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1500 questions
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7 answers

What does sending SK after calling CQ mean?

When I was at a local radio club today, I witnessed a bit unusual response by a station calling CQ using BPSK31, that is to say phase-shift keying, not the regular A1A telegraphy, on the 20 meter band. The communication looked something like…
AndrejaKo
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Identifying regulations for interfering stations

I'm working on tracking down some 2m repeater interference, and I have identified that the offending signal is a spur transmission on a commercial pager service (that lands right on our repeater input frequency). How would I identify regulations…
W5VO
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Choice of PCB coil design for filter inductor at ca 20 to 400 MHz, 5 W

Looking at the diplexer schematic from this nice question, I realized this can completely be done in PCB-formed elements (minus the connectors). (As a kind of counter-action to the original question's intent to get leaded capacitors, I'm not only…
Marcus Müller
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How can quadrature mixing adjust the phase of all frequencies by the same amount? Can it be done in the digital domain?

This came up in some feedback I got when I tried to answer What is IQ in the context of SDRs? and revealed some of my own misunderstanding. Initially, I gave an answer something like (paraphrasing): You could collect I/Q data by taking a second…
natevw - AF7TB
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Is a VHF antenna on a vehicle's body a bad idea?

For context, I'm brand new, with nothing but an HT & 19" dual band (2m/70cm) whip on it. While I'll likely go with a magnetically mounted vertical antenna, I've been thinking of other more covert options. For instance, could I do a 1/2 wave dipole…
conan
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5 answers

Coax fed dipole: shield goes to one side, yet is grounded via chassis line to Earth

Suppose I have a coax-fed half-wave dipole antenna. The coax shield goes to one side of the antenna, the center conductor to the other side. The transceiver's chassis is connected (via the coax connector) to both one side of the dipole and to Earth…
Jack
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3 answers

Why is the electric field orthogonal to the magnetic field from an antenna?

I've read in several places that the electric field is 90 degrees orthogonal to the magnetic field, and both are orthogonal to the direction of the wave from a transmitting antenna. What causes this? Are there any cases where this might not be true,…
Adam Davis
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How to determine frequency and launch angle given a target skip distance?

I would like to communicate with someone 1000 miles (1600 km) away. I'm not sure how to target a specific distance. (image source) I assume it's an interrelation of the following factors: Which frequency I'm using Which ionospheric layer I'm…
bitsmack
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Morse Code Key Grease

I just got an old brass key at a hamfest, and it appears to be in pretty good mechanical condition, aside from some dirt and dust. Taking it apart, the key (apologies for not knowing the exact terminology) is held in place by two cups with four ball…
W5VO
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4 answers

DIY SA612 + RTL-SDR HF receiver: good on laptop, but huge wideband noise on Raspberry Pi

I recently built a SA612 mixer for HF reception. I used an USB-frequency oscilator to shift the incoming frequency up by 28.8 MHz. I used a random wire antenna outside my balcony and connected it to the center-pin of a car antenna mount, and used a…
比尔盖子
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What will I need to receive the ICE/ISEE-3 transmitter?

The ICE/ISEE-3 spacecraft, launched in 1979, is due to pass by the earth in August, 2014. It was commanded to power down completely years ago, but it appears to have failed to do so, and while it could be re-tasked to perform another mission…
Adam Davis
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4 answers

What fraction of 2x2 USA call signs are vanity calls?

I found out a while back that, as things currently stand with the FCC, if you take and pass all three license class exams in the same sitting, you get a so-called "two by two" or 2x2 call -- two letter prefix, region/district number, and two letter…
Zeiss Ikon
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How would I calculate antenna gain?

The concept of antenna gain is pretty important for calculation of link budget and is something I've had contact with. I know that it tells me how focused the waves emitted by the antenna are and I know how to read antenna gain charts. What I don't…
AndrejaKo
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Is the bandwidth of an LCR resonant circuit independent of the capacitance?

Is the bandwidth of an LCR resonant circuit independent of the capacitance, if the inductance and its series resistance are kept the same, and the Q is high? This question and the calculation associated with it were originally posted by a radio…
Harry Weston
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Required SSB sideband and carrier suppression?

Is there a legal (U.S. FCC) or a commonly accepted standard requirement for SSB opposite sideband and and carrier suppression for either manufactured or kit built transmitters? Does the 43+ dB down spurious emissions CFR 97.307 rule apply? Or…
hotpaw2
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