Amateur Radio Stack Exchange
Amateur Radio Stack Exchange

Questions tagged [efficiency]

Use this tag for questions that relate to the efficiency of a system or a component. The efficiency is the amount of useful work performed by the system or component (in radio applications, typically its output power), divided by the total amount of energy provided to the same.

18 questions
19
votes
3 answers

What makes cellphone transmissions so energy cheap?

The modern cellphone can carry on a full duplex conversation for a time period measured in hours on a battery half the size of my handheld transceiver. My transceiver can barely receive for that length of time on its pack, nevermind transmit, and…
Adam Davis
  • 12,095
  • 2
  • 45
  • 106
11
votes
3 answers

Could a weather balloon make a good antenna?

I can't afford a massive tower, but I can get a weather balloon. What kind of set up would work best to get the maximum efficiency out of altitude?
Muze
  • 1
  • 3
  • 11
8
votes
3 answers

What sort of radiation efficiency can one expect from a folded dipole?

It is pretty well established that folded dipoles have much greater acceptable-SWR bandwidth than ordinary dipoles. Radiation efficiency is simply the quotient of radiated power to the antenna feedpoint input power. Seeing that folded dipoles are…
user
  • 4,828
  • 2
  • 29
  • 59
8
votes
3 answers

Estimating the efficiency of a shortened (loaded) antenna

Recently I've build a trap dipole for 20/40/80m bands. I followed an article by John DeGood, NU3E and got following measurements: From balun to 20m trap: 485 cm From 20m trap to 40m trap: 362 cm From 40m trap to the end of the arm: 530 cm You can…
Aleksander Alekseev - R2AUK
  • 4,262
  • 12
  • 48
4
votes
3 answers

Radials on a vertical, spread out evenly or not?

To have a groundmounted quarter wave vertical with a decent efficiency you need at least 16 radials. So normally you would spread them out on the ground evenly around the base. This would give an angle of 360/16 = 22,5 degrees between two…
ON5MF Jurgen
  • 803
  • 6
  • 18
4
votes
2 answers

Calculation of transceiver current draw

My radio manual says its current draw is 22A. But in my naivety I would have calculated as follows: If the radio 'put out' 100W and I have a 13.8V supply then (using the formula power = VxI) 100W/13.8V = 7.2A. So, it looks that I'm way out…
KHWP
  • 143
  • 5
3
votes
3 answers

Is The Lowest Antenna Terminal Feedpoint SWR Always Optimal?

Intuition might lead one to believe that the antenna configuration with the lowest SWR(50) across its input terminals would provide the best radiation efficiency for the antenna system. But is that always a correct assumption?
Richard Fry
  • 2,922
  • 6
  • 18
2
votes
3 answers

Why are variable capacitor plates made from aluminium?

This question comes from doing some research into small magnetic loop antennas for HF. For transmitting, these antennas are often designed with a big, variable, air (or vacuum) tuning capacitor (e.g. butterfly-style). I understand that the currents…
captcha
  • 1,094
  • 10
  • 21
2
votes
1 answer

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

A common belief among amateur radio operators is that the radiation efficiency of a vertical monopole driven against the Earth is much less than that of an elevated, horizontal dipole of the same aperture (and other things equal). But is that belief…
Richard Fry
  • 2,922
  • 6
  • 18
2
votes
2 answers

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

Some antennas have very limited specifications with no stated efficiency. For example, this antenna has the following specifications: Frequency Band 902-928 MHz VSWR <2.0:1 Impedance 50 Ω Gain 9…
DurandA
  • 175
  • 1
  • 6
2
votes
1 answer

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

This is a rather common belief among amateur radio operators, but is it true? A NEC analysis provides some insight on this concept.
Richard Fry
  • 2,922
  • 6
  • 18
1
vote
2 answers

Regulated Power Supply vs Class 2 AC/DC Adapters

I'm wondering if it would be more efficient for me to replace several AC/DC adapters (linear, non-switching) with a regulated power supply? Two of the adapters get very warm and are rated 9 watts input and 3.6 watts (12 volts * 300 ma) output. So…
Aaron Kreider
  • 155
  • 5
1
vote
2 answers

For a given transmitter mains wattage, is its TPO wattage affected by the transmission frequency?

Using a 1000 watt (mains, not TPO) transmitter capable of theoretically transmitting on any frequency, would TPO change based on frequency at which we transmit (LF, MF, HF, VHF, UHF,...)? I mean, is it more expensive in terms of wasted power to…
Redoman
  • 293
  • 2
  • 11
1
vote
3 answers

Bandwidth, Q-factor, Radiation Eff calculations

Is it possible to give approximate answers about what an antenna is capable of? There are a lot of formulas out there, but every single one I found is based on actual measurement; input, output, SWR etc. For example, I want to build a dipole for 450…
Aard
  • 41
  • 2
1
vote
2 answers

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

It's simply a bromide amongst hams that you need to match the output impedance of a transmitter to the input impedance of an antenna, but I never thought through the implications of this until I came across this summary in a reputable textbook: Of…
natevw - AF7TB
  • 7,219
  • 2
  • 23
  • 58
1
2