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  Topic Review (Newest First)
2019-09-13 11:27 AM
rabbit73
Using SDRsharp for Noise Interference Measurements

SDRsharp can also be used to look for noise. It can't show all of VHF-High at once, but it can show part of a channel and the adjacent noise. This is my channel 7:



a closer look:



My channel 9 is much weaker; it's marginal and can't always be received.



The signal is weaker than -45 dB, and is less than 15 dB above the noise floor; not enough SNR.

One nice thing about the spectrum analyzer is that it tells you if the channel is there. If you do a channel scan with your TV tuner and it doesn't pick up a channel, you don't know if the channel is there or not. The spectrum analyzer answers that question.
2019-09-13 11:20 AM
rabbit73
Quote:
Originally Posted by lenlab
I am feeding with a VHF Yagi and a home built grey hoverman without the VHF tophats. I combine the two antennas outside the house. No preamp.

This is the scan of the antenna feed without the FM filter and distro amp:

That's a lot of noise interference, len.
Quote:
Originally Posted by lenlab
Rabbit,

I receive 13.1 very well. However 11.1 I can't receive and 7.1 is spotty. So whatever it is does impact my viewing.
Your scan shows exactly that situation. 13 is mostly in the clear, 11 looks not likely, and 7 is maybe.
2019-09-11 11:21 AM
rabbit73
Quote:
Originally Posted by lenlab View Post
Rabbit73,

I bought the same dongle.
I added an SMA to F adapter cable for the antenna connection.



Try setting the gain at 25 dB. Click on View > Preferences > set gain to 25 dB > click OK



Try it first without the amp, then with the amp.
2019-09-11 09:52 AM
lenlab Rabbit73,

I bought the same dongle. As I said I have it working on my win10 desktop with SDR# (haven't tried other software) and my 2 old laptops with XP and Linux and various software.

On my Dell XP laptop I have installed the simple RTL Scanner and ran it with my antenna feed to get a scan of my VHF spectrum. As soon as I can I will show the results on this forum and elsewhere.



7.1 =175.25
11.1 = 199.25
13.1 = 204.25
2019-09-10 02:55 PM
rabbit73
Quote:
Originally Posted by lenlab View Post
An Update on my journey and experience. I bought an RTL-SDR USB device and then tried out software to get it working.

One caveat is I have no clue what I am doing and what the resulting displays are showing me with the various software discussed
I bought the RTL-SDR.COM dongle and had to learn how to assemble the software to make a spectrum analyzer.



It was new to me also, so it took me many attempts to get it working. I selected the RTLSDR-Scanner software for the spectrum analyzer. SDR# and similar software is fun to use, but the dongle MHz bandwidth is too narrow to scan VHF-High. A spectrum analyzer program stitches together segments to cover the band.
Quote:
I am interested in analyzing my high VHF OTA signal for noise interference.
You need the spectrum analyzer software for that. I learned how to assemble and use two 32-Bit programs and one 64-Bit program.

v1.3.2
rtlsdr_scanner-setup-win32.exe
https://github.com/EarToEarOak/RTLSDR-Scanner/releases



Channels shown above are 7, 9, and 13. Channel 9 (the middle channel) is marginal, it doesn't always have enough SNR to be 15 dB or more above the noise.

Simple earlier version; wait for popup (see Pete's post #47 on other forum)
rtlsdr_scan-windows-32bit.exe
https://sourceforge.net/projects/rtl...r/postdownload
if no popup
v1.0.22180.60082 next page
rtlsdr_scan-windows-32bit.exe
https://github.com/EarToEarOak/RTLSD....0.22617.26540



64 Bit v1.3.0 RTLSDR Scanner v1.3.0 (Pete's post #56 on other forum, not for XP)
rtlsdr_scan-windows-64bit.exe
https://github.com/EarToEarOak/RTLSD...ses/tag/v1.3.0

2019-09-10 10:27 AM
lenlab An Update on my journey and experience. I bought an RTL-SDR USB device and then tried out software to get it working.

One caveat is I have no clue what I am doing and what the resulting displays are showing me with the various software discussed:

SDR# I loaded on my Win10 desktop with no issues and it seems to be working well. I can tune to various FM stations with a small portable antenna and hear them and see the results displayed. However it will be a challenge getting my antenna coax to this desktop.

SDR# loaded Ok on my old Dell Win XP Laptop but I could not get it to work. I can tune to an FM station but as soon as I try to make any changes to settings SDR# locks up and hangs the laptop. Only recourse is to power off. So it is not really working.

SDR Scanner was installed on the Dell WIN XP Laptop and it seems to be working well.

HDSDR is an application I don't see talked about here but it loaded on the Dell XP laptop and works. It seems to be a clone of SDR# as best I can tell with similar displays.

Finally I was able to download and install from the Linux repositories GQRX and have it running on my old Lenova laptop.

So there is hope for making use of old equipment even though there is not much support for Win XP these days as most developers have moved on.

Now that I have three computers with software I just have to get trained somehow on what the heck the displays are showing me. Besides having the ability to listen to a radio I am interested in analyzing my high VHF OTA signal for noise interference.
2019-08-24 03:37 PM
rabbit73 Thank you for the reply. Well, that eliminates those two possibilities.

The next thing to suspect is a high noise level on VHF.
2019-08-24 11:19 AM
lenlab The first filter I tried was a Blonder Tongue ZHLSJ. The one I am currently using is a JVI 25-HLSJ.

Solar electric panels with micro inverters. They shut off when the sun goes down so if they were an issue I would get better VHF at night. Does not happen.
2019-08-23 03:56 PM
rabbit73
Quote:
Originally Posted by lenlab View Post
So there must be some FM noise impacting 7.1. It was not all corrected but the filter helped a lot. Must be some noise still getting past the HLSJ.
Something is there that shouldn't be there, but we don't know what it is yet. I was hoping you could get an SDR dongle going as a substitute for a spectrum analyzer. I use my old Sadelco 719E signal level meter to listen to and measure noise on VHF. It is stronger on VHF-High than on UHF, and very strong on VHF-Low with an indoor antenna. The signal must be at least 15 dB stronger than the noise to be received.





I use a portable battery operated radio tuned to a clear frequency in the AM broadcast band to hunt for noise interference:



FCC advice:
Interference with Radio, TV and Telephone Signals
https://www.fcc.gov/consumers/guides...ephone-signals

I asked you about your solar panels:
Quote:
Originally Posted by rabbit73 View Post
I see solar panels on your roof. Are they solar electric or solar thermal? If they are solar electric, I would suspect inverter interference.
You did say you had solar panels, but you didn't say if they were solar electric or solar thermal for heating:
Quote:
Originally Posted by lenlab
Yes I have had solar for the past 7 years and it never impacted my reception UHF or VHF.
Which kind do you have?
2019-08-23 11:58 AM
rabbit73
Quote:
Originally Posted by lenlab View Post
I bought a new HLSJ a few weeks back and decided to give it a try. After I installed it VHF channel 7.1 was now almost perfect with some minor pixelation showing up from time to time.
That's interesting. What is the make and model of the old HLSJ and the make and model of the new HLSJ?
Quote:
11.1 is still a no go.
You can now do a report from rabbitears.info using their new search map:
https://www.rabbitears.info/searchmap.php

This report is for your location:
https://www.rabbitears.info/searchma...&study_id=5840

This is an extract from that report:



You can click on Current Station Search List or Post-Repack Search List. In both cases 7 is stronger than 11.

I wonder which transmitting site are they actually using, the old ESB (Current), the new WTC (Post-Repack), or AUX and are they at full power?
https://www.rabbitears.info/tvq.php?...ms&facid=73881

If you click on Transmitter Distance in your report, a terrain profile will come up. Both signal paths are blocked by terrain, but the WTC path looks better:



2019-08-23 10:21 AM
lenlab Just another update.

So yesterday I put on VHF channel 7.1 and it was unwatchable as there was what appeared to be noise on the TV screen. I bought a new HLSJ a few weeks back and decided to give it a try. After I installed it VHF channel 7.1 was now almost perfect with some minor pixelation showing up from time to time.

So there must be some FM noise impacting 7.1. It was not all corrected but the filter helped a lot. Must be some noise still getting past the HLSJ.

11.1 is still a no go.
2019-08-13 09:58 AM
lenlab Just a brief update:

I brought my antenna feed out of the distro amp directly into my Samsung TV and it was receiving 7.1 with an SNR (Per the TV Tuner of 16-17 with a lock). The picture was solid for the most part with a rare pixelation.

However still NO to 11.1.

So I checked the same feed into my DVR+ and the results were high signal but pic quality 0. No picture.

So somehow the tuner in my Samsung TV dealt with the situation better for 7.1.
2019-07-19 09:50 PM
ExDilbert
Quote:
Seems strange that I get 100% signal strength on 13.1, 11.1 and 7.1 but 0 quality on 11.1 and 7.1 and 100% quality on 13.1.
The strong signal may be from a source other than the TV signals. FM harmonics seem to have been ruled out so that leaves a puzzle. It's too bad that consumer grade tuners do not offer better diagnostics.

I had a similar issue with a 2 edge channel 13 signal here. That was compounded by power lines that created a lot of noise. With analog signals, interference could be seen and often diagnosed based on its appearance. I always had a watchable picture even if it did have some video noise. With digital signals there is no indication other than degraded signal quality and, depending on the tuner, sometimes not even that. That same channel, now digital and significantly weaker, often disappeared, probably due to EMI or tropo interference, and one day just disappeared. Never did figure it out. It just sat there at 70% signal strength and 0% quality unless tropo gave it a boost. I could easily see the signal on a spectrum analyzer and there was no indication of what was causing the issue.
2019-07-19 07:33 PM
majortom You don't really know what's going on in the VHF spectrum, because to date you haven't looked at it. I would get working on looking at the spectrum as discussed here.
The questions you wanna answer by looking at the spectrum... what is the noise floor doing? IS the signal buried in the noise, or is the signal above the noise and still not decoding?

When my VHF yagi was in the other position, it was definitely a lack of strength.
The same move a few feet one way or the other can get you out of multipath as well in some cases.

Yes Jorgek, the eave mount install WAS a little tricky to do despite 3 people,
"me, myself and I".
2019-07-19 08:32 AM
lenlab majortom,

Nice story. However was your problem caused by lack of signal strength, signal quality or both? I have plenty of signal but 0 quality. Seems strange that I get 100% signal strength on 13.1, 11.1 and 7.1 but 0 quality on 11.1 and 7.1 and 100% quality on 13.1.

Yes they broadcast from different locations but it's only a few degrees apart from my house.

I have 2 vhf antennas at different locations and they both have the same signal quality issue with 11.1 and 7.1. I have tried different orientations and the same results.

I continue to search for an answer. I am leaning on it is NOT FM noise but will still work on that angle. The only other thing that is fixable is maybe cell tower noise?
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