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Author Topic: ARRL Files "Symbol Rate" Petition With FCC  (Read 32654 times)
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Pete, WA2CWA
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« on: November 19, 2013, 10:49:28 PM »

We heard it was coming and now it's been filed.

From the ARRL web site date 11/19/13:

The ARRL has asked the FCC to delete the symbol rate limit in §97.307(f) of its Amateur Service rules, replacing it with a maximum bandwidth for data emissions of 2.8 kHz on amateur frequencies below 29.7 MHz. The ARRL Board of Directors adopted the policy underlying the petition initiative at its July 2013 meeting. The petition was filed November 15....
http://www.arrl.org/news/arrl-files-symbol-rate-petition-with-fcc

The PDF Petition: http://www.arrl.org/attachments/view/News/72517
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« Reply #1 on: November 20, 2013, 05:21:28 PM »

I thought this also included a provision to limit the bandwidth of any signal (including phone) and not just data?

On another forum, there was a recent discussion about some ESSB signal on 75m that was over 20 kHz wide. The statement --by two people-- was that there was no bandwidth limit on phone. Tell me that's not true.
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« Reply #2 on: November 20, 2013, 06:22:58 PM »

How were these people determining the bandwidth of the ESSB signal? Were they trying to determine the bandwidth by using their receiver? In that case then the perceived bandwidth that the signal is occupying is gonna be the actual transmitted bandwidth of the signal PLUS the bandwidth of the receiver. As far I know, and I might be worng, there are no bandwidth restrictions in part 97, it just says to basically use good engineering practices to try to keep things within reasonable limits.
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« Reply #3 on: November 20, 2013, 07:09:45 PM »

I'm not sure how it was measured. But unless they were using a receiver with no filters, I don't think that's "good engineering practices" by anyone's definition.

Any signal (unless it is extremely strong) that can he plainly heard through other QSOs in a crowded portion of an HF band across 20 kHz on a good receiver is just too wide.

I heard hams last winter on 75m across nearly 30 kHz, which were up to 1600 miles distant. (And so did a whole lot of others in many other states). But lacking a specific law and enforcement, I suppose that sort of thing is here to stay.

That's why I prefer the lower end of 160. :-)
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73 Mike 
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Steve - K4HX
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« Reply #4 on: November 20, 2013, 08:45:34 PM »

There's less interference now on 75 meters than any time in the last 30-40 years. The sky is not falling.
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« Reply #5 on: November 21, 2013, 09:23:42 AM »

This brief exchange shows the problem with any bandwidth measurements.

Why propose something which cannot be verified by experimenters?

The only way anyone could guarantee compliance would be with a certificated appliance.

For those who don't like certificated as a word, it's used in FCC docs now.
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Jim, W5JO
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« Reply #6 on: November 21, 2013, 12:04:38 PM »

There's less interference now on 75 meters than any time in the last 30-40 years. The sky is not falling.

From the standpoint of fewer signals you are right, however many of those signals are far wider than those of 40-50 years back.  The band is cluttered with spurious signals that hams of the past would have been cited if they transmitted them, especially those who operate so close to the band edge and products fall outside the band limits.
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« Reply #7 on: November 21, 2013, 12:21:01 PM »

From the standpoint of fewer signals you are right, however many of those signals are far wider than those of 40-50 years back.  The band is cluttered with spurious signals that hams of the past would have been cited if they transmitted them ...

Precisely! That is exactly the situation today, and it is far more common than it should be. That was the point I was trying to make.

Sure, if we have our noise blankers cranked, and/or our receiver is being overloaded, then a clean signal may appear to have splatter or key clicks where none actually exist. But it does not take a rocket scientist with thousands of dollars worth of test equipment to tell if a signal is far wider than it ought to be. All it takes is a little common sense and a good receiver (with perhaps a front-end attenuator) to observe and compare the band width of various signals up and down the bands.
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« Reply #8 on: November 21, 2013, 12:43:05 PM »

If a transmitter is clean to begin with, (IMD) we should be able to reduce bandwidth on the fly, at the audio or DSP level, to suit crowded band conditions.

If a ham wants a smooth relationship with the rest of the whirl and desires to run high power, then he needs to spend time testing and improving his bandwidth and cleanliness. If things are amuck, troubleshooting can sometimes require the same amount of time and skill to correct that he invests in big antennas, big amplifiers and expensive radios.  

Many newcomers think they can buy a signal and automatically be clean. Sometimes it works this way. But there are many reasons for a wide signal that challenge even the best technicians and engineers. Operator error can often be the biggest reason.

An inexpensive SDR spec analyzer has made our jobs much easier.

I look at a clean signal like going out well-dressed to a disco-duck party. We can walk around and have fun without worrying about how we look.   And nobody can tell us otherwise.  

Personally, I don't know how some hams can take the abuse and listen to splatter reports about their signals and do nothing about it. It's like wearing a sign on our back that says "Kick Me in the GD balls - I'm from NJ!"    Cheesy

T


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« Reply #9 on: November 21, 2013, 04:32:35 PM »

Why propose something which cannot be verified by experimenters?

You already know the answer to this one Dave. Because it feels good to do it, even if it cannot be measured and verified by experimenters, and will be enforced poorly, selectively, or not at all by whoever appoints themselves to enforce it. I'm sure it will be every bit as effective as the "Do not call list".

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Rob W1AEX
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Jim, W5JO
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« Reply #10 on: November 21, 2013, 05:15:08 PM »



If a ham wants a smooth relationship with the rest of the whirl and desires to run high power, then he needs to spend time testing and improving his bandwidth and cleanliness. If things are amuck, troubleshooting can sometimes require the same amount of time and skill to correct that he invests in big antennas, big amplifiers and expensive radios.  

Many newcomers think they can buy a signal and automatically be clean. Sometimes it works this way. But there are many reasons for a wide signal that challenge even the best technicians and engineers. Operator error can often be the biggest reason.

I haven't read all the manuals that accompany amplifiers so I can only speak of my installation.  I have an Icom 756 Pro with an Ameritron AL 1200 and the book instructs you to attach the AGC line to your transmitter then follow a pattern to adjust that setting from the amp back to the exciter.  A variable pot adjusts the voltage developed in the amp that is sent back to the exciter

The problem is a bit of delay in the circuitry causes some overshoot.  I noticed it on the scope and found that the best way to solve an over drive problem is to disconnect that AGC wire and simply monitor the AGC on the exciter meter scale.  Not only that but don't keep the AGC level right at the top of the scale.  Let it average near the middle of the scale and vary up and down from there.

Many people don't understand those problems and I wonder just how many guys creat products way outside the necessary passband?  I bet a bunch, then add  ESSB to the mix and you hear it all over 75 and 20 meters.

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« Reply #11 on: November 21, 2013, 06:08:15 PM »


The problem is a bit of delay in the circuitry causes some overshoot.  I noticed it on the scope and found that the best way to solve an over drive problem is to disconnect that AGC wire and simply monitor the AGC on the exciter meter scale.  Not only that but don't keep the AGC level right at the top of the scale.  Let it average near the middle of the scale and vary up and down from there.


Good point, Jim.

I learned the hard way back in the 70's.  For ssb I built a 4X1 linear and had a diode detector tapping RF from the loading cap and rectifying it back to the exciter for ALC.   I tried various fast diodes of the day, but everything I tried produced a pop on the first syllable.  It could be heard up the band at the start of each word - just as clearly as any flat topping.   The amp was essentially flat topping for a few milliseconds until the ALC caught up.

Bottom line is I never use an external ALC anymore.  As you said, simply control the drive in the exciter ALC and limit your drive pep to a level below the max output of the linear amp.  If someone desires heavy processing, it can be just as effective low level.

External ALC, if used only for an emergency overdrive situation, is best left sitting in the turned down position awaiting a serious problem.

T
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« Reply #12 on: November 21, 2013, 07:52:24 PM »

I must hang out on different frequencies or bands than you guys. I've heard few wide signals and rarely been subject to interference from them. The few wide ones were on the typical ESSB freqs. So, I use my VFO and stay away from them. There's plenty of wide open, QRM-free space on most bands, especially 75 meters - way more than 30 years ago.
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Jim, W5JO
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« Reply #13 on: November 21, 2013, 09:58:42 PM »

Most of the crap is from 3.8 to 4 megacycles.  I have not bothered to monitor long enough to find out where they are located, but have used the Icom and my HRO 60 with external pads to listen.  I do know where I am, in Southern Oklahoma , I can find stations up and down the band.

However, those that are there sure take a lot of space.  What is so frustrating for me is the AM stations (my preferred mode) that overdrive their audio so bad that splatter across 10 KC + and - the carrier frequency.  It is so bad that I don't even try in the normal AM portion.  On 3.978 there is a morning bunch that use ESSB and the group on 3.890 in the mornings together keep me off the air at that time.

I guess the really frustrating part is that if anyone tells either group it almost becomes as bad as politics today.  It just isn't worth the problems.  I sure wish the ARRL and/or the FCC would do something to bring the problem to light.
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« Reply #14 on: November 26, 2013, 02:09:23 PM »

Jim,

I really don't have any issue with someone running wider than what many claim is conventional bandwidth (2.7kc?) when they run it clean. I do object to what I see from so many stations that are running so-called 2.7kc signals that are actually 10kc wide with artifacts that can still be heard 30kc away on either side.

Just for my own amusement, I keep a little folder of screenshots that I call "the hall of infamy" filled with screenshots taken when I tune across a horrendous signal. I also keep another folder with pictures of signals that are amazingly clean. The first two pictures below are what I saw about an hour ago from 2 stations "werkin' DX" on 17 meters. One guy (on 18.162) was crushing another pileup 3 kc below and the other station (on 18.164) can be seen extending out beyond the top band edge. By contrast, check out the 5kc wide ESSB signal in the last picture. This guy sounds beautiful and you cannot hear him on either side of his intended bandpass. Of course he knows what he is doing and is running full legal limit with a homebrew rig and homebrew amplifier with meticulous attention paid to IMD through the use of a homebrew pre-distortion circuit. He and the others on the frequency also operate where there is no other traffic. I can't imagine anyone would complain about a signal like this if they tuned across it and I would hate to see someone like that affected by "bandwidth rule-making" that would interfere with what he likes to do with this hobby.

The scenario you described of stations running wide and spewing tons of garbage above and below their operating frequency is a definite problem, and I really don't have a solution to offer for it. However, I would avoid mode labeling the crappy signals out there as ESSB just because they are wide. Most of the so-called ESSB stations that I have listened to are very considerate and clean as a whistle. I certainly have no interest in being a bandwidth policeman, but if I was, I'd email the offender a few screenshots of what his signal looks like. I'd probably also make a nice "Offensive Bandwidth Registry" web page featuring them. My guess is that many of these "hobby radio folks" are clueless about what their signal actually looks like and they would probably be horrified if they saw it. Maybe a picture really is worth a thousand words in these cases...

73,

Rob W1AEX


* 18164_10kc.jpg (132.8 KB, 1144x716 - viewed 1167 times.)

* 18162_9kc.jpg (132.72 KB, 1144x716 - viewed 1098 times.)

* 3630_5kc.jpg (91.09 KB, 1280x720 - viewed 1133 times.)
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« Reply #15 on: November 26, 2013, 05:39:27 PM »

What is so bad about it many don't know what their signal is like, wide signals are not mode specific.  I also hear some Class E signals that I wouldn't put on the air personally.  One thing I will say is I have been on 80/75 meters since the mid 50s and I hear more signals that are wider and contain products out 10-20 Kc today than I ever heard in 1957 when most stations used AM at about 6 Kc.

If a problem cropped up in those years, the station would take a look to see why and correct it be it RF or audio when they were told, in other words, they respeced their neighbors.  You have much less of that today.  I do not care what the mode or power level is so long as the operator considers adjacent frequencies and doesn't produce splatter or harmonics.  They can run as wide as they wish if it does not cause harmful interference.  However those who choose to run wide siganls lose any gain from doing so at my receiver when I use a 2.7 Kc filter so they don't sound a bit different than those who use 2.7 Kc to transmit.  I just wonder how many of the ESSB stations, other than a flex station, do have a filter to match their transmitted bandwidth?

Many of the wide stations do not have a way to restrict their bandwidth when needed, hence a problem.  Then there are those who won't and I see it on CW, AM, SSB and ESSB on almost all bands.  These people remind me of the guys who "own" a frequency and operate over others if someone strays onto a particular frequency and begins operation before the "owner" shows up. 

As for telling the offender, it does little to no good at all as you say and only creates an argument.  I don't even bother to mention the problem anymore, I just move away from them and operate.  I guess the refusal to ackknowledge  problems by those folks is what is bad about the hobby today, and it is much more prevalent than in decades past.
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« Reply #16 on: November 26, 2013, 11:44:06 PM »

As for telling the offender, it does little to no good at all as you say and only creates an argument.  I don't even bother to mention the problem anymore, I just move away from them and operate.

Yes indeed, your last statement in the quote above is the best tactic of all Jim. Migrate to where it's quiet and sit back and enjoy yourself!

73,

Rob W1AEX
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« Reply #17 on: December 02, 2013, 03:49:27 PM »

The ARRL has filed an Erratum with the FCC to correct an error in its “symbol rate” Petition for Rule Making (PRM), filed November 15 with the FCC and put on public notice for comment as RM-11708 a few days later.


More details here: http://www.arrl.org/news/arrl-files-erratum-to-symbol-rate-petition-for-rule-making


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