A question came up on the ham_instructor mailing list this morning with regard to the next update of the Technician Class question pool. Bob, K0NR, wrote:
While reviewing the Element 2 (Technician) question pool, I am reminded that the question pool SWR readings are referred to as “10 to 1”, “5 to 1” and “1 to 1”, etc. I suppose this emphasizes the “ratio” nature of SWR, but it just sounds old school to me—kind of like saying “kilocycles per second.” I just refer to SWR readings as a single number (e.g., 10, 5 or 1). What do you folks think?
Being a freelance writer and editor, I found this to be an interesting question. There are lots of these kinds of grammatical questions, especially when it comes to technical writing. Normally, we just write or say things how we learned them, whether they’re technically correct or not. In this case, I guess that I’d have to say that I still think of SWR in terms of “<some number> to 1” and normally write it as “x:1.”
I next did a quick Google search for “SWR specification.” The results were mixed. For example, the National Instruments Web page, “Understanding Key RF Switch Specifications” simply gives the VSWR as a number, but Anritsu’s “Understanding Cable & Antenna Analysis” gives an example as “1.2:1.” There were numerous other examples of both forms, so while the search was interesting, it didn’t really yield a definitive answer. I guess that’s true of most Google searches, though. :)
Another thing that I found interesting in researching this is that the notation we use—1:1, 2:1, etc.—is called odds notation. Apparently, it’s still used in betting, but I can’t think of another instance in which this notation is used in a technical context.
I asked Steve Ford, WB8IMY, the chief editor of QST, about this, and he said:
For QST, our style is to express SWR in mathematical ratio notation such as “2:1,” never as “2 to 1.”
Ward Silver, N0AX, who edits the license manuals and the Handbook for the ARRL, also replied:
Speaking from experience with the Question Pool Committee, they do not like using equations or symbols in the questions or answers. That includes “:” and they substitute text for it. This is an old habit from the days when text files had to be of the lowest-common-denominator so that everyone could read or print them.
My suggestion is to submit a request to replace “2 to 1” with “2:1” or just “2” so that the question pool is brought into compliance with current practices.
I’m siding with N0AX and will suggest that, at the very least, they replace the “x to x” nomenclature. I’m leaning towards asking them to replace it with the odds notation, i.e. 1:1, 2:1, etc., if only because that’s the QST style. I’m not 100% sure about that second thought, though, so I’d like to hear what you think.
RickB KA8BMA says
Call me old fashioned, but…
My brain clicks when I see X:Y. Instinctively know I’m dealing with a ratio. When expressed this way, my brain is already interpreting the numbers instead of interpreting the meaning of the semtence.
Rob says
It’s a ratio, so saying “SWR of 1.2” is enough. And while all of the other options are valid, they convey no additional information at the cost of several extra words and symbols. We ought to streamline our writing down to just one number, it tells the entire story.
OTOH, I don’t go around correcting people who say “ATM machine.” When friends say “SWR of 1.2 to 1” or such, it doesn’t bother me. I will have to toss the phrase “SWR of 6 to 5” into conversation in the near future however. Might even get ornery and say something like “an SWR of pi to e.” Will report back if I get punched.
Bob K0NR says
Love it!
“My SWR is about 6 to 5, trending to 6 to 6.”
KD8AQT says
I prefer the mathematical expression form. I use ratios all the time in my job.
Bob K0NR says
I’ve been looking around the web for non-radio applications of ratios to see how they handle them. One area I’ve bumped into are aspect ratios of displays, TVs and photos. For example, an old TV might have an aspect ratio of 4:3 while a newer HDTV is usually 16:9. Those ratios help my brain imagine the shape of the display. Notice that they don’t read: 1.33:1 and 1.778:1, which is what we do with SWR. Ratio’ing something to 1 provides no information.
Dave New, N8SBE says
No, but as other folks have hinted at, but not really come out and said it, if you are going to express a ratio, you need to tell the reader what it is a ratio ‘TO”, i.e. 4 doesn’t tell what 4 is a ratio ‘TO”, but 4:1 and 4:3 both do.
Don’t be so anxious to throw the baby out with the bath water. 2:1 is much preferable to just 2, where you ASSUME the reader knows what you are referring ‘TO’.
And of course, you know what happens when you ASSUME. :-)
Wayne Carlson, K2DT says
Maybe we ought to get rid of the term SWR and replace it with SWF (standing wave factor). That’s what the first number is anyway when the second is “1”.
This would be consistent with expressing a VF as 0.82 or 82% rather than a Velocity Ratio of 2.46E8:c
Stephen Trier says
Just say “2”, for two reasons:
First, the “:1” does not add any information. The actual ratio is just as likely to be 100:50 or 11.6:5.8. Once it is normalized to 2:1, the normalization is implied. If it does not add information, we should drop it.
Second, the “:1” odds notation never made sense to me when the VSWR is not an integer. If you are already using decimal notation, why make it a fraction as well? Usually one wants to use either decimal or fraction notation in a final result. (Mixing them is common, of course, while calculating that result.) Couple this with the first reason and odds notation looks more and more dated.
Don’t use QST as a style reference. ARRL makes some curiously archaic style choices, and some are simply wrong (e.g., “a voltage of 5.”) If you want a role model, look instead to the professional literature. We may be amateurs, but there’s no reason we can’t use the language professionals use.
Dan KB6NU says
As I noted, the professional literature uses both notations.
I disagree about not using QST as a style reference. Unless a usage is completely wrong, as in the example you mention, I think we should use it. The ARRL generates the most technical literature in amateur radio, and most hams will be familiar with the way they write things.
And, if their usage is completely wrong, we should try to make a case for them to change it. Actually, this should be the topic for another post altogether. It would be nice to get the ARRL, CQ, and maybe the RSGB to agree on a style guide for amateur radio.