Amateur Radio Stack Exchange
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1500 questions
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2 answers

Base vs center loading a vertical antenna

I currently use a homebrew 40/60/80m vertical consisting of a 5M aluminium tube with a multi tapped coil at the base. The ground plane is the metal roof at my house, and the antenna is not centered in it, but it's next to one of the edges. I read…
hjf
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Can an ultra-wideband system transfer data at high speed without precise clock synchronization?

Recently, ultra-wideband technology has been in the news again. From the Wikipedia article: UWB transmissions transmit information by generating radio energy at specific time intervals and occupying a large bandwidth, thus enabling pulse-position…
natevw - AF7TB
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How do I evaluate and use a toroidial core for my HF double-balanced mixer?

Last year, I planned to make a double-balanced mixer covering the entire 3-30 MHz band as an upconverter for my RTL-SDR receiver, mainly for learning RF circuits and ham radio. Naturally, it requires two RF transformers as baluns, possible 4:1 or…
比尔盖子
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How can I decode SSTV with only macOS software?

Have you used an SSTV decoding application on an up-to-date version of macOS? Which one, and if you built from source, can you share the steps you took to do so? I do not know of a single working macOS application for SSTV decoding. I've been…
Amin Shah Gilani
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Can tropospheric scatter effect be used by 802.11 links?

What are the lowest EIRP and antenna gain requirements that make possible use of troposcatter at the distances of 100 to 150 kilometers assuming conventional WiFi (6 Mbit/s data rate with OFDM/BPSK modulation)? While this is unlikely to work in…
Deer Hunter
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GnuRadio RF transmission, legal and safety issues

I'm trying to run some transmit/receive RF examples that I found online using GNU Radio with USRP B200. I read and heard about some cautions in terms of transmitted frequencies here in the USA which made me slow down! What is the legal frequency…
Hadad
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Kenwood TH-D72A: what's the difference between Tone and CTCSS?

Kenwood TH-D72A supports 3 types of tone: Tone, CTCSS and DCS. What is the difference between Tone and CTCSS? As far as I know CTCSS is basically a continuous transmission of a given low frequency signal mixed with the voice. So it's basically a…
Aleksander Alekseev - R2AUK
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Propagation effects of noctilucent clouds

I know auroras are a propagation mode, but I was wondering with the recent outburst of noctilucent clouds (as reported on www.space.com) brings with it any interesting propagation modes, either on HF or VHF/UHF?
Duston
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Is Field Day a contest?

Is the ARRL Field Day a contest, or is it not a contest? Kindly explain the reasoning behind your answer. A non-ham could not tell the difference.
Mike Waters
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What does "THREE ALPHA in Virginia" mean?

I'm listening to the 40m band during Field Day and I keep hearing things like "You are THREE ALPHA in Virginia," or "do you hold me ONE ALPHA in Eastern Pennsylvania?", or "you are TWO ALPHA Maine." I have no idea what they're talking about, can…
SandPiper
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How do Field Day participants protect from lightning?

I'm planning to attend Field Day this weekend, and the forecast calls for thunderstorms. I can picture a serious issue with a bunch of temporary antennas set up in an open area when a thunderstorm sweeps through. This seems to have the potential…
Zeiss Ikon
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Multiband vertical antenna not working as expected

I built a vertical out of a 5M aluminium pipe. It tunes fine (and wide!) on 20M. I decided to add a loading coil to operate it on 40M, and it also worked fine, albeit not so wide. While I was at it, I extended the coil for operation on 80M as well.…
hjf
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Is there any practical advantage to a parabolic reflector over a high-gain beam antenna?

I've been looking at options for a high-gain directional antenna recently, and I've noted that there are commercially available parabolic antennae for the shorter bands -- specifically 70 cm, with an antenna that probably doubles as a UHF OTA…
Zeiss Ikon
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Preventing CW key clicks

What are "key clicks"? How much does the rise time or bandwidth of a CW signal need to be limited to prevent other QSOs on adjacent frequencies from being annoyed by "key clicks"? Is there a legal limit regarding this (in the U.S.)? How do…
hotpaw2
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Can an HF antenna be put inside a tree?

There are some trees around with branchy tops that seem wider than half of 10M, maybe even half of 20M, and above the nearby rooftops. Can a wire dipole or a vertical be mounted inside a tree? If so, what kind of problems might such an antenna…
hotpaw2
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