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Archive for the ‘Ham’ Category.
Two PCBs from earlier projects were used in this project:
Finished particle sensor in housing, ready for the TTN
This simple Helical Antenna can be used for most LoRa (and other small wireless device) applications, where space constraints exist. The construction is simple, made from wound solid Ag plated copper wire taken from piece of coaxial cable.
Helical axial antenna for 868MHz
Two options how to use this antenna on the PCB modules
Continue reading ‘Small “rubber-ducky” helical antenna for 868MHz’ »
This is simple antenna for 868MHz built in 5…10 minutes. Take about 10cm of RG214, a plate of PCB with the copper at one (or both) sides. Remove the coax shield and inner dielectric on one side in length of about 85mm. You will cut this to proper length during SWR measurements.
Simple antenna made with piece of coax and piece of old PCB.
Continue reading ‘Quick and dirty 868MHz antenna in 5 minutes’ »
This is description of coaxial collinear antenna for 868MHz applications. I designed this for Lorawan gateway.
Antenna tested with lorawan gateway
Continue reading ‘Collinear antenna for 868MHz Lorawan Gateway’ »
I will descvribe here the USB interface between the redio station and the computer which I recently developed and tested. This post is a continuation of the first part, where I described a simple interface for controlling two digital lines using the USB / Serial Converter, where I presented simple interface to control two digital signals (e.g. PTT and CW). This time I will describe an interface that combines more functions:
I had some implementation issues with the microcontrollers and USB virtual com ports, which I have described in detail in the previous contribution, I decided it’s better using the tested solutions. The block diagram of the interface is swhown in following picture:
Block diagram of the interface
Continue reading ‘Tiny, isolated USB to Xcvr interface (PTT, Audio, CAT, …)’ »
In this post, I will first introduce some of the basic technical background of the control of the transmit signal (PTT) and other signals (eg CW or linear activation). The second part will describe the interface development and the final product.
Standard DB9 male connector
This is complete project for 1×6 antenna switch. It was bult in more than 50 pieces around the world and performs really good. Even big guns use it for their systems. The project was designed with help from other OMs (S55O, S59MA, S50LD, S51CT, S51ZJ, SM2WMV/SJ2W and others).
6×1 antenna switch
Do you ever wondered how much magnetic field garbage is around you? This is cheap and easy build to measure magnetic noise or to compare which switching supply is more sh*tty.
Near field probes are nothing new. It’s easy to find one via web search. Here is one good reference for H and E field probes which I found via google image search:
EMC near field probes for H and E field
Low noise amplifiers are very useful. I built one with single BFG425W transistor with adjustable bias current. The schematic diagram is very simple:
LNA schematic diagram
and the PCB is 20x24mm:
LNA PCB
The Pressure, temperature and humidity sensor based on MS5637 HDC1080 originally (Rev. 2) operates via RS485 interface and multidrop HDLC-like protocol. I decided to simplify this for use with Raspberry Pi, arduion or any other mass platforms. First, I took away the RS485 transceiver and second, I simplified the communication.
First adaptation was easy:
Remove RS485 driver and connect Rx/Tx to A/B
Continue reading ‘Simple Rh, T and p sensor with UART communication’ »
