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Old September 2nd 06, 11:53 AM posted to rec.radio.amateur.homebrew
Paul Keinanen Paul Keinanen is offline
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First recorded activity by RadioBanter: Jul 2006
Posts: 85
Default MRX-40 modification

On Sat, 2 Sep 2006 11:52:41 +0800, "Klop"
wrote:


Also
http://www.hanssummers.com/radio/varicap/index.htm
for G0UPL's testing of several common diodes as varicaps.
Red LED's came out top!
Does anyone else have info on using them as varicaps for tuning?


When using a semiconductor in a transparent package, you should
remember that the ambient light will generate a voltage across a
reverse biased junction.

When using a high resistance potentiometer to generate the tuning
voltage, the voltage generated by the ambient light might upset the
voltage across the diode and hence, the capacitance (and resonant
frequency) varies with the ambient light level.

At least keep the ambient light out of any diode with a transparent
package, when used in a high impedance reverse biased circuit.

Paul OH3LWR