Kurt,

you may have replied to Joe, but not as part of this thread. ;)

Karl Heinz - K5KHK?

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Dear all,

I see that this subject leads to interesting different point of views. As I wrote in my previous message, the purpose remains first "educational", just also highlighted by Herb with its reference to Agilent application note 1316.?

I like the proposal of Erik, i.e. to have coupling between input attenuation and RefLevel, if this last one is set to +20 dBm or higher value. However is it something compatible with AGC strategy ? As an example, I have put a stand-alone carrier at 250 MHz for different levels, and below is what I get for AUTO modes (attenuator and RefLevel) :

RF input level +10 dBm : ATTENUATE 30 dB, REF LEVEL +30 dBm
RF input level 0 dBm : ATTENUATE 20 dB, REF LEVEL +20 dBm

This shows that the attenuation values for these two use cases is 10 dB higher than minimum automatic attenuation of 10 or 20dB proposed by Erik. So it could be difficult to couple the two parameters for getting optimum and safe conditions at same time for the tinySA. If I understand correctly the AGC strategy, the idea seems to keep a displayed value which is always around 20 dB lower (for AUTO modes) compared to RefLevel, which for this last one is driven by the attenuation value.

As a conclusion it seems more careful to keep the existing working mode as it is. Never mind for the coupling theory !

Jean-Roger

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On Wed, Aug 26, 2020 at 01:48 PM, Kurt Poulsen wrote:

Hi Erik

I have just written a 30 page document on the TinySA with 95 illustrations for the HAM magazine OZ and in this connection used the markers a great deal. They work excellent (using latest firmware) However MARKER OPS is killing me I have not yet found the “secret” behind the idea as it is screwing up the display setting ? I need to spend more time ?

?

Kurt,
? I'm sure the article will be well received - as is generally the case with your technical publications.? Here's what I have found out about marker ops.

1.? Marker OPS -> Center:? This operation is the one I use most often and is probably the one you are also familiar with.? It makes the current active marker frequency the display center frequency.? I primarily use it to make the active marker frequency the center frequency and then zoom in on it using Frequency->Span button.

2.? Marker OPS -> Start: This operation makes the current active marker frequency the display start frequency.? It took me a while to figure out a good use case for this.? If the active marker is a tracking marker it will move that frequency to the first display point and track the next highest signal to the right.?

3. Marker OPS -> Stop: This operation makes the current active marker frequency the display stop frequency.? For me it has a similar use case as marker->stop.? If the active marker is a tracking marker it will move that frequency to the last display point and track the next highest signal to the left.

4.??Marker OPS -> Span: I expected this operation to change the SPAN setting relative to the current active marker frequency.?I haven't figured out what that relationship is.??

- Herb

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Yep. There is a bug in loading the startup configuration

On Wed, Aug 26, 2020 at 03:29 PM, hwalker wrote:

On Wed, Aug 26, 2020 at 10:32 AM, Igor Jobim wrote:

Erik,

I am testing the commands and have not resulted in the commands below:

trace {store | clear | subtract}

?

For these commands everything works fine:

trace {dBm | dBmV | dBuV | V | W}

trace {scale | reflevel} {value | auto}

?Igor,
? ? Erik intended to include those commands in the final release but there was a deadline to get the tinySA into production, and so, those commands never made it.? The only way they can be referenced is through mistyping a trace command and having the help screen reply back.? The commands should currently be considered reserved.

? ? I believe Erik will either remove them from the trace help screen or or implement them in a future release - if enough users show an interest in them.? The 'clear' command caused Erik the most problems during beta testing.

- Herb

On Wed, Aug 26, 2020 at 09:42 AM, Erik Kaashoek wrote:

I found a good reason to have coupling if ref level is set to 20dB or higher
The noise floor with the widest RBW is, with a ref level of 20dB just visible if attenuation is set to 10 dB
So if a user sets the reflevel to 20 or 30dB, applying a minimum automatic attenuation of 10 or 20dB does not harm as you are not able to see the noise floor so an elevated noise floor does no harm and it protects the tinySA.

Yep. On a $1000.00 plus instrument it would be negligent if you didn't have that type of automatic protection built in.? I guess the same thing on the tinySA would reduce the number of "my tinySA is not seeing anything" complaints.

- Herb

Gary
I have not done ANY testing on tinySA-saver. It is just a crude, incomplete hack to enable nanoVNA-saver to sweep with tinySA.
Unfortunately tinySA-saver is low on my priority list, mostly because I'm not fluent in python

I found a good reason to have coupling if ref level is set to 20dB or higher
The noise floor with the widest RBW is, with a ref level of 20dB just visible if attenuation is set to 10 dB
So if a user sets the reflevel to 20 or 30dB, applying a minimum automatic attenuation of 10 or 20dB does not harm as you are not able to see the noise floor so an elevated noise floor does no harm and it protects the tinySA.

Seems whatever I try to do results in a "complex division by zero" error. Setting marker, clicking on trace...
I am running it from the Anaconda prompt, and I get first error right after starting saver:
Second one when entering frequency in marker 1 box
Gary
W9TD

On Wed, Aug 26, 2020 at 07:49 AM, Jean-Roger Roy wrote:

Erik, Herb

From my return of experience with different spectrum analyzers :

For old style / vintage equipment such a HP8558B, the reference level rotating button is mechanically coupled with the input attenuator (see picture). So the attenuator value follows the set reference level. However you can pull one part of the button for disengage this coupling function (as for manual setting on the tiny SA). The purpose is to have always the most suited RF signal at mixer level, regarding choosen reference level.


For most recent equipments, let's say 1990 and beyond, they increase their attenuation value automatically when the reference level is set to higher values. I have worked with HP8591 or FSA family fron Rohde et Schwarz, and it is always the same behavior. Please note that there is no "power level discover" at first sweep, like on the TinySA. You must pay attention at the default level settings before doing any measurements ! Practically most of (professionnal) users rely on RefLevel regarding RF input level. For professional equipment, it is sometimes hard to find what is the best tradeoff for the value of input attenuator (IIP3, noise figure, etc.). When required the user can decide to set (carefully !) the attenuator at 0 dB, in order to get the best sensitivity.

Now as I am retired, I own a Siglent spectrum analyzer which follows the same rules. Just as an example, here is the behavior for the (auto) attenuator about my Siglent analyzer :

Manual RefLevel set at -10 dBm, Auto Attenuator fixed at 10 dB
Manual RefLevel set at 0 dBm, Auto Attenuator fixed at 20 dB
Manual RefLevel set at +10 dBm, Auto Attenuator fixed at 30 dB

For information there are also intermediate values for attenuator such as 15 dB or 25 dB, when the Reflevel is set at -5 dBm or +5 dBm.

I understand your reasoning, as I just check what is the behavior of the tinySA according to RF input level. You have an automatic setting attenuation, that does not exist on all spectrum analyzers. The Siglent has something similar called "Auto Tune", but it doesn't work at first startup (sweep) of the equipment. RefLevel remains always at 0 dBm, so you need to pay attention at the level settings before starting any measurement.?

I understand perfectly the strategy in order to protect the first stages of the tinySA. My feeling is that there is nothing to change at this side, but if possible introducing the RefLevel driving when working manually. After all, if the user decides to set manually attenuator value or RefLevel, it means normally that he understands what it does. Any of these actions are equally dangerous (not RFLevel for the moment) ! Considering tinySA specifications (Wiki page), and its behavior, could we imagine roughly something like this (input level never exceeds +10 dBm, or +20 dBm for a very short duration) :

Manual RefLevel set at +30 dBm, Auto Attenuator fixed at 30 dB
Manual RefLevel set at +20 dBm, Auto Attenuator fixed at 20 dB
Manual RefLevel set at +10 dBm, Auto Attenuator fixed at 10 dB
Manual RefLevel set at 0 dBm, Auto Attenuator at 0 dB

It could be better for "educationnal purpose" (attenuation value increases with higher RefLevel) to have this kind of behavior, but it could be challenging considering the existing AGC strategy, so don't worry or waste time on this topic. Any of view of other users could be welcome.

Jean-Roger,
? ?Excellent response.? I think you hit it on the head that graduating from the tinySA to a professional level scope will be easier if the user is already familiar with attenuation value increasing with higher RefLevel.? But as you also reasoned, with the existing tinySA AGC strategy it may not be worth the risk of breaking the current well working interface.

? Its only users like ourselves that have used commercial grade equipment that question the automatic coupling between reflevel and attenuation.? Students, enthusiasts and hobbyists won't miss it, and it may be a good thing for them to learn to make the proper settings adjustments? manually.

- Herb

For any attenuation applied the displayed level always reflects the level at the input , regardless of the applied attenuation

My 2 cents: if manual attenuation is selected the IF gain should compensate so the reference level stays the same.
Gary
W9TD

For a first time user, would it be better to have coupled (e.g starting attenuation level) equal to refelevel if reflevel >= 0?
Or should it be better to go to coupled mode if the reflevel is manually set to >=0?
Or leave like it is now?