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1500 questions
10
votes
4 answers
Is use of the phonetic alphabet mandatory?
The phonetic alphabet is often used on amateur radio to spell out names and callsigns more clearly, especially when the clarity may be poorer. However, there are cases where I simply forget certain parts of this - in this case, is it ok just to use…
berry120
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10
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1 answer
What's the difference between "maximum usable" and "critical" frequencies?
In discussing HF ionospheric propagation, you hear about both "critical" and "maximum usable" frequencies. For example:
Above the critical frequency, the ionosphere is unable to refract the signal back to Earth and it escapes to space. The critical…
natevw - AF7TB
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10
votes
2 answers
What is a "calling frequency"?
Doing some study for the ham test, I read a question asking about a certain “national calling frequency”.
What is a “calling frequency”?
What is meant by “calling” in this instance?
SunSparc
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10
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1 answer
Faraday cage in Microwave oven
If I put my mobile phone in my microwave oven and close its door,
Should I be able to get incoming calls ?
Because, I tried it and I was able to get calls, what does it mean?
Does my microwave oven has a radiation leak?
volatile
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10
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3 answers
Is Using PMR446 On A Baofeng GT3-MK3 HAM Radio Legal (If on low power)?
I have a Baofeng GT3-MK3, a great little radio.
Is it OK to use this on the low output setting for general use without a licence, for things like camping/hiking family use etc, if I used the legal frequencies, i.e. 446 in UK?
Jucks
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10
votes
5 answers
What is the highest US amateur license I can get in one sitting?
If I start with no current license, can I take all the exams in one sitting to get to Amateur Extra?
nzc
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10
votes
2 answers
Can every antenna be used both for transmit and receive?
Assuming I have an antenna for receiving GPS signals, can I use it also for transmit — to create a repeater in a tunnel (or some place with no reception)?
volatile
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10
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1 answer
Why bother to have a high power base station when mobile units are generally low-power?
I want to find out why, say in a GSM/cellular system, a base station can be up to 50 watts however the mobile units can be only 100mw (for example).
Surely if the base station ever uses 50w to reach a mobile at long range, the mobile will have no…
code_fodder
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10
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4 answers
Is there an optimum transmission line length for maximum power transfer?
Consider a typical source -> transmission line -> load (i.e. TX->transmission line->antenna) arrangement and assume that the load is not matched to the transmission line characteristic impedance.
It's always possible to select a length of…
Chu
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10
votes
2 answers
Connect two receiving antennas to the same radio
I have built a 1090 MHz ADS-B antenna roughly following some video instructions. It appears to work reasonably.
However, because of how it is placed, it captures signals for more or less a half of the sky. So I would like to build another and put it…
Giovanni Mascellani
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10
votes
4 answers
Has a vehicle magnetic antenna mount ever caused a road accident?
Some people believe that mag mount magnets lose their effectiveness over time, eventually causing a dangerous situation as the antenna could rip loose from the vehicle and become a projectile or distraction at an unfortunate time -- e.g. on a…
Paul
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2 answers
How does the baofeng radio eliminate squelch tail?
All tests are performed in Carrier Squelch mode on all radios without any sub-audible tone or digital squelch involved.
Scenario 1: The Baofeng handheld radio Keys up. Another Baofeng is listening. When the transmitting Baofeng un-keys, the…
Skyler 440
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10
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1 answer
How to design a rubber ducky antenna
I am attempting to design an antenna for a 162.4 MHz omni receive only application and am confident it is going to be difficult if not impossible.
I have very tight specs on space(6" diameter by 3" deep cylinder) so the first antenna I came across…
Josh Cox
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1 answer
Why is the speed of light rounded to 286 Mm in calculations involving frequencies below 30MHz?
I understand that in order to make the maths simpler, frequency ($f$) is expressed in megahertz (MHz) and the velocity of propagation in free space ($c$) for frequencies above 30 MHz is expressed as and rounded to 300 megameters/second (Mm/s). The…
Dan
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10
votes
1 answer
Can I have multiple inverted-vee antenna fed by a single coax?
A friend who recently received his call is planning to setup an inverted-vee for 40/20m bands. Our take is the signal will take the path of least impedance into the correct length antenna wire.
Something like the image attached; it depicts two wires…
VU2NHW
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