HFU HF Underground
General Category => General Radio Discussion => Topic started by: digitalmod on January 30, 2018, 1730 UTC
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8)
After doing so weak signals SWL I am going on the side of SSB for best signals especially in weak signal or low Signal to Noise.
Transmitters are more complex ,but it easier on transmitter because its only one side band and the duty cycle for power is same as an Audio AMP. Low generally.. the transmitter will not fry itself.
Disadvantage : More complex and STABLE receivers were once mandated, but today a 30 dollar SDR and computer meet the rx requirement.
Audio pass band can be tailored, but caveat, more bandwidth will bring in more NOISE, in college I think they said that was Nyquest's law??
Listening to some of the SSB stations I conclude you need a DDS transmitter and adjustable pass band and if that not possible an external parametric band audio equalizer. Audio even in a very tiny 3 kilohertz can be made to sound damn decent.
Of course AM is still vintage and so easy to receive, but only if you have at least a 20db or better signal to noise. That's not smart considering we have enemies listening. keep them guessing
That may most often be difficult and as you all know the bigger the signal the more smoke the radio Police will sniff. :-\
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And, of course, USB is the Manliest of modes.
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Real men operate CW, using a hand key of course and one's own ears for receiving, computer CW is Claytons Radio... ::)
Over a decade ago there were quite a few international broadcasters using SSB on HF, but they all dwindled away, music sounds crap in SSB... 8)
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And, of course, USB is the Manliest of modes.
And where have you been? Scanning the obituaries? You know we have to line up the Earth, the Moon, and the Sun tomorrow night.
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No, music transmitted from a DDS transmitter and received on a stable SDR with about 3 kHz band pass sounds damn decent.
Examples Yetti radio and CNR on my sdr sound at least as good as AM and less noise.
The reason early ssb failed was the same reason DRM will fail.. nobody has the receivers in shortwave to make the programming even available, much less sound as decent as 20-20,000 hertz you routinely get from DSB = direct satellite Broadcasting or
the Web. As long as the Web bandwidth keeps expanding all RF broadcasting will end.
You Asussi already have Sheperton bite the dust. Its just the beginning. :o
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From a listener point of view, I'd say... it depends on what the transmitting station is using for equipment. Some stations sound great with SSB, Wolverine and Radio Free Whatever for example (there are others). OTOH there's some that are using an unmodified "rice box" rig, or at least it sounds that way. Tinny narrow audio. Maybe off frequency by a hundred Hz or more, enough so music is painful to listen to. You don't need to be GPS reference locked, although it would be nice! ;D But it should be pretty trivial to calibrate your radio now and then. We listeners would appreciate it. If there's two pirates on the air, one with great audio, and one without, which are the listeners going to listen to?
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Back in my SSB days, I can count on one hand the number of airchecks I received that were on the correct frequency. If your listening to music that is unfamiliar, it is very difficult to get the frequency right. Agreed, frequency standards would fix the problem, but most receivers are not that stabile to begin with. AM with a good sync detector, or DSB with some carrier leak is a good compromise between fidelity and the ability to correctly tune.
I'm sorry but 3K doesn't cut it for me. If I wanted to listen to music through a telephone I would. Set it for 10 KHz and let the listener decide how much noise they want to listen to.
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8) Yeah, 10 kHz would be great, but you would need "tinker" with the DDS and transmitter to get a pass band that decent.
Then, at ten kHz, on shortwave is problematic since more channel noise can decrease your listeners pleasures.
If you go AM you need a whole lotta power to keep the s to noise acceptable. For a free radio station that could attract SHARKS, since any idiot can tune AM, but much better radios and SWL ops needed to tune SSB.
I recall about twenty or maybe more years ago, I heard a VOA transmission with carrier inserted. It carried two programs. One on USB and another on Lower. 8) BTW talk about sidebands, CHU time signal only transmits the USB and the carrier. Its cool to see it on the SDR. Case in point, the Toronto parallel station CFRX. Its said the transmitter is a Kw double side band, but when I listen except certain times of day.. selective fading, carrier dropping down below here good fidelity is heard and so on.
The big ones 1 million watt ERP stations even have fades. I can hear about anytime of year the 500kw, maybe 3 megawatt ERP
India Radio station on 7550. But its a non hi fi copy. :-X
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Those are called feeder transmission, used to carry programs to distant relay stations in ISB. It was mostly used before satellite became common, and is still sometimes used as a backup solution should the uplink fail.
I honestly think the FCC has better things to do than police large swaths of HF spectrum. They know we're here. Just listen to the 'licensed' ham bands and you tell me if there is much enforcement going on.
Most receivers have bandwidth controls. Run 5-10 KHz audio, and let the listener decide what they want to hear. Don'f forget there is a law of diminishing returns with regard to transmitter power. You have to dump a lot of watts into the sky to get another S unit, in most cases it's not worth it due to the stress placed on everything from the transmitter and what is powering it, to the feeder and antenna networks.
I still run 10-13KHz audio. At least give the listener the choice to decide how good or poor they want it to sound.
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Red Hat, the sharks could strike, but frankly they need a compliant. FCC doesn't do squat without a compliant.
That's why I think keeping it decent, maybe not long transmissions and on various frequencies at random times is best safe guard a Free Shortwave has. The interest commercially and otherwise in shortwave decreases every year. Grave yards are full of shortwave broadcast transmitters. ABC just ditched after 70 or more years its Over Seas service. Not enough listeners for the expense. They actually took Shep off the air for two weeks as a TEST to see who or how many listeners would Email them.
They got a very small response and I think that site is now sheep and goats? 8)
Also, I am shocked that 500kw transmitters exist. Can you imagine paying for an extra 250 kw and get half an S point.
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Red Hat, the sharks could strike, but frankly they need a compliant. FCC doesn't do squat without a compliant.
Sure they could, and historically, you either needed to be in the wrong place at the wrong time (it happens) or do something stupid, like broadcasting for long stretches from an urban residence. That is why I built my station to be easily movable. Pack up the gear and go...across the state or 6 states over. No big deal, all I need is a back lot and we're good to go. Parks, fields, or an abandoned parking lot. All good candidates.
We may get it one day. It happens to a lot of guys after a while. Its the risk you take to play the game.
Also, I am shocked that 500kw transmitters exist. Can you imagine paying for an extra 250 kw and get half an S point.
Nautel just lit up a 2MW AM in Hungary I believe, and a 400KW on 800 KHz in Bonaire. Someone is buying these things.
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I also run full 10Khz bandwidth and use DDS for my carrier.. I think most SW Listeners would much rather listen to high fidelity commercial broadcast quality. than to listen to 3Khz SSB. for music..
AC
Nautel just lit up a 2MW AM in Hundary I believe, and a 400KW on 800 KHz in Bonaire. Someone is buying these things.
Man I would love to see that schematic for the final PA's
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For a free radio station that could attract SHARKS, since any idiot can tune AM, but much better radios and SWL ops needed to tune SSB.
If you are going to be an SWL, you're going to be tuning in SSB at some point in your lifetime. It's sort of the low barrier to entry for the hobby. Everybody who is going to listen on SW to a pirate can basically handle tuning SSB to within 10-30 Hz. It's not terribly complicated.
Put some music into an SSB TX sometime and listen to it on a nearby AM RX. You will recognize that it is music regardless. Now imagine that signal getting into your neighbor's telephone or TV. They are also going to recognize it as music too. That won't help your case.
The authorities can tune SSB just like they can tune AM. They can DF SSB just as well as they can DF something with a carrier.
Your argument makes no sense.
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Most receivers have bandwidth controls. Run 5-10 KHz audio, and let the listener decide what they want to hear.
+1 on that.
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Also, I am shocked that 500kw transmitters exist. Can you imagine paying for an extra 250 kw and get half an S point.
The Hungarians paid a lot of money for that 2 MegaWatt TX because they have a lot of expats living within 2000 km of Hungary who want to hear something from the homeland and sometimes their listening conditions aren't that great. The extra dB isn't for the folks living down the road from the TX, it's for the folks 2000 km away driving in their car, coping with MW band interference.
(I also wouldn't want to live within 30 km of that TX, but that's another story.)
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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/ (http://www.nautel.com/solutions/high-power-mw-nx-series-100kw-2mw/)
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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.
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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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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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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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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.
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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)
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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.