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1500 questions
7
votes
3 answers
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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7
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2 answers
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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7
votes
1 answer
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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7
votes
2 answers
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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7
votes
1 answer
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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7
votes
4 answers
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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7
votes
2 answers
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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7
votes
1 answer
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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7
votes
1 answer
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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7
votes
3 answers
How does Wi-Fi antenna work?
Since I'm working with wireless communications, I decided it would be good to educate myself a little and at least get a basic understanding how does a Wi-Fi antenna work.
My first question is about the most basic 2.4Ghz antenna that is usually…
xba
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7
votes
3 answers
Using an RTL-SDR as a spectrum analyzer
I've been trying to get into RF electronics, but one thing that is holding me back is lack of test equipment. I have an old analog oscilloscope, but that doesn't help much for things like verifying filter frequency or looking at harmonics. So far I…
user9103
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7
votes
2 answers
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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7
votes
5 answers
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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7
votes
3 answers
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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7
votes
8 answers
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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