It seems every radio service has its own signal reporting method. Why are they different? Is one better than another? How do they compare, and what do they mean? Let’s consider how (and what) information is conveyed, and how these different schemes compare.
In amateur radio, the “RS(T)” (the “T” only in CW reports) system is used, which stands for Readability, Signal Strength, and Tone (see Chart 1).
|9||-----||Extremely Strong||Pure DC|
|8||-----||Strong||Trace of Ripple|
|7||-----||Moderately Strong||Smooth Ripple|
|5||Perfectly Readable||Fairly Good||Musical Modulated Note|
|4||Readable with Almost No Difficulty||Fair||Rough AC Note|
|3||Readable with Considerable Difficulty||Weak||Low-Pitched Not|
|2||Barely Readable||Very Weak||Very Rough AC|
|1||Unreadable||Barely Audible||Hissing Note|
Chart 1. RS(T).
It’s great for contesting, DXing, and weak signal work because it’s short and to the point — something needed in these three situations mentioned. Unfortunately, it leaves out other information that can be useful (this is discussed further in the SWL [short-wave listener] SINPO section).
In the case of Readability, this is somewhat subjective. One example that comes to mind happened to me when a friend of mine came over to my shack for a bit of HF work. He spent most of his ham career on VHF FM; due to the qualities of FM, that meant relatively good signals because there isn’t a lot of the noise on FM as there is in other modes — especially on HF. I, on the other hand, work a lot of CW and SSB on HF which means getting clobbered by adjacent frequency signals and atmospheric noise is something that’s commonly dealt with.
Therefore, the HF operators train their hearing (with a lot of practice) to decipher the less-than-perfect signals. In other words, experienced HF operators could hear stations that the VHF/UHF only operators may have difficulty hearing (especially back before signal processors or active audio filters were invented).
The signal strength report in the RS(T) system doesn’t come from the receiver’s signal strength meter as some might assume, since the meter doesn’t tell the whole story. This is also in part due to the variations in how an S-meter is calibrated.
We’ve all experienced meters that appear stingy or overly generous. This is due to manufacturers not always following either of the standards that have been set. (Given the variations between meters I’ve seen, I’ve even gone so far as to wonder if some manufacturers are even aware of standard calibrations of S-meters!)
One drawback of the RS(T) system that becomes obvious is — as with the shortcomings of other signal strength reporting systems — they don’t consider other factors in evaluating a full explanation of the incoming signal. For example, getting clobbered by heavy (strong) interference can make a strong signal appear less strong by comparison.
This demonstrates that while the RS(T) system is a good start and expedient to use, there’s a certain something lacking in providing a complete overview of what a signal is actually doing. For this, we need to take a look at what is used in shortwave listening (SWL) as this system is a bit more expansive in the information it provides. Granted, something this detailed may be impractical (time consuming) for rapid contacts (like when DXing or contesting), but might be worth considering for “ragchews.”
Since SWLers aren’t rushing through a contact to maximize their number of contest points, they have a better opportunity to really listen to a signal and therefore give a better assessment of the situation and provide more detailed reports of what’s actually going on (see Chart 2).
|No.||Signal Strength||Interferance (QRM)||Noise (QRN)||Propogation (QSB)||Overall Merit|
|4||Strong||Almost None||Almost None||Almost None||Good|
|1||Very Weak||Very Strong||Very Strong||Heavy Fade||Poor|
Chart 2. SINPO.
The SINPO system stands for Signal Strength, Interference, Noise, Propagation Effects, and Overall Merit.
The signal strength can, in part, be assessed from the signal strength meter, although often (i.e., when available), some SWLers will compare a received station’s strength with another readily available station on the same band and similar distance away. (Finding a reference on the same band will preclude the effects of propagation differences between bands).
Since SW broadcaster’s power levels and antennas are published (information from major stations is probably common knowledge of many experienced station engineers anyway), the person receiving the reception report (usually the station engineer) will have an easy way to check how well their station is doing when compared to another known quantity.
Interference (man-made, like signals from adjacent frequencies or another station on the same frequency, ignition pops from nearby vehicle ignition systems), noise (QRN or background noise on a band which can vary quite a bit due to nature like sunspots, other atmospheric noise, etc.), and propagation fluctuations can be caused by fade, flutter, signal inversion, or signal strength fluctuations as they get reflected off of passing aircraft, and so forth. This is summed up by an overall rating.
Other commercial radio services follow the amateur radio example of very brief reporting systems. Most often used is Ten-code (code words used to represent common phrases in voice communication) from 11 meters (Citizen’s Band) which was established by APCO (Association of Police Communication Officers) and is used in various forms in various public service sectors as well, and is modified slightly for civilian use. (If anyone is interested in a comparison and definition chart, one is available in the article downloads, or email me at [email protected].)
The Ten-code simply has 10-1 (weak signal) and 10-2 (strong signal), or a direct reading from the “S” meter — for example, a report of a signal strength of “five pounds” (in the CB vernacular) means S-5 on the meter. The Ten-code also provides short-hand methods for other information being conveyed as well (such as “10-36” being a request for the time, “10-4” confirming that a message was understood, “10-27” being a frequency change, and so forth).
In that respect, the Ten-code can be seen as a combination of the amateur radio RS(T) signal reporting system and the abbreviation system of the Q code.
|S Unit||Old Ham Standard||World Standard|
|9||50.00 μV||40.00 μV|
|8||25.06 μV||20.04 μV|
|7||12.56 μV||10.04 μV|
|6||6.29 μV||5.03 μV|
|5||3.15 μV||2.52 μV|
|4||1.58 μV||1.26 μV|
|3||0.79 μV||0.63 μV|
|2||0.39 μV||0.31 μV|
|1||0.19 μV||0.15 μV|
Although each signal reporting system has its own merits, it would be less confusing (especially for those of us involved in multiple radio services) if there were a single common signal reporting technique. However, is there a “one size fits all” solution?
I’m not sure if there’s any one good answer to these (and other) questions but at least we’ve explored what’s available, so that when the reader would like to explore other radio interests, they’ll have had an introduction to signal reporting techniques. NV
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