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1500 questions
21
votes
4 answers
What's the pinout for "Kenwood" 2.5mm TRS/3.5 mm TRS connector?
I've seen many Chinese HTs (Baofeng, Puxing, Wouxun, QuanSheng etc.) using the so-called "Kenwood connector", which has a 2.5 mm TRS connector and a 3.5 mm TRS connector. It looks something like this:
I've seen it used for serial ports, speakers,…
AndrejaKo
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21
votes
1 answer
Why do people say, "get a nickel," on repeaters?
Sometimes, I'll hear someone say "wait a moment, I'm getting a nickel," and then drop the carrier only to resume talking. Why?
webmarc
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21
votes
5 answers
Good wire for wire antenna?
What properties should I look for in a good wire for building a wire antenna? Could anyone recommend something specific for me?
Timtech
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20
votes
10 answers
What antenna on a BaoFeng UV-5R Pro will give me better reception?
I am happy with my BaoFeng UV-5R Pro but the local UHV VHF repeater and simplex reception is terrible, even for contacts less than 50 kilometers. I assume that it's because the rubber-ducky antenna on it is terrible. What can I replace it with that…
Warren VE3WPX
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20
votes
4 answers
What is the peak voltage at the tips of a dipole antenna?
What is the peak voltage present at the very end tips of half-wave dipole antenna in free space, and how might this peak voltage relate to transmitter type, transmitter power, RF frequency vs. antenna half-wave frequency mismatch, feed line, SWR,…
hotpaw2
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20
votes
2 answers
How to detect common-mode currents or “RF in the shack”?
Let's say we already know that if your antenna is not suitably constructed or connected then you can get current on the shield of your coaxial feed line which will flow through the shielding/grounding of your equipment, becoming “RF in the shack”,…
Kevin Reid AG6YO
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20
votes
6 answers
SDR: Quadrature demodulation vs direct RF sampling
I see that many SDRs use a quadrature demodulator and sample I and Q signals.
But is it possible to downconvert the RF signal instead, sample it with only one ADC, and get the same capabilities of digital postprocessing?
So if we want to observe…
BarsMonster - R2AYN
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19
votes
3 answers
What makes cellphone transmissions so energy cheap?
The modern cellphone can carry on a full duplex conversation for a time period measured in hours on a battery half the size of my handheld transceiver. My transceiver can barely receive for that length of time on its pack, nevermind transmit, and…
Adam Davis
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19
votes
1 answer
How does moving a feedpoint off-center in a dipole affect the resonant frequency and resistive load?
Specifically, I understand that OCF dipoles change the SWR, but does it do this via reactance or resistance, or both?
Bill - K5WL
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19
votes
5 answers
Why do folded dipoles have greater bandwidth than ordinary resonant dipoles?
This is something I've read in passing, but never encountered an explanation of why. For example, Wikipedia says:
Another common place one can see dipoles is as antennas for the FM band; these are folded dipoles. The tips of the antenna are folded…
Phil Frost - W8II
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19
votes
3 answers
How does a mag mount antenna achieve a ground plane?
I've been thinking for some time about magnet mount mobile antennas and wondering how they establish their ground plane. Consider that many mag mount antennas have some kind of protective coating on the magnet. Consider also that most cars have a…
Peter KB1AVL
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19
votes
3 answers
SDR sampling bandwidth - do the bits per sample matter?
I'm looking at data converter chips for a homebrew SDR design, and I see that I can choose not just the sampling frequency, but also the bits per sample.
Obviously the sampling frequency has to be several times the target frequency, but what effect…
Adam Davis
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19
votes
6 answers
What defines music, per amateur radio regulations?
Sometimes when I access IRLP nodes, they have a very short melody telling you that you are connected; or when my local repeater's net begins, it does the famous doorbell 8-note sequence. What is the fine line of prohibited and allowed with respect…
Skyler 440
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19
votes
5 answers
FCC sends "Notice of Dismissal" with quite threatening language just for denial of a vanity callsign?
I had applied for a vanity callsign which wasn't available. That was in March. The FCC license system shows my old callsign is still in effect.
Today, after a longer absence from my mail, I open a "Notice of Dismissal" which says in a wordy way lots…
Gunther Schadow
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19
votes
5 answers
What do "QRM" and "QSB" refer to?
An answer on Basic QSO format? mentions things like "QRM" and "QSB". What do those terms mean?
Amber
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