# ARRL

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## Keeping Oscillators Straight

Jun 28th 2013, 20:04

#### Joanie

Joined: Jun 24th 2013, 14:48
Total Topics: 0
Total Posts: 0
I do not know if this is an original idea or not, but it is one that has been really useful for me over the years. I have been tutoring basic electronics theory and circuits, with the related math, on a Junior College level for the last 8 years. One of the things that a lot of my students have had a lot of trouble keeping track of is: "What are the main attributes of the three primary types of oscillators?” Over time, I have come up with a strategy that makes this easy. As this is also a question that often times comes up in element 4 exams, as well, I feel that this might be a good way to help aspiring Extra Class candidates remember the differences as well.

Having said that, the three most common types of oscillators used in Amateur Radio are the Colpitts, Hartley and Pierce oscillators. There is an easy key here that can help students remember the essential characteristics between the three types of oscillators, based upon the first letter of each type: Consider:

Colpitts : C = Capacitor/Capacitance: A Colpitts oscillator is controlled by a capacitive divider network.

Hartley: H = Henry, the unit of inductance. A Hartley oscillator uses a tapped inductor to control the frequency of the oscillator.

Pierce: P=Piezoelectric. A Pierce oscillator uses a crystal to control the frequency of the oscillator.

I have found out that those I mentor find this as easy as 3.14159 as a way to memorize the fundamental way in which the three types of oscillators differ from each other on a basic level.