Vertical Y Axis Scale Questions


Wonderful program; thanks so much for all the work, and making it available.


a. The vertical (y axis) scale on the Spectrum view defaults apparently to 0 to 150 max.
How should these numbers be interpreted ?

b. Any other options for this scale, such
as db, or…?


Hi Bob.

It’s quite difficult to make it into a ‘meaningful’ scale as it is simply the number that’s received from the radio to indicate the signal amplitude at that particular frequency. This depends on various settings in the radio, although it is something that we would like to implement if possible.



In addition I would indeed prefer having the level displayed in dBm that the receiver (R8600) does have locally. There is probably just a simple conversion factor between the raw data from the receiver and a corresponding scale


This program by W7AY displays spectra with a somewhat calibrated vertical scale:

Ken actually took data on his 7610 with calibrated sources and worked out the conversion factor, including the rf gain knob and attenuator.

We might some day incorporate features like that into wfview.

As for the various signal meters, we all know how to convert between dBm and S units and microvolts. These meters all show the same data. There might be a digit more of precision available on some modes but I think it is probably not as calibrated as we might hope it to be. The 8600 can provide 4 digits or precision, but who has calibrated their 8600 with a higher precision source lately?

Anyway I might add the other scales next time I touch up the code behind the metering. But it could be a while.

de W6EL

issue created and targeted for one of the milestones…

Another vote for alternate scales, including the S-Meter, since ICOM decided that 3db per step was ok, I would like to see the more standard 6db per step as an option.


Hi Dave,

I’ve often thought about that one. I have no idea why they did that on some radios and not on others. I can only surmise that it was a mistake which was quickly accepted as the norm and perpetuated.

de W6EL

Right, Elliott. The calibration at S9 and above is good, But S7 is really S8, S5 is S7, S3 is S6. S1 is S5. Why they did this, I don’t know. Easy enough to change in SW! Maybe an option ‘3db or 6db per S unit’


I will look into it next time I am working on the meters.

Do you know of any websites where they have documented this? I remember reading about it, but I would like to see somewhere where it was measured and documented.


de W6EL

I am against it tbh. We need to show what the rig shows. Signal strength indication is of no use.

SNR is the thing that helps in making a QSO work.

S2 and readable is better than S9+30 and not readable.

So if this is going to happen, it must be a box

[x] keep how the rig reports
[ ] lie about it, fantasize a number

Personally, I am against the error. And it is one.

Icom made an error in their calculation, and it is only present on their modern radios. Their older rigs are fine.

There actually is a standard for measuring dB and for measuring S-units, and it clearly was not followed. No radio is perfect, but an SDR of all things should not be showing this level of error.

I am all for units with meaning when possible. I agree, SNR is more meaningful than just absolute signal level. Nonetheless, the value reported is not correct.

Were there a similar error in frequency we would surely wish to correct it.

In any case, of course, it will be an option. I would not wish to deprive anyone of their (erroneous) numbers.

de W6EL

Hi everyone

I personnaly own a IC-R8600 (and had by the way as well an IC-R9500 which was well calibrated) and I have access as well to an IC-7600 and IC-9700 in my radioclub at work for which I’m the president.

And I’m working in an RF lab with all the measurement instruments possible so If one wish to get some measurement done, let me know I would be pleased to help.

Stephane, F1TJJ

I don’t think it’s an error, it just depends where you derive the indication from.

the only thing that counts is SNR for me. If someone is S9 and the noise is at S8, I hardly (if at all) understand what’s being said.

With bandnoise S1 and signal at S3, it’s discernible. It also depends on the BW. In cw mode I can have no deflection at all, with a strong station well beyond S9 150 Hz above or below and still copy the signal.

At the club here we have R&S stuff all over the place and we did some MDS measurements for fun and got my 7600 S-unit vs signal defined and imported in hamlib. Pretty sure a different 7600 will show other numbers…


Elliott, per your request. From, page 15:



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IARU defines S-meters levels with the S9 point at -73 dBm < 30 MHz and -93 dBm > 30MHz with 6db per S-point.

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Yes this is it exactly. Icom used 3dB per s-unit because they likely did:


Instead of


And what this basically amounts to is that the person who wrote the code was familiar with power measurements but not with how ADCs work. The ADC measures voltage! You must use 20 as your log multiplier.

For on air comparisons of different antennas, for example, you now have to ask if someone is using “standard s units” or “Icom units”.

Either scale can be moved for the S9 level to work out, but it will not be correct on the other numbers.

The Icom scale is effectively based on dBmV rather than dBmW due to this error.

Now the 8600 is s nice opportunity to fix this since it proports to provide raw dBm. We should be able to write in the S units at their correct place.

Great information in this thread. AB4OJ did a nice job capturing this. I will have to see exactly which radios he saw it on.

de W6EL

I wouldn’t blame the software guy who did wrong. he’s a software guy probably not familiar indeed with RF.
I would blame the validation process which has not captured a such mistake !

When I had the R9500 I did such measurement and the S-meter was well calibrated. The AOR AR5000 is not in comparison.

I’ve found out measurements I did in 2010 for Yaesu FT-736, AOR AR-5000, ICOM R9000. One can see that the old Yaesu was useless with only 30dB of dynamics. The R9000 wasn’t bad for a pure analog receiver. Thge AOR pretty bad.

R9000 deca is actually R9000 < 30 MHz

Hi Stephman,

That is actually very interesting! I feel like when there’s a microprocessor involved (inside the radio), there really is no excuse to not use a lookup table to correct the measurement. So it may imply that for some of these radios, there’s actually some drift in tolerance of sensitive parts or perhaps last-minute changes to the hardware that didn’t make it to the software.

On the older analog rigs that I work on, I always calibrate S9 at -73dBmW, and then I go check at S5. I can usually get the analog meter within a hair of both (perhaps a hair low at S9 and a hair high at S5), but going down to S3 or S1 there will be more error. And I think that’s understandable when all you have to work with is an electro-kenetic meter and analog “pseudo-log” amplifiers.

Well, we will keep this open as an idea. I’ll make sure we default to just showing whatever the radio does (otherwise we will get untold emails about the error in our meter), but having an option to correct the measurement using the best-available correction factors would be nice. Actually, on our old wiki, we have this down as item 031. It’s been on my mind for a while. We have a computer available, we should be able to help!

Unlike most contests, you all are really 5 by 9 on this thread :slight_smile:

de W6EL

Here are AB4OJ’s test results for the 7610. Also 3db steps below S9, similar to the 7300, but not exactly the same.
Found on page 18 of