[PPRAANet] Fwd: Fwd: double sideband supressed carrier
Dan Martin
mardan1492 at comcast.net
Wed Jan 2 20:00:04 EST 2019
There is this advice from my FT-991A ops manual:
> ADVICE:
> By convention, LSB is used in the 7 MHz and lower Amateur bands for
> SSB communication, and USB is used on the 14 MHz and higher bands (the
> 10 MHz band is used for CW and data modes only).
Then, there is this article
(http://www.arrl.org/files/file/Technology/pdf/McElroy.pdf) that
features a photo, with the caption:
> Figure 4 -- This photo of General Curtis LeMay, then K3JUY/K4RFA, from
> the July 1961 issue of QST, announced his nomination as chief of staff
> of the US Air Force. During the mid '50s, Gen LeMay had concerted
> Strategic Air Command communications from AM to SSB, based on his ham
> experience with the newer mode.
There is also this article
(http://www.sgcworld.com/whatisssbtechnote.html) about why AM is better
for some purposes, principally commercial broadcasting:
> *Broadcasters Need Fidelity*
> You might wonder why SSB modulation is used for some applications and
> AM is used for broadcasting. Broadcasters must have excellent audio
> fidelity when transmitting music; otherwise, the typical radio
> listener will tune to another station. In order to achieve excellent
> fidelity when transmitting music, both sidebands and the carrier are
> necessary. To produce this AM signal, the transmitter is, in effect,
> working as three transmitters: one to produce a strong carrier for
> each of the sidebands, an upper sideband, and a lower sideband. The
> result is that approximately half of the transmitter power is "wasted"
> on a blank carrier and the rest of the power is divided between the
> two sidebands. As a result, the actual audio output from a 600-watt AM
> transmitter (300 watts of carrier + 150 watts on each sideband) would
> be the same as the SG-2000 150-watt SSB transmitter.
Finally, there is this from the ARRL (http://www.arrl.org/voice-modes):
>
>
> Overview
>
> Voice over radio channels (radiotelephony or just "phone") is probably
> the most popular form of Amateur Radio. A number of modulation modes
> are available to support voice work.
>
> * *AM* (Amplitude Modulation - double sideband, full carrier) is the
> oldest form of voice modulation. A CW carrier signal is
> controlled (modulated) by an audio voltage, so that the amplitude
> of the radio carrier ranges from zero (at negative audio peaks) to
> 200% (at positive audio peaks). Generation and reception of
> traditional AM can be done with relatively simple circuits, and it
> is still in use by a small, but hardy group of amateurs. (See the
> AM Phone page
> <http://www.arrl.org/am-phone-operating-and-activities>.) Nevertheless,
> most ham voice activity on HF has moved to SSB (see below).
> * *Digital Voice* is a new technique built around analog to digital
> converters and codecs that sample a voice signal, compress it, and
> transmit it as a bit stream. Like other digital media, digital
> voice offers interference free communications if the radio signal
> is strong enough to overcome the general noise and interference level.
> * *FM* (Frequency Modulation) is the voice mode of choice for local
> VHF / UHF operations, fixed or mobile, simplex or repeater based.
> It offers good performance with simple equipment requirements.
> The audio signal controls (modulates) the frequency of the
> transmitter over a small range.
> * *SSB* ("sideband", Single Sideband Suppressed Carrier) is the
> descendant of traditional AM. Compared to AM, SSB requires less
> than half the bandwidth and it offers much more "talk power",
> since the unnecessary carrier and second sideband are not
> transmitted. SSB requires more frequency stability and somewhat
> more complex circuitry than AM, but essentially all mainstream
> amateur gear for the HF bands now supports SSB voice.
>
Dan Martin, KD0SMP
On 1/2/2019 4:48 PM, John Bloodgood wrote:
> Attachments are generally not allowed on the reflectors.
>
> Traditional AM is double sideband, full carrier where basically half the power is eaten up by the carrier which contains no information. Not only is most of the power wasted, but since the information on each sideband is the same, it wastes bandwidth.
>
> DSB-SC (double sideband - suppressed carrier) is essentially AM, but the carrier is removed so all the power goes into the modulated signals carrying the information. Much better from a power standpoint, but still wastes bandwidth.
>
> ISB (independent sideband) is kind of like DSB-SC in that it has no carrier, except the upper and lower sidebands have different information on them, such as voice on the lower sideband and data on the upper sideband. Note that some systems have multiple upper sidebands and lower sidebands such as USB2, USB1, LSB1, and LSB2, all containing different information. Used to use ISB a lot for long haul comm in the military when in the field/deployed including 2 sideband and 4 sideband systems.
>
> SSB (single sideband) uses only one of the two sidebands (LSB or USB) and has no carrier.
>
> AME (AM equivalent AKA SSB-RC) is essentially SSB, but with a reduced carrier so that it can be demodulated by a normal AM radio, but it takes half the bandwidth and puts more power in the information than AM does.
>
>
>
>
>
>
>
>
> John Bloodgood, KD0SFY
>
>
> ________________________________
> From: ppraanet-bounces at mailman.qth.net <ppraanet-bounces at mailman.qth.net> on behalf of Glenn <n3ulw at comcast.net>
> Sent: Wednesday, January 2, 2019 3:41 PM
> To: ***Reflector PPRAA***
> Subject: [PPRAANet] Fwd: Fwd: double sideband supressed carrier
>
>
> I had to strip off the attachments as it made the message to big!
>
> This topic came up on the Thursday night PPRAA net. Dick, KD8EQ took it
> upon himself to find the answer. Thanks Dick!!
>
> Glenn
>
> n3ulw
>
> P.S. next time in your car the radio's, in newer cars, that shows the
> station and what song is playing and with sound is using DSB-SC
>
>
> RDS is one place where DSB-SC is used.
>
> 73 Dick KD8EQ
>
> Links
>
> https://en.wikipedia.org/wiki/Double-sideband_suppressed-carrier_transmission
>
> https://en.wikipedia.org/wiki/Radio_Data_System
>
> Subject: Fwd: double sideband supressed carrier
> Date: Wed, 2 Jan 2019 15:04:45 -0700
> From: Glenn <n3ulw at comcast.net>
> To: ***Reflector PPRAA*** <ppraanet at mailman.qth.net>
>
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