View Full Version : Amplifiers and Oscillators
kg4yvf
02-20-2003, 02:11 PM
Hey some of you hams hat have technical knowledge, please start a discussion on the uses of the class A AB B and C amp. Where is there best use. Those that have knowledfge of any technical nature I would like to hear from.
Here are the basics...
http://www.earth2.net/parts/?course/90801004/
wb6bcn
02-20-2003, 07:45 PM
</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">Amplifiers and Oscillators, Technical Discussions[/QUOTE]<span id='postcolor'>
The article Harry linked to is a good item for the classes of amplifiers. #As for oscillators, any amplifier with a gain greater than 1 can be an oscillator. #All thet is required is positive feedback. #Sometimes amplifiers become unintential oscillators. The most sommon oscillators are the Colpits, #Hartley, Pierce, and Clapp.
Hartley Oscillator: #Feedback is from the center of an inductor.
Colpitts Oscillator : Feedback is from the center of two capacitors.
Clapp Oscillator: #Series tuned version of the Colpitts Oscillator.
Pierce Oscillator: #Common type of crystal Oscillator. #May have properties of the Hartley or Colpitts incorperated in the design.
Not all oscillators have amplifier devices of 3 or more elements. #There are relaxaton oscillators and negative resistance oscillators that use 2 element devices such diodes and neon bulbs.
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ADDED INFO
The Hartley, Pierce, Clapp, and Colpitts oscillators are most commonly used in radio frequency devices where the relaxation oscollator is most commonly used for light flasher, lamp dimmers, and motor speed controllers. The negative resistance oscillator was common in microwave receivers and transmitters.
There are other oscillators used in other applications, but the ones mention are the most common one in use, or used in the last 60 years.
Sorry Doug...
Here's oscillators...
http://www.earth2.net/parts/?course/90902002/
wb6bcn
02-20-2003, 08:29 PM
</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (N0PU @ Feb. 20 2003,12:12)</td></tr><tr><td id="QUOTE">Sorry Doug...
Here's oscillators...
http://www.earth2.net/parts/?course/90902002/[/QUOTE]<span id='postcolor'>
http://www.qrz.com/iB_html/non-cgi/emoticons/confused.gif? "Sorry" for what??: Both what you have linked to and what I wrote answer the question in different ways. Both have valid information.
I was kidding Doug...
I think what this fella is looking for is some old war stories...
The worst oscillator story I can think of at the moment is one about some old UHF gear I was working on aboard ship... These oscillators had a rotary switch kind of arrangement where these 'variable' caps were on the drum and were made from 'tabs' sticking out...
The way you adjusted this beast was to turn the switch so a set of tabs were straight up... bend the tabs a little and then rotate the switch back to see if ya got it right.... for hours and hours at a time...
These tabs were right over the power supply... wonderful design... and the heat from the PS would warp the tabs just enough to throw the whole thing off freq about once a week...
And we had 6 of those transmitters...
I made a career out of those things for awhile...
Who made those awful things? Mackay? Sunair?
That has been 25/30 years ago... I don't remember for sure... I wanna say Collins, but that may be wrong... Lot of equipment since then and I get part-timers disease... I only remember part of the time....
W1RFI
02-20-2003, 09:18 PM
An old RF engineer joke quips that the best way to design an oscillator is to build an amplifier. :-)
73,
Ed Hare, W1RFI
K6UEY
02-21-2003, 09:23 AM
You forgot to mention another use of the relaxation oscillator is by your local power company as a device to drive any HF Ham up a telephone pole. Due to generally lack of proper installation or maintaince poor insulators can develop capacitor plates that charge up in a high voltage field then arc over and produce a relaxation effect oscillator which can ruin your day on HF.Once the plate arc's over it neutralizes and begins to charge again going through the cycle of producing a big burst of wide band noise.
Ed I remember those oscillators were on the test,the way I always remembered them was the C in colpits was the tapped capcitor and the hartley was the the tapped inductor. #Of course the pierce was a harmonic generator quite commonly used to get to the VHF frequencies along with the dollar oscillator.
You mentioned before the many pages needed today to study,I think if the answers to the questions had been posted in the old days as they are today there would have been many more pages to study to get a ticket.
ENJOY!! It is later than you think.......73, # ORV
http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif