"Chad Wahls" wrote in message
...
It's not hard to stumble upon an article here or there speaking of peaking
a
radio.

People speak of spreading coils, etc.

Now, I'm no RF designer. But those LC circuits are FILTERS not REGULATING
devices.

Not entirely. They have filter like characteristics but also perform an
impedance matching function too.

Soooooo.

When you spread a filter coil to gain power do you actually gain it in the
desired bandwidth (usable) or do you get the same amount (4watts) of
usable
transmit and a ****load more harmonics at power levels over the power at
your usable freq causing your audio to suck due to oscillation? (I know,
long sentence)

I just don't get how changing ONE parameter to an LC network will gain
power, But I DO see how it will knock it way the hell out of alignment.

Or am I wrong?

The correct answer is "it depends". Without knowing the exact filtering
setup it is possible to get more power while still maintaining low harmonic
emissions, but this is not a given. The real problem is not increasing your
carrier power, but supplying enough audio power to fully modulate the higher
carrier power. The audio level you hear is due to the power in the two
sidebands, upper and lower. The more power in the sidebands the louder the
audio at the receiving station. The sideband power is completely supplied by
the modulating audio. That's why some CBers use sideband radios. A 12 watt
PEP sideband radio has significantly more power in the single sideband it
transmits than you get in a modest higher power AM transmitter's upper or
lower sidebands. You only need one sideband, but to get the signal you need
the other station to be using a sideband radio too.

The problem with peaking a cheap AM radio is often there is insufficient
audio power to fully modulate the carrier. The audio power is supplied by a
small audio power IC in the radio normally with a rating of around 2 watts,
which is just enough for a 4 watt carrier. Some may use a small discrete
transistor amp stage, but anyway the idea is the same. The IC's are designed
to work with one particular load and increasing that loading, for more
power, can cause the chip to fail. So what happens is the radio gets peaked
for more power, makes the S-Meter needle fly farther up scale, and the rest
is in the mind of the operator while the radio tech walks away with your
money, which you wasted.

For those interested in a bit of the math check out:

http://www.kc8ldo.home.dyndns.org/AM_Modulation.htm

This web site is heavily graphics orientated so a fast Internet connection
is highly recommended.

--
Leland C. Scott
KC8LDO

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