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Good day everyone, Just thought I would share something I started during the lockdown, nothing new or revolutionary but it has kept me entertained :) My Fluke 77 has served me well since 1984 but is showing sings of age so I said to myself, why not build a bench DMM? This is a simple DMM, old technology and uses 7 segment display. The heart of the DMM is MAX1496 ADC chip, an arduino controls the functions and range. It is still pretty much a work in progress, attached is a photo of it. With pubs now open probably this DMM will wait for a while :) Cheers, Elia, M0ZHN
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adf4351 pll help
4
Hello i recently bought a chinese pll adf4351 evaluation board and used the belt with arduino nano my programmed frequency 2.514 GHz with + 5db output works but looking with the spectrum analyzer i see some spurs i wanted to know if there are changes to be made and improvements. Regardless with the green colored card it looks better there are no spurs thanks in advance for the help 73 iw5bsf Roberto
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Convolution - a possible way to provide improved RBW for the tinySA?
4
I have very little knowledge of DSP, so would appreciate if anyone here can help out. One of our club members M0KGW suggested that the RBW of the tinySA or homebrew simpleSA could be improved using convolution. The idea is if you know the response of the SI4432 FIR filters, (we can measure this) then by sampling at smaller frequency step increments and using convolution then it should be possible to recover some of the information to get improved resolution bandwidth (RBW). Improved RBW is desirable for measuring intermodulation of transmitters. Consider say two signals at close spacing, say 1kHz apart. The SI4432 has a minimum RBW of 2.6kHz so by stepping at say 2kHz intervals it is not possible to pull out these two signals. If a smaller frequency step is used, then as the signals come in and out of the filter passband the RSSI value will change - the RSSI at each frequency step will be the sum of the filter response for each signal. Given the frequency response of the filters it should be possible to extract the two signals using convolution in the frequency domain. 45 years ago I might have been able to work out the maths for this, sadly no longer. Also sad to say I had not even heard of convolution before M0KGW mentioned it. Is this idea practical and if so how to go about coding it? I would certainly like to give it a go and see how it works in practice. 73 Dave M0WID
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How mixer responses to different PORT and LEVEL
2
Sorry long post Since i saw posting on mixer at time of TinySa development hot time in this forum, i would appreciate advises on how mixer reacts to signal coming from different PORT and LEVEL. This is for ham receiver. Normal ham receiver has filter to reduce the f3 and f4 as described below. Assume it only has average filter and it is in strong interference field day, so, f3 and f4 still very strong after leaking through the less than perfect filter and reach the mixer. Assume mini circuit ade-1 mixer as used inside TinySa Actual freq, wanted receive freq is 7.03MHz. Two unwanted freq is 3.52 and 3.51 MHz and their sum is same 7.03 MHz. Modern ham receiver have half octave filter and will attenuate it quite a bit but can still leak through in field day or similar. Yes, they do make contest grade receiver with extra strong filter but that is not the issue here. My question is how this mixer will response in what manner. Question 1. Does mixer act differently toward "a pair of signal both coming from RF port (as in ham receiver unwanted out of band interference) and the normal pair of signal, wanted signal, called f1, from rf port at says -90 dBm and a much stronger signal from Lo port at 7 dBm, called f2. As the example mixer, the IF port will have sum and difference at -95 dBm, as 5 dB conversion loss at f1+f2 and f1-f2. As for the unwanted interference coming from RF port, called f3 and f4 , is it true that it need to be "quite strong" before f3 and f4 can produce their own set of mixed output at IF port, at f3+f4 and f3-f4 (which is no use here) Beated product IMD interference signal, f3+f4 shall has same IF frequency as wanted signal f1-f2 (or f2-f1) Question2 When both f3 and f4 are weak and at similar level as the wanted f1, -90 dBm. How much dBm will the mixed output of f3+f4? Will it be very weak? Question 3 What will happen when f3 and f4 both rise to says, -40 dBm, quite strong as incoming signal but much less than the normal beating signal Lo at 7 dBm? Will it start to produce siginificant output at f3+f4? Question 4. What are the signal level condition that f3 and f4 can generate at IF port, f3+f4, at same -95 dBm of the wanted f1-f2 signal? How strong f3 and f4 need to be? Assume f3 and f4 are same level Sorry for long post. Many thanks for your time in reading this. Much Appreciated.
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NanoVNA information
Interesting and easy to understand instruction video for NanoVNA: https://www.youtube.com/watch?v=_pjcEKQY_Tk _._
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DIY Dual-trace O-scope
Might be interesting... https://www.instructables.com/Dual-Trace-Oscilloscope/?utm_source=newsletter&utm_medium=email Arv _._
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DIY O-scope
Might be interesting... https://www.instructables.com/Make-Your-Own-OscilloscopeMini-DSO-With-STC-MCU-Ea/?utm_source=newsletter&utm_medium=email Arv _._
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Hello, when sweeping from 0 - 10MHz (without an input signal) I always get a higher noise floor starting @ 0Hz - 2MHz. Does anyone has an idea what could be the reason and can this eventually be impoved to get the same noise level as for higher freqeunzies? Disconnection the mixer/ BPF from RX SI4432 dielivers the same picture. Thanks Peter ps. I'm using for TinySA Arudino Zero from Protoneer as recommended by Erik.
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My home build VNA uses a single SI5351 to generate both the test signal and the LO for the downmix to the audio IF where the I/Q demodulation is done. The VNA has some problems in isolation and one possible cause is leakage from one output of the SI5351 to the other output so we should measure how good/bad this is. One output of the SI5351 is connected to the SA with 30dB attenuation. The other output of the SI5351 is not connected. The third output is always mute and not frequency has been setup The SW steering the SI5351 uses for each output a separate VCO to have fully independent frequency control. Different attenuation levels where used to verify the seen signals where not created due to IMD in the SA. First with 10MHz on one outputs and the others muted. Seems OK, all spurs are at least 70dB down. And yes, there is a small mistake in the auto marker algorithm of the SA Then with a second output active at 15MHz. The second output is visible at -55dB, but also a strong spur at 5 MHz (-62dB). This already explains the isolation problems in the VNA Will it get worse at higher frequencies? First with two outputs both set to 50MHz, a nice clean signal And now with the connected output set to 50MHz and the open output to 52MHz. The level of the spurs is only 42dB down. When you send this as LO to a mixer with a LO-IF isolation of 30dB the not connected output will appear at -72dB in the IF output of the mixer which fully explains the (lack of) isolation performance of the VNA using this SI5351 But is this a result of the output stages doing some mixing or is it earlier? Lets test with the connected output again set to 10MHz and and the open output to 66MHz Measurement at other frequencies have confirmed that the direct output leakage increases with increasing frequency but the other spurs (like seen above) are not directly related to the selected output frequency. The modulo difference between the frequencies of the two outputs determines the level and position of the spurs and these follow a pattern that repeats a number of times over the total frequency range. It may be possible that the coupling/leakage is through the PLL loop in the SI5351. More to investigate. Thoughts, feedback is welcome.
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Can't Install TinySA-saver
3
#tinysa
Maybe slightly OT: I'm trying to install the TinySA-saver utility on Debian 10, but I'm getting an error I can't solve. I cloned the code from https://github.com/erikkaashoek/tinysa-saver and following the instructions, I did a: python3.7 -m pip install . This greets me with an error Complete output from command python setup.py egg_info: Traceback (most recent call last): File "<string>", line 1, in <module> File "/usr/lib/python3.7/tokenize.py", line 447, in open buffer = _builtin_open(filename, 'rb') FileNotFoundError: [Errno 2] No such file or directory: '/tmp/pip-install-veacg6g9/PyQt5/setup.py' ---------------------------------------- Command "python setup.py egg_info" failed with error code 1 in /tmp/pip-install-veacg6g9/PyQt5/ All required packages are installed (even the ones that you 'may' need. Suggestions, anyone, please ?
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Arduino based component tester
14
Just saw this on YouTube, a smple Arduino based component tester. https://www.youtube.com/watch?v=Fpf5F8YUsVY There is a link to a website with schematic, BOM and Code. Code is probably the basis for some of the ones available on ebay for around $15. But, if you have the parts around it would be an interesting project . -- DuWayne, KV4QB
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Hello,New to the group. Here¡¯s a dummy load I created. It¡¯s a 50 ohm 250W resistor connected to a BNC bulkhead in an aluminum case (you can see the model number in the first photo).Happy to have found the group!73,DaveKC3GPMSent using Zoho Mail
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Observing a few odd things and following on from the post in the tinySA group where the 2.6kHz filter was removed I added a test mode to my ESP32 version to test the FIR filters, I called it RX Sweep, and added a trace store facility to the web page. The test mode uses a fixed LO set and fixed input - I used the 15MHz -30dBm reference, and varies the RX frequency. In this case the IF is set to 434.12 which is at the upper end of the SAW filter passband and minimises the effect of the IF breakthrough at low frequencies. The results are essentially the same at different IF in the SAW filter passband and anyway the signal to the receiver is fixed frequency and strength for this test. Results for the 2.6kHz(light blue - store 1), 2.8kHz(orange - store 2), 3.1kHz(purple - store 3), 3.2kHz(green - store 4) and 3.7kHz (blue) filters are shown below: Some interesting observations. Most significant is that the passband is offset from the nominal IF on these narrow filters, and some of the filters have significant ripple (2dB on the green 3.2kHz filter). It looks like there is some benefit from using the 2.6kHz filter Here is another capture, this time 112.1kHz(light blue - store 1), 181.1kHz(orange - store 2), 225.1kHz(purple - store 3), 248.8kHz(green - store 4) and 335.5kHz (blue) filters . By now the filters are centred on the IF but there are significant differences in the RSSI values for different filters, some filters give a nice flat passband response, others have significant dip mid band. I am using cheap modules ex China - I wonder if this is repeatable from chip to chip or if these devices are cast offs that have failed a test in some way and found their way onto the usual auction sites? Either way looks like some form of self calibration to correct the RSSI value for different filters is needed, and an offset in IF or LO to shift into the passband at narrow filters. I expect this is already included in the tinySA product? 73 Dave M0WID
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Good evening all, I have been thinking about a tracking generator to go with the tinySA so I drew the below block diagram of how I understand TG works. Is this feasible? Is it worth prototyping and testing? Would love to hear your thoughts. 73 Elia, M0ZHN
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IMPROVING RBW WITH THE AT86RF215M
5
#tinysa
hello all, i just discovered this group and their efforts... congratulations for the SA analyzer and its fantastic price. you have killed to us the desire of design/build our own SA, hi hi i can not find the schematic anywhere, so i will talk in reference i could see in http://www.carnut.info/tinySA/tinySA.html https://www.changpuak.ch/electronics/Arduino-Project-VISIONARY.php from my point of view, the worst performance of the SA is RBW, limited by the receiver channel bandwidth. for a communications application, during some time i have been looking "one-chip" transceiver with a very narrow channel bandwidth. in fact I landed here to discover which chip you were using... well, some weeks ago I found this chip: AT86RF215M 3.03EUR@25UNITS in MOUSER http://ww1.microchip.com/downloads/en/devicedoc/atmel-42415-wireless-at86rf215_datasheet.pdf AT86RF215 / AT86RF215IQ / AT86RF215M Sub-1GHz/2.4GHz Transceiver and I/Q Radio where you can extract the zeroif IQ data stream 13+13bits with a sampling frequency of 4Msps max. i am not sure if you need some other functionality in the SI4432 "one-chip" transceiver, but it seems a good idea to connect AT86RF215M to a STM32F4? and, doing decimation, improve the dynamic range and RBW (1bit more reducing 4 times the sample speed) some devices of the STM32F family include a delta-sigma digital filter ("DS demodulator") it is not very well documented for this purpose, but it seems possible to do decimation by hardware. well, this is my 2cents to this nice project that it will save a lot of time to lots of people 73 from catalonia, ea3ghs eduardo
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EMRFD Closeout Sale
10
Great opportunity to get this classic book. Experimental Methods in RF Design (Classic Reprint Edition) Immerse yourself in the communications experience. Build equipment while understanding basic concepts and circuits. Clearance stock-out price! Item No. 1017 - $20.00
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My homebrew project is nearing completion Two pictures for those interested -- HBTE Files section: /g/HBTE/files Erik, PD0EK
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Updated #tinySA tinuSA code
8
#tinysa
I pushed a new version to github of both the tinySA.ini and the tinySA.exe that now also allows the scanning of the BPF This version is updated to follow the regular linux command line structure. Commands and arguments are separated with a space and each command is terminated with a '\n' This ensures using a slow arduino nano with a even slower serial interface will still work without having to change the command parser. You will have to adapt the pin numbers to your choice of processor and disable the display if you do not need it -- HBTE Files section: /g/HBTE/files Erik, PD0EK
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LO Alternative to Si4432
14
Good evening, Not wanting to digress from the current design, I have stumbled across this: VISIONARY SA ( https://www.changpuak.ch/electronics/Arduino-Project-VISIONARY.php ) It is somewhat similar to the tinySA but uses LM61E2 as the LO. Seems to be a better choice for an LO than the Si4432. Perhaps will try and see if I can give it a go. Just sharing my thoughts... 73 Elia, M0ZHN
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Image Name
Sat 8:39am
Sat 8:39am