Phil Frost - W8II
  • Member for 8 years, 2 months
  • Last seen more than a month ago
  • United States
Effect of different metals for antenna elements
42 votes

Considering just electrical properties, the most significant parameter for your selection of antenna conductor is resistance. You want to keep the resistance to a minimum, because when current flows ...

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FCC sends "Notice of Dismissal" with quite threatening language just for denial of a vanity callsign?
38 votes

Isn't bureaucracy wonderful? Perhaps I can translate into plain English: Your application is in a dismissal status effective 03/09/2021 without prejudice in accordance with Section 1.934 of the ...

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Using a balun with a resonant dipole
38 votes

Well, the canonical answer is that the balun converts the dipole (BAlanced) to coax (UNbalanced). But what does that mean? For transmission lines (twin-lead or coax) to not radiate, each conductor ...

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Which HF bands are best during the day and which are better at night?
Accepted answer
27 votes

HF propagation over long distances is by skywave propagation, the reflection and refraction of radio waves between Earth's surface and the ionosphere. The ionosphere is a consequence of radiation from ...

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Why do amateur radio operators call an RF choke a balun?
26 votes

"Balun" is a portmanteau of "balanced" and "unbalanced". Anything made to interconnect a balanced and unbalanced load can be called a balun. A common-mode choke (like a ...

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Is it illegal to key up and not identify?
24 votes

Bad etiquette and illegal. Bad etiquette because anyone else scanning the repeater will hear your useless silence, and illegal by §97.119: §97.119 Station identification. (a) Each amateur station, ...

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Is free space path loss dependent on frequency?
Accepted answer
21 votes

Mathematically yes, the value of that equation increases with frequency. However, that's not to say there's some physical mechanism for frequency-dependent attenuation in free space. Rather, the ...

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How can I protect equipment against a lightning strike?
Accepted answer
19 votes

There's a lot that can be said about lightning protection, but it usually boils down to doing all of these things: make good, low impedance connections to Earth bond all Earth connections together ...

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What is a Gamma match in the context of the driven element of a Yagi antenna?
19 votes

Clearly capacitance is the key Capacitance is just one part of it. The gamma match in your question is three things: A sort of folded dipole, performing an impedance step-up A parallel shorted ...

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What is the effect of using different number of radials with ground plane antenna
Accepted answer
19 votes

An ideal vertical doesn't have radials: it's half a dipole sitting upon a perfectly conductive, infinite plane. Under these idealized conditions, its radiation pattern is identical to a dipole's ...

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Is there a simple, DIY, antenna suitable for HF receive only?
Accepted answer
19 votes

Receive antennas are the easiest thing ever. You just need two things: something that conducts electricity another thing that conducts electricity Attach one to the center contact on a BNC connector....

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Why do repeaters use cavity filters?
Accepted answer
19 votes

A cavity filter is inductors and capacitors. Something like this: (from amateur-radio-wiki.net) There are several reasons these are not constructed from more common discrete inductors and capacitors....

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SDR sampling bandwidth - do the bits per sample matter?
Accepted answer
18 votes

The bits per sample will affect the dynamic range of your receiver. There's a lot of math that I'm sure you can find, but here's the intuitive explanation: A digital signal can represent only ...

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Can I reduce RFI/noise at the antenna?
Accepted answer
17 votes

First, I'd be sure it's actually the antenna picking up the noise, and not something else. If you don't have a balun on that dipole, probably your feedline is picking up all the noise in your house. ...

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Using a balun with a resonant dipole
17 votes

A dipole is a particular machine for creating EM fields. The idea is to set up a voltage between the two halves of the dipole in such a way that an EM field is created and efficiently radiated away. ...

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Are antennas circuits?
Accepted answer
15 votes

What do you mean by "circuit"? Do you mean there's a loop of conductor from one side of a battery to the other, possibly with some other conducting components along the way? How about this circuit? ...

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What does a noise blanker really do, and what are the side effects?
Accepted answer
15 votes

Some types of noise are very short bursts of energy. Car ignition noise is one example. Power-line noise caused by switching triacs in light dimmers is another. For example, see the top image here: (...

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How Could Superheterodyne Receiver Ever Work?
Accepted answer
14 votes

The answer is simple: filtering. For example, let's say the desired signal is at 800 MHz, and the intermediate frequency (IF) is chosen to be 100 MHz. Mixing the 800 MHz signal with a 900 MHz local ...

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How to detect common-mode currents or “RF in the shack”?
14 votes

One way to tell is by its effects. Do you hear a garbled version of yourself in nearby speakers when you transmit SSB? Do GFCI outlets pop even though no one is being electrocuted? Does handling the ...

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What is a linear RF amplifier?
Accepted answer
14 votes

Google defines "linear" as "arranged in or extending along a straight or nearly straight line." Wikipedia tells me that "linearity refers to a function or relationship which can be graphically ...

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If two antennas of 50 Ω and 377 Ω have VSWR=1:1, then which one is more efficient?
Accepted answer
14 votes

With the information you've provided, there is no way to tell. Feedpoint impedance and VSWR have no relationship to antenna efficiency. See What is the relationship between SWR and receive performance?...

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How to reduce RF in the shack when using vertical HF antenna (no radials)
Accepted answer
14 votes

You may be surprised to hear this, but the antenna you describe isn't actually a vertical, but a dipole. One half of the dipole is the IMax-2000, and the other half is your feedline. You can not ...

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What is the relationship between SWR and receive performance?
13 votes

Simplified answer: There is no relationship between SWR and receive performance. There is one condition for this simplification to be true: the received RF noise floor must be above your receiver's ...

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How does moving a feedpoint off-center in a dipole affect the resonant frequency and resistive load?
Accepted answer
13 votes

I'm going to assume we are discussing ideal, resonant dipoles. Consider what's happening inside the dipole. Say you are transmitting a carrier. Say at one point in this carrier's cycle, the voltage ...

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Why do we use decibels in radio?
Accepted answer
13 votes

We use decibels because they are the most intuitive representation when our primary concern is signal quality. Signal quality changes not in proportion to the power added (in watts), but rather to the ...

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Is there an optimum Antenna Feedline Length for mobile installations?
Accepted answer
13 votes

In the absence of common-mode currents, then the optimum feedline length is 0, because a longer feedline only increases your feedline losses. These losses are due to the resistance of the wire, ...

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What is the definition of DX?
Accepted answer
13 votes

As Wikipedia puts it: The name of the hobby comes from DX, telegraphic shorthand for "distance" or "distant". There is no objective definition. If it's far enough that it might be a difficult ...

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SDR: Quadrature demodulation vs direct RF sampling
Accepted answer
13 votes

Sure, it would work. In fact, if you've ever used something implementing some digital mode that interfaces with an SSB tranciever, this is exactly what is happening. Many TNCs and most PSK-31 software ...

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Can SDR receivers be detected remotely?
Accepted answer
12 votes

You might be able to detect a regenerative receiver. This is because this receiver topology uses positive feedback to increase the Q of the tuned circuit. If the feedback is too much it becomes an ...

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When would we ever want to use a voltage balun in ham radio?
Accepted answer
12 votes

You'll find voltage baluns in plenty of circuits. For example, the QRP Labs receiver module: HPSDR Pennywhistle (twice, T1 and T3): The Elecraft KX3: A voltage balun can do some things a current ...

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