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1500 questions
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What does the Friis transmission equation represent and how is it derived?

I've read that the Friis transmission equation can be applied to calculate path loss in ideal space. However, I'd like to better understand the factors that define it and what it represents, and why it is the equation it is.
Phil Frost - W8II
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Regenerative receiver interference?

Can a regenerative shortwave receiver (especially an old vintage unshielded tube or transistor model) connected to a wire antenna generate HF interference? If so, what are some ways to prevent one from generating such interference (but still…
hotpaw2
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How to measuring ferrite core efficiency vs frequency

There is an unknown ferrite toroid. I would like to figure out whether it can be used in an audio transformer, or maybe in a 1:4 transformer on given HF frequency. The experiment I came up with is following. I can wind a 1:1 transformer using this…
Aleksander Alekseev - R2AUK
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How does a Faraday cage block an EMP?

If you search the Internet for Faraday cages, you'll find a lot of information about using homemade cages to protect radios from EMP damage while in storage. A lot of that information is either contradictory or isn't backed up by satisfactory…
mrog
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Is there a public standard for 8 and 10 character grid locators?

We have a question about the algorithm for conversion from coordinates into grid squares here, and this is an extension of that. I've noticed that there are several web-sites (for example here, or here, or here) and Android applications which will…
AndrejaKo
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Passively reducing ground loss?

Would a disconnected wire or conductive mat below a low height antenna reduce ground losses? A tuned length of wire under a wire antenna might be suitable for NVIS gain. But would a bunch of space blankets or unconnected random length wires or mesh…
hotpaw2
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Double power-handling ability of RF amplifier output transformer

I want to base the output network for a 500W push-pull HF amplifier on "A 250W Broadband Linear Amplifier" described in Chapter 17 of the 2014 ARRL Handbook. I need advice on whether and/or how the 1:4 impedance step-up transmission line transformer…
Brian K1LI
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Configuring an SDR for CW?

So I'm developing my own SDR software from scratch (I like to "own" the code). The channel between the RF-to-USB hardware and the software is 192kHz sample-rate IQ audio samples. The degrees of freedom seem to include at least 4 frequencies and a…
hotpaw2
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Is it practical to use a slug-tuned variable inductor in an antenna matcher (aka "antenna tuner")?

I will soon need an antenna impedance match (aka "antenna tuner"), because I'll initially only have a single antenna for my HF rig (needs to cover 80m, 40m, 20m, 15m, and 10m). Obviously, in order to manage SWR, I'll need a matching network, quite…
Zeiss Ikon
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Is a 5 watt UHF/VHF handheld considered QRP?

QRP doesn't have a strict definition, though 5W or less seems to be a common threshold. So would "QRP operation" usually be considered to include UHF/VHF handhelds?
Phil Frost - W8II
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Can ferrite beads lower coax cable velocity factor?

For VHF and UHF, it seems reasonable to slip ferrite beads over a coaxial cable to act as a transmission line common mode choke. It also seems reasonable to use beads with the smallest diameter possible. This can lead to ferrite-over-cable lengths…
Chris K8NVH
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distance between shack and antenna

I am putting a 40m antenna in my attic and I was wondering would it be safe to have a shack in the room right below the attic (10ft of coax or less) or should I have my shack in the basement/ground level (50ft coax). Are there any health effects of…
Bogdan YU2DBC
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Antenna options for a 10x20m property with a large metal roof?

I live in a house that sits in the middle of the city, in a lot 10x20m in size. The first 6x10m are covered by a metal roof with a rather low angle (IIRC only 50cm difference between the highest and lowest point). The rest is concrete roofing. I…
hjf
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What are the official Baofeng websites in the USA?

Which Baofeng website(s) in the USA is (are) official (that is, selling genuine Baofeng radios, programming cables, and accessories)? Which "Baofeng" websites are NOT, allegedly selling counterfeit radios and programming cables? A Google search…
Mike Waters
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How does aluminum siding on a house affect an inverted-vee antenna next to it?

My two-storey house is wood with alumninum siding. I had wanted to install an inverted-vee antenna with its midpoint hanging from the eave, and endpoints near the ground, but this would place the wire of the antenna about a foot from the siding. …
Cyberherbalist
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