Archive for the ‘Ham’ Category.

6×1 antenna switch

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

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Cheap sh*t magnetic pickup

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

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Adjustable gain LNA

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

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Simple Rh, T and p sensor with UART communication

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

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Pressure, temperature and humidity sensor based on MS5637 HDC1080 Rev.2

Gal ordered some PCBs from PCB-Way a while ago. It was multiproject panel with several PCBs. One of the modules was double sided revision of the Pressure, temperature and humidity sensor based on MS5637 HDC1080 which was posted while ago.

Pressure, temperature and humidity sensor based on MS5637 HDC1080

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Simple HF amplifier for QRSS beacon

This is 5 minutes soldering project. There is no schematic, just simple circuit, something between “dead bug” and conventional PCB design. I did this in two steps. First attempt was complete failure. Local OM told me that any power mosfet can operate as power amplifier for HF. Ok, maybe not just any. I tested with couple of them including IRFZ24N. Finaly I took “proper”  MOSFET for higher frequency and the circuit worked pretty good:

Simple output stage for QRSS beacon assembled in "mixed" technology

Simple output stage for QRSS beacon assembled in “mixed” technology

I will briefly describe this quick and simple project and I hope readers would enjoy it.

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USB/RS485 converter on a double sided PCB

USB/RS485 module on a single sided board worked successfully for several months. The code is now stable and I decided to order small batch of double sided PCBs for this project. Here is documentation:

RS485/USB interface on a double sided board

RS485/USB interface on a double sided board

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UV index sensor with RS485 interface

This is another sensor in weather-sensor series. It is based on silabs Si1133.

Schematic:

uvindexsch

Si1133 Sensor schematic with RS485 interface

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Pressure, temperature and humidity sensor based on MS5637 HDC1080

This is anothe small module to measure air pressure, temperature and humidity. Two sensors are on-board: MS5637 and HDC1080. Microcontroller is small cortex M0 in TSSOP-20 housing from STM: STM32F070CxP. The SN65HVD72DGKR provides RS485 interface functionality with half duplex mode. Voltage regulator, reverse polarity protection and some LED indicators are provided on-board. Complete module is 10x55mm, produced on single-sided PCB, easily producible in every home lab with proto-PCB capability.

RH, T and air pressure sensor with RS485

RH, T and air pressure sensor with RS485

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USB to RS485

Testing of sensors with RS485 using PC without proper interface is not possible. Since RS232 interfaces are very rare, the interface should be hooked to USB. The interface between USB and RS485 can be soldered with one of the many FTDI interfaces with added RS485 driver, or bought as assembled module. There is always the third option. I made it from scratch.

I took smallest STM32F0 with USB and UART interface. The best thing with UART in the STM32F0 is that signal for driver enable is provided within hardware. The complete pinout of the microcontroller is:

pinout

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