# 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.

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### 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 ...
3k views

### 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?
2k views

### 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 ...
762 views

### 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 ...
467 views

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 ...
260 views

### 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....
1k views

### 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. ...
104 views

### 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.
374 views

### 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 ...
126 views

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

The suggestion has been made on various ham-related websites that improving the conductivity of the Earth around a ground rod produces a worthwhile improvement in the e-m radiation from a vertical ...
62 views

### 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 ...
128 views

### Comparing antenna effeciency

Let's say I have three dipoles, one is resonant at some frequency and is matched at the antenna, the second is shortened with loading coals and is also matched at the antenna, the third is shortened ...