Why are SSBs so susceptible to noise?

[Cadence]

Originally Posted by snokid

you guys make it sound like finding the noise on your boat is hard.....

1st get out of the marina
2nd turn off all the breakers (except the radio lol)
noise should be gone. If not check antenna, and grounds...

now turn breakers on one by one
when the noise comes back figure out which item is making the noise, then either turn it off when you are using your radio or repair or replace it.

make sure while performing this test all your fancy electronics are off cell-phone, computers, tablets....

I know it's old tech, but so is that fancy cell-phone you might be using... do you remember the days of analog cell phones?

Get a hundred of miles off shore your choices for reaching someone go down SSB I still think is one of the best choices....

Bob

Re: analog in the bag?

[Paul Elliott]

Originally Posted by tanglewood

I think you guys are missing the point. The problem is that I need to do anything.

To use my cell phome at home, I don't have to turn off all the power in the house. And I don't have to go through each circuit breaker to locate and suppress sources of inteference. All that is built into the cell phone.

I'm not askimg how to get rid of the noise. i'm askimg why the manufacturer hasn't done it for me in the design of the radio, like for every other radio based device that one buys today.

The answer seems to be "because". A little bit because AM is harder to deal with, but mostly it seems to simply be because they haven't done it.

No.

The answer is "because the modulation techniques used for cellphones, satphones, VHF FM, etc, are completely different and have different behavior in the presence of noise, and because the HF radio frequencies have vastly different radio noise conditions than VHF and UHF frequencies."

Modern cellphones, satphones, etc, use modulation such as GMSK, QPSK, nQAM, etc, to carry digitally-coded data and voice. Noise and other interference do not cause noise in the demodulated and decoded signals, until the noise gets so bad that the decoding error rate exceeds capability of the Forward Error Correcting codes. Even plain FM analog modulation rejects most forms of noise up to a point.

SSB, by definition, responds to on-channel noise and fairly heroic methods are needed to mitigate this. Yes, basic filtering, including notch, impulse blanking, adaptive impulse blanking, and adaptive passband filtering can reduce the noise somewhat, but nowhere near the way that digital modulation and forward error correction can. The advantage of SSB is that it can work with much weaker and noisier signals than can digital systems (for voice communication).

Also critical to the comparison is the frequency of operation. Marine SSB uses the HF bands (3-30 MHz) These frequencies have *much* greater levels of atmospheric noise than do the VHF (30-300 MHz) and UHF (300 -
3000 MHz) frequencies. This includes broadband hiss, and impulse noise from worldwide lightning strikes. Also, man-made noise sources tend to fall in this region. Even the much smaller amount of man-made noise in the VHF/UHF region only propagates line-of-sight, and the levels generally start out *much* lower than do the HF noise sources.

So while marine SSB could benefit from more aggressive noise-reduction technology, there are intrinsic and non-negotiable reasons why the noise behavior will never be as good as seen with cellphones.

[transmitterdan]

Paul Elliott is right. I would just add that because HF has tremendous propagation distances is precisely why it picks up more noise than VHF or UHF. Your HF receiver can receive signals from pretty much anywhere in the world and even the entire solar system. A cell phone can only hear signals from about 2 miles or so. If HF bands were not noisy they would be useless to cruisers.

[Auspicious]

Originally Posted by tanglewood

I think you guys are missing the point. The problem is that I need to do anything.

I suggest that you are the one missing the point. As Paul and Dan point out marine VHF FM and cell phones (various sorts of high order QAM) hide the interference from you. They work until they don't work, much like over-the-air digital TV. It works until it doesn't.

Originally Posted by tanglewood

To use my cell phome at home, I don't have to turn off all the power in the house. And I don't have to go through each circuit breaker to locate and suppress sources of inteference. All that is built into the cell phone.

Unless you cell phone doesn't work at home. You can give up, or buy a microcell that uses wired Internet, or discover that your kitchen microwave or home WiFi or some other internal source in the house is why you can't connect your cell phone at home. That assumes you aren't in a gully where topography is your problem.

Originally Posted by tanglewood

I'm not askimg how to get rid of the noise. i'm askimg why the manufacturer hasn't done it for me in the design of the radio, like for every other radio based device that one buys today.

Because you are obstinately hanging on to your preconception instead of pursuing understanding.

[Cadence]

I may be dumb as a rock? It seems SSB is only using one half of the carrier and the AM is put in on the receiving end. It would seem noise is generated after the signal is received? Any mismatching of an antenna is only reducing received signal strength.
Again. JMHO

[S/V Illusion]

Originally Posted by tanglewood

I think you guys are missing the point. The problem is that I need to do anything.

To use my cell phome at home, I don't have to turn off all the power in the house. And I don't have to go through each circuit breaker to locate and suppress sources of inteference. All that is built into the cell phone.

I'm not askimg how to get rid of the noise. i'm askimg why the manufacturer hasn't done it for me in the design of the radio, like for every other radio based device that one buys today.

The answer seems to be "because". A little bit because AM is harder to deal with, but mostly it seems to simply be because they haven't done it.

It's kind of like the first PCs. If you didn't know someone who was a geek, you were SOL getting the thing to do anythhing usful. PCS evolved, but SSBs haven't.

Manufacturers like icon who obviously make marine radios already has the rechnology to minimize noise. It has nothing to do with availability but for one exception - that being limited market.

Icom as just one example sells lots of radios which effectively limit noise. So do most others. What none do is put it in a box labeled marine with minimal controls which boaters generally don't know or want to learn how to manage.

[Paul Elliott]

The Shannon Law (or Shannon-Hartley Law) lays out the fundamental and essential relationships between signal, noise, and bandwidth. Anyone who deals with developing or understanding modern communications methods and issues needs to have at least a passing knowledge of this topic.

This may be more technical than many here will be interested in, but here is a nice paper on signals, noise, the information-carrying capacity of a channel, and how Claude Shannon developed his incredibly groundbreaking work in Information Theory:
http://citeseerx.ist.psu.edu/viewdoc...=rep1&type=pdf



Other good related links:
Claude Shannon: https://en.wikipedia.org/wiki/Claude_Shannon

The book "The Information" by James Gleick: https://www.amazon.com/Information-H...information%22 -- This is a well-written, fairly non-technical exploration of the history of Information Theory.

[Paul Elliott]

Originally Posted by Cadence

I may be dumb as a rock? It seems SSB is only using one half of the carrier and the AM is put in on the receiving end. It would seem noise is generated after the signal is received? Any mismatching of an antenna is only reducing received signal strength.
Again. JMHO

Actually, SSB transmitters only transmit one of the information-carrying sidebands. AM transmitters send both (redundant) sidebands, and a carrier which conveys no necessary information at all. This way, in SSB *all* the transmitted power goes into the voice information, and none into an otherwise wasted carrier. Also, single sideband takes up less bandwidth, and so allows for more useable channels in a given frequency span.

Any antenna mismatch is more important at the transmitter end, as it does affect the transmitted signal strength. At the receiver end, the atmospheric noise is usually strong enough that we are more concerned with signal to noise *ratio* than absolute signal strength. Receivers are usually sensitive enough that even a large antenna mismatch can often be ignored.

Of course well-performing antenna systems are good, it's just that they are less critical for receiving than they are for transmitting.

[transmitterdan]

There are systems for sending digital data via HF bands. Sailmail, digital radio Mondiale and ham radio standards have been developed. They have the noise free feature but the cost is pretty high (except for ham radio) and very few people have compatible receivers. So these standards are not practical for emergency communication. And in an emergency a little noise is the least of problems. Typically away from civilization the noise levels are quite reasonable and it is pretty easy to eliminate all sources of noise from your boat. Just start turning stuff off until the radio is the only thing running. You will be amazed how quiet SSB can be.

[snokid]

Tanglewood

The reason is pretty simple

your cellphone requires an external system to work (a network of antenna's)
Different types of modulation and freq's.

you can take a ham radio and do just what you are talking about. They are called repeaters, ham's form a group and install an antenna up high someone between them. At that location there's a radio that listens for a signal then rebroadcasts that signal out.

Now that little fm vhf in their hands is able to talk hundreds even thousands of miles all for 30.00

Ok so we can talk local just like a cellphone no problems no noise...

Now we come to the problem of talking long distances....

on a boat you are kind of limited. ssb and sat phone.

Ok let's look at these two options.

Sat phone will be quiet almost always work sounds really good huh?

SSB will always work but will take some knowledge to be useful.

one more option

get a ham ticket

Why? First it's knowledge Passing even the tech novice class test will give you some knowledge to how things work so when they don't work you will have a chance to fix it.

With the ham HF band you can have e-mail, weatherfax, even a text message type of thing.

Bob

[S/V Illusion]

Originally Posted by snokid

Tanglewood

The reason is pretty simple

your cellphone requires an external system to work (a network of antenna's)
Different types of modulation and freq's.

you can take a ham radio and do just what you are talking about. They are called repeaters, ham's form a group and install an antenna up high someone between them. At that location there's a radio that listens for a signal then rebroadcasts that signal out.

Now that little fm vhf in their hands is able to talk hundreds even thousands of miles all for 30.00

Ok so we can talk local just like a cellphone no problems no noise...

Now we come to the problem of talking long distances....

on a boat you are kind of limited. ssb and sat phone.

Ok let's look at these two options.

Sat phone will be quiet almost always work sounds really good huh?

SSB will always work but will take some knowledge to be useful.

one more option

get a ham ticket

Why? First it's knowledge Passing even the tech novice class test will give you some knowledge to how things work so when they don't work you will have a chance to fix it.

With the ham HF band you can have e-mail, weatherfax, even a text message type of thing.

Bob

I think he is more the appliance operator mentality not interested in the how/why it works.

The is no such thing a story a "tech novice" license. The latter doesn't exist anymore. Regardless, neither is a new indicator of technical competency as these license class tests measured only bare fundamentals and license legal constraints such as frequency limits.

You are correct in that the only technology marketed now which does a good job of minimizing noise is with ham radios.

[snokid]

Originally Posted by S/V Illusion

The is no such thing a story a "tech novice" license. The latter doesn't exist anymore. Regardless, neither is a new indicator of technical competency as these license class tests measured only bare fundamentals and license legal constraints such as frequency limits.

I haven't kept up on classes of licenses in all parts of the world not sure if the novice ticket is still offered in other area's but yes novice was done away with a long time ago. I only include it because this isn't just read by us us residents.

Bob