HF linear amplifier theory

[DougTee]

I am seeking a tutorial on the theory of HF linear amplifiers. I can be confused by all the information. Some circuits use hand made coils on ferrite rods and others use a single device resembling a SIP integrated circuit. I am familiar with audio and guitar amplifiers. I have not experienced radio amplifiers. Thanks DougTee

 

[Nigel Goodwin]

I am seeking a tutorial on the theory of HF linear amplifiers. I can be confused by all the information. Some circuits use hand made coils on ferrite rods and others use a single device resembling a SIP integrated circuit. I am familiar with audio and guitar amplifiers. I have not experienced radio amplifiers. Thanks DougTee

It's a complicated subject, but basically RF amplifiers are usually tuned, even if it's a fairly broad tuning. Construction is also extremely critical, an RF amplifier can easily become an RF oscillator!.

You don't have your location filled in, so I can't comment on your particular location, but in the UK the RSGB publish a number of amateur radio books which will help to explain it.

 

[k7elp60]

In the US the Radio Amateur's Handbook, published by the ARRL, (www.arrl.org) has the most information in my opinion. It covers receiving and transmitting. Which relates to signal and power amplifers.

 

[DougTee]

Thank You! I went the the arrl site and found an extensive library available. I can have them sent to me. I did not find a listing for the amatuer radio operators handbook. I wonder if I am searching in the proper index? Can it be out of print ? :cry: Thank you for the help, K7elp60.


:arrow: Mr. Goodwin: Is there a web address for the RSGB where I might inquire about educational materiel? DT

 

[DougTee]

Mr. Goodwin, as regards a amplifier becoming an oscillator; my experience has been that improper use of feedback,or no feedback used and inadequate or missing capacitative shunting is usually the cause. I can believe that other factors can also cause this condition. I have found that failed capasitors in guitar amplifiers can cause unwanted oscillation, also. DT

 

[Nigel Goodwin]

Mr. Goodwin, as regards a amplifier becoming an oscillator; my experience has been that improper use of feedback,or no feedback used and inadequate or missing capacitative shunting is usually the cause. I can believe that other factors can also cause this condition. I have found that failed capasitors in guitar amplifiers can cause unwanted oscillation, also. DT

All that is fairly true, but HF linear amplifiers don't usually use feedback, you don't have the gain to waste.

Incorrect layout can cause inadvertent positive feedback, the higher power the amplifier, and the higher the bandwidth, the more critical it is.

A simple google search found https://www.rsgb.org/, the technical book section of their shop lists a number of publications, including the ARRL Handbook.

 

[k7elp60]

Doug,
Sorry for the wrong name, over the years they have shortned to just to the Handbook. Here is a picture. I noticed that they had some year old copies available also. The theory doesn't change but some of the construction articles do. Perhaps the older one is a lot cheaper.