ESP8266 Temperature and Humidity Web Service

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After I successfuly tested HTTP server using Arduino and Ethernet Shield, I decided to try to accomplish the same thing using wireless connectivity. I decided to use ESP8266 on NodeMCU board. That is microcontroler with wireless interface all in one package, and quite low priced which makes it interesting for various purposes.

ESP8266 is supported within Arduino IDE which is big plus, as one can use the same development environment.

Soon I realized that popularity of this platform is well earned. It was very easy to set it up. Most of the trouble is setting up Arduino IDE to compile and upload to board. […]
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Arduino Temperature and Humidity Web Service

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I needed simple device that is able to measure temperature and make it available for collecting that info from remote places via Internet. Arduino platform was the first thought and it ended up as expected: nice and simple.

For hardware I used Arduino UNO, Ethernet Shield and DHT22 Temperature and Humidity sensor.

Ethernet Shield pinpoint matches Arduino UNO so it is simply attached on top of it. It provides RJ45 connector for ethernet connection and SD card socket which I did not need for this small project.

All pins on Ethernet Shield are pass-through which means all Arduino pins are available on the this shield too. […]
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Baofeng LiIon charger modification

My idea was to be able to use this to charge Baofeng radio in various power conditions including in my car and this voltage was a problem. I noticed comments that charger should not be connected to higher voltage than 10 Volts. So I modded charger to fit higher voltage. baofeng-charger-mod

Iron Powder Toroid Cores Color Codes

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Iron Powder Toroid Cores part numbers are presented using format Tddd-m where dd is core diameter in tenths of inch and m is material grade. Also, cores are color coded to represent material grade.

Material grade defines frequency range core may be used for. There is no strict standard for coding but for informal purpose this table can be used.

Color Frequency
0 Tan/Tan 50 MHz – 350 MHz
1 Blue/Clear 150 kHz – 3 MHz
2 Red/Clear 250 kHz – 10 Mhz
3 Gray/Clear 20 kHz – 1 MHz
4 Blue/White 3 MHz – 40 MHz
6 Yellow /Clear 3 MHz – 40 MHz
7 White/Clear 1 MHz – 25 MHz
8 Orange/Clear 20 kHz – 1 MHz
10 Black/Clear 15 MHz – 100 MHz
12 Green/White 30 MHz – 250 MHz
15 Red/White 150 kHz – 3 MHz
17 Blue/Yellow 20 MHz – 200 MHz
42 Blue/Red 30 kHz – 80 kHz


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LCD ESR tester – multimetar

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Zamislite da možete da imate univerzalnim merni instrument koji meri sve: otpornost, kapacitet, induktivtet, diode (obične i zener), tranzistore (bipolarne, FET, MOSFET, JFET), tiristore…

Otiđite u maštariji još dalje: zar ne bi bilo sjajno da ne morate uopšte da se cimate nego prosto ubodete komponentu u instrument a on sam prepozna šta ste uboli i izmeri karakteristike?

I povrh svega, da to lepo pregledno prikaže na ekranu?

Luda ideja, ali još je luđe da to u stvari postoji i to čak radi i više nego što ste izmaštali. A najluđe je što je vrlo jeftino. Ovakav tester košta oko 15 do 20 dolara, a meri maltene sve što ubodete u njega. […]
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APRS/Packet Radio audio cable for connecting Kenwood/Baofeng/Wouxun to Samsung SIII

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Here is a schematics of audio cable connecting Samsung SIII to Kenwood/Baofeng/Wouxun or other compatible radio.


Samsung SIII uses four pin 3.5 mm TRRX connector that differs than standard TRRX.

This cable can be used for APRS/Packet Radio. Most popular program for this purpose is APRSDroid. ALso can be used for Echolink, audio recordings, or similar usage.

You have to adjust volume output on both Samsung phone and radio to avoid distortions. Cell phone cannot control PTT of radio so you have to turn on VOX on radio to enable triggering TX when signal should be transmitted.

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Remote Controlled Antenna Switch

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Antenna switch in a stack

Remote controller for antenna switch in a stack

As I live in apartment building I have apparent problem with setting up ham radio antenna. The obvious place to set up antenna was the roof as it  is easily accessible. Due to small space and me not wanting to make mess of a wires, I decided to use compromise vertical multiband. A friend had spare DunaX-GPN4B (40, 20, 15 and 10m) so it was obvious choice. I had to put down about 30m of coax cable to my apartment, and soon I was in the air.

Not for long I found out that I do miss 80 meter band a lot. […]
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Universal CAT and programming USB to RS232 TTL interface for ham radio

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As soon as I got first two ham radio rigs, I needed to connect them both to PC, to program memories or use CAT control from logging software. I realized that it is impractical to have as many USB to RS323 adapters as rigs.

As serial connection for radio requires just RX, TX and GND lines, and it is the same for most of modern radio stations. It is actually only radio connector that is different – signaling is the same.

It showed up quite easy to build simple multirig adapter. All you need to do is to use existing USB to serial interface adapter, cut it’s cable in two and insert male and female three pin 3.5 mm jack (commonly used as stereo audio connectors). […]
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