[Elecraft] time for KPA1500 - but why "no tubes?"

[Don Wilhelm]

WOW,  I do not understand the distinction - there must be some harmonic 
suppression circuits that reduce the 2nd harmonic emissions from an 
amplifier (40 dBc if I recall), so whether that is done using a fixed 
tune output circuit, or whether that is achieved by the use of an 
external antenna tuner is a moot point.  The bottom line is that 
somewhere in the path between the PA tubes (transistors, MOSFETs), there 
must be a path from the grid(, base, plate) to ground that will afford a 
transition to 50 ohms (and X - j0) solution that will yield greater than 
5 watts on all bands (or in the case of the K3, 6 meters).

So use whatever tuner matching section between the amplifier and the 
antenna is a good and prudent challenge.  The inductance at the highest 
frequency will be greater than 3 times the 'oscilloscope oscilloscope 
and probe -

73,
Don W3FPR

On 2/20/2012 11:34 PM, Hank Garretson wrote:
> On Mon, Feb 20, 2012 at 8:18 PM, Ron D'Eau Claire<ron at cobi.biz>  wrote:
>
> Note that "No Tune" means, simply, "Fixed Tuned", set for a 50 ohm
>> non-reactive load on each band. If we don't have an antenna reasonably flat
>> across the whole band we add an "Antenna Tuner" to the output which is
>> simply moving the tuning we used to do on the xmtr output to an outboard
>> box!
>>
> Not exactly. My "No Tune" ACOM 2000A will automatically handle up to 3:1
> SWR on all bands except 160 where the limit is 2:1. Sometimes output power
> is reduced, and sometimes an external tuner is helpful. but for the ACOM at
> least, "No Tune" does not mean "Fixed Tune."
>
> 73,
>
> Hank, W6SX
>
> Mammoth Lakes, California
>
> Elevation 8083 feet in John Muir's Range of Light
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