Topics

Spectral analyser


Gerard
 

Good evening, I am a bit new in this field and I do not have all the material for in-depth analysis
My first question is whether you can emulate a spectrum analyzer with an oscilloscope and an HF generator
I have a 2*50MHZ oscillo and a FY6900 60MHZ generator that offers a lot of possibilities (see doc)

Another possibility is to use a card and connect it to a PC
There’s this one over there for 45$ (37€)
Module de source de signal, analyseur de spectre, carte de source de signal, outil d'analyse de domaine de fréquence RF, avec interface USB, suivi: Amazon.fr: Commerce, Industrie & Science

I rely on your expertise
Thank's for your answers

cdt


Ashhar Farhan
 

Spectrum analyser needs 80 db or measurement range. Oscilloscope will not provide that. Nor can it distinguish between frequency components. For instance, if your transmitter has a third harmonic that is 30db down, it cant register that.
Your cheap bet is to get an Antuino for 100 dollars. It is an swr meter and a simple spectrum analyzer with limitations, but entirely adequate for homebrewing. 
The other alternatives are the tiny spectrum analyzer that I have heard but not used. Finally, you could invest in a Rigol. At over $1000 usd, buy it with a tracking generator. It is bjg ticket bu entirely worth it.
- f

On Mon 11 Jan, 2021, 1:53 AM Gerard, <kabupos@...> wrote:
Good evening, I am a bit new in this field and I do not have all the material for in-depth analysis
My first question is whether you can emulate a spectrum analyzer with an oscilloscope and an HF generator
I have a 2*50MHZ oscillo and a FY6900 60MHZ generator that offers a lot of possibilities (see doc)

Another possibility is to use a card and connect it to a PC
There’s this one over there for 45$ (37€)
Module de source de signal, analyseur de spectre, carte de source de signal, outil d'analyse de domaine de fréquence RF, avec interface USB, suivi: Amazon.fr: Commerce, Industrie & Science

I rely on your expertise
Thank's for your answers

cdt


Jerry Gaffke
 

Here's the forum for that tiny spectrum analyzer:
    https://groups.io/g/tinysa


On Sun, Jan 10, 2021 at 05:20 PM, Ashhar Farhan wrote:
The other alternatives are the tiny spectrum analyzer that I have heard but not used.


MadRadioModder
 

You can buy the TinySA on eBay for about $60 USD.  Works relatively well. Ive given away several to people that can’t afford the Rigol. 


MRM

 


On Jan 10, 2021, at 9:23 PM, Jerry Gaffke via groups.io <jgaffke@...> wrote:

Here's the forum for that tiny spectrum analyzer:
    https://groups.io/g/tinysa

On Sun, Jan 10, 2021 at 05:20 PM, Ashhar Farhan wrote:
The other alternatives are the tiny spectrum analyzer that I have heard but not used.

--

…_. _._


Evan Hand
 

Gerard,

The board that you listed is for 33MHz to 4400, outside of the uBITX frequencies. 
To be able to use for spectral purity, as well as the IF frequencies, you would want a unit that can measure up to the 3rd harmonic of the highest frequency that the transmitter will output.  for the uBITX that would be 150MHz.
 You also want the lower frequency to be below the lowest transmitter output/signal to be measured.  For the uBITX that would be 3MHz or less.
The last thing to be aware of is the resolution bandwidth RBW.  The smaller the better.

The TinySA is a good low-cost spectrum analyzer, with just one shortcoming: The RBW is only 3kHz.  That makes it hard to measure IMD values for audio signals on transmitters.  For the $60 it cannot be beaten. 

A midlevel SA will have an RBW of less than 100Hz, like the Rigol and Siglent models.
https://smile.amazon.com/s?k=B01LFZWYFW&ref=nb_sb_noss
https://smile.amazon.com/s?k=B00CLWJA38&ref=nb_sb_noss

When assembling your tools, be sure to include an attenuator or tap to limit the power sent to the SA.  Here is a link to one that can be built that I use.  It costs about $10 for the parts without shipping costs:
http://www.ad5x.com/images/Articles/Tap50dbRevA.pdf

With the TinySA you may also need a step attenuator to improve measurement performance:
https://www.ebay.com/itm/NEW-0-82DB-VARIABLE-STEP-ATTENUATOR-50-OHM-for-Ham-Radio-Transmitter-etc-USA/303637657384?hash=item46b236f728:g:ELwAAOSwpItfIosC

NOTE: you still need the tap, as the attenuator is rated for 1/4 watt (250mW).

There is also the SDR dongle software for SA.  That is good for the IMD but has issues with spaning for third harmonics in a single scan.  I have used the TinySA and an SDRPlay RSP1A to get what I need so far.  The total cost of all is around $250US.  Still less than the lower-cost Rigol equipment.

One day I will break down and order one of the midlevel SA listed above.  Currently leaning towards the Siglent based on reviews and specs.

Above are my thoughts based on my experiences.  YMMV
73
Evan
AC9TU



 

Hi Gerard,
actually the frequency measurement through a generator and an oscilloscope is possible only if you can synchronize the oscilloscope with the generator and if you have a mixer followed by a medium frequency and a logarithmic detector at the oscilloscope input, some time ago I made a small spectrum analyzer for my old HP181, it worked fine, it had a dynamics of about 90dB and a bandwidth of 300MHZ, the mixer was a module from Microcircuits, the MF and the quartz filter were a part of an old project of QST (analyzer for penniless HAM) and the logaritmic detector was a module with an AD8307.
The circuit isn't complex to build, but is it worth it?
Today there are so many KITs and so many small spectrum analyzers at such affordable prices that I don't think you need to venture into a home construction.
Do not be fooled by a VNA (vector network analyzer), it cannot act as a spectrum analyzer except through the FFT which, as is known to all laboratory technicians, poses many problems in interpreting the displayed data, including false harmonics, aliasing and unwanted beats, it's easier to blunder than to know exactly which armines your oscillator or TX is kicking out.
The technically best solution is to invest a few dollars in a decent Spectrum Analyzer (check that it has the possibility of a VCO voltage output to drive the sweep of your generator) and with that, combined with your generator and a simple AD8307 Logaritmic Detector module , you can do all the functions you want of any VNA.
Greetings de
--
IW4AJR Loris


Gerard
 

Thank's for your answers
I’m gonna look at this from the January 14th fall sales

cdt


Jerry Gaffke
 


Here's a list of reputable vendors from the tinySA wiki:
    https://tinysa.org/wiki/pmwiki.php?n=Main.Buying

Note that randl.com sells it for $49.95 (plus about $10 shipping) here in the US,
seems a better bet than going with a random ebay seller:
    http://www.randl.com/shop/catalog/product_info.php?products_id=75243

It's a successful product, clones of dubious quality are starting to show up.


Jerry, KE7ER



On Sun, Jan 10, 2021 at 10:40 PM, MadRadioModder wrote:

You can buy the TinySA on eBay for about $60 USD.  Works relatively well. Ive given away several to people that can’t afford the Rigol. 


Gerard
 

Jerry,
Thank you for that information.
Actually looking closely it is clones on cheap sites.
Actually on Jeff’s website, there are some with the wrong packaging. It's the jungle to see good or wrong.
WRONG:



GOOD:


However, I do not know where the error is on the label on wrong. Perhaps the frequencies. If you know?

And finally a software (Included?) allows you to connect your laptop. Interristing.
For europe and orignal it’s passion radio 79€ or 96$ + ship. A bit expensive






cdt


Roy Appleton
 

Did NOT buy the tinySA from someone on ebay. You will be guaranteed to receive a clone that will not pass its own self test! Only by from the approved list vendors.

Roy
WA0YMH

On Mon, Jan 11, 2021, 10:31 AM Jerry Gaffke via groups.io <jgaffke=yahoo.com@groups.io> wrote:


Here's a list of reputable vendors from the tinySA wiki:
    https://tinysa.org/wiki/pmwiki.php?n=Main.Buying

Note that randl.com sells it for $49.95 (plus about $10 shipping) here in the US,
seems a better bet than going with a random ebay seller:
    http://www.randl.com/shop/catalog/product_info.php?products_id=75243

It's a successful product, clones of dubious quality are starting to show up.


Jerry, KE7ER



On Sun, Jan 10, 2021 at 10:40 PM, MadRadioModder wrote:

You can buy the TinySA on eBay for about $60 USD.  Works relatively well. Ive given away several to people that can’t afford the Rigol. 


K2ICC
 


On Mon, Jan 11, 2021 at 12:24 PM Roy Appleton <twelveoclockhigh@...> wrote:
Did NOT buy the tinySA from someone on ebay. You will be guaranteed to receive a clone that will not pass its own self test! Only by from the approved list vendors.

Roy
WA0YMH

On Mon, Jan 11, 2021, 10:31 AM Jerry Gaffke via groups.io <jgaffke=yahoo.com@groups.io> wrote:


Here's a list of reputable vendors from the tinySA wiki:
    https://tinysa.org/wiki/pmwiki.php?n=Main.Buying

Note that randl.com sells it for $49.95 (plus about $10 shipping) here in the US,
seems a better bet than going with a random ebay seller:
    http://www.randl.com/shop/catalog/product_info.php?products_id=75243

It's a successful product, clones of dubious quality are starting to show up.


Jerry, KE7ER



On Sun, Jan 10, 2021 at 10:40 PM, MadRadioModder wrote:

You can buy the TinySA on eBay for about $60 USD.  Works relatively well. Ive given away several to people that can’t afford the Rigol. 


Roy Appleton
 

If you check the list you will see RandL are currently safe to buy from.

Roy
WA0YMH

On Mon, Jan 11, 2021, 11:37 AM KD2QMZ <syracusepro@...> wrote:

On Mon, Jan 11, 2021 at 12:24 PM Roy Appleton <twelveoclockhigh@...> wrote:
Did NOT buy the tinySA from someone on ebay. You will be guaranteed to receive a clone that will not pass its own self test! Only by from the approved list vendors.

Roy
WA0YMH

On Mon, Jan 11, 2021, 10:31 AM Jerry Gaffke via groups.io <jgaffke=yahoo.com@groups.io> wrote:


Here's a list of reputable vendors from the tinySA wiki:
    https://tinysa.org/wiki/pmwiki.php?n=Main.Buying

Note that randl.com sells it for $49.95 (plus about $10 shipping) here in the US,
seems a better bet than going with a random ebay seller:
    http://www.randl.com/shop/catalog/product_info.php?products_id=75243

It's a successful product, clones of dubious quality are starting to show up.


Jerry, KE7ER



On Sun, Jan 10, 2021 at 10:40 PM, MadRadioModder wrote:

You can buy the TinySA on eBay for about $60 USD.  Works relatively well. Ive given away several to people that can’t afford the Rigol. 


Jerry Gaffke
 

I'm pretty sure they cloned the label like they did everything else.
It's all open source, cloning is acceptable to do.

But these copies are there for the money, they have tried to build a copy but may have failed in some ways.
Every dollar they can shave off their material cost by using 3rd rate parts means more profit.
Thorough testing of each unit before shipping would cut into the profit.
They haven't spent 6 months trying different things to see what works best.
They don't necessarily understand all the minor issues that can make a difference in performance.

The above is not always true.
It could well be that a competitor pops up in the next few months that has a better product.

Jerry, KE7ER


On Mon, Jan 11, 2021 at 09:10 AM, Gerard wrote:
However, I do not know where the error is on the label on wrong. Perhaps the frequencies. If you know?


Scott McDonald
 

I'll second that - I took a chance on an Ebay vendor several weeks ago as it was advertised as a version 0.3, not the version 0.4 clone, but when it arrived and I opened it up, it was a v0.3 clone.

Happily got my money back through Ebay because of the fraudulent representation, and got to keep the clone, which is pretty much functional, but 50 bucks at R and L for the real thing was a much better deal.

Scott ka9p 


-----Original Message-----
From: Roy Appleton <twelveoclockhigh@...>
To: BITX20@groups.io
Sent: Mon, Jan 11, 2021 11:24 am
Subject: Re: [BITX20] Spectral analyser

Did NOT buy the tinySA from someone on ebay. You will be guaranteed to receive a clone that will not pass its own self test! Only by from the approved list vendors.

Roy
WA0YMH

On Mon, Jan 11, 2021, 10:31 AM Jerry Gaffke via groups.io <jgaffke=yahoo.com@groups.io> wrote:

Here's a list of reputable vendors from the tinySA wiki:
    https://tinysa.org/wiki/pmwiki.php?n=Main.Buying

Note that randl.com sells it for $49.95 (plus about $10 shipping) here in the US,
seems a better bet than going with a random ebay seller:
    http://www.randl.com/shop/catalog/product_info.php?products_id=75243

It's a successful product, clones of dubious quality are starting to show up.

Jerry, KE7ER


On Sun, Jan 10, 2021 at 10:40 PM, MadRadioModder wrote:
You can buy the TinySA on eBay for about $60 USD.  Works relatively well. Ive given away several to people that can’t afford the Rigol. 


Scott McDonald
 

Amazingly, the language on the label of the clone I received from Ebay wasn't even copied well.

On the back the word "AVOID" is spelled "AVDIO", "Spectrum" is spelled "Spertrum" and "DISCHARGE" is spelled "DISQHARGE".


Scott ka9p


-----Original Message-----
From: Jerry Gaffke via groups.io <jgaffke@...>
To: BITX20@groups.io
Sent: Mon, Jan 11, 2021 11:55 am
Subject: Re: [BITX20] Spectral analyser

I'm pretty sure they cloned the label like they did everything else.
It's all open source, cloning is acceptable to do.

But these copies are there for the money, they have tried to build a copy but may have failed in some ways.
Every dollar they can shave off their material cost by using 3rd rate parts means more profit.
Thorough testing of each unit before shipping would cut into the profit.
They haven't spent 6 months trying different things to see what works best.
They don't necessarily understand all the minor issues that can make a difference in performance.

The above is not always true.
It could well be that a competitor pops up in the next few months that has a better product.

Jerry, KE7ER


On Mon, Jan 11, 2021 at 09:10 AM, Gerard wrote:
However, I do not know where the error is on the label on wrong. Perhaps the frequencies. If you know?


Jerry Gaffke
 

That's quite funny!

They probably shopped the labels out to the local printer with the lowest bid,
didn't really care about minor errors so long as it mostly looked right.
Does make you wonder how thorough a job they did in copying the electronics.

I might have trouble cloning a label with Chinese ideographs.

Jerry, KE7ER


On Mon, Jan 11, 2021 at 10:07 AM, Scott McDonald wrote:
Amazingly, the language on the label of the clone I received from Ebay wasn't even copied well.
 
On the back the word "AVOID" is spelled "AVDIO", "Spectrum" is spelled "Spertrum" and "DISCHARGE" is spelled "DISQHARGE".
 


Ashhar Farhan
 

On Mon, Jan 11, 2021 at 11:49 PM Jerry Gaffke via groups.io <jgaffke=yahoo.com@groups.io> wrote:
That's quite funny!

They probably shopped the labels out to the local printer with the lowest bid,
didn't really care about minor errors so long as it mostly looked right.
Does make you wonder how thorough a job they did in copying the electronics.

I might have trouble cloning a label with Chinese ideographs.

Jerry, KE7ER


On Mon, Jan 11, 2021 at 10:07 AM, Scott McDonald wrote:
Amazingly, the language on the label of the clone I received from Ebay wasn't even copied well.
 
On the back the word "AVOID" is spelled "AVDIO", "Spectrum" is spelled "Spertrum" and "DISCHARGE" is spelled "DISQHARGE".
 


Evan Hand
 

The original design was public knowledge, not sure on the authorization to build.   Here is a link to instructions that I found:
https://mail.google.com/mail/u/0/?tab=rm&ogbl#label/Dev%2FHBTE/WhctKJVjQhNWNvzGgmNNmGVxkQCPqQLLwbJMRXmvLHNWRjWGwVHxbTVzXNqDjBhRrBRcdsG

At this point, I believe that the difference in cost between the parts and the fully assembled and tested TinaSA is not enough to warrant building.  I would recommend purchasing from a reputable seller of the original.

FWIW
73
Evan
AC9TU


Jerry Gaffke
 

Evan,

You are correct.
I was following the tinySA group a year ago, the preliminary design is still freely available.
Assumed the design being manufactured would be open source hardware.
It is not, and that is perfectly understandable. 
They need to get some return on the design effort and tooling up the manufacturing line before the clones take over.

From    https://tinysa.org/wiki/pmwiki.php?n=Main.FAQ
> Question:  Is the design of the tinySA public domain?
> Answer:  The tinySA schematic and PCB design are not public domain. The embedded software of the tinySA is FOSS (free and open source software) according to the GPL v3 and can be found at https://github.com/erikkaashoek/tinySA

Trying to build it from scratch would be fun, but there are far easier ways to save a few dollars.
If curious, the build instructions as of a year ago can be found here (you might have to sign up as a memeber):
    https://groups.io/g/HBTE/files/Tiny%20Spectrum%20Analyzer/Build%20instructions%20for%20the%20Tiny%20Spectrum%20Analyzer.pdf

Jerry, KE7ER




On Mon, Jan 11, 2021 at 01:59 PM, Evan Hand wrote:
The original design was public knowledge, not sure on the authorization to build.   Here is a link to instructions that I found:
https://mail.google.com/mail/u/0/?tab=rm&ogbl#label/Dev%2FHBTE/WhctKJVjQhNWNvzGgmNNmGVxkQCPqQLLwbJMRXmvLHNWRjWGwVHxbTVzXNqDjBhRrBRcdsG

At this point, I believe that the difference in cost between the parts and the fully assembled and tested TinaSA is not enough to warrant building.  I would recommend purchasing from a reputable seller of the original.

FWIW
73
Evan
AC9TU


Arv Evans
 


Gerard

It takes a bit more than a signal generator and an oscilloscope to do
spectrum analysis.  In its most basic form your signal generator could
serve as the local oscillator for a mixer circuit and the oscilloscope as
the visual monitor at the output of that mixer.  Problem with this is that
you need some sort of tuned circuit at the RF input side of the mixer
to avoid seeing a very wide RF spectrum, and signals also detected
from harmonics of the local oscillator.  You could make your own
spectrum analyzer.  The learning curve for such a design and
construction would be steep, but maybe rewarding.

As an alternative, there are a number ot tiny spectrum analyzers that
would do the job for you at a price well below US$100.  There are 
several VNA (Vector Network Analyzer) units, also under US$100, that
could be used to perform something similar. 

Depending on what you are trying to do, it is possible to perform many
system tests using rather simple test equipment.
  • Simple voltage presence tests can be done with an LED and a
    resistor as a voltage probe.  (put a capacitor in series and this
    unit can tell you if the voltage is AC or DC).

  • An op-amp can be wired in a balanced input to determine if the
    two inputs are equal or if one of the inputs is different from the
    other.  Use an LED at the output to show which state is present. 
    A calibrated potentiometer on one input can be used to balance
    that input with the unknown input.  Calibration on the pot knob
    could then show the voltage on the other input.

  • A very simple direct-conversion receiver circuit can be used
    to locate and measure the level of an unknown frequency. 
    Also good for finding the frequency of an LC network. 

  • A balance bridge circuit (a center-tapped secondary on a
    toroid) can be used to roughly measure the Q-factor of a component
    or tuned circuit.  Also good for finding the value of L or C. 
    If you know any two of the LCF parts you can calculate the other.

There are many more examples of simple circuits being used in place of
expensive test equipment.  The usual trade-off is that you might have to
calculate some of the resulting values to arrive at the final answer.

Arv  K7HKL
_._


On Sun, Jan 10, 2021 at 1:24 PM Gerard <kabupos@...> wrote:
Good evening, I am a bit new in this field and I do not have all the material for in-depth analysis
My first question is whether you can emulate a spectrum analyzer with an oscilloscope and an HF generator
I have a 2*50MHZ oscillo and a FY6900 60MHZ generator that offers a lot of possibilities (see doc)

Another possibility is to use a card and connect it to a PC
There’s this one over there for 45$ (37€)
Module de source de signal, analyseur de spectre, carte de source de signal, outil d'analyse de domaine de fréquence RF, avec interface USB, suivi: Amazon.fr: Commerce, Industrie & Science

I rely on your expertise
Thank's for your answers

cdt