Amateur Radio Stack Exchange
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How does the length of a metal sleeve around a (shieled) coax cable affect antenna performance?

A post on http://adsbexchange.com/forums/topic/beginners-2-cantenna-easy-diy-antenna-to-improve-rangeplane-count uses a $\frac{\lambda}{4}$ sleeve made of a pop can beneath a $\frac{\lambda}{4}$ wire protrusion made from the core of a coaxial cable…
Jonathan
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How would you get an "I'm alive" message to family in another state using amateur radio?

I'm researching options for getting an "I'm alive" message during a disaster response out to family in another state that aren't HAMs. There are likely to be a lot of possible answers that are art and style rather than one "right" answer, so some…
Matthew Wetmore
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How big can an antenna be before I need planning permission in the UK?

Presumably setting up a 1m high antenna in a back garden isn't going to be an issue, but setting up an 80m high antenna would likely cause complaints! How high an antenna can I legally construct in the UK without going through the route of applying…
berry120
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How does rpitx generate arbitrary SSB data with a clock peripheral?

While it wasn't the first to do so, the rpitx software seems to be the most active and mature implementation of what its own comments call "a code fragment by PE1NNZ". The trick is explained in Guido's original Direct SSB Generation by frequency…
natevw - AF7TB
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What is Hinternet, in simple terms?

I've been reading about HInternet a bit, and all explanations I find are detailed technical explanations. I have no idea who pays for internet connectivity, where the internet sources from, etc. Just articles about the frequencies used and…
mr danker
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Decimation to listen to FM radio with gnu radio

I am trying to listen to FM station using an SDR and GNU radio. I have followed this procedure Is there a reason that the decimation is done gradually? For example would it make a difference if I change audio decimation to 1 in WBFM Receive and…
Jack
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Why aren't there baluns that do BOTH balanced/unbalanced transformation and common mode current attenuation?

I have read myself blue, about baluns. Especially 1:1 ones. Some claim they're only there to balance the unbalanced signal, and that's what's in the name also, but I find several that claims that the main thing at the point of a balun is common mode…
Hans Neve
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Is there a standard data format for station/channel/band information?

Does there exist a de facto standard data (file) format, or even several common formats, for representing information about radio stations, channels, and/or bands? I am writing software which would like to be able to make use of such data sets where…
Kevin Reid AG6YO
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What is the attraction of vertical antennas for HF?

I understand that MW broadcast stations use vertical antennas because that polarization works much better for groundwave propagation. But in amateur radio, I would assume the focus for communications on the HF bands would be via ionospheric…
natevw - AF7TB
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License upgrade - retake required?

It's been more than a year since I passed my Technician and General exams and obtained my license. If I were now to go for my Extra class license, would it simply be a matter of taking and passing the Extra exam, or would I need to pass the previous…
KD8TGR
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I have 60 feet of coax but only need 20 feet; can I loop up the excess?

I was given about 60 feet of good cable with connections but only need about 20 feet. Can I loop up the end or do I need to cut and put a new connector on?
Dant1316
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On Anderson Powerpoles, does the red on go on the left or right?

When attaching a red and black pair of Powerpoles together, which way should I do it to ensure that it will plug into the most number of other people's gear? When looking from the top of the connector (the side where the "tongue" is not visible)…
Arthur
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How can I construct a practical loop antenna for 2m band?

How can I construct a practical loop antenna for 2m band to use in a fox hunt? Is it even possible to construct a hand-held antenna for the 2m and 70 cm bands? I tried to calculate the dimensions using a few online tools and formula, and the…
KF5RRR
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Battery sizing for power draw

Note that this question isn't about battery capacity, at least not per se. I have a 100 Watt mobile transceiver. At 12 V and assuming 50% efficiency, that means it draws a little under 20 Amps at full power. It's currently being powered by a pair of…
Dan KD2EE
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What exactly does an unun do to the impedance of a transmission line?

If I have a load Z_L and a length of transmission line with impedance Z_0 I know how to compute the impedance at the input to the transmission line (using smith chart or using telegraph equation). But now suppose I attach a 4:1 Unun to the (input)…
DrEntropy
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