snip
A one farad capacitor can only supply one amp for one
second at one volt. Hardly worth the expense.

It can only prevent a voltage drop on the first few peaks
of a SSB modulated signal. It's usefulness would be almost
totally drained after speaking just one appropriate word, pointless.

Then there is not much point in using them in any kind of DC power supply, is
there? Of course there is. Do the math, Tnom:

Oranges and apples...............
P.S. you are a idiot for even equating the two


A good car battery has, on the average, an source impedance of around 0.01 ohms
(dropping 1 volt per 100 amps, which is a darn good battery). Ten feet of #8 AWG
has a DC resistance of 0.0063 ohms, and we'll just assume that the negative lead
is grounded at 0 ohms. So the total source impedance at the input of the amp is
0.0163 ohms. Now take an amp that can do 500 watts PEP. Assuming 50% efficiency,
that means it can draw a maximum of 79.4 amps @ 12.6 volts. But since the source
impedance is 0.0163 ohms, the voltage is going to drop 1.3 volts on the peaks,
reducing the peak output by 50 watts or more. This is a type of soft-clipping
and can result in some significant AF -and- RF distortion. And that's not
considering the temperature coefficient of copper, which shows more resistance
as it warms up from carrying lots of current, making the situation worse.

Adding caps at the power input leads of the amp can significantly reduce the
source impedance of the power supply. It -can't- provide more power than the
supply is capable of providing,

But for how long........."Do the math"

but it -can- smooth the voltage ripple just like
in any other type of power supply. And what if the vehicle is running? Do the
math: If you have a 100 amp alternator (at 13.8 volts), it has a source
impedance of .138 ohms, which is significantly higher than the battery, so it's
not going to be much help. In fact, because it's going to be so heavily loaded,
it's going to introduce some ripple into the power lines, ripple that can be
reduced by using caps at the input of the amp.

How much capacitance is needed? There is no easy equation. There are a number of
factors, such as the source resistance of the battery and alternator, resistance
of the wire, ESR of the capacitors, average modulation percentage, PEP watts,
etc, etc. Because of the very low impedance required by the amp, low ESR is
paramount. Despite the advertised claims, the 'monster' caps usually have an ESR
of several ohms, much higher than is usable. Computer-grade electrolytics have a
much lower ESR. Using many smaller caps in parallel is better than one big cap
because the ESR is much lower. Those are just a few things to consider. But the
general rule is to keep adding caps until they no longer make any improvement.


I'm really suprised, Tnom. After all the times you have shot your mouth off and
been proven wrong on technical topics, you -still- haven't learned to think
before you speak. Maybe next time.


One thing I am not surprised at........You will ignore the facts, like
you normally do to flame the group or express your pseudo
theory.


Yeah...Right, A few farads will make a justifiable difference. You're
to funny.