OTA Signal Analyzers, Meters, Aimers, Bench Gear, Diagnostic Software

Just finished using the RTLSDR rtl_power script to scan the full UHF band.

I'm using the keenerd repo from github. To generate the heatmap, I'm using the rtl-gopow utility.

I then used an ImageMagick script called grid to create gridlines every 48 pixels ( 125KHz * 48 = 6MHz )

Command:

The results:

UHF 14 through 51

Well, its all relative...based on the SNR, I wouldn't call 20 dB for a station 70 miles away poor, especially if it is reliable and stable over time. The fuzzier the constellation is, the more error correction is helping to recover any bits received in error in it's travels over the air interface...
It is very cool to be able to rotate my antenna and see the impact on the received constellation graphically in real time...
For 8VSB, there isn't much need for every signal to be in the 30 dB SNR range where the user is... The way I understand it, if the SNR was measured right there at the transmitter, it would likely be in the mid 30s dB tops. If not, it could be a sign of something unhealthy going on, possibly even resulting in some near out of spec skirts in it's output spectrum.

While reviewing the driver source code, I was also able to find clues in the source code as to when the demodulator sees multipath, so I have altered code a bit further to indicate that in a kernel debug message that ya can see in kernel logs (not passed to user land for anything).. Kinda cool too, but without access to real chipset documentation or test equipment, I have no way to confirm. Just reading the original driver author's comments in the code, and taking a guess as to what he/they meant at the time they wrote it.

The cable signal probably wasn't the best signal available. I see many other QAM channels in the 38 to 39 dB range. I don't normally look at CATV signals,
but I did want to test it to make sure it was able to display the 256 QAM constellation too.
IMO for a wired cable signal that you are paying for, there shouldn't be much variation from one channel to the next. I haven't found a cable signal that was 'marginal' reception wise and probably won't.

At any rate it's not to be confused for real test equipment which none of us will ever have at our disposal, but is not bad for a $70 USB tuner.
All in all, I am really liking this tuner...

BTW, updateDVB is the same application that I use for looking at satellite signals (as mentioned earlier in this thread), and none of the constellation plot capability required any modification to the application side. I only modified the kernel module for the device, and the application worked straight away.

majortom said:

list of devices using the lgdt3306a demodulator, with linux support
hauppauge quadhd (pcie, sans analog)
hauppauge hvr2255 (pcie)
hauppauge WINTV_DUALHD_01595 (usb, sans analog)
hauppauge 955q (usb)
plus the xbox branded version of 955q

The only one of these that I have tested is the 955q.
But in theory the others should work for this also.

Click to expand...

A few more USB devices that would work OK with UDL's linux-media modifications.
Signal Strength in dBm, SNR in dB, spectrum_scan, but no iqplot.
Hauppage 950Q.
Geniatek (mygica) a681 (aka Mohu USB TV Tuner for Windows 10).
Which can be had on ebay for ~ $25 US.
I bought 4 of them for $10 a piece about a month or two ago in order to work on getting it working in Linux.
originally it did not, but it does now with UDL's kernel.
In addition I have since confirmed the Hauppauge Wintv DualHD works as well, along with iqplot.

Edit: Full disclosure, I did have 1 of 4 of the a681 devices fail on me.
I suspect it failed while taking windows10 updates, when I had the windows drive in,
was hoping to gather more logs to help in getting the linux driver functioning, when it went brain dead.
They did send me a new one to replace it at no charge however.

Not to denigrate your excellent work in signal analysis, I found the Hauppauge 950q quite lacking in tuner sensitivity in comparison to my Panasonic Plasma's tuner, neither WGRZ or WUTV were viewable during the winter months and WKBW was pixellated most of the time, none of my Erie regular stations showed an image, WFXP (which is now less strong than WSEE) came through with my tv's tuner but not even a hint on the Hauppage 950Q.


These USB dongles and external tuners do have a LOT of nice features but I have yet to find one that matches my tv's tuner (now using a Samsung 55nu8000 with even better tuner than the Pansonic Plasma).

I'm in a unique spot, 170' AGL and am blessed to receive WGRZ at 106.8 miles and WKBW at a similar distance year round. None of the external tuners I've bought have come close to matching what my tv's have given, the worst being the Homeworx/Mediasonic HW 150PVR, second worst Hauppaugge 950Q,and the HDhomerun Hdhr4-2us which was close but still not equal to my tv's tuner. None of these were able to show a solid picture during winter on the above mentioned channels but my tv does.

Anyone wanting to do some testing is welcome to my 950Q and Homeworx HW150 FREE, just post honest result and pay postage, the Hauppauge will probably cost $3-4, the homeworx maybe $20. PM for details.

Lately was working on this cheap USB tuner dongle, sold by mohu, which is a rebadged usb device from Geniatek, model A681.

When I rcv'd it, there was no driver available for Linux. There still isn't in the mainline kernel, but we added support for it in Updatelee's media tree and in darksky's raspberrypi tree. It uses a MaxLinear mxl603 tuner, and Panasonic mn88436 demod.
Makes for a cheap alternative, as they can be found on amazon for ~$30.
I was lucky and found mine for $10...

https://gitlab.com/Dark-Sky/rpi-udl-linux/commits/master
https://gitlab.com/updatelee/v4l-updatelee

It works pretty well so far and to my knowledge is the only atsc device I have come across which supports all 4 key metrics, strength dBm, cnr in dB, post viterbi bit error rate and packet error rate in dvb v5 api format. Supports spectrum scan now also.

So, dvbv5 applications such as this one can report the metrics the way the v5 api is designed.

I wouldn't mind trying, but not being a developer, would probably not meet their standards.
Maybe some day I will send an email to one of the developers, see if they would help to get it in there.
I can hook you up with an image for say the raspberry pi, would take all the thinking out of it, plug and play.

Darsky has this all tidied up in Manjaro Arm for the pi nowadays too. Manjaro Arm is hosting his image for the pi3b, pi3b+ (aarch64 though).
basically download image, send to an sd card with 'etcher' via linux or windows, plug sd card in to pi and boot it. Follow the on screen steps to intialise host, username, etc, and when it reboots it resizes the root partition to max allowable given the size of the sd card automatically.

Else if ya wanna install Arch Linux on an X86_64 machine, I have some PKGBUILDs We can point ya to, in order to do all the compile and install legwork for you... For the kernel piece at least.

Edit: Cheap tuner I was mentioning. Works OK in windows too once you install the Win 10 driver
https://www.amazon.com/Mohu-USB-TV-Tuner/dp/B07PYLGWSN