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
--

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.

Just copy/paste the images. If you see them inline with your text they should be OK
--

On Tue, Oct 5, 2021 at 01:39 PM, BryanF wrote:

1. What components are used in the setup for testing IIP3?? Specifically, what is the "T"-shaped component that connects to the low port of the TinySA at say 6:43 ()?? Is it just a SMA tee adapter, a splitter/combiner, or something else?

Its just an SMA tee

2. What was used to create the 9 MHz and 10 MHz signals in that video?

Two separate fairly clean (harmonics below -40dB) signal generators, each with additional low pass filters to bring the harmonics down to below -80dB

3. Related to question 2 above, how clean do the signals need to be?? I have a Rigol DG1022 that I'm guessing does not produce the cleanest signals.

Try to get et least below -70dB

4. Assuming the 9 MHz and 10 MHz signals are cleaned up with a filter (low pass or bandpass), any suggestions for reasonably priced ones?? For example, the Mini-Circuits SLP-10.7+ are almost $40 each.

I made my own low pass filters, much much cheaper than the mini-circuits and much better also, see this excellent calculator:?
Select low pass,?Chebyshev, 5th order, cut off frequency same as output frequency. E12 component values. 0.1dB ripple

?
--

20dB attenuator wasn't enough for the level of signal we get here, so swapped it for a 30dB SMA attenuator into the TinySA. Goes to show that you really do need to keep well within the TinySA's input amplitude level. Signals now look nice and square ..

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

It's quite interesting plugging the TinySA into the TV coax socket in the lounge ..

These questions are about the video here:

1. What components are used in the setup for testing IIP3?? Specifically, what is the "T"-shaped component that connects to the low port of the TinySA at say 6:43 ()?? Is it just a SMA tee adapter, a splitter/combiner, or something else?

2. What was used to create the 9 MHz and 10 MHz signals in that video?

3. Related to question 2 above, how clean do the signals need to be?? I have a Rigol DG1022 that I'm guessing does not produce the cleanest signals.

4. Assuming the 9 MHz and 10 MHz signals are cleaned up with a filter (low pass or bandpass), any suggestions for reasonably priced ones?? For example, the Mini-Circuits SLP-10.7+ are almost $40 each.

Thanks,

Bryan

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Here is a webinar that is maybe of interest .



John

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Is there some type of overlay to see the Tv channels portion of the spectrum?
--
Joe-NP3AR

This is where the typical CATV band pass filters come in very handy, low loss and very steep skirts. They are well documented and cost pennies.