Coaxial 75 Ohm / 50 Ohm transitions used for impedance transformation

In the upper UHF range, a lambda twelfth impedance transformation is no longer possible with coaxial cable. Here I can recommend a combination of 50/75/50/75 Ohm transitions.

 

 

 

Quiz-Taster mit Arduino

Für den Schulunterricht habe ich diesen Quiz-Taster entwickelt. In seinem Inneren werkelt ein Arduino:

 

 

Das verwendete sketch ist sicher verbesserungswürdig, aber es tut seinen Dienst: 

 

[code]
#include "pitches.h"

int Taster1 = 13;
int Lampe1 = 12;
int Taster2 = 7;
int Lampe2 = 6;

int myCounter1 = 0;
int myCounter2 = 0;
int myCounter3 = 0;
int myCounter4 = 0;

void setup() {

pinMode (Taster1, INPUT);
pinMode (Lampe1, OUTPUT);
pinMode (Taster2, INPUT);
pinMode (Lampe2, OUTPUT);

digitalWrite (Lampe1, HIGH);
delay (250);
digitalWrite (Lampe1, LOW);
digitalWrite (Lampe2, HIGH);
delay (250);
digitalWrite (Lampe2, LOW);
digitalWrite (Lampe1, HIGH);
delay (250);
digitalWrite (Lampe1, LOW);
digitalWrite (Lampe2, HIGH);
delay (250);
digitalWrite (Lampe2, LOW);

int melody[] = {
  NOTE_C4, NOTE_G3, NOTE_G3, NOTE_A3, NOTE_G3, 0, NOTE_B3, NOTE_C4
};

int noteDurations[] = {
  4, 8, 8, 4, 4, 4, 4, 4
};

// iterate over the notes of the melody:
  for (int thisNote = 0; thisNote < 8; thisNote++) {

    // to calculate the note duration, take one second divided by the note type.
    //e.g. quarter note = 1000 / 4, eighth note = 1000/8, etc.
    int noteDuration = 1000 / noteDurations[thisNote];
    tone(8, melody[thisNote], noteDuration);

    // to distinguish the notes, set a minimum time between them.
    // the note's duration + 30% seems to work well:
    int pauseBetweenNotes = noteDuration * 1.30;
    delay(pauseBetweenNotes);
    // stop the tone playing:
    noTone(8);
}}

void loop() {

if (digitalRead (Taster1) == LOW)
   {digitalWrite (Lampe1, LOW);
   myCounter1 = 0;
   myCounter4 = 0;}
 
  if ((digitalRead (Taster1) == HIGH) && ((myCounter3) == 0))
  {digitalWrite (Lampe1, HIGH);
  if ((myCounter1) == 0) {tone (8, 300, 1000);}
  myCounter1 = 1;
  myCounter4 = 1;
  delay (250);}

   
if (digitalRead (Taster2) == LOW)
  {digitalWrite (Lampe2, LOW);
  myCounter2 = 0;
  myCounter3 = 0;}

  if ((digitalRead (Taster2) == HIGH) && ((myCounter4) == 0))
  { digitalWrite (Lampe2, HIGH);
  {if ((myCounter2) == 0) {tone (8, 600, 1000);}
  myCounter2 = 1;
  myCounter3 = 1;
  delay (250);}
  }}
[/code]

Satelliten Bodenstation im mini-Format

 "TinyGS" ist ein Zusammenschluss von kleinen LoRa-Sende/Empfängern dafür geschaffen, Datenpakete mit Satelliten im LEO-Orbit auszutauschen. Da solche Gerätchen mittlerweile sehr klein sind, fällt die ganze Bodenstation entsprechend winzig aus. 

Dabei bieten diese Gerätchen, die zu einem Preis von ca. 20 Euro erhältlich sind, auch Konnektivität über Bluetooth und Wifi. Zudem verfügen sie über einen 0,96" OLED Bildschirm und über ein Li-Po Akku Manegement. 

Es wird für LoRa wahlweise der Frequenzbereich der ISM-Bänder im 433 MHz- oder 868 MHz-Bereich abgedeckt.

 

 

 

HELTEC LoRa 32-Modul im Größenvergleich 

 

Old TV antenna filter tuned for the 868 MHz ISM band

The quality of old professional TV-transmitter filters are superb. I tuned an "Hans Plisch" bandpassfilter with 4 cells for the 868 MHz ISM band (863 MHz - 870 MHz).

 

"eggbeater" antenna for the 868 MHz ISM band

I made the antenna of an insulated copper wire with a diameter if 1.8mm (3.5mm with insulation).

The centerfrequency of the 868 MHz ISM band (863 MHz - 870 MHz) is 866,5 MHz. 

The circumference of one loop is: 27295 / 866,5 MHz => 31.5cm

The lengh of 1 radial for best swr is: 11264 / 866,5 => 13cm

The distance between the lower edge of the loop and the Radials are 3412 / 866,5 MHz => 4 cm

In my case, these values ​​gave the best results. 

Using a different wire will likely result in different values.

"Eggbeater-antenna" for the 868 MHz ISM - band

 Simulation of an "Eggbeater-antenna" for the 868 MHz ISM band

 

 

 

This simulation was done with the "MMANA-Gal basic" program.