E007048.PDF

(80 KB) Pobierz

series 06

048

Diode Radio for Low Impedance Headphones

B. Kainka

If you ever look at construction notes for building old detector

type radios the type of headphones speciﬁed always have an

impedance of 2

* see text

zie tekst

* voir texte

siehe Text

A1

*

*

. Nowadays the most commonly

available headphones have an impedance of 2 × 32 Ω, this rel-

atively low value makes them unsuitable for such a design.

However, with a bit of crafty transformation these headphones

can be used in just such a design. To adapt them, you will

need a transformer taken from a mains adapter unit, the type

that has a switchable output voltage (3/4.5/6/9/12 V) without

the rectifying diodes and capacitor. Using the different taps of

this type of transformer it is possible to optimise the imped-

ance match.

For the diode radio (any germanium diode is suitable in this

design) the key to success is correct impedance matching so

that none of the received signal energy is lost. The antenna

coil on the 10 mm diameter by 100 mm long ferrite rod is made

up of 60 turns with a tap point at every 10 turns; this is suit-

able for medium wave reception. If a long external aerial is

×

2000

Ω

L1

D1

AA119

*

*

Tr1

Ge

C1

C2

500p

10n

2x 32 Ω

30 : 1

004033 - 11

used it should be connected to a lower tap point to reduce its

damping effect on the circuit. You can experiment with all the

available tapping points to ﬁnd the best reception. With such

a simple radio design, the external aerial will have a big inﬂu-

7-8/2000

Elektor Electronics

77

138912214.071.png

138912214.082.png

138912214.093.png

138912214.104.png

138912214.001.png

138912214.012.png

138912214.023.png

138912214.024.png

138912214.025.png

138912214.026.png

138912214.027.png

138912214.028.png

138912214.029.png

138912214.030.png

138912214.031.png

138912214.032.png

138912214.033.png

138912214.034.png

138912214.035.png

138912214.036.png

138912214.037.png

138912214.038.png

138912214.039.png

138912214.040.png

138912214.041.png

138912214.042.png

138912214.043.png

138912214.044.png

138912214.045.png

138912214.046.png

138912214.047.png

138912214.048.png

138912214.049.png

138912214.050.png

138912214.051.png

138912214.052.png

138912214.053.png

138912214.054.png

138912214.055.png

138912214.056.png

138912214.057.png

138912214.058.png

138912214.059.png

138912214.060.png

SUMMER CIRCUITS COLLECTION

ence on its performance. Tip: If your house has metal gutter-

ing and rain water pipes, it will be possible to use these as an

aerial, as long as they are not directly connected to earth.

Those who live in the vicinity of a broadcast transmitter may be

able to connect a loudspeaker directly to the output or if the

volume is too low, why not try connecting the active speaker

system from your PC?

(004033)

138912214.061.png

138912214.062.png

138912214.063.png

138912214.064.png

138912214.065.png

138912214.066.png

138912214.067.png

138912214.068.png

138912214.069.png

138912214.070.png

138912214.072.png

138912214.073.png

138912214.074.png

138912214.075.png

138912214.076.png

138912214.077.png

138912214.078.png

138912214.079.png

138912214.080.png

138912214.081.png

138912214.083.png

138912214.084.png

138912214.085.png

138912214.086.png

138912214.087.png

138912214.088.png

138912214.089.png

138912214.090.png

138912214.091.png

138912214.092.png

138912214.094.png

138912214.095.png

138912214.096.png

138912214.097.png

138912214.098.png

138912214.099.png

138912214.100.png

138912214.101.png

138912214.102.png

138912214.103.png

138912214.105.png

138912214.106.png

138912214.107.png

138912214.108.png

138912214.109.png

138912214.110.png

138912214.111.png

138912214.112.png

138912214.113.png

138912214.114.png

138912214.002.png

138912214.003.png

138912214.004.png

138912214.005.png

138912214.006.png

138912214.007.png

138912214.008.png

138912214.009.png

138912214.010.png

138912214.011.png

138912214.013.png

138912214.014.png

138912214.015.png

138912214.016.png

138912214.017.png

138912214.018.png

138912214.019.png

138912214.020.png

138912214.021.png

138912214.022.png

Plik z chomika:

Inne pliki z tego folderu:

Elektor Electronic #275 March 1999.pdf (20071 KB)
bge.jpg (22 KB)
detail1.htm (5 KB)
detail2.htm (5 KB)
detail3.htm (6 KB)

Inne foldery tego chomika:

Zgłoś jeśli naruszono regulamin