[Elecraft] Any AM detecting go'en on?

[N2EY@aol.com]

In a message dated 9/28/02 11:31:59 AM Eastern Daylight Time, k6se@juno.com 
writes:

> Don, KD5NDB wrote:
>  
>  "Its nice to have a radio that can deliver 100 watts out using less power
>  than it takes to heat the filaments in the old tube radios and probably
>  10 times more  reliable."
>  ----------
>  I'd sure like to find a radio that efficient!  5 volt filaments at even
>  25 amps uses 125 watts.  My power-efficient K2 uses 13.8 volts at 15
>  amps, or 207 watts, when running 100 watts RF out.

And most of that 207 watts goes to the KPA100. 

Compare that to a pair of 807s or 1625s running 100 W out in Class C:

Plate: 750V @ 200 mA (150 watts)
Screen: 300V @ 16 mA (~5 watts)
Heaters: 6.3 V @ 1.8 A  (~12 watts)

Total: 167 watts input. 

>  ==========
>  
>  "With the exception of high power amps I think we should let the glow
>  bottles die. If you can even find them you have to mortgage the house to
>  buy them. I'm not sure how much longer power amps will use tubes as it's
>  getting more cost effective to build them solid state as well.  (From
>  someone who spent 10 years swapping tubes."
>  ----------
>  I recently bought a new 12BY7 for my old TS-830S for $5.00.  I had no
>  trouble finding it and not a bad price, considering the increased cost of
>  living since the '80s.
>  
>  Mortgage the house?  When you consider even the price of high-power
>  vacuum tubes, they're not as expensive as they were years ago.  For
>  example, in 1970, a pair of 3-500Zs cost $90.  Today, when the cost of
>  living is certainly more than three times what it was then, you can buy a
>  pair of 3-500Zs for $250.  The relatively low-powered and common-used
>  6146A which cost about $5 in 1970 can still be bought new for about $15
>  for the ruggedized military version (6146W).

Adjusted for inflation, many parts are cheaper than ever before. Only 
problemd with finding tubes are:

1) You have to search a bit to avoid paying big bucks
2) Certain types have become unobtanium or have been made expensive by 
audiophiles
>  
>  Unlike Don, I have never had to swap tubes out in any of my kilowatt
>  amplifiers (in over 47 years).  My Alpha 76CA has thousands of tough
>  hours on it in contests and chasing DX, and still is going strong with
>  the original tubes.  IMHO, short PA tube life is due to either:
>  
>  1) The tube was factory-defective (one-year warranty), or
>  
>  2) Care was not exercised in driving the tube (watch that grid current
>  religiously!)
>  
3) Amplifier had uncorrected parasitic problems or other operational flaws

4) Amplifier pushed the tube beyond ratings. Some manufactured amps try to 
get every milliwatt out of a bottle, while others are not careful of things 
like filament voltage. 

>  Until solid state high power RF amplifiers are as cost-effective as
>  vacuum tube amps, I'll stick with that "archaic" technology.

The commercial users who have to be on the air 24/7 and who pay dearly for 
preventive maintenance can justify the higher cost of SS high power. Most 
hams are not on the air near enough to wear out a properly-operated final 
tube in less than a decade or two.
  
73 de Jim, N2EY