P5
Perfect
The image is completely clear and correctly decoded. Colours, details and text are clearly visible.
- No visible noise
- No interference
- No slant or synchronisation problems
- Good colour and contrast
- All text is readable
Operating Practice
SSTV Signal Reporting
Signal reports are an important part of amateur-radio communication. They tell the transmitting station how well its signal and image were received.
SSTV operators can use the P System to report picture quality, or the more complete RSV System to describe readability, signal strength and video quality.
Useful feedback
Why Signal Reporting Matters
A signal report is more than a friendly number exchanged during a contact. It provides useful technical information about how the transmission arrived at the receiving station.
An accurate SSTV report can help an operator evaluate radio conditions, transmitted audio, tuning, antenna performance, signal strength and final picture quality.
Reports are especially useful when testing new equipment, adjusting audio levels, comparing antennas or investigating interference and propagation conditions.
Picture quality
The SSTV P System
The SSTV P System describes the visible quality of a received picture. The letter P stands for Picture.
Picture quality is reported on a five-point scale. A report of P5 describes a perfect or nearly perfect image, while P1 means that the image is only barely visible.
The P report describes the picture—not only the signal.
A strong radio signal can still produce a poor picture when the
audio is distorted, the receiver is incorrectly tuned or the
transmission suffers from interference.
Understanding the ratings
P5 to P1 Explained
P4
Very Good
The image is clear and easy to recognise, but contains slight noise or a small imperfection.
- Minor background noise
- Small amount of fading
- Slight colour variation
- Nearly all details remain clear
- Callsign and text are readable
P3
Good
The image contains noticeable noise or distortion but remains clearly recognisable and useful.
- Visible noise
- Some interference or fading
- Partial loss of fine detail
- Main subject remains recognisable
- Most important text can be read
P2
Fair
Heavy noise, fading or distortion has damaged a considerable part of the picture.
- Heavy visible noise
- Reduced colour and contrast
- Important details may be missing
- Some text is difficult to read
- The picture can still be identified
P1
Barely Visible
Only a small part of the image is visible. The picture is difficult to identify because of severe reception problems.
- Severe noise or interference
- Large parts of the image are missing
- Very poor colour or contrast
- Callsign may be unreadable
- The image is only barely recognisable
The P-System and Larry Peterson, WA9TT
The P-signal reporting system was developed by Larry Peterson, WA9TT, as a way to provide SSTV operators with a more useful description of received picture quality.
A traditional report such as 595 may be perfectly understandable to an experienced radio amateur, but it was never designed specifically to describe an SSTV image. Two pictures received under very different conditions can therefore end up with similar conventional reports, even though their visible quality is clearly different.
The P-system approaches the report from the picture itself. Instead of concentrating only on signal strength and readability, the operator considers how well the SSTV image was actually received.
This is why the P1–P5 scale is so useful: it gives both stations a quick indication of the visible result. P5 represents an excellent or virtually perfect picture, while the lower P values indicate increasing degradation until the image is only barely usable.
Developing the system was not simply a matter of choosing five labels. Larry used statistical analysis and numerous on-air experiments to test whether the reporting method corresponded with what operators were actually seeing on their screens.
His work was published in the January 2017 issue of CQ Magazine and the P-signal reporting system was later included in the ARRL Handbook.
Today the system is increasingly used by SSTV operators, particularly in North America, because it gives the transmitting station something much more useful than a number alone: an indication of how the transmitted picture actually arrived.
You can also read the personal story behind this work in our Ham Radio Heritage section: Larry Peterson, WA9TT – A Lifetime in Amateur Radio →
Meaningful reports
Be Honest with Your Report
The purpose of the reporting system is to provide useful feedback. Giving every received image a P5 report makes the report less meaningful.
A truthful P3 or P4 report is often more useful than an automatic P5. It tells the transmitting operator that the picture was received, while also indicating that noise, fading or another problem was visible.
An accurate report is not unfriendly or negative. It helps operators assess their station and understand the conditions during the contact.
A good operator gives an accurate report
A P5 report should be reserved for a genuinely excellent picture. A received image with visible noise is usually better described as P4, P3 or lower.
The complete report
The RSV Reporting System
A complete SSTV signal report is often written as three numbers using the letters RSV:
Readability
Describes how easily the transmitted audio, callsign or accompanying voice communication can be understood.
Scale: 1 to 5
Signal Strength
Describes the strength of the received radio signal, traditionally using the receiver's signal meter or an operator estimate.
Scale: 1 to 9
Video Quality
Describes the visible quality of the decoded SSTV image. This is comparable to the P1-to-P5 picture scale.
Scale: 1 to 5
Example:
An RSV report of 584 means that readability was
perfect, the radio signal was strong and the picture quality was
very good but not completely perfect.
Maximum report
What Does 595 Mean?
595
A Perfect RSV Report
The first number, 5, means that the transmission is perfectly readable.
The second number, 9, means that the received radio signal is extremely strong.
The third number, 5, means that the received SSTV picture is perfect.
A report of 595 should therefore describe an exceptionally good reception. It should not automatically be used for every successfully decoded picture.
595 does not simply mean “I received your image.”
It means that readability, signal strength and picture quality
were all reported at their highest level.
Practical examples
Example SSTV Reports
595 – Perfect
Maximum RSV report
Perfectly readable, extremely strong signal and a perfect SSTV picture without visible noise or distortion.
594 – Very Good Picture
Slight image imperfection
Perfect readability and very strong signal, but the image contains slight noise, fading or another small defect.
583 – Good Picture
Noticeable noise
Perfect readability and a strong radio signal, while the decoded image contains clearly visible noise or fading.
472 – Fair Picture
Difficult reception
Readable with little difficulty, moderately strong signal and a heavily damaged but still recognisable image.
Understanding image defects
What Reduces an SSTV Picture Report?
The picture report should reflect everything visible in the final decoded image. Several different reception problems can reduce the P or V value.
Weak Signal
A weak signal may produce grainy noise, coloured dots, missing lines and sections that cannot be decoded.
Signal Fading
Changing HF signal strength can create horizontal bands, colour changes or damaged areas across the picture.
Incorrect Tuning
Incorrect SSB tuning can cause a slanted image, colour errors or failure to recognise the transmitted mode.
Electrical Noise
Power supplies, computers, LED lighting and other electronics can produce interference visible in the image.
Audio Distortion
Audio that is overdriven, clipped or too loud may damage synchronisation and colour information.
Other Stations
Overlapping transmissions and nearby signals may create lines, patterns or missing picture information.
Synchronisation Errors
Missing or damaged synchronisation pulses can cause image tearing, shifted lines or incorrectly positioned sections.
Clock Difference
A small timing difference between systems can cause the complete picture to lean sideways.
Wrong SSTV Mode
Selecting the wrong mode manually can produce incorrect colours, dimensions or an unreadable image.
Signal and image are different
Can a Strong Signal Produce a Poor Picture?
Yes. Radio signal strength and decoded picture quality are related, but they are not the same measurement.
A station can arrive with a very strong S9 signal while producing only a P2 or P3 picture because of distorted audio, incorrect tuning, local interference or excessive transmitter deviation.
The opposite is also possible. A moderately strong but clean signal may produce a very good P4 or P5 picture.
This is why an RSV report contains separate values for signal strength and video quality.
During an SSTV contact
How to Give a Report
A report can be included in a transmitted SSTV image, spoken by voice or sent through another agreed communication method.
Picture-Only Report
Use a P report when you only want to describe the quality of the decoded image.
TNX FOR THE SSTV IMAGE
YOUR PICTURE REPORT IS P4
SLIGHT NOISE
73
Complete RSV Report
Use an RSV report when readability, signal strength and image quality are all being reported.
TNX FOR THE SSTV QSO
YOUR REPORT IS 584
GOOD SIGNAL – SLIGHT NOISE
73
Better operating practice
Common Reporting Mistakes
Giving Every Image P5
A picture with visible noise, fading or distortion should normally not receive the maximum P5 rating.
Automatically Sending 595
A 595 report means that readability, strength and picture quality were all at their maximum value.
Reporting Signal Strength Only
An S9 signal does not automatically mean that the received image deserves a P5 or V5 report.
Ignoring Image Distortion
Slant, incorrect colour, missing lines and synchronisation errors should be considered when selecting a picture report.
Being Too Polite
A lower but accurate report is not an insult. It is useful technical feedback for the other operator.
Confusing RST and RSV
RST uses the final digit for CW tone. SSTV reporting uses the final RSV digit for video or picture quality.
Better received images
How to Improve SSTV Picture Quality
Tune Accurately
Correct SSB tuning is essential. Even a small tuning error can change audio frequencies and distort the image.
Adjust Audio Levels
Audio should be strong enough for reliable decoding but should never be clipped or distorted.
Improve the Antenna
A suitable antenna with a low-noise feed line can increase signal strength and reduce decoding errors.
Reduce Local Noise
Identify and remove interference from chargers, power supplies, lighting and network equipment.
Use the Correct Mode
Allow the software to detect the SSTV mode or select the correct mode when automatic detection fails.
Record the Audio
Recording the complete transmission allows the image to be decoded again with different settings later.
Frequently asked questions
Signal Reporting FAQ
What does P5 mean in SSTV?
P5 means that the received SSTV image is perfect or extremely close to perfect. It should have no significant noise, interference, slant or missing picture information.
Is P3 a bad report?
No. P3 means that the picture was successfully received and remains clearly recognisable, although noticeable noise or distortion is present.
A truthful P3 report is useful feedback and is better than an inaccurate P5 report.
What is the difference between P5 and 595?
P5 reports only the quality of the SSTV picture. A 595 report is a complete RSV report: readability 5, signal strength 9 and video quality 5.
Can an S9 signal receive a P2 report?
Yes. A strong radio signal can still produce a poor picture because of incorrect tuning, distorted audio, interference, excessive deviation or synchronisation problems.
Should every successful image receive P5?
No. Successfully decoding an image does not automatically mean that the image is perfect. The report should reflect the amount of noise, distortion and lost detail visible in the final picture.
Can I use P4 without giving an RSV report?
Yes. A standalone P report is useful when you only want to describe picture quality. Use RSV when you also want to report readability and signal strength.
Is the P report measured automatically?
Usually not. The receiving operator examines the decoded picture and selects the rating that best describes its visible quality.
Good operating practice
Accurate Reports Help Everyone
Good SSTV operators do not automatically give perfect reports. They give accurate reports.
An honest report helps other operators improve their stations, compare antennas, adjust audio levels and understand current propagation conditions.
The next time you receive an SSTV image, look carefully at the completed picture before sending your report. A genuine P3, P4 or P5 carries far more useful information than an automatic 595.
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