Amateur Radio Stack Exchange
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What is the frequency range 2300-21950 kHz used for?

I was checking out the gizmo mentioned in this question, and I see that it can receive "shortwave" in the frequency range 2300-21950 kHz. Most times I see "shortwave" mentioned, it's by sales or nontechnical people to describe any number of things.…
YetAnotherRandomUser
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FFT showing 2 signals - GNU Radio

I receive OOK signals from a remote control in 433MHz. I'm using a dongle RTL-SDR on GNU Radio. The FFT output signal from the RTL-SDR Source block is represented on the picture: My question is, why i have two signals with similar amplitude?…
Marcos Pinho
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How can I determine/measure power rating of a DIY air capacitor?

I've build an air capacitor like the one described in this article, although I used 1 mm thick single side copper boards (FR4) instead of solid copper sheets. I would like to use such capacitors in my next projects, e.g. an antenna tuner and a…
Aleksander Alekseev - R2AUK
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Are there any good, consistently receivable signals in the US for HF receiver testing?

Having built my first HF receiver, I'd like to know if I'll need to search around for transmissions that happen to be occurring, or if there are reasonably strong signals I can count on being present regardless of the time or day? I just want a…
Adam Davis
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Why are the lower HF frequencies not working during winter day time?

Currently my location is Nepal. We use the ICOM f-7000 radios without the antenna tuner. We use the frequencies round about 5-9 MHz, for communication over distances between 150 and 400 km. During the summer time during the day the radio works fine…
Angry Hooman
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Why are hand-wound coils so common if commercial inductors are available?

In most schematics of ham radio receivers and transmitters the inductor is mostly given specifically as the number of turns around some certain toroidal ferrite ring (for example). This corresponds to a certain inductance, which more often than not…
DK2AX
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RF Antenna - V pole - Should one leg go to ground and the other to signal?

I'm attempting to follow this white paper in order to build an antenna. This is my first antenna and as such I have a rather simple question. DIY 137 MHz APT Weather satellite antenna by Adam-9A4QV https://www.youtube.com/watch?v=9WNmhfpWxdk Should…
Cody Smith
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What is the best approach for measuring return loss of a home-made 3cm horn?

Let's assume I have built a SMA-to-waveguide transition that flares out into a horn antenna. There's no flange between transition and horn, it's made of a single metal sheet. The antenna has tuning screws, and my goal is to find the screw position…
mpb HB9EGM
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Is this the Correct Ferrite Core to Reduce RFI as a Common Mode Choke?

I have a Flex 3000 connected via RG-11 coax to a inverted V fan dipole tuned for 40m and 20m on my roof. I have an "ugly" balun up on the mast by the antenna. I further have the feed-line going into a lightning suppressor where the line enters into…
Etep - VE6ETP
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Dipole antenna radiation field equation

Can anybody provide me with an idealised formula that describes the radiation pattern of an omnidirectional dipole antenna? In particular I am interested in the formula that creates a plot similar to the following: Note: I am looking for a…
David
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Size of ground plane disk for vertical antennas?

I’m looking for information about the diameter of a ground plane disk that I can use with a regular car radio and car type antennas in my home. DIY would be best, or any other ideas for a antenna that will work. I have tried Google, but have found…
Gregory DeHart
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Does a parabolic reflector dish change circular polarity?

I've been receiving satellite signals in the L-band (~1.7GHz), recently. These signals are RHCP. So far, I've been using a DIY helical antenna in axial mode, and a patch antenna with cropped or clipped corners. My favorite tool to calculate the…
polemon
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Is a US Extra class exam from the '90s valid to upgrade from Advanced class today?

If one passed the Extra written test in the late '90s at an ARRL test center but did not get the 20wpm endorsement, yet is an Advanced operator, would they now be upgraded to Extra class or do they need to retest? As I stated, I passed the written…
Adam Albanowicz
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Can my laptop pick up CB radio frequencies?

I was on my laptop watching a show and I paused to look something up and since there was no sound I could hear a voice talking. It sounded distorted like it was coming over a radio and I couldn't make out what was saying. There does not appear to be…
Christian Castellanos
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It it really useful to terminate unused 75Ω outputs on a coax splitter?

When discussing improvements to my home HDTV Antenna/distribution system a colleague brought up the need to terminate all coax, even unused splitter ports. My understanding of the way terminator works is that they prevent wave reflection, which can…
Thomas Guyot-Sionnest
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