ARRL Petitions to delete SS APC

OK, well, they must be teaching engineering different now.

So FM Stereo would be SS because it multiplexes several signals in a very wide bandwidth. It doesn't have to be orthogonal does it?

OK, I think I can pass the new question pool.

 

Huh? A signal is wider because it is passing several signals so it must be Spread Spectrum?

Your logic makes no sense.

Is an amplitude modulated signal Spread Spectrum because it is twice as wide as a SSB signal?

They are not teaching engineering any differently to my son in college right now than when I went 36 years ago. They learn how to define phenomena using math. Of course it was about second grade when they learned that 1000 is much greater than 36. They would have also been able to tell you in 2nd grade that a 22Mhz channel using OFDM is much, much wider than a 3khz channel using OFDM.

Perhaps you should reconsider denigrating someone's engineering knowledge without first considering your own math skills.

tim ab0wr

 

Well, maybe I'm just not reading you right.  I think you're saying that FDM with less than some number of frequency divisions is not Spread Spectrum, but if you have FDM with more than some number, then it is spread spectrum.

Since FM stereo has less frequency divisions (AM is not Multiplexed) but is as wide as OFDM with more frequency divisions, then the SS definition merely depends on the number of divisions in the FDM, and not merely the bandwidth.

Am I getting closer?

 

Expressed visually:

 

Guess I'll stick to the healthy midle way of stereo fm

 

You are getting closer.

Remember, FM stereo actually consists of three signals added together. You generate a left+right signal, a left-right signal, and a pilot tone. You sum these three together and they become the signal you use to generate the FM stereo signal. The actual bandwidth of the FM signal is 2(modulation index + 1)(max modulating freq). The highest applied signal is around 50khz. With a modulation index of 1 you get a 200khz bandwidth signal.

So you can see that an FM Stereo signal is not spread spectrum. It would be like sending a combined signal through your 2m rig that has had three audio signals (0-3khz, 3khz-6khz, and 6khz-9khz) summed together. Each of the audio signals could be from a different microphone. Doing this would not cause you to send a spread spectrum signal, you would just be sending a wider FM signal because the highest audio signal is *higher*.

I'm not sure where you are getting the "frequency divisions" for FM stereo.

The bandwidth being sent *is* dependent upon the number of divisions you use for a spread spectrum signal. FM stereo doesn't have divisions so it doesn't apply.

tim ab0wr

 

Except for the few of us here discussing it, this does not seem to be a very hot topic. So far there have only been a handful of comments on the petition and most are a one line for or against comment. Very little in the way of technical justification for or against the proposal. Maybe SS is just a little too esoteric for the average amateur.

73,
Mike WA3KYY

 

It's not "too esoteric" if it increases the noise floor for most Amateurs using traditional modulation methods. Technical (and semi-technical) examples HAVE been given. But there's been little proof given that the increase in power and resulting increase in the noise floor will NOT harm other users, particularly if allowed on bands where SS is presently not permitted.

 

CW, SSB, AM, and FM all raise the noise floor. The noise floor is only noise if everyone takes the day off.

 

Yes, they all raise the noise floor, but in a different manner that a SS signal.

Saying that Spread Spectrum only raises the noise floor a little bit can be very misleading. It raises it a little bit only if a little bit of power is used. Only a little bit can be significant, however.

SSB, by it's nature, allows multiple conversations to progress on the same frequency because of its intermittent nature. Uncompressed voice has a dynamic range of over 20db. And that doesn't even count the pauses between words or even syllables. Different voices can be picked out of a crowd with as small as a 6db difference. This allows sharing of a frequency among as many as three conversations.

CW is somewhat similar except the conversations have to be separated by enough that the brain can distinguish the different tones and when they stop and start.

FM doesn't share frequencies well at all, primarily because there is a carrier transmitted. Secondarily because of the capture effect of FM demodulation. Operation with FM, however, has evolved to use this as an advantage instead of a disadvantage.

Spread Spectrum, because of its nature, can share with other Spread Spectrum but it is NOT a good neighbor to analog signals like SSB and CW. It is a better neighbor to FM, at least up to a certain point.

The Gaussian noise from SS signal is what is called a masking type noise. While people might be able to work a CW or SSB signal 3db above the noise, the intelligibility ratio is going to be low for normal operational styles. 6db is a better indicator of being able to progress a conversation in a reasonable manner. Even a 1db raise in the Gaussian noise floor will raise the masking noise level enough that normal conversations will become very difficult.

Narrow band signals such as CW and SSB are not considered masking type noise. They are narrow-band signals that can be tuned out. Even with FM another frequency can be chosen for operation.

So saying that CW, SSB, and FM raise the noise floor is comparing apples and oranges.

tim ab0wr

 

Tim makes a good point. With SS, the analog modes will experience increased noise "everywhere," not just on discreet frequencies.
All the SS proponents are saying is the noise floor will be raised "a little bit," but do not define that as 0.1 dB, 1.0 dB, 3 dB, 10 dB, or anything else, especially with increased power of 100 watts. It's sort of like being "a little bit " pregnant.

Why not DROP the idea of allowing any SS on 6 M and 2 M from the current proposal, and allow the higher power where SS is allowed NOW, until the SS operations at the increased power levels can be shown one way or another, whether they have a detrimental affect on analog modes.

 

Think of a multilane highway--when everyone sticks to their own lane traffic can flow smoothly even if the traffic in the lanes is moving at differing speeds.
' Now toss in a speeding motorcycle constantly weaving ,jumping from lane to lane,squeezing through the "holes" and a wreck is a near certainty.At least,all the other users of the road will be inconvenienced so one can have "fun".

There have always been people who decry the existence of order,calling it "pigeonhole" mentality,etc.

The original rules ere designed so the most people could enjoy the hobby while causing the least disruption;until you can prove why the change is good,we remain skeptical.
Ham radio (and society) have thrown out a lot of the old rules and gotten increased chaos.I don't think it is an improvement.

There probably is room on 6 and 2 for "narrow" wideband signals equivalent to the old wide fm as long as they operate on a few designated spaces. Ditti 223. .
I sincerely doubt the goodwill to be derived from a bunch of hams running 100 watt ex-part devices on the shared bands.There are tens of millions of people enjoying wireless computing and telling them "tough,we are licensed and you have to like it" isn't a way to win friends in politics.

 

ex-part=ex-part 15 (sorry)

 

What you say is reasonable however there are two points to be made:

1. Most of the Digital Elite here have very little "goodwill" or so it seems. They say (and you agree) "trust us". IMHO, the goodwill should come now by agreeing to segregate digital use into its own subband. We all win that way. But the motif du jour here is "we want it all and we want it NOW". No?

2. The Petition seeks to allow SS on 6 and 2 meters. Sounds harmless, right? Don Rotolo of CQ Magazine is pushing now for 9kHz bandwidth on HF for OFDM data use with Reed Solomon encoding. OFDM is a Spread Spectrum mode and Reed Solomon encoding uses filters to improbe performance under noise/fading/atmospherics. So it's 6 and 2 meters today, HF tomorrow. Gimme, gimme, gimme from barely 1% of Amateurs.

So I say that since our Digital Elite buddies won't show any "goodwill" now, let the 99% of Amateurs who will be trashed by these proposals just say NO! Retract these current petitions and put a new one together calling for segregated digital use without taking away from AM/SSB/CW and I'll say yes.

 

Please post comments to the FCC before the comment period expires!  I have also posted a "head's up" on the VHF contesting reflector.