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one has to navigate these days to get a ham license. The
process is not well described and may be more complex
than the technical exam to get the license. Whose job is it
to make the method more well known and understood?
Anyway, we appreciate you clearing this up.
Lou Frenzel W5LEF
On page 10 of the June ‘ 12 issue, "Spotlight on
Bacteria" claims the light goes through 25 m. (Was an
"m" missing? Perhaps 25 mm 1"? Otherwise, that would
be 25 m or approx. 75 ft!)
Phil Karras KE3FL
Good catch, Phil! It should have been micrometers
(µm.) Looks like the µ was dropped.
Unlocking Phones (Not!)
After reading Louis Frenzel’s article, "What is 4G
Wireless" — which was pretty helpful and timely since
I’m researching smartphones to buy for the first time
(I currently use a feature phone) — I have a question. Can
unlocked phones from Europe and Asia be used just as
well in the US? Especially re: Internet service? Would the
Internet service be at high speeds (3G or 4G)?
I was told by a TMobile in-store sales rep (I subscribe
to TMobile) that even if I get an unlocked phone
intended for the markets in those continents, I wouldn't
be able to use the Internet very well in the US, because
Europe and Asia use different channels within the same
bandwidth. Or something like that. I may not be using
the right terminology. Conceptually, what I understood it
as is the phones in Europe and Asia are within the same
range of frequencies as the US for Internet, but within
that range, the European and Asian phones use a
different frequency than the US, so I wouldn't get any
"reception," so to speak, for the Internet, or very little.
He said that Samsung specifically sets phones for
TMobile at a certain channel so that they work within its
network. I asked if those channels could be changed,
and he said no, it would be very difficult; they're preset.
What are your thoughts? Thank you for any feedback!
The T-Mobile rep is right. The smartphones used in
Europe and Asia use different bands and frequencies so
generally do not work in the US. There is no way to
change the frequency. They are fixed. In general,
unlocking a phone is a nightmare. It causes more wasted
time and grief unless you are a super guru hacker type.
You will not save money this way. Bite the bullet and get
a US phone.
A Matter of Degrees
This note was prompted by Ron Hackett's article
"Interfacing the DS18B20 Digital Thermometer" and the
necessary code decision needed to account for below
zero temperatures (page 18 in the June ‘ 12 issue).
A clean way to convert degrees C to degrees F is:
F = (C + 40) 9 / 5 - 40. This way, no decision needs to
be made in code for less than zero degrees.
To change from degrees F to degrees C, one need
only exchange the 9 and 5: C = (F + 40) 5 / 9 - 40.
The reason this works is because a graph of F and C
temperatures cross at - 40.
Thank you for your suggestion for avoiding making a
decision in code for less than zero degrees C.
I assume your formulas would work in a programming
system that is able to handle negative numbers. However,
the PICAXE BASIC compiler is limited to computations
involving positive integers. In the example on page 18, if
the temperature is - 5 degrees C, PICAXE BASIC is not able
to compute the value of (- 5 + 40) in your formula; in fact,
we can't even assign a value of - 5 to a variable. As a result,
it's necessary to do separate calculations in code for
positive or negative values (adding or subtracting
magnitudes accordingly), and then assign the appropriate
sign ("+" or "-") to the result. I hope this clarifies the issue.
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