List page: RF
Tag specific RSS FeedYour TV can see through walls:
(RF)This is a spectogram of the signal from a local TV station, as seen by an an indoor dipole antenna:
... read more.Inside a 1 dollar radar motion sensor
(Electronics) (RF)I recently got some cheap RCWL-0516 microwave motion sensors, mostly because I was wondering how China managed to make a radar for under a dollar:
... read more.Long range links with tiny radio modules
(RF) (Programming)WiFi and Bluetooth capable microcontrollers are very popular for hobby projects, but at the best of times offer a range of around a hundred meters. Indoors, with with walls and other obstacles, the usable range is often less then 20 meters.
... read more.The Principle of Error Correction
(RF)This article is not about any particular method of error correction, but about the general and rather simple principle that underlies all of them. The goal of error correction is to convey information as reliably as possible over a noisy communication channel using fixed power and time.
... read more.CDMA: Unpacking signals
(RF)There are a lot of cases where multiple devices have to communicate simultaneously over a single radio channel, or wire. Examples include mobile networks, 2 way radios, satellite communications and local area networking.
... read more.Modulating and amplifying signals with (electro)magnets.
(Electronics) (RF)This is a functional AM modulator (and with the help of a rectifier, an amplifier) built entirely out of transformers and inductors:
... read more.A simple wireless power demonstration circuit
(Electronics) (RF)
The core principal behind most wireless power systems is electromagnetic induction, where current flowing through a coil generates a magnetic field, and a magnetic field generates current in a coil.
... read more.A super simple directional microwave antenna
(RF)Variations of the “Cantenna” project have been floating around on the internet for a long time (mostly intended for 2.4 GHz WiFi). However, despite the abundance of calculator tools, there is a lot of conflicting information and very little in the way of explanations. I will try to explain how they work, the math for designing one, and provide measurements for 2.4 GHz WiFi 5 GHz WiFi, and a correct calculator tool.
... read more.Exploring NFC communications with a crystal radio.
(RF)NFC smart cards are commonly used for a wide variety of applications including contactless payments, building access control, and 2 factor authentication. These smart cards have no power source, yet are capable of bidirectional communication, storing data, and performing cryptographic operations. In each of these cards is a circuit straight out of the 1900s: The crystal radio.
... read more.Improved micro FM transmitters
(RF)Here are the full schematics for a (slightly improved) FM bug and beacon with a class-C output stage described in the last post.
... read more.Fun with tiny FM transmitters
(RF)It is surprisingly easy to make a working FM transmitter with just one transistor and a handful of passive components.
... read more.How to build a single transistor regenerative receiver
(RF)
A Crystal radio is a great project, just a coil of wire, diode, and variable capacitor creates a working MW AM radio. Unfortunately, even the best crystal radios are not very sensitive, you are unlikely to pick up more then one or two signals.
... read more.