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
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