artifact is also roughly half a horizontal division, somewhat delayed from that
reduction in PGA gain.? I think it's just that the PGA gain register and the RSSI register
are not in any way synchronized.? A quirk of the Si4432 design.

I think the solution is to leave the AGC off.
Each time the RSSI register is read, check the value to see if it is getting close to
either the upper or lower limits.? If it is, then adjust the PGA and/or LNA gain manually,
wait for a millisecond or two, and then re-read the RSSI register
before advancing to the next frequency of the scan.

A couple curiosities I don't really have an answer for:

1)? Why is the 20dB of LNA gain shifting showing up as only about a third
of the scale of the 24dB of PGA gain shifting in the blue trace???

2)? If PGA gain changes are not synchronized with the RSSI register,
how is it that changing the LNA gain bit is synchronized with the RSSI register?
The LNA is positioned before the PGA in the Si4432 receiver architecture,
the RSSI is way back toward the end of the receive process.

Jerry, KE7ER?


Hide quoted text

?

On Tue, Feb 18, 2020 at 02:15 PM, m0wid wrote:
I have been away, and will be the rest of the week, so no time to play, however last night I did add back in the matching components for the SAW filter.? It eventually dawned on me that a highly selective SAW filter at the IF was not ideal when doing a pass with wider RBW.? Apologies for being stupid.
This is the trace now - still the artifacts from agc changes.? Is this unique to my module, perhaps I have a dodgy one?? The artifacts do not appear, or change position, with different signal levels, and do not appear if the gain value is fixed.
Re: Taking a Arduino Nano to 3.3V...It's possible, but it won't connect for the PC app...

 
Edited

UPDATE - UPDATE - UPDATE

I want to go on the record that my statement on Sunday pertaining to the Arduino Nano cannot be modified for 3.3VDC by changing the regulator and doing some additional wiring was a flawed statement. I found on a completely different forum that the information on how to modify a Arduino Nano was also flawed and the schematic I used to modify my Nano from that forum had at least two issues that made the Nano not operate in my setup once modified to their schematic. Once I found those issues and repaired them to be correct to the V3.2 Nano schematic the Nano in my setup is running excellent, seen by the TinySA Windows application as a COM4 device and it perfectly capable of 'steering' my setup perfectly.

Please disregard the title of this message and carry on with modifying your Nano with the CORRECT information found on this forum.

73 de Marty, KN0CK
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