Re: Uhf TV monitoring, Antenna testing
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
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Re: Uhf TV monitoring, Antenna testing
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Yes, i experienced the same in my last post
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Re: TinySA15dB/30dB Attenuator, different readings
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!
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Re: Uhf TV monitoring, Antenna testing
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 :(
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Re: Uhf TV monitoring, Antenna testing
When using a browser to post, do you also get small images when adding the full size picture as an attachment?
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For more info on the tinySA go to https://tinysa.org/wiki/
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Re: TinySA15dB/30dB Attenuator, different readings
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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For more info on the tinySA go to https://tinysa.org/wiki/
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TinySA15dB/30dB Attenuator, different readings
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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Re: Uhf TV monitoring, Antenna testing
> 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
+++++
On 2021-10-06 1:05 a.m., OneOfEleven
wrote:
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.
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Re: Uhf TV monitoring, Antenna testing
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.
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Re: Uhf TV monitoring, Antenna testing
Just copy/paste the images. If you see them inline with your text they should be OK --
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For more info on the tinySA go to https://tinysa.org/wiki/
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Re: Questions Re Measuring IIP3 Of LNA
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? --
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For more info on the tinySA go to https://tinysa.org/wiki/
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Re: Uhf TV monitoring, Antenna testing
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 :( ..
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Re: Uhf TV monitoring, Antenna testing
It's quite interesting plugging the TinySA into the TV coax socket in the lounge ..  
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Questions Re Measuring IIP3 Of LNA
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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Re: Uhf TV monitoring, Antenna testing
I wish I had such a video when I worked in cable.? Thank you for finding it.
?
Kind Regards,
Dave
Dave Reiser
Phone:
301-216-5394
Mobile:
301-802-1929
Email:?
davereiser2outlook.com
520 Russell Avenue, Gaithersburg, MD 20877
?
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Re: Uhf TV monitoring, Antenna testing
Here is a webinar that is maybe of interest .
John
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Re: Uhf TV monitoring, Antenna testing
I would be interested in seeing one.? Here is the raw data to make one.? In the QAM column, each channel can have 10 or more 6 MHz channels compressed into one QAM 6 MHz
channel.? Also channel numbers don¡¯t follow.? ??For example, if I want to watch channel 975 my set-top converter will tune to channel 121.? That¡¯s totally up to the cable company.
?
Kind Regards,
Dave
Dave Reiser
Phone:
301-216-5394
Mobile:
301-802-1929
Email:?
davereiser2outlook.com
520 Russell Avenue, Gaithersburg, MD 20877
?
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From: [email protected] < [email protected]> On Behalf Of
Jose Cruz
Sent: Monday, October 4, 2021 3:10 PM
To: [email protected]
Subject: Re: [tinysa] Uhf TV monitoring, Antenna testing
?
Is there some type of overlay to see the Tv channels portion of the spectrum?
--
Joe-NP3AR
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Re: Uhf TV monitoring, Antenna testing
Is there some type of overlay to see the Tv channels portion of the spectrum?
--
Joe-NP3AR
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Re: Uhf TV monitoring, Antenna testing
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.
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Re: Uhf TV monitoring, Antenna testing
The following Is an addition to the comments made by Erik and Jim Allyn regarding the measurement of Cable TV signals in 75 ohm systems with the TinySA:
The typical CATV system in the US, carries up to 135 6MHz 256QAM digital channels in the downstream (program) spectrum. As Erik notes, measuring this spectrum on a normal cable drop is generally not an issue as the average level of an individual carrier is from -5 to +10dBmV. Converting dBmV to dBm, you subtract 48.75dB from the dBmV reading = dBm. So 0 dBmV is? =? 0 dBmV -48.75 = -48.75 dBm. Obviously well below the allowable safe threshold on the TinySA. However, as you have 135 channels present, the power of each carrier adds together on a power log basis. i.e. 10 log 135 = 21.3 dB. As all the channels are held within 3dB of each other, you can assume the total power is 21.3dB higher than a single channel. In the case of the 0dBmV (-48.75 dBm) carrier level, for 135 carriers, the total constant power is -48.75 + 21.3 or -27 dBm. This is a level recommended as a good level for reliable readings on the TinySA and thus is a safe level. .?
Where this becomes a problem is if you attempt to directly measure the output of an in-house CATV amplifier commonly used to overcome drop cable and splitting losses in the house. The typical output of these types of amplifiers is 40 +/- 10dBmV. If +40dBmV/CH, the dbm level of a single channel is +40dBmV -48.75 = -8.75 dBm. The total power for 135 channels is thus -8.75 +21.3 = +12.55 dBm. This is above the critical limit for the Tiny SA. . If the output of the amplifier is +50dBmV, the total power is now 22.55 dBm, which is enough to blow the input mixer in the TinySA and on some commercial SA's as well.?
You must always consider the addition of signal power for multiple signals on any cable being measured. CATV spectrums are of concern because of the large number of carriers and the continuous power in the digital QAM modulation. Always use an input attenuator for initial measurements until you confirm the levels are safe to measure without it.
As to the 50/75 ohm differential between standards, The error to be expected when measuring between standards is about 1.8dB.?
I have used the TinySA to make numerous measurements on cable systems and have found the instrument measurements accurate, and for the price, compares favorably with typical CATV instruments.? ----------------------------------------- From: "Jim Allyn - N7JA" To: [email protected]Cc: Sent: Friday October 1 2021 5:02:08PM Subject: Re: [tinysa] Uhf TV monitoring, Antenna testing
It may very well be dangerous to connect your tinySA directly to
your TV/data cable.? TV channels typically run around 0 dBmV
per channel, which is only 13 nanowatts.? You can run a lot of
those channels into your tinySA.? However, cable systems
also? have "upstream" channels, which is what your cable modem
uses to send data back to the cable company.? Upstream
channels are typically around 50 dBmV, which is 1.3 milliwatts, or
+1.3 dBm.? However, systems can have more than one upstream
channel, and the DOCSIS specification says the upstream power level
can be +65 dBmV (even higher in some cases), which is 42.2
milliwatts, or +16.25 dBm.? The tinySA is rated for a maximum
input level of +10 dBm.? I would definitely use an external
attenuator if I were going to hook my tinySA to the cable system.
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DAVE REISER WA3TRS
John Cunliffe W7ZQ