Amateur Radio Stack Exchange
Amateur Radio Stack Exchange

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1500 questions
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6 answers

Is it conventional to sign using the phonetic alphabet like people do in the military or aviation?

I know that most amateur operators simply sign at the beginning or end of a message, like The weather is good, Kz1XXY Would it also be customary to say that in phonetic form? Kilo zulu 1 X-ray X-ray Yankee
HeavenlyHarmony
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Vertical antenna on HF?

What are some of the advantages and disadvantages of using a vertical antenna on high frequency? Are there any better antenna types that I should use?
Timtech
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dBm signal minus dB

I've got a 27dBm signal that I'm going to put through a 6dB attenuator. How do I work out the resultant signal in dBm? I've tried Googling that without any luck.
Chris Pavey
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3 answers

Can I use a helical ground plane radial in the same way that a loading coil works?

I'm working out the science behind mounting an antenna on a vehicle, and I came across the concept of ground planes. This answer says that longer is better but don't worry about it too much, but this article focuses on 1/4 wave ground planes, as do…
YetAnotherRandomUser
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What is the permissible frequency error for US amateur radio transmissions?

What are my requirements as a licensed Amateur Radio operator in the US to keep to a single frequency? How much drift can I have during transmission and still be within my license? Does it depend on the mode or band? Note that I'm not asking about…
Adam Davis
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How to derive antenna gain from radiation pattern

I need to calculate the antenna gain in both dimensions: azimuth and elevation. The datasheet of the antennas I am using has two different radiation patterns, one for the elevation and one for the azimuth. Given the two angles I can derive 2…
gabriel-shatana
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3 answers

What exactly is a "balanced modulator"?

While studying for his U.S. General class license, my son wondered about the "balanced modulator" referred to by a few questions in the FCC pool. Quoting KB6NU's General Class study guide to give a sense of the two questions: Filters are also used…
natevw - AF7TB
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Is this a broadcasting antenna?

We bought an old house and found an antenna inside the attic of the house. I don't know much about antennas or radio but searching in Google I found a similarly shaped one and it describes it as a broadcasting one. Is that what this antenna is? If…
Wilreyca
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What's an appropriate core material for a loopstick antenna?

A loopstick antenna, if you don't know, is a coil of many turns around a high permeability core. They are frequently encountered in AM receivers and look like this: This particular example is actually two antennas on one core. What type of material…
Phil Frost - W8II
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What is the logic behind RG cable codes

What is the logic behind the names of different RG cables? The Wikipedia's Coaxial cable page has a list of different coaxial cable standards but I cannot find the internal logic of the naming. I would assume that coding pretty much anything would…
OH2FXN
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How do I maintain my frequency during a contest?

Suppose I am operating a busy HF contest, and I have found an open frequency to call CQ. I make a number of contacts, and then suddenly another station starts to call CQ right on top of me. The other station is either matching my frequency or within…
W5VO
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Is there a practical way for hams to participate in cellular-related technology advances?

My understanding is that there used to be more timely overlap between commercial and amateur radio technology — e.g. helping study ionospheric propagation, relatively early adoption of SSB technology, up through re-purposing business equipment for…
natevw - AF7TB
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How were 1920s hams able to measure megahertz frequency?

I was reading 200 Meters and Down but one thing that was unclear to me was that hams in the 1920s were operating on the 200 meter frequency, which is around 1.5 Mhz .... or 1500 kilocycles to use the old phrasing. What's unclear to me is how they…
RoboKaren
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How is full duplex implemented without swamping the receive circuitry?

I've seen a few references to full duplex SDR radios, and I'm wondering how can one transmit and receive at the same time without overwhelming the receiver, and without heavy filtering such as the cavity filters used in repeaters.
Adam Davis
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GNU Radio sinusoid multiplication does not produce perfect results

I created a simple sketch in GNU Radio that multiples two signals. One is a sine and the other is cosine. I paste a screenshot of it and its results below. I have heard that in DSP, we can do almost perfect signal processing. Hence, I assume…
Denis
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