What those scanner bars really mean .. ?

[SCPD]

So .. it has been an interest of mine for some time and I had a friend pull out the test gear and he tested 'several scanners and their bars' for me today. Yes .. everyone was sober during testing. :wink::wink:

But yes .. he measured the RSSI of the scanners indicated.

This test shows you the level of signal needed for 3 different scanners and the signal needed for each bar.

As noted .. there are some scanners that I have but were unable to test today. Those being the Uniden HomePatrol 1/2 and Whistler WS-1095, hopefully to be added in the future.

But here you go ..

The end result ... 5 bars is roughly an S5 signal. So to me, that is hardly what I would call a strong signal. I feel this is done to make you think that your signal is stronger than it really is. It does sell scanners I am sure.

The attachment ... a text document shows the testing results.

Happy scanning .. now that you have a better idea what those bars really mean.

 

[VE6RHS]

One microvolt?

I see the 436 (almost) keeps 1 bar at -107, which is 1uV (microVolt).

Interesting.....

 

[Voyager]

Criticize all you want - at least the industry is consistent. Many ham manufacturers try to out s-meter their competition - knowing that "comparisons" of the same level signals will result in higher meter readings.

BTW, what is the difference between 0 bars and squelch threshold? How do you test for 0 bars?

 

[SCPD]

Criticize all you want - at least the industry is consistent. Many ham manufacturers try to out s-meter their competition - knowing that "comparisons" of the same level signals will result in higher meter readings.

BTW, what is the difference between 0 bars and squelch threshold? How do you test for 0 bars?

I am not so much criticizing but educating. The education part comes in when people believe that 5 bars = strong signals.

In my mind .. that is not the case. I would like to see it more even from weak to strong.

Right now .. it is more weighted to the weak end where an S4-5 signal will typically give you full bars.

I had this discussion with one of my friends recently .. it was like "it is 5 bars so it has to be strong". My answer .. "how do you know, as the bars are meaningless as you have no real idea what constitutes a bar". This test was the result of that conversation.

I personally love my Icom R7000 where I have a true RSSI. One that has been calibrated and I know is reliable.

I am sure you already know, but I prefer a dBm reading .. much like some SDR software that gives a digital reading of your signal strength, as compared to bars. But I expect we will never see that on scanners.

The testing results are listed a bit different on the 3 scanners as the PSR500 for example will show 1 bar until there is no signal and the squelch closes. The 436HP for example .. will show no bars and the squelch remains open (until you hit min squelch activation).

So .. I tried to explain it, but yes the text file may not make it clear. I also am sorry about the formatting but did not want to spend lots of time formatting it. I have a spreadsheet but was not sure how many would be able to read it .. so text was chosen for universal reading.

 

[Voyager]

S-meters have not been accurate since they deviated from the Collins standard. Ham manufacturers are some of the worst offenders.

I took "that is hardly what I would call a strong signal" as criticism. "Strong" is relative. Remember - there is no labeling on the s-meter. It's simply 5 bars. Maybe they intended it to mean S-1 to S-5 in which case it would be fairly accurate. Not all S-meters go to S-9+60.

RSSI is not necessarily calibrated any more than an S-meter. After all, any S-meter is technically an RSSI. Each can be "calibrated" to what the designer wants it to read.

But, yes, a dBm readout would be preferable. Of course, then you would get "isn't 2 dBm strong???"

 

[SCPD]

S-meters have not been accurate since they deviated from the Collins standard. Ham manufacturers are some of the worst offenders.

I took "that is hardly what I would call a strong signal" as criticism. "Strong" is relative. Remember - there is no labeling on the s-meter. It's simply 5 bars. Maybe they intended it to mean S-1 to S-5 in which case it would be fairly accurate. Not all S-meters go to S-9+60.

RSSI is not necessarily calibrated any more than an S-meter. After all, any S-meter is technically an RSSI. Each can be "calibrated" to what the designer wants it to read.

But, yes, a dBm readout would be preferable. Of course, then you would get "isn't 2 dBm strong???"

For me .. I just like to be able to tell how Signal X is vs Signal Y or how Antenna A compares to Antenna B. You cannot really tell that on 5 bars on your scanner.

So for that I use my R7000 (or even SDR software) cause that is the best meter I have .. other than some of my commercial gear with -dBm values.

I have a chart on my wall for just this purpose. It shows dBm values and microvolt signal levels for my R7000.

Oh .. 2 dBm IS strong, even in my books.

 

[Voyager]

You get my point. I should have said "isn't 2 dBm weak???"

I would use the SDR display over any meter just based on size (resolution). (and often do)

 

[SCPD]

Added 3 Scanners today .. HomePatrol 1 and HomePatrol 2 as well as Whistler WS-1095.

Those are all the scanners that we have available to us. I could have done the PSR800 etc but I think we know that the results are likely the same as the WS-1080. Besides I did not want to disassemble my shack more than I did.

This is a PDF and much better formatted.

Happy Scanning ..

 

[Voyager]

Better formatted, but difficult to compare HP-x to others due to the page break.

Could you add green and red background colors to indicate the best in column and worst in column respectively? That might make any exceptionally good or bad values stand out more.

It still looks like everything is within a few dB of each other for the respective number of bars.

 

[SCPD]

Better formatted, but difficult to compare HP-x to others due to the page break.

Could you add green and red background colors to indicate the best in column and worst in column respectively? That might make any exceptionally good or bad values stand out more.

It still looks like everything is within a few dB of each other for the respective number of bars.

Actually .. thinking about it for a minute, there really is no point of doing that as there are no winners or losers here. The sensitivity of all these scanners have been posted here on RR before. If that is what the reader is interested in .. they just need to check this exact forum for those numbers.

This is not trying to show which one is more sensitive than another.

 

[Voyager]

OK. I was just trying to establish a RANGE of dBm values for a given bar level at a given range. I wasn't trying to establish winners or losers. Given that s-meter readings are relative, there isn't any info to establish winners or losers anyway.

My basic impression is that they are all about the same for a given frequency and number of bars (within a few dB).

 

[SCPD]

My basic impression is that they are all about the same for a given frequency and number of bars (within a few dB).

Especially when we tested the HomePatrol units today .. and how close they were. But that makes total sense as Paul Opitz of Uniden stated that they are very much the same rf wise.

The benefit for users .. is that if you own a scanner that was tested, you get an idea that 1 bar is roughly equal to an S1 signal .. likewise 5 bars is closer to an S5 signal.

I think we accomplished what was set out at the beginning, and that was to give some idea what a bar means on these different scanners.

Even from scanner to scanner and how the bars work on each is a bit different.

The one thing that this tells me .. that Uniden and Whistler did their homework when doing this, as I think we both know that when your Whistler gets 5 bars and your Uniden gets 2 we would see posts here asking why. So I am not surprised at all that the results are reasonably close overall.

Personally .. I like the PSR500 where any signal is a bar.

 

[Voyager]

Personally, I like the SDRs where the signal is a graph.

But, thanks for the data.

BTW, I printed it out and will highlight it myself to get an idea of the range.

 

[majoco]

I know Wikipedia is written by anyone with an opinion, but here's what they say...

IARU Region 1 Technical Recommendation R.1

In the 1930s it was already agreed that S9 corresponds to 50 μV at the input terminal of the receiver, but this was not a measure of the power received as the input impedance of receivers was not standardized.

The International Amateur Radio Union (IARU) Region 1 agreed on a technical recommendation for S Meter calibration for HF and VHF/UHF transceivers in 1981.[5]

IARU Region 1 Technical Recommendation R.1 defines S9 for the HF bands to be a receiver input power of -73 dBm. This is a level of 50 microvolts at the receiver's antenna input assuming the input impedance of the receiver is 50 ohms.

For VHF bands the recommendation defines S9 to be a receiver input power of -93 dBm. This is the equivalent of 5 microvolts in 50 ohms.[6]

The recommendation defines a difference of one S-unit corresponds to a difference of 6 decibels (dB), equivalent to a voltage ratio of two, or power ratio of four.

Signals stronger than S9 are given with an additional dB rating, thus "S9 + 20dB", or, verbally, "20 decibels over S9", or simply "20 over 9" or even the simpler "20 over."
Examples

A weak signal with signal strength of S2 corresponds to received power of -115 dBm or 0.40 microvolts in 50 ohms on HF.

A strong signal with signal strength of S8 corresponds to received power of -79 dBm or 25 microvolts in 50 ohms on HF.

Some signal generators are calibrated in dB above 1uV and have an output in emf. For example to set an HF receiver's S-reading to S9 set the signal generator output to 34 dB above 1uV
S-reading HF Signal Generator emf
μV (50&#937 dBm dB above 1uV
S9+10dB 160.0 -63 44
S9 50.2 -73 34
S8 25.1 -79 28
S7 12.6 -85 22
S6 6.3 -91 16
S5 3.2 -97 10
S4 1.6 -103 4
S3 0.8 -109 -2
S2 0.4 -115 -8
S1 0.2 -121 -14

The table is a bit of a mess. Some time ago I made a chart which seems to conform with the data...

 

[SCPD]

I am well aware of the standards ... but I think we will find that they are often not always used in practice.

Scanners probably have the worst RSSI of any radio item you will find. Unless you go to some receivers such as Icom, AOR etc are you likely to find something better.

Of course .. SDR software typically displays much better values than scanners, which make them good for testing etc. That is what I use them for anyways.

But for quick comparisons .. I use my Icom R7000.

 

[Voyager]

Just curious if you would agree with the following:

"Scanner manufacturers have followed the S-meter standards fairly well, but the S-meters only go up to about S-5."

 

[SCPD]

Just curious if you would agree with the following:

"Scanner manufacturers have followed the S-meter standards fairly well, but the S-meters only go up to about S-5."

Smiles. Yes .. that is pretty accurate. But the fact remains that even a relatively moderate signal will give you 4/5 bars.

So if you expect a truly strong signal to be the criteria for full bars .. you will find that not to be the case. In my mind .. S9 or above is a strong signal. Below that .. not really.

I think we know that more bars may sell more scanners ... or at least a lot less 'my scanner is broken threads here'. :wink::wink:

 

[DJ11DLN]

I've always taken the RSSI on scanners with a large grain, maybe a block of salt. They differentiate between a weak signal and an acceptable one and that's about it. Never did consider them in the same class as the S-meter of even an old Cobra CB, much less a good quality comms receiver. More like the bars on a cell phone: "Yes, there's a signal, maybe the phone will work/No, there's not, you are screwed till you go somewhere else."

But they can be useful, as discussed in another post recently...