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Re: [Amps] Designing the Cleanest Linear with RF Negative Feedback

Subject: Re: [Amps] Designing the Cleanest Linear with RF Negative Feedback
From: "" <>
Date: Sun, 18 Dec 2005 19:54:10 GMT
List-post: <>
Hi Tom,

Low distortion -- An low effort alternative.

If the low level section of the FT-1K is clean enough (-75 dB distortion)... 

Apply feed-forward correction to your FT-1K amplifier.  This will provide a 
clean (-65dB distortion) 25-50 watts to drive a single stage linear amplifier.  
Caution: no ALC allowed!

Follow the above with say... a 2:1 turns ratio (4:1 impedance) balun driving 
your 4CX3000A in swamped grid (200 ohm R) style.  This will reflect a nice 
friendly (constant) 50 ohm load to the FF/FT-1K combo.

For narrowband use, manual adjustment of the sampling & cancellation loops 
should work fine.  If one wanted to employ this technique over 1.8-30 MHz, 
automatic nulling would be useful.

I believe that this approach will require LOTS less effort overall to acheive 
your 1.5KW, -55dB distortion goal.

Again, this is only feasible if the FT-1K SSB generator is clean enough to 
start with... 

73 & Good morning,
   Marv WC6W


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