[ARC5] AM linear amplification

[spr at earthlink.net]

Folks,

I think I was told that the newest transmitter at KGO (50 kW in San Francisco) has an efficiency of 90%, line in to RF out.
That is seriously high eficiency!

Regards,

Scott Robinson


-----Original Message-----
>From: Richard Knoppow <1oldlens1 at ix.netcom.com>
>Sent: Dec 19, 2016 5:22 PM
>To: arc5 at mailman.qth.net
>Subject: Re: [ARC5] AM linear amplification
>
>Harris introduced the pulse modulated transmitter for AM some time ago 
>but I don't remember the date. The idea is that the modulation audio is 
>sampled at some high frequency, say around 70Khz and converted to a 
>variable width pulse. The pulses are applied to the final amp plate and 
>are integrated by the tank circuit. The result is AM but the transmitter 
>is capable of very high efficiency along with wide, flat, frequency 
>response and low distortion if done right. The original pulse modulated 
>transmitters were tube amps but Harris and others have gone to solid 
>state.  The kind of thing you describe would produce the same result 
>using an array of lower level switched devices.

>    A modern 50KW transmitter has a line demand of well under 100 KW.