Amateur Radio Stack Exchange
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1500 questions
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What is the record for highest successful (automated) CW transmission rate?

I understand high speed CW is used with meteor scatter, because the path only exists for a few seconds after the meteor passes. I was wondering if automated high speed CW has an effective "speed limit". I suppose bandwidth regulation would impose a…
Paul
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Twisting copper wire for a less-flexible DIY antenna

I am making DIY antenna for a home project. The antenna is going to be "V-dipole" with leg length about 53cm. Unfortunately, I didn't find a thick copper wire, but I have a lot of thin core from tv antenna cable. I am attending to twist a few thin…
Deliaz
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FM spectral amplitudes during silence

General setting I'm playing around with an RTL-SDR and recently captured some FM spectrum in Hannover, Germany. I want to undersand what's going on, so I've read a lot about FM and its spectra, but I can't completely make sense out of…
Hemanti
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Simple DIY AM receiver for 25/28 MHz

I'd like to build a simple AM receiver for 25 and/or 28 MHz to receive DCF77-formatted time code. It doesn't have to be extremely sensitive or selective - the local clock oscillator will keep time while it cannot receive the time code during my rare…
oh7lzb
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Website for Sat details

I used to use the Amsat website for finding out the status of Sats and other info, like operating frequency etc. It was proving useful, and I like the pass predictor also. Seems nowadays though there's error messages with the database, I get: *…
user521
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Does a Canadian amateur radio operator’s certificate expire?

I obtained my Canadian Basic with Honours certificate in the late 90's and haven't done much with it since. Was looking to get back into the hobby. Has my certificate expired? Do I need to take the test again?
wkm
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Do vacuum variable capacitors have higher Q than air variable capacitors?

Do vacuum variable capacitors have higher Q than air variable capacitors? They are not commonly seen in tuners or crystal sets. But they are mentioned as superior to air variables for resonating magnetic loop antennas opposite the feed point --…
Paul
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Does the Crystal Radio really work?

I am in 12th std, the reason why I am mentioning this is that we are given a PROJECT to do in Physics subject. And then one day I searched the internet and found this amazing thing called 'Crystal Radio'. And when I showed it to my group(since it is…
radiantshaw
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Relicensing after a decade, can I reacquire my old call sign?

The background, I got a US Tech+ license back in the 1990's when I was in middle school. At the time I did it for the novelty of getting licensed in something and not a bit to imitate my brother. Since I wasn't using the license at the time I let it…
BSteinhurst
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What about the digital mode ROS causes some to consider it spread spectrum?

The FCC disallows amateur spread spectrum communications below 220MHz. At the moment the relatively new digital mode, ROS, is considered, by some, to be spread spectrum. So this mode is getting little to no use in the US. It doesn't seem much…
Adam Davis
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What organizations in the USA can I join to participate in emergency preparedness?

I want to get involved in emergency preparedness. What organizations, if any, are there in the United States that support disaster recovery and emergency management?
dcaswell
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Can X-rays be used for communication?

I keep increasing my frequencies and want to get up the spectrum more and more. My current project is pointing a powerful focused LED from a peak and I will try to pick it up with a telescope and some sort of photo detector to receive the AM light.…
Skyler 440
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Is the 3-cm band serviced by any commercial main-stream ham radio transceiver?

Wikipedia writes to say The Radio Regulations of the International Telecommunication Union allow amateur radio operations in the frequency range 10.000 to 10.500 GHz, and amateur satellite operations are allowed in the range 10.450 to 10.500 GHz.…
VU2NHW
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Signal path to maximize RFI rejection in an urban environment

Urban ham here (Cambridge, MA - FN42ki - KC1JZE) looking for tips to make this hobby possible in the city. I rarely can hear both sides of HF phone transmissions, and have yet to make contacts despite dozens of attempts on 80/40/20m using commonly…
Jeremy Gilbert
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Impedance matching using Smith Chart and relationship to reflection

I've been reading the impedance matching chapter of Bowick's excellent RF Circuit Design book and I have a question. For those who haven't read this book (or have but can't remember!), the chapter discusses L and 3 element matching networks (very…
Buck8pe
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