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Here’s a video of the power fluctuation. (Homemade power meter from QST.)

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Here’s a video of the noise.

Can you post a video of this?
Make sure the sma connectors are tightened well
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The 6dB attenuators are to ensure the signal generators do not create harmonic products caused by the signal from the other generator. Isolation.
The input signal to the LNA should be such that intermodulation products are strong enough to observe, so well above whatever the tinySA may generate internally.
Being close to the compression point of the LNA for sure will generate a lot of intermodulation.

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It looks like you have 6dB attenuators before the SMA tee.? Why is this given that (presumably) you can just adjust the level of the signal generators?

I presume the output level from the SMA tee (or resistive combiner if used) should be near the max input signal level of the LNA being measured (e.g, before it begins to compress)?

Thanks,

Bryan

Still the same description, but they call it an improved version. However, reading through the fine print they say that the self test might fail especially after software upgrade. They do maintain that the function is not impaired, a statement we all know is bogus.
The link is for entertainment purposes only, not a buying recommendation, unless you want to waste your money since you will NOT get a money return from Ali Express for those units. After all they warn you about all the short comings.



John

On my unit (ver. 1.3317) if the Cal Out mode is selected right after powering on, and a frequency selected, there is noise around that carrier, and a connected power meter fluctuates rhythmically. Tapping LOW Out or HIGH Out immediately stops this behavior.

Hay OneofEleven, I was re-reading your earlier reply and noted you apparently were referencing transmitters, so I assume you are talking about broadcasters. I was describing closed cable TV systems. Here our off air broadcasters also publicly publish their carrier data just like? the satellite operators do. But even for them, where they reside on a cable systems spectrum, on which EIA carrier they are embedded on, that data is not general knowledge outside the system. Great thing about digital programming is that you can put a program anywhere in the spectrum and call it up under whatever channel number you choose to assign to the set top box. With this technology, you can get real deep in the weeds. But the core interest here is how convenient, accurate, and economical the TinySA as a spectrum analyzer is to be able to effectively make reliable measurements of these carriers. Cable systems spend 3-5k $ to equip field techs with instruments to measure levels and digital parameters, most have a rudimentary spectrum analyzer function which is useful but not flexible for in depth analysis.? ?

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From: "OneOfEleven"
To: [email protected]
Cc:
Sent: Thursday October 7 2021 2:34:41PM
Subject: Re: [tinysa] Uhf TV monitoring, Antenna testing

On Thu, Oct 7, 2021 at 09:14 PM, Ted Chesley wrote:

Normally the only programming data available to the customer (or outside observer) is the listing of program channels as tuned by the digital set top box. Tables of programming maps to the individual carriers, as well as dedicated band assignments are only available to the systems technical personnel.??

I guess we're lucky in the UK then by the sounds of it because we're given all the transmitter site details (transmitter location, expected coverage, list of TV channels on which multiplexed streamed, stream center frequency, bandwidth, power and modulation). ie ..

Hi One of Eleven, Yep I would say you are better informed than most customers (or outside observers) in the US. Normally, here, that info is not widely disseminated outside the systems. With clear channel QAM and a network analyzer you can find most of the embedded carrier characteristics, but as almost all data program transmissions are encrypted (even the off air broadcasters),on the cable, it's more difficult. Some smaller rural systems or stand alone operators still carry un-encrypted digital but the big guys do not. In contrast, as? you know, in the satellite world, there are charts of this info widely published as it is necessary for the individual customer to program his own receiver, but in cable this is done from the network, or central headend, and the customer has no control over the process. Also, considerable manipulation of programming occurs frequently and these programming matrix's are constantly changing.

On Thu, Oct 7, 2021 at 09:14 PM, Ted Chesley wrote:

Normally the only programming data available to the customer (or outside observer) is the listing of program channels as tuned by the digital set top box. Tables of programming maps to the individual carriers, as well as dedicated band assignments are only available to the systems technical personnel.??

I guess we're lucky in the UK then by the sounds of it because we're given all the transmitter site details (transmitter location, expected coverage, list of TV channels on which multiplexed streamed, stream center frequency, bandwidth, power and modulation). ie ..

Jose and Dave, I have attached a doc with a quick overview of the layout of the typical cable TV spectrum (USA). Might be helpful to those interested. I have also attached a doc on measuring the 256 QAM carriers in such a system with the TinySA.?

On Tue, Oct 5, 2021 at 11:26 PM, OneOfEleven wrote:

Having trouble posting full resolution images for some reason :( ..

Hello OneOfEleven,

It is my experinece that inline images should not be wider than about 600 pixel.

Appending an image with 1073 pixel will work if you deposit the image file in a cloud,
e.g. Dropbox and insert here the link to that file. See below.
NanoVNA-App_tinySA-350MHz-101.jpg
If a click on that link does not work, open the link in another tab of the web browser.

73, Rudi DL5FA

?

Yes, i experienced the same in my last post

Hi Erik,

Thanks for responding!

Just thinking, not sure if this is possible: Maybe you can add a overload indicator in the main screen?
This way the operator can see quickly if the reading is correct - or not correct due to overloading


Keep up the good work!

On Wed, Oct 6, 2021 at 09:56 AM, Erik Kaashoek wrote:

When using a browser to post, do you also get small images when adding the full size picture as an attachment?

Seems not :(

When using a browser to post, do you also get small images when adding the full size picture as an attachment?

You are overloading the tinySA when using only 15dB internal attenuation. The IMD causes mixing products outside the channel.
This is because the power to the mixer is the sum over a broad bandwidth and thus much larger then the peak power at any frequency.
You can check this using the MEASURE?CHANNEL POWER function
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Hi All,

In my test setup i am analyzing a DAB signal.
I am using a 20Db hardware attenuator, and the TinySA internal 15 or 30Db attenuator.
When the Tiny's 30Db attenuator is used, the signal looks fine - but when i use the 15Db attenuator, the signal looks completely different.
Am i doing something wrong, or has this something to do with overloading the TinySA / internal spurs?

Thanks

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> A suggestion.

> Prepare the text and images in the word processor of choice. Print the word processor's file as a portable document file, ".pdf". Make a covering post to the group and attach the .pdf.

> John

> at radio station VE7AOV

+++++

No luck :(

It works if I do a private reply in this group (get a full resolution image) but not if it's a public reply.

No luck :(

It works if I do a private reply in this group (get a full resolution image) but not if it's a public reply.