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1500 questions
13
votes
4 answers
What is an antenna tuner? Why bother with resonant antennas in the first place?
There are a lot of antenna tuners on the market that have various capabilities in terms of how they can allow random radiators to work with our transceivers.
What exactly do they do? My understanding is that they can neutralize the imbalance…
SDsolar
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13
votes
3 answers
Is a vertical noisier than a dipole, and if so, why?
I've had people tell me, anecdotally, that a vertical is noisier than a dipole. Is this true, and if so, why?
If it is true:
Is this additional noise, such that SNR is degraded, or is the vertical just more sensitive overall, making noise and…
Phil Frost - W8II
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13
votes
3 answers
What is the role of digital data modes in emergency communications?
Emergency operations are typically reliant on voice traffic today. Are digital data modes used at all in emergency operations, and why/ why not? Couldn't data modes be used to pass information more efficiently than voice?
JC Hulce
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13
votes
5 answers
How can I add amplitude modulation to this transmitter?
I recently built this circuit, and could hear a nice full quieting signal on my short-wave radio with a 7.2 megahertz crystal for the 40 meter band.
What is the simplest way I could Amplitude Modulate this signal with a microphone or computer output…
Skyler 440
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13
votes
2 answers
How do I receive ATV with GNU Radio?
How do I receive Amateur television (ATV) — e.g., NTSC in the U.S. — with GNU Radio so I can play the A/V in, e.g., the VLC video player? Are there any example GNU Radio block diagrams to accomplish such a task?
cf. this for an example on how to…
Geremia
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13
votes
4 answers
Handheld Dipoles
A problem with handheld devices is poor grounding. I read from someone else's question that dipoles don't need a ground. Why don't they make little handhelds with two antennas instead of one, or a little T antenna, which has extendable arms?
_ _ …
Skyler 440
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13
votes
4 answers
How To Join Packet Radio BBS
I'm a complete newbie here, and on the Southeast Coast of the USA. I don't even own a ham radio yet. Some preppers and I got to talking about a dystopian time of Internet collapse where shortwave radio might be an important factor of survival. This…
Radio1
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13
votes
3 answers
How do I prevent radio signals from tripping a GFCI?
My wife woke up several nights by a metallic "thunk". It happened to be while I was talking on 10 meters and turned out to be the ground fault circuit interrupter (GFCI) on her hair dryer cord. Apart from the obvious answer of leaving it…
Peter KB1AVL
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13
votes
3 answers
Conductive boom vs non conductive boom: what's the difference on a Yagi?
I designed a Yagi antenna using 4nec2, assuming that I would use a non conductive boom.
If I use an aluminum boom but I insulate the elements from the boom, can I keep the same design? How does it affect performance, in particular SWR?
It is a 2m…
GmodCake
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13
votes
2 answers
Direction finding: How to find a stuck FM transmitter on 70cm?
There's a blank carrier on a 433 MHz FM voice frequency here. How should we go on about finding the transmitter's location? Practical procedure? Could be somewhere downtown.
oh7lzb
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13
votes
3 answers
What is the effect of using different number of radials with ground plane antenna
I'm new to electronics and telecommunication at all, I having trouble with understanding the difference between 2, 3 and 4 radials, as I've searched online I've learned that I can use only 1 radial(and it makes sense) but when using 2, 3 or 4 its to…
Aviel Fedida
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13
votes
4 answers
When may a ham operate beyond the privileges of their licence class?
As far as I know, all radio amateurs are assigned privileges on
Power Output
Mode of operation
Operating bands
as a function of the class of licence they hold. These privileges differ from one jurisdiction to another.
When may a licencee operate…
VU2NHW
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13
votes
2 answers
When is RF grounding necessary, and when is it not?
I've seen many installations, particularly at field day and also in second-floor installations, where RF grounding is ignored entirely. What are the drawbacks to this and when is it absolutely essential to have RF grounding?
Bill - K5WL
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13
votes
2 answers
Why is an exemption for music given to NASA broadcasts of manned space flight missions?
FCC 97.113 Prohibited transmissions reads:
(e) No station shall retransmit programs or signals emanating from any type of radio station other
than an amateur station, except propagation and weather forecast
information intended for use by the…
PearsonArtPhoto
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13
votes
6 answers
Calculating Antenna Length on the FCC Exam vs. in Reality
I have seen the following formulas for calculating half and quarter wavelength antennas:
Formula for $\frac{1}{2}$-wavelength antenna (in free space):
\begin{equation}
\mathrm{Length~(feet)} = \frac{492}{f_{MHz}}
\end{equation}
Or is…
Dan
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