OTA signal strength metrics

Reception, channel detection, network issues, CableCARD setup, etc.
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Sion
Posts: 420
Joined: Fri Dec 28, 2012 12:18 pm

OTA signal strength metrics

Post by Sion »

Are there any technical explanations available for the HDHR OTA tuners?
When I look at signal strength like this:

Signal Strength 67%
Signal Quality 60%
Symbol Quality 100%

What do those metrics mean, and how are they calculated? In RF world, signal strength is usually represented with units of dBm, not percent. Also what's "symbol quality" and why's it important?
Finally I'd be interested to know things like the tuner's Noise Figure, minimum Signal/Noise ratio, minimum signal strength for lock, etc., if possible.

ckwsp101_tv
Posts: 17
Joined: Fri Mar 13, 2015 4:46 pm
Location: marin county , ca

Re: OTA signal strength metrics

Post by ckwsp101_tv »

I'm also in the Bay Area.
Still sorting out changes due to the repack

This what I found on this and other forums on silicondust metrics.


http://forum.tvfool.com/showthread.php? ... #post62379

ckwsp101_tv
Posts: 17
Joined: Fri Mar 13, 2015 4:46 pm
Location: marin county , ca

Re: OTA signal strength metrics

Post by ckwsp101_tv »

What are possible causes of rolling or varying signal quality and intermittent symbol lose?
Signal quality shows 5-10% swings with symbol lost.


Hardware Model HDTC-2US
Firmware Version 20200521
Device ID 10519452
enabled diagnostics

I'm in the SF bay area.
My prior posting regarding reception challenges aged out the forum.
Stage 9 repack happened May 1.

My Hi VHF reception now good enough.
Using dual stacked Antenna Craft Y10-13

Now issues are with stations coming from San Francisco Sutro Tower
UHF.stations.
Increased number of impaired time shifted recordings.

KBCW-DT 44.1 (RF 28)
KPIX-TV 5.1 (RF 29)

My existing Antenna Direct 91 XG antenna was good enough prior to repack.
AD 91 XG low UHF channel gain not as good for my current situation.

My guess is multi-path or other impairments as I'm at the bottom of a valley. 2 edge signals from Sutro Tower.

NedS
Silicondust
Posts: 1365
Joined: Mon Dec 10, 2018 12:38 pm

Re: OTA signal strength metrics

Post by NedS »

ckwsp101_tv wrote:
Tue Jun 09, 2020 6:22 pm
Hardware Model HDTC-2US
Firmware Version 20200521
Device ID 10519452
enabled diagnostics
The VHF range is very odd; lots of really strong noise in between channels. I'm surprised that's the range you're not having issues with. The diagnostics only really give a snapshot, so it's hard to see what exactly is going on in the UHF range from that, but have you tried just one antenna to see if the signals are more stable? Even if it's not strong enough, just to see if the fluctuations are still present.

ckwsp101_tv
Posts: 17
Joined: Fri Mar 13, 2015 4:46 pm
Location: marin county , ca

Re: OTA signal strength metrics

Post by ckwsp101_tv »

Hi

Good to know about VHF "noise".
Matches my early experience when adopting over the air reception with HDTC-2US in 2015.
In 2015 VHF signal strength was higher when I pointed single Y10-7-13 away from transmitting antenna.

Here is report.
https://www.rabbitears.info/searchmap.p ... y_id=16913

Behind a hill when pointing at San Francisco Sutro Tower.
http://forum.tvfool.com/showpost.php?p= ... stcount=35

The VHF less stable with a single antenna.
Also behind hill with pointing to those stations.
Horizontal stacking better than vertical stacking.

http://forum.tvfool.com/showpost.php?p= ... stcount=33
Since repack KNTV (RF 13) comes in better.

Aiming 91 XG at physical horizon.

http://forum.tvfool.com/showpost.php?p= ... stcount=29

Rolling signal quality sign of multi-path interference on UHF channels?

Before repack and when all stations using main antennas reception was ok.
Lost stuff when stations went to aux antennas.
After repack UHF signals from Sutro Tower experiencing more events.

I'm considering stacking 91 XG to help with .KQED,KBCW and other stations coming from Sutro Tower.
Cannot go higher at this time.
Still need pre-amp as cable run 100 feet. to Samsung TV and HDTC-2US.
During a problem event,
the Samsung TV Signal Quality display shows bouncing at a slower rate.

Well new generation tuner may work better in high noise multi-path environment?
I will experiment with antenna configuration and placement before considering new tuner.

jasonl
Expert
Posts: 15299
Joined: Sun Oct 28, 2007 9:23 pm

Re: OTA signal strength metrics

Post by jasonl »

The 91XG sacrifices a lot at the lower frequencies to maximize gains on frequencies that aren't even used for TV anymore, but so does pretty much every other antenna in this country so it's not like you're going to find anything better in this country. But, if you look to the UK and their grouped aerials, the XB16A from ATV (https://www.aerialsandtv.com/product/xb16a-aerial) is the best UHF antenna I've seen for use here, since their A group pretty much exactly matches the post-repack UHF band in the US, and it therefore doesn't need to sacrifice anything. It's not cheap at £63 for the antenna and £57 shipping to the US (last time I asked them, anyway), or about $150 (US) total, but it's probably the best you're going to do without designing and building your own antenna.

New tuners might help too. Order one of the ATSC 3 models when they start taking preorders.

ckwsp101_tv
Posts: 17
Joined: Fri Mar 13, 2015 4:46 pm
Location: marin county , ca

Re: OTA signal strength metrics

Post by ckwsp101_tv »

That you for reviewing my situation.

Sion
Posts: 420
Joined: Fri Dec 28, 2012 12:18 pm

Re: OTA signal strength metrics

Post by Sion »

My apologies for not following my own post for a month... but geeze, no answer to the original question? I thought this would be a straighforward question. Just wondering what those things mean, and how they are calculated...

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nickk
Silicondust
Posts: 15984
Joined: Tue Jan 13, 2004 9:39 am

Re: OTA signal strength metrics

Post by nickk »

100% = 0 dBmV = -48.75dBm. Every 5 points lower is 3dB lower.

JefferMC
Posts: 11
Joined: Sat Jun 06, 2020 7:34 am

Re: OTA signal strength metrics

Post by JefferMC »

nickk wrote:
Fri Jun 12, 2020 10:44 pm
100% = 0 dBmV = -48.75dBm. Every 5 points lower is 3dB lower.
So there's the answer for Signal Strength. Can you answer his question about what the meanings of Signal Quality and Symbol Quality in some detail?


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nickk
Silicondust
Posts: 15984
Joined: Tue Jan 13, 2004 9:39 am

Re: OTA signal strength metrics

Post by nickk »

Signal Quality is scaled for each modulation type such that 50% is the minimum signal-to-noise requirement.

Symbol Quality is an indication of how many uncorrectable TS frames have been lost in the last second (logarithmic scale). The Symbol Quality needs to be 100%.

Sion
Posts: 420
Joined: Fri Dec 28, 2012 12:18 pm

Re: OTA signal strength metrics

Post by Sion »

That's super helpful. Thanks. I had not seen that page before (obviously! LOL)

ckwsp101_tv
Posts: 17
Joined: Fri Mar 13, 2015 4:46 pm
Location: marin county , ca

Re: OTA signal strength metrics

Post by ckwsp101_tv »

jasonl wrote:
Thu Jun 11, 2020 5:47 pm
The 91XG sacrifices a lot at the lower frequencies to maximize gains on frequencies that aren't even used for TV anymore, but so does pretty much every other antenna in this country so it's not like you're going to find anything better in this country. But, if you look to the UK and their grouped aerials, the XB16A from ATV (https://www.aerialsandtv.com/product/xb16a-aerial) is the best UHF antenna I've seen for use here, since their A group pretty much exactly matches the post-repack UHF band in the US, and it therefore doesn't need to sacrifice anything. It's not cheap at £63 for the antenna and £57 shipping to the US (last time I asked them, anyway), or about $150 (US) total, but it's probably the best you're going to do without designing and building your own antenna.

New tuners might help too. Order one of the ATSC 3 models when they start taking preorders.
FYI

I put up a 2nd 91XG in a horizontal stack pointing at Sutro Tower transmitter.
Showed improvement to put me on right side of "digital cliff".
Was able to time shift record many hours with good results compared to prior situation.
Using wide distance between booms to mitigate multi-path issues.

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