Amateur Radio Stack Exchange
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1500 questions
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Is it safe to mount an active scanning antenna close to an hf antenna?

I live in the centre of a seaside town in the UK. Because of lack of space I have a random wire antenna in the loft of a small house, and pick up a lot of noise on the top band Sunday morning CW ragchew. I am about twenty hilly miles from most of my…
Harry Weston
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Ferrite rod or core permeability determination

Is there a simple empiric way of determining the permeability (mhu) of a ferrite object (be it a ring, rod or any form)? I've been thinking this for a rod: if I wind coils with different number of turns (same wire, just wind or unwind it) and…
Luca
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Moving from Australia to the US, Amateur radio license transfer?

Moving from Australia to the US, is there a way to transfer my license in any way, or do I need to sit the exams in full? I'm wondering if there is any concept of "credit" towards licensing, so I wouldn't need to sit all three exams (assuming I was…
David VK2VXK
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What are the most common RF connectors encountered in amateur radio?

SO-239, PL-259, UHF, NMO, SMA male/female, reverse SMA, oh my! Some of these may even refer to the same thing with different names. Can someone list the most common connector types and show a picture of each? Also, please explain common acronyms or…
Dan
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Is bending the tips of the antenna wires going to affect the effective length?

I'm looking at designs for low cost DIY yagi antennas for a fox hunt, and pondering coat hanger wire and PVC piping. I'd like them to be built by the youth who will be doing the fox hunt, but that requires some safety considerations. If I plan to…
Adam Davis
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Does AM demodulation make use of the redundant information in both sidebands to eliminate noise?

XLR microphone cables, for example, make use of the dual channels out of phase to cancel noise by injecting the inverted and non-inverted signal into one end of the cable. Then any noise injected along the way will presumably be equal, and…
Bill - K5WL
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What are the electrical differences between smaller and larger coaxial cables?

How do different sized coaxial cables, such as RG-58 and RG-8, compare in terms of electrical properties such as loss? Do different cable types have different losses at different frequencies? From test pool question: T9B10
JC Hulce
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Troposcatter: really all that bad?

The previous question, Packet Radio at 100 miles and specifically, Phil's answer raised an interesting question: In a 50–100 km distance situation where Line-Of-Sight beams aren't an option for communicating data, can we, given the technological…
Marcus Müller
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What exactly is impedance?

I see "impedance" used everywhere. Equipment has an input and output impedance. Antennas and feedlines all have this 'impedance' thing. For someone that understands DC electronics, Ohm's law and a little bit of complex numbers, what is impedance?
Xunie
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How does FM encode BOTH amplitude and frequencies of full audio signal spectrum?

How does frequency modulation encode both amplitude and frequency of the modulating audio signal only by varying frequency? How do both components get spread across and encoded in the side bands? I generally understand that AM side bands occupy…
Tom Zahner
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How to talk to the ISS

I have a UHF/VHF transceiver capable of transmitting on UHF and receiving on VHF or vice versa on channel mode. I finally got a directional Yagi antenna so reception/transmission shouldn't be a problem. I live in Colorado, USA. Which frequencies…
Skyler 440
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Super-low-tech VHF low-pass filter construction?

Related to this question: Is it legal to broadcast an FM radio signal with a Raspberry Pi Zero? Is it possible to build a super-low-tech low-pass filter for VHF harmonic suppression without a PCB or any other non-trivial-to-find components? (e.g.…
hotpaw2
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Dipole Antenna Current Distribution at any Time Instant

Above is a connection of half-wave dipole antenna. The book states that the current profile is same at any given time instant on both the radiators, each of quarter wavelength length. Now my confusion is clearly the coaxial cable is connected to…
user3001408
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Can 433 MHz amateur bands be used for ISM purposes?

From this poster, http://info.tek.com/AM-RSA306-Spectrum-Poster.html, it indicates that a band around 433 MHz is globally-accepted for use as an amateur band. Can this same band be used for industrial-scientific-medical (ISM) purposes? Pertaining…
plu
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Store-and-forward capable satellites in operation?

The amateur satellite community used to have a small fleet of pacsat satellites (AO-16 and friends), which were capable of store-and-forward message passing: you could upload messages to the LEO satellite on one side of the world, and download the…
oh7lzb
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