[AMPS] Misc. Oscillations

[measures]

>
>Hi Guys,
>
>> The simple fact is that some amplifiers are built with almost the same
>> components that were used in the 100 watt transceivers.  Bandswitches,
>> parasitic suppressors, and even tank coils in some amplifiers are not
>> significantly larger than in the old tube drivers.
>
>My DX-100's tuning capacitor is smaller than the tuning cap in a 
>my SB-220, and every other amp I have.
>
>I can still make it arc (like I can the SB-220 cap) if I mistune the 
>amplifier, over-drive it, operate it without a load.
>
>If you designed a PA that would never arc or fail under any of the 
>many variable conditions of the real world, very few people would 
>buy it. Most amateurs couldn't even afford it. 
>
€ Not one owner of an AL-80 or AL-82 that toasted one or more 
bandswitches has spent more than $15 to seemingly correct the problem.  
OTOH,   AL-80s and AL-82s seemingly have above avg. stability.   TL-922s 
toast more bandswitches.  

>> There is a practical problem in the design of amplifiers, however, since
>> the components of the amplifier (in a properly designed amplifier) are
>> larger. This means that the spacing between components increases - which
>> leads to greater stray inductance and capacitance.  This may be a
>> significant cause of problems for high powered amplifier design and
>> construction.
>
>No. The most significant cause of problems are limitations in what 
>you can afford to do and still have a marketable product. The 
>market, not the engineering, dictates how much money there is to 
>spend.

€  A rheostat to adj. fil/heater potential costs under five dollars 
wholesale.  Do any MFJ-Ameritron amps have one?  Would people pay a bit 
extra for such a feature?  

>
>Putting in $500 dollars worth of cost to everyone, just so it corrects 
>$1.00 worth of average cost per customer, is rarely done with any 
>product. Amateur radio products, with their low profit margin, are no 
>exception.      

€  A low VHF Q suppressor for the AL-1500 would cost about $1.20 plus 
labor.  Replacement tubes reportedly cost over $600.  The next time you 
run into one on the air, ask how many tubes were consumed during the 
warranty period.  Congrats to Dick Ehrhorn  and Henry Radio for having 
enough gray-matter to use a vhf suppressor with the 8877.  
>
>The only bad part about this "parasitic stuff" is the bad information 
>circulated doesn't even help people understand what to do to solve 
>problems, or why failures actually occur.

€  The photographs of crispy-crittered Ameritron/MFJ bandswitches on my 
Web site should be fairly easy to understand.  
>
>None of this stuff is magic, or hard to understand. 

€  When I spoke to you on the telephone, you could not tell me what 
constituted a stable layout.  

cheers, Tom.  

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