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Author Topic: Why does radio comingle english/metric units?  (Read 3616 times)

Posts: 2

« on: August 10, 2004, 01:07:19 AM »

Being new to radio, it stikes me as odd that this international hobby is not all metric.  It's really surprizing to see formulas like 468/frequency with answers in feet.  So in all honesty I don't get it.  Radio is basically applied physics, and that's been using exclusively SI units (aka metric) for gosh I don't know how many decades.  In college I studied geology (science) and not engineering so maybe that's a source of my confusion.

What's the story here?

Brian Ness
North Hollywood, Calif, USA

Posts: 2198

« Reply #1 on: August 10, 2004, 02:40:35 AM »

Chalk it up to (many) American (and British) Amateurs refusing to "go metric;" many of them (and their publications, such as those from the ARRL) insist on "feet and inches," instead of metric units.  Of course, it WOULD sound rather silly to be using those "80 Inch" repeaters, or ragchew on the "250 foot" band.

Posts: 14491

« Reply #2 on: August 10, 2004, 08:21:54 AM »

It's not only amateurs. Most of the electronics and engineering world is that way. I guess someone just likes to keep us converting back and forth. Any mechanical layout (panels, etc) is so much easier to do if you work with metric where everything is easily divisible by ten.

Bob  AA4PB
Garrisonville, VA

Posts: 1

« Reply #3 on: August 10, 2004, 11:26:08 AM »

Frankly, I don't see this as a problem especially in this day and age of electronic calculators which you can buy for a few dollars that will do amazing things.

Years ago, when selling auto/truck parts, I committed to memory, the figure .039074, THE figure for converting ball bearing dimensions from inch to metric or vice versa.  (Most automotive bearings have been metric, since before most of us were born.  So are spark plugs.)

The one thing you have to realize, is that there IS NO metric standard in some things, either.

Having sold car parts, for example, which also entailed logging/industrial equipment, I can tell you that there is very little standardization for

Bolt thread:     In various "metric" countries,  you may indeed find lots and lots of 10mm or 12mm or whatever size bolts, but the thread pitch common in various countries is far from standard.

Pipe fittings, brake, fuel, and hydraulic tube fittings, none of those are very standard.  While Japanese "bolt thread" is close to some American size, it is just a little bit smaller, and some European sizes are different from both.

Years ago a certain logger bought a multipurpose piece of logging equipment made in Finland or somewhere "over there."   With use, hydraulic hoses began to fail.  He'd bring in a hose, and we would have to cut the oddball end off the hose, braze/silver solder it to a new crimp end, and make a new hose.  You simply could not get the proper hose ends to fit the equipment.

Later, when he brought in a cylinder, we discovered, by accident, that the adaptor from the hoses to the cylinder, had "close" (very close) to US size at the cylinder.  For at least some of those, we replaced the oddball adaptors with US.


Posts: 256

« Reply #4 on: August 10, 2004, 11:31:17 AM »

Anyone remember JPL's lost Mars probe, where some scientists calculated trajectory in metric and others used feet and inches? Needless to say one side forgot to convert to the others and now there's a very expensive and useless spacecraft flying out in the middle of nothing.

Posts: 1368

« Reply #5 on: August 10, 2004, 01:24:25 PM »

Radio may be Applied Physics, but when I go to Home Depot to buy a spool of wire to build an antenna, the spools are sold in feet.  And when I pull wire off the spool to measure it, my tape measure reads in feet and inches.  And when I'm trying to decide if it will fit in my backyard, well, I know how many feet long my backyard is.

Whatever works, you know?

Posts: 1

« Reply #6 on: August 10, 2004, 05:29:43 PM »

"""""many of them (and their publications, such as those from the ARRL) insist on "feet and inches""""""

Actually, nothing could be further from the truth.  When the U.S. was intent on trying to "convert us"  (remember the cars with the dual/numbers on the speedos?)   QST listed many of its projects, such as antenna projects, in metric units,


Why, you ask?,   Why because my dear fellow,  if I go down to the local plumbing/building supply "joint" and want a piece of piping/tubing/round stuff-with-a-hole-in-it,  and I were to tell "the man" that I want this here piece 'o pipe that's so many millllllimmemmeiciekteers big, he'd look at me and, well, it wouldn't be pretty.

The thing is, 1/2 inch AMERICAN PIPE SIZE (for example) is NOT 1/2 inch.  I'ts "sorta" 1/2 inch on the INSIDE, and depending on whether it's skedule 40, 80, PVC, or what, it could be a LONG way from 1/2 inch on the inside.  But it's still CALLED that.

The ARRL comes along, with, let's say, a J pole project, and here they are specifying copper tubing in so many millimeters, often in OUTSIDE measurements, which leaves you to go to incredible frustration trying to figure out what they REALLY meant.

Posts: 1897

« Reply #7 on: August 16, 2004, 02:23:05 PM »

No differant than 143/freq for results in meters. It commonly arises probably because wire is sold by the foot, land is surveyed in feet, and building structure footprints are dimensioned in feet in the US.  Proper SI units (vs general metric usage) would use radians (2*pi*f -- dimensionless) not MHz in the denominator and 968 m in the numerator too. Just an oddity ob the US's continued use of english measure in much of commercial trade and everyday use.

An aside: use of english units drives my daughter (teenage) nuts (in principle anyway -- she says "just teach metric exclusively and in 15 years..."), but it becomes so intuitive in the culture the habit is hard to break. I have a good feel for a gallon of gas, a mile of travel, 30 mi/gal, 76°F outside temperature, etc, but have to think about 20L/100km, 24°C, etc. I have offered to change the digital t-stats in the house to read in °C instead though, so we'll see what 16°C an night, 19°C by day is like.

Deep down though I think she's on the right track -- to go fully metric, gasoline by the liter, water by liters or cu meters vs gallons or hundred cu ft, soda in 355mL cans not 12 fl oz, hamburger & bread by the kilogram or gram (should, technically, be Newtons, as Kg is a mass unit not weight, but...), roadsigns/exit numbering (where by road mile not serial) and distance reference markers ("mile markers"), rainfall, storm windspeeds and barometric pressure (aviation excepted(?) where, IIRC, the world standard is inHg pressure and 100's feet altitude?) is going to be an adjustment.

At the risk of severe digression, thoughts? Counterpoints? Observations?

Posts: 1

« Reply #8 on: August 19, 2004, 12:23:59 AM »

Well, I'd be for it, "except"

there really is no world standard on stuff like plumbing components, so, what are we in the U.S. going to adopt?  Japan? Germany? France?

How about simple fasteners on auto/trucks?   The Japanese may use, say, 10 mm bolts just like the Germans, but the thread pitch is different.  I remember we used to '''''''cringe''''' when a friend of my  boss'es used to come in with, what, his Citroen?  NOBODY had bolts to fit that stupid thing, and our business carried a LOT of fasteners at the time.  (The joint I worked for occupied one street face of a city block, hardware, parts, welding, fasteners, etc.)

Worse yet is hydraulic fittings, including brake fittings.

This is just stuff I'm familiar with.

What are you gonna do about the millions of houses in the US, expect plumbing/hardware stores to carry "adaptors" from whatever "metric" plumbing we convert to, so people can repair their old U.S. size plumbing?

Not that easy, is it?

Ya know something else funny, used to be auto engine bore sizes.

The catalogues used to specify stock bore sizes in fractional sizes, yet of course when you bore one out, the rings/pistons come in thousands of overbore, as in "bored 60 over."

I remember when the "new new new"  Chev 302 camaro engine came out, "us kids" finally found out that "all" it really was--the same 'ol "bored" 283 we USED to call a 301.

What's even more stupid is the naming of some engines by the manufacturer's --

I don't remember, I think AMC had a 401 which  CornNationalInterBinder  was putting into some of the Scouts and other pickups, except that IHC already had their own 401, so they RENAMED the AMC a 400.   Of course the mechanics would open the hood, take one look, and go into the parts stores (us) and ask for parts for a "401."   We'd look in the book, there's the 401 (IHC) give them the parts, and naturally they don't fit.

What was REALLY bad was the years that GM started putting different brand engines into different brand cars, you know, a chivvy in a Firebird?

THEN to make matters worse, somewhere arount '76-80 or so, they made "some" of the Buick/Olds "metric" oil filters.

Here's the problem.  Some filters, for these different "swapped" engines would screw on, but don't work, don't even seal up.  Then along comes "metric" which "the thems"  stupididly made "almost" the same size, so some mechanic could just cross thread the thing right on there.

One year,  Wix filters (same as NAPA) didn't even print an application for GM cars--they just said to go out and read the serial number and decode it!!!!!!

Posts: 10091

« Reply #9 on: August 19, 2004, 10:43:31 AM »

American cars, for years, have contained intermixed metric and US hardware. It seems that, mostly, "body" bolts are metric and engine hardware "US".

So you might need a 10mm socket to remove the bolt that holds the coolant overflow reservoir to the fender, but a 1/2" socket to tighten the alternator belt.

Very annoying.

Mike N2MG

Posts: 136


« Reply #10 on: August 26, 2004, 01:18:13 PM »

 When I was in junior high school back in the 70's we were learning the metric system because the US was trying to go metric like the rest of the world. But it never took hold in America and was eventually dropped from the school cirriculum never to be heard from again.
 It has nothing to do with Hams. The ENTIRE US didn't go for it.

Posts: 2

« Reply #11 on: August 28, 2004, 01:30:37 AM »

Thank you all.  This thread has been both educational and useful.  So the answer is due to the adaptability of engineers who have learned to think in multiple systems of units.  We have read in this thread evidence how non-standard the world actually is, and how mechanical types must keep alert to this fact of life.  It's proper for engineers to be schooled for the realities of the job market.

Taking all this into account here is my conclusion:  there is no excuse for not publishing all amateur radio articles using at least meters, liters, and kilograms.  No excuse.  To the best of my knowledge these three units are standard worldwide.  Obviously some components like 1/2-inch copper pipe are literally defined this way, but cut that 2 meter dipole into a 1 meter length.  Assume others know what that means because surprise we do!

If you are good adaptable engineers, then your choice of units to write into articles is arbitrary because it's simple for you to convert.  Please don't make the rest of us do it.  Why?  You are compounding the confusion for new guys like me who struggle with hundreds of difficult new concepts from electric potential to EM radiation.  Believe me you are.  You do nobody a service by publishing for example, to cut that 2-meter dipole to 39 inches.  Use metric and us new guys will "get" the concepts easier, not to mention you enlargen your worldwide audience.

Again thank you everyone for replying.

Brian Ness
North Hollywood, Calif, USA
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