Hello,
I am looking at building the simple signal tracer at PastTimesRadio.co.uk
Here is the schematic:
And here is the component list:
Components List
Resistors (0.25W Carbon)
R1 22K
R2 4.7K
R3 3R3 (3.3 Ohms)
VR1 22K Linear with switch
Capacitors
C1 1nF Ceramic Disc (300V)
C2 0.1uF Ceramic Disc (300V)
C3 10uF 25V Electrolytic
C4 68nF Polyester / Milar
C5 0.1 uF Polyester
C6 470 uF 25V Electrolytic
Semiconductors
D1 OA79 germanium signal diode
IC1 LM380N
Misc.
Miniature L.S. 8 Ohm 300 mW
Veroboard, connecting wire,
9V PP3 battery, probe,
suitable enclosure.
I have pretty much everything required, but do not own any Germanium Diodes, I have been looking for them in the UK, but many places do not stock them anymore and the diodes on ebay such as 1N60Ps are disputed as being Shottky diodes and those that aren't are quite expensive and only have 2nd class delivery (and I am not a patient man).
In the build blurb for the circuit, it states the following "The detector or demodulator diode should be a good quality germanium type, OA79 or similar. Don't be tempted to use a silicon diode - it won't work !"
So now to my questions:
I have gone through my diode box and have checked a selection from each of the types on two digital multimeters and also on my cheapy Chinese component tester, almost all show between 0.5V and 0.6V forward voltage. However, one set of diodes (which I can't fully confirm the number which begins 1N581X, where X is smudged and unreadable on all the diodes) all show a forward voltage of between 0.175V and 0.185V on the digital multimeters and show a forward voltage of 0.285 or so on the component tester (see below):
So my questions are, would these diodes work in place of the required OA79 given that the have such a low forward voltage, or is there something else that Germanium offers as well as a low forward voltage that would negate their use? If so what is it please?
TIA, Ed.
I am looking at building the simple signal tracer at PastTimesRadio.co.uk
Here is the schematic:
And here is the component list:
Components List
Resistors (0.25W Carbon)
R1 22K
R2 4.7K
R3 3R3 (3.3 Ohms)
VR1 22K Linear with switch
Capacitors
C1 1nF Ceramic Disc (300V)
C2 0.1uF Ceramic Disc (300V)
C3 10uF 25V Electrolytic
C4 68nF Polyester / Milar
C5 0.1 uF Polyester
C6 470 uF 25V Electrolytic
Semiconductors
D1 OA79 germanium signal diode
IC1 LM380N
Misc.
Miniature L.S. 8 Ohm 300 mW
Veroboard, connecting wire,
9V PP3 battery, probe,
suitable enclosure.
I have pretty much everything required, but do not own any Germanium Diodes, I have been looking for them in the UK, but many places do not stock them anymore and the diodes on ebay such as 1N60Ps are disputed as being Shottky diodes and those that aren't are quite expensive and only have 2nd class delivery (and I am not a patient man).
In the build blurb for the circuit, it states the following "The detector or demodulator diode should be a good quality germanium type, OA79 or similar. Don't be tempted to use a silicon diode - it won't work !"
So now to my questions:
I have gone through my diode box and have checked a selection from each of the types on two digital multimeters and also on my cheapy Chinese component tester, almost all show between 0.5V and 0.6V forward voltage. However, one set of diodes (which I can't fully confirm the number which begins 1N581X, where X is smudged and unreadable on all the diodes) all show a forward voltage of between 0.175V and 0.185V on the digital multimeters and show a forward voltage of 0.285 or so on the component tester (see below):
So my questions are, would these diodes work in place of the required OA79 given that the have such a low forward voltage, or is there something else that Germanium offers as well as a low forward voltage that would negate their use? If so what is it please?
TIA, Ed.