I have spend many many hours over Internet with the hope to found a simple but accuracy watt-meter, and i have finally stumbled on the… Trinity Virtual RF Power Meter.
I encourage everybody that looking for a powerful simple power-meter to build the Trinity RF meter, designed by Daniel from rfcandy.
Most important features:
- Wide frequency range 10 MHz to 2.5 GHz.
- Measure down to – 60 dBm (0.001 uW or 0.225mV)
- Absolute and relative power measurement
- Present measurement in dBm, Watt, Volt and Screen Gauge Meter
- External Gauge Meter for accurate reading
- Digital filtering to reject 50/60 Hz noise
- Optical communication barrier to prevent noise
- DC input blocking
- No complex trimming
- Self-test with LED indication
(To reduce the cost, if you don’t want to buy the full kit, you can order only the pcb and the preprogrammed PIC).
I have recently buy from ebay a small board called « DDS Function Signal Generator Module Sine Square Sawtooth Triangle Wave « , first its not a DDS like you think … yes, the wave are produced by a Atmega16, and the signal is very dirty, there is no any output filter.
If you are looking for a true DDS generator, look here
I work right now on the Trackuino APRS Beacon, but especially a version for vehicles. Trackuino is a APRS tracker based on Arduino. Is intended for use by licensed radio amateurs. « By operating on the standard APRS frequency, the signal can be picked up by an Internet gateway and reported on www.aprs.fi, so anyone with an Internet connection can track the beacon in live ». I’ll add two temperatures sensors for monitor indoor/outdoor temperatures.
A first idea of the system, the project is under prototyping.
I have recently found two Si515 VCXO oscillator in my *old stock*, this kind of oscillator , produce by Silicon Labs, can be modulate in the « VC » version , with 10khz bandwitch.
The Si515 VCXO utilizes Silicon Laboratories’ advanced PLL technology to provide any frequency from 100 kHz to 250 MHz. Unlike a traditional VCXO where a different crystal is required for each output frequency, the Si515 uses one fixed crystal and Silicon Labs’ proprietary synthesizer to generate any frequency across this range.
So i decide to investigate if i can build something with this stuff …my parts are on 169mhz. Maybe some nice modules to transmit data, weather or whatever! …
Update 27/08, The output of VCXO is very dirty, i have added a low pass filter to eliminate spurious parasite. The values was calculated with RFSim99
I’ll come back in few week’s … after holidays, with some new projects, stay tuned :p
This hack, backward me in 1996/1998 during my college years, the pager system was at its peak, there was 3 commercial services and networks here, in France:
- TamTam, the Cegetel/SFR paging services, stopped in 1999, using ERMES protocol.
- KOBBY, from Bouygue Telecom, stopped during 2005, using ERMES/FLEX protocol.
- TATOO, from FT/Orange, using POCSAG, the only still functioning, right now, since 2000, exploited by a Deutsch company, E-Message.
The Kobby and TamTam use VHF frequency band (Around 168Mhz in my memories), and the TATOO receiver use UHF band (466.025 MHz – 466.05 MHz – 466.075 MHz – 466.175 MHz – 466.20625 MHz – 466.23125 MHz.). POCSAG protocol is basically easy to decode, with software like POC32 or PDW
« POCSAG is an asynchronous protocol used to transmit data to pagers. The name comes from Post Office Code Standardization Advisory Group, this being the British Post Office which used to run nearly all telecommunications in Britain before privatization. The modulation used is FSK with a ±4.5 kHz shift on the carrier. The high frequency represents a 0 and the low frequency a 1. Often single transmission channels contain blocks of data at more than one of the rates. » wikipedia
Bellow is a dessication of a MOTOROLA MEMO Pager Receiver (Tatoo, commercial name).
The pager is composed of two circuits, a board with a displaying circuit for the lcd, a vibrator, a piezzo buzzer, a backup batterie for the RTC, and a MC68HC68 microcontroler, he probably contain the program to decode/translate the signal and pager ARP address.
The another board is dedicated to RF reception, you can see a antenna, simple loop of metal, probably a narrow rf input filter, and a strange unidentified IC « 99Z32″, maybe a RF IC Receiver …
Now the goal is to identified the pin’s function on the connector. I have already put my Rigol probe on the Pin 4, and i can see a low/high signal (see bellow). I’ll will try to translate this signal for PDW or POC32 software soon. Any help is welcome.
I started to listening the signal (blue) from my UBC 785 on 466.20625 Mhz, in parallel with the signal from the pager (yellow), it seem to be a inverted signal.
After feed the signal through a Max232, but no good result with the decoder software! *sic*, maybe need a little amplification before …
Few months ago, i have been looking for a robust easy FM broadcast solution, basically, i want simple solution, not the classic complex plan like > Stereo encoder = PLL = VCO = PA … < after some investigations i have found the NS73M FM Transmitter module from Niigata Seimitsu Co is a hight quality transmitter IC, can be controlled by a controller (via SPI/I2C), the features are:
87.5 – 108 Mhz Coverage
Very Small package
I2C or SPI control
I have made 3 boards for this projects:
ArduiFM_Unit, its the main board with the NS73 and controller (Atmega328P)
BackConnector, the back board with input-sound, jack/RCA, and RS232 connector (future option for RDS)
Control_Cmd, is the front board with the button, up/down/backlight/set
The one of disadvantage have found is not RDS possibility because the sound is already modulated and mixed into the NS73, you cannot add signal.
right now, you can see the main µC board, LCD, audio connector, IHM board mounted, a DB9 connector is installed for a RDS future option. Now, the project need a power amplifier … stay tuned.
In the past two years, i have released two version of GPS logger, with a lot of default like, poor autonomy, need to take off the sdcard to get the log, no function to upgrade the code easily, by the way, i have redesigned a new version with a lot of news feature, see bellow.
- Better autonomy.
- Be lightweight and portable.
- Be rechargeable easily.
- Got log directly from USB.
- Upgrade code via IDE Arduino through USB.
- Future options implemented for improvement.
- Many more …
- µC Section
The hardware run around a Teensy 2 this very small board run with a ATMEGA32U4 8bit AVR 16 MHz Processor, 25 I/O.
Issue encountered: On the first board prototyp i have mounted a PA6B without problem, when i powered up the pcb for the first time the GPS try to lock to satellite, in this case the 3d fix output should continuously output one-second high-level with one-second low-level signal, in theorical, regarding the data sheet, when the GPS is locked on the satellite, the output pin should continuously output low-level signal, but in my case, the output give me a high level signal, probably du to the firmware, so i decided to re-upgrade with the default factory firmware, the software, firmware, and guideline are available here. Be careful, the factory firmware set the baud rate to 9600bps, not 4800.
To ensure fast hot start, the batteries pin is connected directly to the li-ion batt, the receiver has valid time, position, almanac, and ephemeris data, enabling a rapid acquisition of satellite signals.The voltage should be kept between 2.0V~4.3V. So, its OK.
- Power Section
The power come from a BlackBerry batteries (1100mha in this case), a charge pump, DC/DC converter (LT1302) give 5v/600ma from the 3,7v batt, available in SOIC-8 package, it’s a very powerful converter and can start as low as 2v. Two LP2981 give two separate 3,3v power line for the GPS and Teensy.
- Charging the Batt
Power charging is assumed via a LTC4054-4.2 a standalone Li-Ion Battery Charger with Thermal Regulation in ThinSOT package, the charging current is set with a simple resistor, i found 1,5k good value for around 1h30 of charge, the charge control is drive thought a N Channel MOSFET (2n7002) the signal come from the Teensy, just plug the USB cable and push the button to turn the PIN 17 High. Another option, is play with a « usb_configured » variable inside Teensy’s USB code which indicates if the PC has configured the USB device. Accessing that variable is the best way to know if a PC is connected to Teensy. But its not implemented yet.
Original code come from Adafruit, and it run on Teensy with some majors modification.
I have removed unused libraries like avr/sleep.h, and GPSconfig.h header, the SoftwareSerial.h, NewSoftSerial.h libraries was replaced by <AltSoftSerial.h> for better performance. More informations are available in the commented sketch.
Loading the code
- First, download and install Teensyduino software and libraries, complete instruction are here.
- Download and unpack AltSoftSerial Library to /libraries directories.
- Run Arduino 1.0 and load the code.
- Select Teensy 2.0 in the tool menu.
- Select USB Type Disk SD Card + Keyboard
- Finnaly, select CPU Speed to 8Mhz
A « N Channel MOSFET » (2n7002) is connected to the Enable pin of GPS, in case of you need to drive the GPS. In normal operation keep Enable Pin floated or connected to Vcc.
Power saving method
Since is a embedded project, for better batteries life, we need to run with a maximum save of power, some good way:
- Run Teensy and GPS with 3,3v power supply.
- Lowering the clock speed at 8Mhz.
- Write GPS data only every 10 seconds, in hiking we no need very accuracy in fact.
- The data is stored only when the GPS give valid fix.
- Disabling the « Analog to Digital Converter ».
With this power measure, we can switch from 27.3 mA power consumption to only 10.6 mA
The total power of TeenLogger is around 45ma with GPS satellite tracking, and give around 15/17 hours of complete logging.
I have recently build a RF power meter, called « Trinity FR Power Meter » from Daniel’ webpage , in my case in need to measures often up to +-/30-40 db, so i need to put attenuator between power source and RF power meter to avoid saturation or rf-in stage destruction…
Here some links to calculate easily a Pi attenuator:
I have made two versions, 40 and 50db, put in small rf enclosure box, with two BNC connector RF In/Out: