VK3RTV
DIGITAL ATV

REPEATER STATUS : Fully operational DIGITAL TV Output

The VK3RTV reporting system

When a user asks the repeater (VK3RTV) for a signal report it will report back a level of P1 to P5. The received signal is measure by looking at the AGC of the receiver and converting that to 5 levels that are reported by the control system when asked. With an analogue signal input to the repeater this was closely aligned with the picture strength reporting as described below in the analogue section. With the digital signal input the signal report actually reports back a measure of the received strength of the signal as measured by the AGC in the receiver (not the picture strength) and converted to a level of P1 through to P5. With a digital signal its either P5 or P0 as described below. This may confuse occasional watchers when the systems show a P3 or P4 report for what they are seeing as a perfect picture. Remember the repeater is reporting what it see's / receives and that may be different to what you see at your end. The colour bars and beacon mode are sent from the repeater and the quality will be as good as it gets if you want to make comparisons.


How to report the strength of a DIGITAL ATV signal

Picture Strength

The aim is to achieve a P5 picture and Q5 audio as described below in the analogue section. With the signal being sent in a digital format we now have the situation where all of the bits that make up the signal must be received for them to be decoded into a picture. In simple terms this means that you either have a perfect picture (P5) or you don't have a picture at all (P0). There is a level where you can received a picture that has lots of coloured blocks in it or keeps locking up. The level where this occurs is called the threshold and is right on the edge of being good enough, a slightly better signal will mean a perfect picture and a slightly weaker one will mean no picture at all.

Audio Quality

Sound / Audio is measured in a similar way to the picture. The audio is either there or its not and if the signal is on the threshold as described above you may hear popping and cracking noises when the picture breaks up. If there are strange background noises like buzzing etc when you have a P5 picture then that is more than likely coming from the original (transmitted) source signal or you have a problem like a ground loop at the receive end. Like the picture measurement above in reality you either have a perfect audio signal (Q5) or no audio (Q0). "Q" is used here to identify the "quietness" of the audio signal.


How to report the strength of an ANALOGUE ATV signal

Picture Strength

The series of images with increased levels of "snow" are a rough guide to what ATVers would refer to as P0 to P5.

ATV users may have a poorer quality than the repeater as their signal into VK3RTV may be weak.

P0 Picture P1 Picture P2 Picture
P0 very poor signal. P1 more picture than snow. P2 detail in picture.
Every ATVer attempts to achieve a "P5" picture with "Q5" audio.
P3 Picture P4 Picture P5 Picture (perfect)
P3 more detail than snow. P4 great detail, bit of snow. P5 perfect picture.
Pictures courtesy VK3KHB

Audio Quality

Sound / Audio is measured in a similar way to picture except the "snow" is heard as "shussss" or "hisssss".
Lots of "shussss" or "hisssss" which is referred to as noise is a Q0, up to no noise being a "Q5".
"Q" is used here to identify the "quietness" of the audio signal.

This series of 3 second wave files (~23KB each) with decreased levels of "noise" are a rough guide for Q0 to Q5.

Q0 wave
Very Noisy, hint of Audio
Q1 wave
Audio is above Noise
Q2 wave
more Audio than Noise.
Q3 wave
~50 audio / ~50 noise
Q4 wave
A little bit of Noise
Q5 wave
Very quite no Noise.
Wave files courtesy VK3KHB