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1500 questions
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3 answers

Is a boom important to a Yagi?

I am trying to make a yagi for a 900M. The tinkering starts causally with some 1.2mm welding wire (cut to size based on K7MEM yagi calculator, direct soldering, no special matching as suggested on K7MEM page) glued to a 1mm plastic strip, since I…
Ben
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2.4 GHz Antenna for RC copter

What is the best omni-directional antenna design for any RC flying objects? Many times I've lost signal and my copter falls due to lost signal. (Using default antenna). Since the receiver and transmitter position will be in different altitude, I can…
gbluez
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6
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How to achieve highest Q-factor in inductors for 6-160m amateur bands?

When building filters for ham bands (direct sampling SDR frontend) - it is common to build filters using 2,6,10,12 material toroids. Are there any recent developments that offer lower losses / higher-Q in amateur bands? (6-160m) Are there any other…
BarsMonster - R2AYN
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How is FT8 modulated with both upper side band and FSK?

This Wiki shows FT8 mode is USB and its modulation is FSK. I don't get the difference between mode and modulation, I thought they are the same thing? Aren't signals modulated in a single method, transmitted and then demodulation with a receiver with…
Dan
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All male BNC connectors have a rubber gasket: are they rain-proof by design?

This question is about the BNC connection interface itself and not how the coax is attached (assume the coax is attached in a rain-proof way). While inspecting a male BNC connector we noticed that there is a rubberized gasket in the back that the…
KJ7LNW
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2 answers

How do I keep the bomb squad from winning a foxhunt?

I want to hold a fox-hunt in a relatively public location, such as a park or college campus. The fox that I've built uses an ammo can with a rubber duck antenna. It occurred to me that this combination makes for a somewhat suspicious package. My…
W5VO
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2 answers

Why do biconical antennas have a wide bandwidth?

Why does a horizontal biconical antenna have a wider bandwidth than a dipole of similar length? What's the physics behind the biconical geometry having a bandwidth uncoupled from its length in wavelengths, as for a (near) resonant half-wave dipole.
hotpaw2
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Circuit to send MCW on 2m FM

I regularly practice Morse with a friend on 2m NFM by holding our tone generators, which we also use for personal practice, close to the microphone. We send text by CW, read it back, and discuss how we are doing and how can improve our "fists".…
Harry Weston
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3 answers

Is there any PC remote control software for the Baofeng UV-5RE Plus?

I saw on YouTube that some software, with another brand transceiver, can command the transceiver to scan a range of frequencies and display a running waterfall display of scanned results. Can such a setup work with a Baofeng UV-5RE Plus transceiver?
EEd
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Why would a VNA not make a good Spectrum Analyzer? Or an SDR a good VNA?

Happy to be corrected where I'm wrong in any of this but in broad strokes my understanding is: Spectrum Analyzer measures input signal strength while sweeping across frequencies, measuring RF emissions often includes "tracking generator" to output…
natevw - AF7TB
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SDR - FM Radio station interference

I want to learn about software defined radio and how wireless transmission work in general. So I started messing around with SDRSharp and a little antenna I bought. I figured I would start looking at known frequencies like local radio stations.…
DotNetRussell
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6
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2 answers

Does amateur radio induce a health risk?

Electromagnetic Exposure wise, does Amateur radio (Particularly 1.8 to 440 megahertz) induce a health risk due to RF radiation? Other than the Maximum Permissible Exposure (MPE) limits, which will cause RF burns etc., are there any studies that…
Skyler 440
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Power rating of a selfmade air coil

A colleague was winding an air coil himself. It's a 110µH coil with 200 windings for an 80m antenna, intended to be used on a 600 W transceiver. He used a copper lacquer wire with 0.6mm diameter. After finishing the coil, he wondered whether 0.6mm…
Thomas DK3TU
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1 answer

Resonant RF Transformer Substitution

I'm looking at a RF transformer filter design that appears to be using the primary-side transformer inductance as part of a second-order band-pass filter (first schematic). This isn't the only filter in the design, but I believe I have isolated it…
W5VO
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Parameters needed to calculate inductor value to achieve proper phase delay?

I'm thinking about trying a coil in my collinear 5/8λ antenna, instead of the 3/8λ phasing delay line between the lower and upper elements pictured below. I figure that a coil with a certain inductance could give me a current delay of nearly 90° and…
Louis Seaman
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