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First, happy new year for everyone, best for 2018.

I know its awaiting project for some people. APRS Tracker with DRA818V is under test.

Some issues with PCB and software has been discovered.

– GPS head don’t send correctly NMEA sentence, probably du to header connector problems. FIXED

– Some crystal issue, maybe due to PCB trace impedance. Trying to compile the code and running with the internal 8mhz oscillator. Also can be a good solution to avoid stability problems with temperature variations. I have also designed the PCB for a external SMD crystal @16mhz.

– Need some rework about ADXL335, to enable GPS only when movement are detected. Currently under testing.

– I have discovered that the PD pin (power saving control) of DRA module, need around 0.6/0.7v to wakup before sending PTT activation. It’s can be achieved by using PTT command also, but i have find a rising time, the module need to set PD high around 2000ms before sending data. It’s may be can be fix through a trick into the software. Right now best solution is to tie PD pin to Vcc, but with the cost of 70ma, instead 1uA with sleep mode. Sadly the datasheet of DRA module didn’t give lot of information’s.

– I will finally use RA08H1317M module for PA, because it can by powered directly from 12.5v and give 8W output power.

– FakeSmartBeaconing seem to work …

Measure

Dummy Load 50 Ohms – DC to 3Ghz

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N’ayant pas de charge non rayonnante dans mon labo, j’ai tenté l’aventure d’en fabriquer une avec des matériaux de recuperation, le tout d’après les plans d’ON6TN, www.on6tn.be, helas j’ai eu des problèmes d’etancheité et de rouille au bout de quelques jours …

Je me suis tourné vers ebay, ou l’on trouve pour moins de 2€ (port inclu), des petites « charges » de 50 ohms pouvant encaissé plusieurs centaine de watts.

Pour la construction j’ai opté pour un tube de laiton (pas d’oxydation) de diamètre 40mm, et de longueur 200mm, deux chutes de laiton ou de cuivre feront l’affaire pour faire des bouchons aux extrémités. La charge trempe dans de l’huile de lin, relié via un bout de coaxial 50ohms sur un connecteur N. Le tout soudé au fer a étamé.

No bad.

APRS

APRS IGate with DireWolf and MC3362P receiver

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Currently under testing, a APRS iGate with Raspberry under DireWolf, and a good sound card SoundBlaster3 USB, didn’t want to use a dedicated VHF receiver for that so i have take a old good MC3362P from my first 2 meters receiver, old board from F5RDH project, i have removed the local LO (L/C), and replaced it by a ADF4351 (integrated voltage controlled oscillator), in Europe APRS QRG is 144.800Mhz, so i need 144.800 – 10.7 = 134.100Mhz, some lines of code with a Arduino can easly program ADF4351 to generate this frequency, the ADF’ board come from ebay for some $$, Mc3362P need around 80~100mv of level. The LO give around -5db output, that just enough for the mixer.

MC3362P Low-Power Narrowband FM Receiver
Rx144 part list
Rx144 board and pcb
Modified schematic

RED areas need to be removed:
-frequency control P1 and component around,
-P2 squelch control, tie R12 to Vcc,
-remove audio amplifier U2, no needed
-remove local oscillator L/C, L2, C9, and R4, put 100nf on pin 21, connect pin 22 to your LO (134.100) with 100nf.

MC3362P is a « obsolete » part since around 2005′ year, but still available on market, some sellers on ebay, or Futurlec (1.90$)

Go to github and install DireWolf on your Raspberry

Dire Wolf is a software « soundcard » AX.25 packet modem/TNC and APRS encoder/decoder. It can be used stand-alone to observe APRS traffic, as a tracker, digipeater, APRStt gateway, or Internet Gateway (IGate). For more information, look at the bottom 1/4 of this page and in https://github.com/wb2osz/direwolf/blob/dev/doc/README.md

All part are inside a 1U rack, recycled from old switch

Rf Input on  BNC connector, RJ 45 to connect the Raspberry, external USB port, and power.

Power part

The MC3362P receiver with the LO on 134.100Mhz.

On top, the hard drive on the usb hub, at bottom, the Raspberry Pi with the USB Sound Card.

TO-DO: Connect the RJ45 socket to Rpi, & install a properly safety shut down power system for Rpi.

MCU-µC

Small, cheap UPS for Raspberry

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As you know, if you use Raspberry, the operating system on SdCard is very fragile, that the reason you need to power off properly the system to avoid corrupt files system. This small circuit can help you.

There is no PCB, all component was recycling, coming from old stuff, 10000uf capacitor, 3A diode from computer power supply, the battery from cell phone or old wearable device, except the StepUP converter and the battery charger are from ebay, for 1$ (shipping included).

The main power supply feed the relay coil and the Raspberry through D3, big capacitor is here to avoid voltage drop out, and D3 is here to avoid voltage feedback and latch delay for the relay.
Vcc 5.5v is converted to 6.5v. During this time the TP4056 li-po charge the battery. If main power fail, the relay RL1 turn to initial state, 3.7v from battery can feed MT3608, and keep supply the Raspberry, in my test i can still have Rpi under good power condition during around 10min, so it’s work fine with « short » power failure.

I plan to implement a power management system to power off properly the Raspberry (through GPIO), 10 minutes or more is just enought, may be with a Arduino Nano, or with a simple timer with capacitor and transistor.

My testing conditions was with a Rpi B1, and wifi dongle, with LCD touch screen, the power was +5.5v 2A.


Domotic, Gadgets

Monitor your Raspberry enclosure

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A small gadget to monitor the power supply and enclosure temperature of your Raspberry.

My Raspberry Pi server host a OpenVPN service, Onion Pi Tor proxy access point, and EasyIOT.

The power supply come from a old Pc, and the enclosure from a plexi-glass slab.

It’s based on Arduino, so there is no schematic, sketch is available here, it’s just a Atmega328P with a DS1820 temperature sensor,
analoginput A0 is used to monitor Vcc power supply through a voltage divider.
I2C interface for LCD2x16 is wired to A4/A5 pin. You will need <LiquidCrystal_I2C.h>, <OneWire.h> libraries.

You can defined the threshold in the code, to monitor Vcc value, more or less than 5 volts for example, that the same for temperature.

Alert will be displayed on the screen, also a digitalwrite() (choice what pin you want), can drive a fanless, LED, relay to off the power-supply, or drive a Raspberry  I/O pin (emergency power-off, email alert …)

Gerber file available