[Amps] Solid State HF High power linear amps

[Will Matney]

Sam,

See below;

*********** REPLY SEPARATOR  ***********

On 3/28/05 at 9:22 PM S. J. Blackwell wrote:

>>
>>Yup,
>>
>>Plus the solid state designs splatter something awful without a filter on 
>>the end. Most amateur amps have a switchable filter on the output 
>>(switchable between each band)
>
>Not so. The filters are for harmonic control. My 1KW MRF150 amp (2ea 4x150 
>amps in PP parallel with combiners beats the socks off all of the standard 
>ham xcvrs except some that operate the  outputs class A. This is 
>particuliarly true for 5th and higher order IMD.

Every amateur amp using solid state transistors I've seen has a switchable filter in the output. Plus, from experience on running transistor amps, they did in fact splatter worse than a tube amp where the pi or pi-l tank acted as a low pass filter. Harmonics is what's in question and what I consider splatter along with IMD included.

>
>Most transistors for this frequency range (2-30 MHz) run on 12-18 Vdc and 
>just a few higher. The transistors were really designed to be used as a 
>single push-pull stage even though they can be split and combined.
>
>Not so . My MRF150's operate at 50 volts.

Go look at how many transistors are rated for 50 volts as compared to 12-18 Vdc for 2-30 MHz. There's more 12-18 Vdc I've seen from every manufacturer. 50 volt semis are great for a base amp but for a mobile which supplies 12-14 Vdc, you'd need an inverter or something to step it up. That's why I think the 12 V versions are more popular and more part numbers from the manufacturers.

>
>I agree about the  tube amps can take a hit and keep on ticking. I have
>kept 
>my Alpha 89. (Which also has better IMD expectation than a 4CX800 amps,
>but 
>not much better than the MRF150's higher order IMD. (The ones that really 
>mess up the band) The 4CX800' do make the best econonic  sense.
>
>
>73,
>Sam Blackwell, W5LU


Best,

Will