"Roy Lewallen" wrote in message
...
It sounds like a technique I remember calling "controlled carrier". The
carrier power was reduced when you weren't talking, then was increased
with the audio in an AGC-like manner. Sounded a little weird, but not
badly distorted. The objective was to reduce the average dissipation of
the final stage, so smaller tubes and a lighter duty power supply could
be used.

But I don't see why you'd use a method like this with a low power
transmitter, since it's trivial to make one that easily handles the
power requirements of standard AM. So I don't really think that's what
is meant by "swing". I'd bet good money that whatever "swing" is, it
doesn't improve quality or signal strength, and very likely introduces
distortion that causes splatter. If the transmitter was designed for
100% modulation of a 4 watt carrier, and you reduce the carrier without
a proportional reduction of the audio, you'll be overmodulating and
consequently distorting and splattering.

What are the supposed benefits of this "swing"?

Roy Lewallen, W7EL

CBers are very susceptible to urban myth and legend. Not understanding the
"normal" nature of an AM carrier, often they won't see the needle move very
much (assuming some cowboy jockey hasn't been in the rig snippin' and
clippin'), they get kind of excited. "HEY! I ain't got no "swang", so
therefore, they think they
aren't "gittin'" out. Voodoo techs have been able to take advantage of this
by monkeying around with the sets and/or using funky, cheap meters to show
the unknowing how much their radio is "swangin'". "LOOK! Ya got 8
watts o' carrier and 40 watts of 'swang'"! The CB guys eat it up! AND
willingly part with $$$ to get this "Swang". Swing is fully embedded in CB
psyche and, like the "coax length" (18 FEET! 18 FEET! Ya gots to have 18
feet of coax!!!!!!) bullsh--, it is part of the "holy" grail of CB radio!
LMAO!


J

Such as believing that an M3/CB Fools' Licence makes
then into a Radio Ham overnight.

"Jerry" wrote in message
news
CBers are very susceptible to urban myth and legend.

Jerry, you can trust me when I say that hams have their full share of
beliefs in voodoo physics and misunderstandings about how even the
simplest phenomena take place. A quick scan of the
rec.radio.amateur.antenna archives provides ample evidence in itself,
but there's plenty of other evidence scattered about.

So let's not be too hasty at calling the kettle black.

Roy Lewallen, W7EL

Jerry wrote:

CBers are very susceptible to urban myth and legend. Not understanding the
"normal" nature of an AM carrier, often they won't see the needle move very
much (assuming some cowboy jockey hasn't been in the rig snippin' and
clippin'), they get kind of excited. "HEY! I ain't got no "swang", so
therefore, they think they
aren't "gittin'" out. Voodoo techs have been able to take advantage of this
by monkeying around with the sets and/or using funky, cheap meters to show
the unknowing how much their radio is "swangin'". "LOOK! Ya got 8
watts o' carrier and 40 watts of 'swang'"! The CB guys eat it up! AND
willingly part with $$$ to get this "Swang". Swing is fully embedded in CB
psyche and, like the "coax length" (18 FEET! 18 FEET! Ya gots to have 18
feet of coax!!!!!!) bullsh--, it is part of the "holy" grail of CB radio!
LMAO!


J

There is no limit to AM modulation, it is not limited to 100 percent
in the positive direction. It is limited to 100 percent in the negative
direction, to prevent cutoff. Positive limits are set by the mdoulation
linearity of the output stage with increasing positive voltage.
Most AM BC broadcasters in this country use assemtrical modulation
for this reason.

You're dead right of course Peter.

i believe you're AM broadcasters are limited to 125% positive while here
in the UK we have 100% positive peak limit.

FYI the late model Nautel PDM broadcast transmitters are capable of
around 200% positive peak and up to 50KHz in frequency response!

Broadcast transmitters are limited for obvious reasons.
--
Philip de Cadenet G4ZOW
Transmitters 'R' Us
http://www.transmittersrus.com

Chris wrote:
I will probably get some flames from this but here it goes. I have been into
CB radio for a number of years but don't agree with most of what I hear.
That's just one of the reasons I'm looking to amateur radio. One of the
things I often hear in CB circles is that one should turn a 4 watt AM radio
down to 1 1/2 watts and let it "SWING". How is this possible? What really
happens when you do this? I think I know. So, how much carrier should you
have for an amp or final stage with a known max output. In other words, if
it can produce 8 watts max unmodulated carrier, is a 4 watt carrier ideal?
If it produces 100 watts, is 50 watts ideal? How much "space"does it need
for proper modulation? Is there a website that explains this well? I'm an
electronics tech thirsting for knowledge.

In amplitude modulation, the strength - "amplitude" - of the carrier is
adjusted by the audio you wish to transmit.

The degree to which this strength is adjusted is the "modulation
percentage". If the carrier is cut completely at negative voice peaks,
and strengthened to twice its normal level at positive peaks, then the
signal is said to be "100% modulated".

The receiver at the other end can only detect the *changes* in carrier
strength - not the carrier itself. If you reduce the modulation
percentage, you reduce the strength of the changes - the strength of the
signal the other guy can hear.

On the other hand, the laws of physics prohibit negative power. Once
you've modulated 100% - and reduced the carrier to zero at negative
peaks - you CAN'T go any further. It's physically impossible. If you
try, you'll generate sharp cutoffs that result in "splatter" - strong
interfering noises in adjacent channels. (and your signal on the
channel you're meaning to transmit on will become seriously distorted
and difficult to understand) [0]

So the point is, you want to modulate as close to 100% as practical
while ensuring you never *exceed* 100%.

For normal "high-level" modulation the amount of audio power required to
achieve 100% modulation is half the RF power. A 4-watt carrier requires
two watts of audio to modulate it 100%.
--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com

[0] It is possible to exceed 100% in the *positive* direction -
increasing the carrier beyond twice its normal level - without causing
distortion and interference. Such schemes are common at AM broadcast
stations. I'm not aware of any CB radio that contains such a circuit.

Ok Chris...here's the deal with "swing"...it's pretty much BS. By turning the power down to 2 watts and letting the xmtr go to 10 watts is just going to cause splatter, TVI and a whole host of other problems just so you can show off to your CB buddies how much you can make the s-meter swing on thier end. Anything in excess of 100 percent modulation is a waste of power and will make you sound like ca-ca. Unless you want to be a smartass and a prick, follow the guide below.

100 percent AM modulation as far as us hams are concerned is unmodulated carrier times 4. So if you have a 375 watt "dead carrier" with 100 percent modulation you will show a peak reading of 1500 watts with modulation (ham legal limit, BTW)...so a 4 watt dead carrier...well 100 percent modulation will be 16 watts. That's with a linear response out of the modulator and final circuitry...FCC rules say 4 modulated 5 as far as wattage for CB. The AMC (automatic modulation control) does this (4 watts dead key, 5 max "swing") by providing a non-linear response out of the modulator and final circuitry combination, accomplished usually with a diode or diode and potentiometer. Removal or adjustment of these devices, along with realignment, (peaking out to coin CB terms) can acheive the desired modulation result described here. Type in CB mods into google and you'll find a bunch of stuff if you're so inclined.

To also pick another statement out from your post, "That's just one of the reasons I'm looking to amateur radio."

That's your best bet...get your ham license. Blows 11 meter away. Take it from an ex freebander who now is a licensed ham.

john

Hope that answers your question