Author Topic: Broadcasting in SSB many advanategs a few disadvantages  (Read 1023 times)

redhat

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Re: Broadcasting in SSB many advanategs a few disadvantages
« Reply #15 on: February 01, 2018, 0347 UTC »
Man I would love to see that schematic for the final PA's

Its 640 of these.  4 NX400's into a combiner.  Each transmitter is 4 cabinets with 40 modules per cabinet.  Each module is good for something like 4 KW, in normal service they run around 2.5KW carrier.  Conventional class D with non-overlap circuitry included in the module.

http://www.nautel.com/solutions/high-power-mw-nx-series-100kw-2mw/

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« Last Edit: February 01, 2018, 0351 UTC by redhat »
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ChrisSmolinski

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Re: Broadcasting in SSB many advanategs a few disadvantages
« Reply #16 on: February 01, 2018, 1104 UTC »
I still run 10-13KHz audio.  At least give the listener the choice to decide how good or poor they want it to sound.

I adjust my bandwidth based on receiving conditions and transmitted bandwidth. I find that usually +/-5 kHz is the maximum for a strong AM station (assuming the station's audio is that wide), otherwise I am adding mostly noise, as even with a strong signal there doesn't seem to be much audio content up there, it is mostly noise. But yes it is nice to have the choice.
« Last Edit: February 01, 2018, 1143 UTC by ChrisSmolinski »
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digitalmod

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Re: Broadcasting in SSB many advanategs a few disadvantages
« Reply #17 on: February 01, 2018, 1741 UTC »
 FCC needs somebody to compliant before that station gets DF ed .. In old days, in early sixties, they actually did have radio sheriffs monitoring to get somebody. With technology and growing need for personnel elsewhere that's over for decades.
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redhat

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Re: Broadcasting in SSB many advanategs a few disadvantages
« Reply #18 on: February 01, 2018, 1921 UTC »
Again, they have the technology and still maintain a network of monitoring stations.  They know where we are in most cases, but my guess is, they don't have the resources to chase everyone, just those they perceive to be a threat to themselves or others.

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digitalmod

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Re: Broadcasting in SSB many advanategs a few disadvantages
« Reply #19 on: February 02, 2018, 0002 UTC »
 wanted to add a tech note. In sideband there is a translated up converted signal that is in essence audio. Just has an envelope at an RF frequency. In communications the information signal must be lower in frequency than the so called carrier. That's why the Navy nuclear sub transmitter cannot transmit speech or even key the 2 million watt carrier. They in fact, phase modulate the carrier. The reason is 20khz Yes, that right.. the same frequency as upper end of good human hearing, is the carrier.
No baseband could possibly amplitude modulate that frequency and the rules of the genius Shannon (he was a scientist at Bell Labs) must be obeyed. Of course its the rules of nature.. LOL. The information rate of such nuclear communications to subs is very low BAUD They must trade time for bandwidth !
Now, for purpose of discussion. A transmitter must be phase linear when transmitting information in sideband. The OLD transmitters could not reach even 2 or more kilohertz base band because the phase lock loops were phase correction the carrier frequency at a rate comparable with the audio base band! It sound water like.
But today its a different ball game DDS is rock stable. No phase noise. Nothing is being feed back to keep frequency stable.
Hence audio out to any reasonable bandwidth can be transmitted.. BUT most sideband transmitters available without tinkering band limit the base band signal. Hence 3.2 kHz is pretty much where it sits because the transmitter was intended for speech.
But short little nurds know well you pull out the baseband filters and the rainbow comes out. That is 15 kHz of baseband.
Who has these transmitters?? I think some smart dude with a Flex radio.. LOL
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Josh

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Re: Broadcasting in SSB many advanategs a few disadvantages
« Reply #20 on: February 02, 2018, 1844 UTC »
SSB has advantages for both tx and rx side of things but not if you want to just chill with your old tube rig in am mode.

ThElectriCat

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Re: Broadcasting in SSB many advanategs a few disadvantages
« Reply #21 on: February 02, 2018, 2035 UTC »
I would tend to agree that transmitting in SSB brings benefit, especially for low power broadcasters such as part 15 and pirate broadcasts, and although SSB has a lower fidelity than AM by traditional standards, that is because of a bandwidth restriction, rather than the inherent limitations of the mode itself.  If one were to use a 10 or 15 KHz audio signal to drive an SSB transmitter(without a narrowband filter of its own), the audio quality would be equal to or greater than an AM transmitter. the only 2 problems with this are as follows;
1. the average SSB receiver has a narrowband filter, which will limit the audio quality regardless of the transmitter.
2. the signal must remain very well tuned for the receiver to demodulate the audio properly.

In the modern age, with fancy SDR receivers and PLL or DDS transmitters than can be locked to an accurate frequency reference (WWV/GPS/OCXO/RubidiumTO) these problems are easily dealt with, and the savings of 66% of your power not used for the carrier, and another 17 not used for the other sideband, it may be the right choice in SOME situations.

(P.S. I love AM as much as the next guy, just saying its not the only right way)
wj DMS-105a-2, and whatever wire, loop, or other antenna I can get my hands on

TheRelayStation

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Re: Broadcasting in SSB many advanategs a few disadvantages
« Reply #22 on: February 02, 2018, 2049 UTC »
I would tend to agree that transmitting in SSB brings benefit, especially for low power broadcasters such as part 15 and pirate broadcasts, and although SSB has a lower fidelity than AM by traditional standards, that is because of a bandwidth restriction, rather than the inherent limitations of the mode itself.  If one were to use a 10 or 15 KHz audio signal to drive an SSB transmitter(without a narrowband filter of its own), the audio quality would be equal to or greater than an AM transmitter. the only 2 problems with this are as follows;
1. the average SSB receiver has a narrowband filter, which will limit the audio quality regardless of the transmitter.
2. the signal must remain very well tuned for the receiver to demodulate the audio properly.

In the modern age, with fancy SDR receivers and PLL or DDS transmitters than can be locked to an accurate frequency reference (WWV/GPS/OCXO/RubidiumTO) these problems are easily dealt with, and the savings of 66% of your power not used for the carrier, and another 17 not used for the other sideband, it may be the right choice in SOME situations.

(P.S. I love AM as much as the next guy, just saying its not the only right way)
and i agree with you but this is also the reason why i tend to keep the band pass audio on my TX at 5Khz since most receivers band pass filter (excluding SDR's) are generally fixed at 5-6Khz anyway.
even with 10Khz band pass audio, to effectively hear 8-10Khz requires the transmission to be received stronger than it would be at 5Khz so its pretty much useless for low power transmissions that are being received with less than an S9.
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