[BC] How would you build it?

[richardbrianjohnson at verizon.net]

 I would first understand that a 1 kW transmitter is really a 4 kW transmitter at 100 percent modulation. With 125% modulation and typical losses, it is really a 6kW transmitter so it needs to be able to produce 6kW of output power continuously, year after year, with low power line voltages, high power line voltages, and poor source power-factor.
 
"Modern" methods of generating an AM signal with a DSP and then amplifying it result is very low overall efficiency --scratch that.

I once proposed an AM transmitter that, using digital techniques and high-efficiency power-generators, to produce the following on-carrier RF __power__ supplies:

1, 2, 4, 8 ,16, 32, 64, and 128 __volts__. these would be digitally-switched to produce a 8-bit modulated AM carrier. That would produce a theoretical distortion of 1/ 255 =  0.3 percent.

Of course, this was back in the '70s so it was immediately poo-pooed as being a pipe dream of someone who just discovered digital signal generation -- back when Harris came out with PSM and a conventional (for the time) RF stage.
 
I understand that someone is doing that now, but I don't know who. It would be a good method.
 
 Cheers,
Richard B. Johnson
http://www.AbominableFirebug.com
 
On 07/30/14, Cowboy<curt at cwf1.com> wrote:
 
On Wednesday 30 July 2014 03:12:41 pm Rob Landry wrote:
> OK, here's a thought: if you had to custom-build an AM broadcast transmitter capable of, say, 1 KW, how would you do it?

Truthfully ?
Pretty much the way Nautel is building them today.
Maybe not quite as sophisticated, but the basic premise.

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