Keith Dutson wrote:
>>I was trying to build a 2M antenna out of the 2001 Handbook, the dimensions
>
> are in MM, but I could never get it done, I would cut the elements off to
> the correct MM length in the morning, but by afternoon and 100 degree heat,
> they were too many MM long, so I had to cut them again,next morning, I
> checked and they were too short so I had to throw them all away and start
> again.
>
> Most measurements are specified at standard ambient temperature and pressure
> (STP). In layman's terms this means the measurement should be taken at room
> temperature (70ish F) and sea level (29.5ish in Hg). Obviously, for metals,
> the pressure is not a significant factor.
>
> 73, Keith
Nor is temperature going to be when making a 2m antenna. The expansion of the
metal will not be
measurable with a ruler (they will both expand at about the same rate), but
furthermore, fractional
changes in length will be small compared to the fractional changes of frequency
you will make.
I can't see why people (especially hams, most of whome have an IQ > 80) have
difficulty with the
metric system.
Most (well the semi-intelligent ones anyway) seem to be able to handle the fact
there are 1000 milli
Ohms in an Ohm, 1000 Ohms in a 1 kOhm, 1000 kOhms in a 1 MOhm. Some may even
use Giga Ohms
occasionally, although they are not used that often.
So what is the big deal about 1000nm = 1 um, 1000 um = 1mm, 1000mm = 1m, 1000m
= 1km etc?
If someone said lets use some measurements for resistance, that were not based
on multiples of 1000,
but something like
12 Ohms is a Yonk (equivalent to 12" is a foot)
3 Yonks are a Foobar (equivalent to 3 feet is a yard)
1760 Foobars are a Spanner (equivalent to the stupidty of 1760 yards in a mile)
That makes 1 spanner equal to 63,360 Ohms.
I think most would think it a stupid idea, and prefer to stick to mOhm, Ohms,
kOhms, MOhms and GOhms,
which have nice sensible ratios of 1000 between them.
You can work in ratios of 1000 for resistance, inductance, capacitance,
voltage, current etc, so why
not do the same for length, mass, force etc? Any attempt to change those ratios
of 1000 would be
resisted by most.
Of course, we could always base the unit of capacitance equal to the
capacitance between the earth and
the Sun. Then the Sun-mercury capacitance would be larger (I expect) and the
Sun venus capacitance
would be smaller (I expect). I say "I expect", since you would need to know the
distance as well as
diameter, and I can't be bothered to sit and work these things out.
Come on, accept that metric is more logical and use it!!!
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