Browse over 10,000 Electronics Projects using the Page Numbering provided at the bottom of each Page.

Portable HF Transmitting Loop Antenna

Portable HF Transmitting Loop Antenna

This tunable magnetic loop antenna disassembles into small but rugged pieces and can be tuned from 14 MHz to 30 MHz.
For those unfamiliar with magnetic loop antennas, the principle behind them is simple. A small conducting loop (often on the order of 1/10 wavelength) is broken and a capacitor bridges the gap. The loop’s inductance, combined with the added capacitance, forms a high-Q tank circuit. A coupling loop or other matching network delivers power from a transmitter, exciting the tank circuit at its resonant frequency. By changing the capacitance, the antenna can be tuned over a fairly broad range of frequencies.

For any given tuning, bandwidth is very limited, due to the high Q of the circuit. Efficiency is limited by the resistance of the conductor. While the resistance of copper pipe is vanishingly small, the radiation resistance of such a tiny radiator is often even smaller. My loop, for example, has a radiation resistance of 20 milliohms at 14 MHz, but its ohmic resistance is more than 40 milliohms! The lost power (two thirds of it in this case) does little for global communication, though it may contribute ever so slightly to global warming.

Visit Here for more.

 

More Articles to Read

Single-Sided USB Charger
Single-Sided USB Charger
A FPGA controlled RGB LED MATRIX for Incredible Effects – the Hardware
A FPGA controlled RGB LED MATRIX for Incredible Effects – the Hardware
Using Nanotimers to Reduce IoT System Power Consumption by an Order of Magnitude
Using Nanotimers to Reduce IoT System Power Consumption by an Order of Magnitude
Replace a microwave’s beeping with the Windows XP startup sound
Replace a microwave’s beeping with the Windows XP startup sound
A DIY Laser Scanning Microscope
A DIY Laser Scanning Microscope
Reverse-engineering the surprisingly advanced ALU of the 8008 microprocessor
Reverse-engineering the surprisingly advanced ALU of the 8008 microprocessor
ESP8266 LED lighting: QuinLED v2.6 PCB
ESP8266 LED lighting: QuinLED v2.6 PCB
Switching LVDS Graphics in a Laptop Computer
Switching LVDS Graphics in a Laptop Computer
Teleknitting: TV-based string art
Teleknitting: TV-based string art
DIY Bubble Machine
DIY Bubble Machine
Start your day with Nerf target practice!
Start your day with Nerf target practice!
Teardown of a Peaktech 6225A
Teardown of a Peaktech 6225A

Top




Shares