Signal strength or Signal quality

I have seen references to the 5 green dots as signal strength indicators.

But those dots behave as though they are a signal quality indicator. In other words an indicator of the amount of error correction being applied. Or in the worse case uncorrected errors.

I came to this conclusion after noticing that when I am using a channel which I know has a low signal strength, it will still scan at 5 green dots. (Low signal strength verified by my TV set.) And then I get the occasional macro blocking on that channel. Usually when there is some rain in my area or in the station’s transmitter area, or someplace between us.

I never get anything but 5 green dots after a scan! Which would be reasonable if it was measuring signal quality and I rarely see macro blocking anyway.

But if the 5 green dots are indicating signal quality, then they are much less useful in troubleshooting reception problems. As the signal strength went down the dot reading would look good, then marginal, and then terrible. And that would happen over a narrow range of signal strengths. (Another indication of the cliff effect.)

So are those 5 dots indicating signal strength or signal quality?

I have no idea what tablo uses to determine what constitutes various green dot levels.

You can have a channel with a strength level of 65 and a sound to noise(S/N) ratio of 18 or below.

And a channel with a strength level of 53 and a sound to noise ratio of 20+.

The channel with a S/N 18 will have more errors and more uncorrected errors then a channel with S/N of 20+.

Signal quality is based on the range your antenna is able to pull in channels as well the signal power output from the channel provider. I’ve tried various antennas and finally settled on an outdoor ViewTV WA-2708B antenna with 242 km range or 150 miles. I’m able to pull in 35 Canadian and USA stations pointing the antenna towards Seattle from Vancouver. I’m on a 14th condo with it mounted to a weighted camera tripod which makes it like having my own tower based on the height and clearance. I’ve waisted far to much money on indoor antennas where the manufacturer claimed it’s just as good. Nothing beats an outdoor antenna other than having cable tv :wink:

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While that is normally true, it’s not always true.

I live in a city where there are two hi-vhf channels that broadcast from the same location, have the same power, and have the same antenna height. They also have the same directional characteristics.

Yet one of these channels, for a ground floor antenna, has a signal strength in the 63 range but S/N of 18 or less with many errors. The other has a signal strength of 53 but S/N of 20+ with no errors. An OTA antenna above 20 feet has no problems.

Different antenna makers and models. The only reason I noticed this was that a few years ago a tablo user was trying to receive these channels from within 4.5 miles and had problems with the one channel.


“The channel with a S/N 18 will have more errors and more uncorrected errors then a channel with S/N of 20+.”

That would be reasonable if the stronger signal also had some multi path which exceeded the receiver’s ability to overcome it.

We are not aware of multi path the way we were with NTSC but it is still there. Just hiding in the background. Modern receivers do a very good job of compensating for multi path but nothing is perfect.


“Signal quality is based on the range your antenna is able to pull in channels as well the signal power output from the channel provider.”

You say ‘signal quality’ but you mean ‘signal strength’ which depends on the quality of your antenna.

If I am pointing an antenna, I want to see the signal strength. With peak received signal strength, signal quality will follow. (Assuming that the peak received signal is within the range of RF levels required by the receiver and that multi path is within the receivers ability to eliminate it.)

Would you rather know that you can not receive that station because of signal quality?

Or would you rather know that you have an acceptable signal strength but poor signal quality. Poor signal quality which might be traceable to interference from a ham radio operator nearby, or a defective dimmer in your home?

Take it from a retired broadcast engineer who spent 30+ years working in the RF field. You want to know that you have an acceptable signal strength.

I only care about signal quality.

I can go to tvfool or antennaweb and get a fairly good idea of signal strength and channel availability. This gives me a hint on the type of antenna I need.

But it really can’t tell me that the guy two houses down is running an industrial arc welder 10 hours a day.

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“I only care about signal quality.”

So what do you do when tvfool predicts that you should have plenty of signal but your signal quality measurement is indicating low?

Just assume that you must have plenty of RF signal? Or begin to check and recheck everything? Or order a better antenna?

My suspicion is that you plug that RF cable into a television set which allows you to read the relative signal strength.

But hey, I am a practical man, you should do whatever works for you.