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8 votes

Calculation of transceiver current draw

Some of both! It's normal for a linear power amplifier for HF to be something like 50% - 60% efficient. So to make 100W, the radio probably needs 170 - 200 W. There are other power draws in the radio,...
hobbs - KC2G's user avatar
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7 votes
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Radials on a vertical, spread out evenly or not?

The purpose of the radials is to increase the effective ground conductivity, thus reducing losses. As you propose to have 16 radials but in four groups, I'd expect the efficiency to be somewhere ...
Phil Frost - W8II's user avatar
6 votes
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Calculation of transceiver current draw

The rest (of the current) is why your transmitter requires heat sinks (and/or airflow for thermal dissipation). Linear amplifiers are usually not anywhere close to 100% efficient. A high SWR might ...
hotpaw2's user avatar
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6 votes
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Estimating the efficiency of a shortened (loaded) antenna

I applaud you for diving into this topic. The notion of trap efficiency has been driven largely by antenna marketing FUD (Fear, Uncertainty, and Doubt) with implicative phrases such as "no lossy traps"...
Glenn W9IQ's user avatar
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5 votes

Estimating the efficiency of a shortened (loaded) antenna

"The ARRL Antenna Book" uses the lumped circuit model for HF loading coils which is an inaccurate thing to do in a distributed network circuit with reflections. The helix model in EZNEC presents a ...
Cecil - W5DXP's user avatar
5 votes
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Could a weather balloon make a good antenna?

Hoisting a vertical antenna with a balloon seems to be a fairly-common trick for Field Day. A web search for tethered balloon antenna returns many interesting ...
rclocher3's user avatar
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4 votes
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Regulated Power Supply vs Class 2 AC/DC Adapters

If by “a regulated power supply” you mean specifically a non-switching one as your second paragraph, then “a regulated power supply” and “an AC/DC adapter (linear, non-switching)” are exactly the same ...
Kevin Reid AG6YO's user avatar
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4 votes

Could a weather balloon make a good antenna?

Please reconsider your weather balloon hoisting scheme, at least if you plan to use helium as your lifting gas. Helium is a non-renewable resource derived from fossil fuel (natural gas wells are the ...
Zeiss Ikon's user avatar
  • 4,107
4 votes

Radials on a vertical, spread out evenly or not?

The effects of using unequal length buried radials on the radiation patterns of a monopole are not very significant, as shown by the NEC4.2 analysis below.
Richard Fry's user avatar
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4 votes
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How to compute the efficency of an omnidirectional antenna from its gain?

There isn't a way to calculate efficiency from gain, in general. If you had the gain for every possible direction then you could integrate over the entire sphere and calculate the total radiated power ...
Phil Frost - W8II's user avatar
4 votes

How to compute the efficency of an omnidirectional antenna from its gain?

Given the information supplied, and no other independent measurements, you can't really tell. You could guess, by looking at the size of the antenna, which is ~3.25 wavelengths long, and figuring that ...
hobbs - KC2G's user avatar
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4 votes

What's the maximum possible "DC input to radiated RF" energy efficiency of a radio transmitter system?

A partial answer, more about matching than about transistor amplifiers: you need to match the output impedance of a transmitter to the input impedance of an antenna No this is the wrong way around. ...
tomnexus's user avatar
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4 votes
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Can the reactance on a transformer load, be "corrected" on the transformer primary, to improve transformer efficiency?

Is the reactance on the output of a transformer, that is connected to a reactive load, seen on the input of the transformer? Yes (transformed by the transformer's impedance ratio, and modified by any ...
hobbs - KC2G's user avatar
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3 votes
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Lumped Solution for Impedance Matching vs. Ferrite Transformer

The statement above is...? True or false, depending on the losses of these components at any given operational frequency, and the bandwidths you need to achieve, as well as the impedance curve of ...
really not Constantine A. B.'s user avatar
3 votes

Radials on a vertical, spread out evenly or not?

As long as the radials are symetrical it will make no noticable difference. A single radial opposite the other half of a dipole or 2 radials opposite each other will yield a reasonable pattern. The ...
Keith Martineau's user avatar
3 votes

Why are variable capacitor plates made from aluminium?

Copper indeed would be better. Silver would be better yet. These materials, however, are heavier and less rigid than aluminum. So there is that. To aluminum's advantage, it can be laser cut at very ...
Gan Uesli  Starling's user avatar
3 votes

Does Improving Earth Conductivity Near a Buried Ground Rod Improve Antenna System Performance?

Below for some perspective on this topic is a NEC4.2 analysis showing the difference in performance of a 40m, 1/4-wavelength, unloaded, base-fed vertical monopole antenna system when driven against ...
Richard Fry's user avatar
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3 votes

What Are Some of the Most Important Characteristics Applying to the Radiation of Monopole Antenna Systems?

VERTICAL MONOPOLE, EARTH, and BURIED RADIALS as FACTORS in ANTENNA SYSTEM RADIATION EFFICIENCY Considerations: The components shown in the ...
Richard Fry's user avatar
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2 votes

Do Buried Radials for Vertical Monopoles Need to be No Longer than the Monopole Itself?

Below is a NEC4.2 study comparing the fields radiated by an eighth-wave, series-fed vertical monopole driven against sets of thirty buried radials of 1/4 and 1/8 wavelength (other things equal). The ...
Richard Fry's user avatar
  • 2,922
2 votes

Is The Lowest Antenna Terminal Feedpoint SWR Always Optimal?

Below is a table showing that this is not always the result, for every antenna configuration. In this case, the configuration with the lowest system SWR(50) also has the lowest system radiation ...
Richard Fry's user avatar
  • 2,922
2 votes

Is The Lowest Antenna Terminal Feedpoint SWR Always Optimal?

No, minimizing the SWR at load (antenna) interface is not sufficient for the minimization of the end-to-end loss at system level (Transducer Loss). A Figure (screenshot) might be helpful for ...
Jens's user avatar
  • 181
1 vote

Can the reactance on a transformer load, be "corrected" on the transformer primary, to improve transformer efficiency?

Don't lose sight of the purpose of a balun or unun. While baluns generally can be combined with impedance transformers, that's really a separate function that just happens to be combined into the same ...
user10489's user avatar
  • 6,485
1 vote
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What's the maximum possible "DC input to radiated RF" energy efficiency of a radio transmitter system?

The maximum power transfer theorem (MPTT) assumes that the source impedance and voltage are fixed, and asks you what load impedance gets maximum power in the load, assuming that the source is an ideal ...
Simon Farnsworth's user avatar
1 vote

How Accurately Does NEC-based Antenna Software Calculate Vertical Monopole Antenna System Radiation Efficiency for "Far-Field" (Only) Conditions?

Below is a graphic of a short monograph addressing this issue.
Richard Fry's user avatar
  • 2,922
1 vote

Does Improving Earth Conductivity Near a Buried Ground Rod Improve Antenna System Performance?

If by improving conductivity, you mean flooding several acres or square miles with ocean (or saltier) sea water (or via natural intrusion near a low lying shoreline or wetlands), or installing a solid ...
hotpaw2's user avatar
  • 13.5k
1 vote

Estimating the efficiency of a shortened (loaded) antenna

Calculating the current distribution on the antenna might be a way to determine the radiation resistance, but to arrive at efficiency will require incorporating loss in the equation. It will be tricky:...
Phil Frost - W8II's user avatar
1 vote

Bandwidth, Q-factor, Radiation Eff calculations

The radiation efficiency of all antenna systems is the quotient of its radiation resistance and the sum of the real (energy-dissipating) resistive losses comprising that system. Some M-o-M software ...
Richard Fry's user avatar
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