I agree with Joe
Look at the broadcast industry where the TX is usually 24/7 CCS
operation. Solid state has replaced tubes on MW up to 2 megawatts in
power. ON VHF FM transmitters go to 40 Kw with solid state
amplification and there are high powered solid state UHF TV
transmitters. The key to a good solid state amp is thermodynamics. If
the solid state junctions can not be cooled fast enough, there will
eventually be a failure. The new LDMOS fets get more heat from the
junction to the outside of the case than do earlier style of FETs. They
can also withstand infinite SWR and other abuse.
The only amatuer solid state amplifier I like to date is the Tokyo
HIpower 2.5K but even it gets hot when running the full limit with
PSK31. The technology is easily there and well proven it is just that
there are not really many solid amateur designs produced to date. That
said, there are poor tube designs on the market as well it is just that
they fail in a different manner.
Tubes are going away, especially at amateur power levels. I just spoke
with Richardson last week. Most new non Chinese tubes are NOS at the
manufacturer but are not being produced. This means once they are gone,
they are gone.
On 4/29/12 6:58 AM, Joe Subich, W4TV wrote:
>> I'm an ardent "tube" amp man for this reason. They're significantly
>> more robust and bullet proof in the longevity stakes.
> I don't believe that for a minute if you compare apples to apples.
>
> Most of the tube designs have been significantly "over engineered".
> That is, the tubes have excess plate dissipation for the power output
> and grids that will take a significant beating.
>
> If one looks at amplifiers like the MLA-2500 or Alpha 76 series with
> tubes that have grid dissipation in the 10 watt range and no grid
> protection ... tubes that have become unobtainium ... there are plenty
> of owners that have been reduced to tears at the cost (or lack) of
> replacements. Even the 8877 is not exactly an "unforgiving" tube
> when used in designs that lack proper grid protection and the 3-500Z
> are not safe in an unmodified TL-822.
>
> Given proper design and protection, modern solid state devices will
> last a lifetime unlike tubes that *will* need to be replaced due to
> filament/cathode aging. Transistor amplifiers don't suffer from
> catastrophic arcing and certainly don't represent the electrocution
> danger of tube amplifiers.
>
> There are pros and cons on both sides of the solid state vs. tube
> debate but choose the appropriate amplifying device, operate it
> within its design parameters, keep it cool and provide the proper
> protective circuits and either will provide years of trouble free
> service.
>
> 73,
>
> ... Joe, W4TV
>
>
> On 4/24/2012 9:32 PM, Leigh Turner wrote:
>> It's a pity vendors of solid-state QRO amplifiers don't offer purchasers an
>> accompanying low-cost insurance policy to cover them against the inevitable
>> day when the finals blow up for whatever reason and reduce the owner to
>> tears at the huge expense of carrying out out-of-warranty repairs.
>>
>> I'm an ardent "tube" amp man for this reason. They're significantly more
>> robust and bullet proof in the longevity stakes.
>>
>> Leigh
>> VK5KLT
>>
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