radio Archives - Perfect 3D Printing Filament

A simple, low current mini-whip antenna #Radio #3Dprinting

Ray Ring at Circuit Salad posts the design and build of a simple, low current mini-whip antenna.

I decided to try using a small wide band E field type antenna with my newest receiver design… the Mini SDR, and the results have been gratifying. There many useful articles describing this type of antenna; so I won’t go into much detail about how it works. More or less it functions as a capacitive E field probe and therefore is very sensitive to EMI. However, if placed outside away from house wiring and provided with a modest local ground reference..the antenna is a good performer.

The circuit uses a JFET source follower and a BJT follower stage to provide impedance transformation of the Hi Z capacitive terminal to a 50 ohm Z drive for a transmission line. This circuit works fine but has some drawback, namely requiring 65mA of current and having a somewhat large input capacitance, which reduces performance with frequency. Ray says:

I decided to use a wide bandwidth op amp to simplify the circuit, reduce current, and provide a little voltage gain. The op amp I chose was one I have used before for RF amplification..the LT1818.

See more in the post and the video below.

The quest for an ideal cat beacon

Via the About using electronic stuff blog: One day their beloved cat Milo went missing

…fortunately the worst things I started to imagine were false. Mio came back home. We conclude she might be being locked by mistake in a barn from the neighborhood. That’s where started the idea of a small RF beacon for Mio. It should to be very small, at least a month of battery life, and can enable a kind of search with a receiver.

Some tests were done with three different RF modules:

A basic 315Mhz transmitter
LoRa module based on SX1278 at 433MHz
ST electronics module base on SPIRIT1 at 868Mhz

3D cases were printed for each module to use with a 3V coin cell. Studies started with the ST module:

I’m not sure about the reception range, is it enough to locate the beacon by walking around in the village? That’s why I should continue to study the other solutions. For example, I just saw it exists with a 433MHz ceramic antenna as well. Maybe it enables the use of the LoRa module at low power. They are still interesting as their modulation scheme makes the reception very sensitive.

This post is part 1 of a multipart investigation – we look forward to additional work.

Fake Walkie-Talkie for Fake Ghost Tours

Sean Hodgins walks us through his fake walkie-talkie project. It uses a radio module, GPS module, a VS1053 sound chip & more. The case is 3D printed to look like the vintage style handheld radios. The audio apparently is broadcast to a tour participants’ phone.

My best friend is launching an awesome project called Fake Ghost Tours and it’s absolutely hilarious. I had to make something for them!

The code is on GitHub here and the video is below. Great project!