[Amps] Speaking of Palomar

[TimNebo at aol.com]

In a message dated 3/13/03 10:50:52 AM Pacific Standard Time, 
w8ji at contesting.com writes:

> There is no such thing as a class AB1 bipolar amplifier.
> 
> Bipolar transistors linear amplifiers, by electrical requirements, draw
> base
> current over at least half the input cycle. Sub 1 indicates no device input
> current over any part of the RF cycle (or in some cases that drive voltage
> never exceeds bias voltage).
> 
> The RF base current attempts to reduce the base voltage and force bias
> negative. A simple diode to ground does not help unless current through the
> diode is dozens of times greater than peak base current. I'd wager they do
> not have proper biasing.
> 
> The way to test this is to RF decouple the leads from a meter, and measure
> dc voltage at the base. If you see it drop when drive is applied, the bias
> is unstable. If it goes less than .6 or .7 volts that means the transistor
> is moving into class C when drive is applied.
> 
> Most CB amps and amps without active bias or properly designed shunt bias 
> do
> that.
> 
> 73 Tom
> 



your correct tom, the ab1 was a typo after a days work and a few 807's after 
the job. however these plaomar amps are indeed a biased amp whether it be the 
simple diode method or not it works rather well and has for years. you guys 
may inquire more to dennis o. who is a member of this list as he has been 
involved in directly designing solid state bias circuits for amp 
manufacturers and is resposible for a very nice regulated bias circuit that 
he's created. he outlined it some here not long ago but didnt go into total 
detail. i will not try to defend these amps or say there good qaulity or 
anything else but i will say that picking a battle against them as your major 
focus in life must surely mean whoever may do so has a very laid back life 
with no real life problems at all and must be commended. i hope i shall only 
be so lucky when the biggest problem in my life is minor interference to my 
radio hobby.