Are the AM bandwidth wars getting ready to restart

[nq5t]

This is a rant.

I asked a simple question on a list associate with a US radio brand, about the AM bandwidth capability of a soon to be released SDR transceiver.

As usually happens, the side comments about "no one needs more than 3 KHz" and "exceeding 100% positive modulation is illegal" and the "rules" say 6 KHz total bandwidth is the maximum allowed", and ... well, you probably know the drill.  Even the mention of AM draws the same wizard/guru/expert/rule-monitoring people out — every time.

One of these guys (who apparently only runs his broadcast rig with a 3 KHz brick wall filter?) implied he was one of the new Volunteer Monitors (or whatever they're called), and was going to be having conversations with Riley on bandwidth.  The implication being he was going to take care of that pesky bandwidth problem and start reporting offenders.  I don't know what any of it means in real terms of course.

I'm just sitting here p*ssed off and tired of the ration of emails I've been getting after asking a simple question regarding AM transmit audio bandwidth, and needed to blow off some steam :-)

[K1JJ]

Hi Grant,

I wouldn't sweat it.

The FCC reviewed the amateur radio bandwidth debate years ago and decided that ham radio is an experimenter's service and did not issue any bandwidth restrictions. They are sometimes wiser than we think.

As far as I know there are NO transmit bandwidth rules or limitations regarding phone/ssb  operation.  The operator makes the decision on how wide to be and it's cool as long as the transmitter is reasonably clean. The FCC will issue a citation for a signal with serious spectral problems, but not for bandwidth where the station is reasonably in the clear - and not intentionally QRMing someone else. This can be a subjective decision at times related to intent.

Since then and in our favor, the phone bands have been expanded.... more room for more bandwidth.    Also, just listen to 75M any Saturday night at peak time - there are definitely less ham QSOs going on compared to when the FCC reviewed this area years ago.  These two add up to less demand for frequency bandwidth.

15-30 years ago there were epic ssb vs: AM battles over frequency. They were very common. But now I haven't heard any serious battles in at least 5 years.  

I think the FCC responds more to intentional QRM interference than anything else.  But to stay in favor, be aware of our own transmit bandwidth and know what is going on around us. Dynamic filter control of our rigs can make it even easier.  Run the bandwidth you want and have fun.  

There will always be complainers and people who hate to see others having fun. In my opinion, the AMers have more fun than any other group in ham radio. The enthusiasm is contagious.  Focus on improving your rigs and hanging with the people on AM and the distractors will just go away. There's nothing to worry about regarding bandwidth restrictions for the rest of our ham lives.

Tom, K1JJ

[WD8KDG]

I'll try to not offend.

With today's technology, it is impossible to hide poor operating habits. Having lived in a cave for a decade or two, a new IC7300 arrived just a few months ago. Amazing how good they sound on AM with a bandwidth of 6KHz or so. Watching the waterfall display, it is an eye opener of other IC7300 users and even with a properly tuned amp, still around 6KHz.

Then there is the guy with a 20V3 taking up 30KHz in the same QSO causing grief above and below center carrier frequency. Most of the time the 20V3 operator needs some audio lessons. Way too much muddy lows. The 30KHz is intentional to keep SSB from getting close, but also limits other AM QSO's in the getto. That entire group's goal it to use as much spectrum as possible, crank up the positive peaks on those Flex rigs, and be frequency hogs. An Apache Lab owner joined in a while back and I had to open the IF bandwidth on the R390/A to 16KC before that rig started to sound half way decent.

No, I don't want to see bandwidth limits. But I see the need. So at what point is it an experiment or poop for brains?

Rant over,
Craig   

[nq5t]

I fully agree with you, Tom.  I think everyone here who is a responsible AM operator would, too.

I haven't had a "big rig" for several years, since relocating to a place where it isn't practical (rig space or antenna farms).  All of the iron in my QRZ page pics has gone on to good homes.  

But I erred in asking a question on a list, and was (and continue to be) pounded on, publicly and privately.  All I did was ask "what is the maximum AM audio bandwidth?"  Like I said, I was up to my ears in "bandwidth" rants, lectures, and insults.  I've asked the list moderator to kill the thread.

The spittle against AM is clearly alive, healthy, and virulent.  We just need to watch our backs.  Hopefully, I'll be on the air again soon with a good modern rig, small amp, and decent AM performance.  Maybe even Ranger or Viking II/DX-100 levels or so :-)

PS:  I'm really enjoying the thread on filtering and following it all closely.  Very useful and good stuff!

Grant NQ5T

[nq5t]

Then there is the guy with a 20V3 taking up 30KHz in the same QSO causing grief above and below center carrier frequency. Most of the time the 20V3 operator needs some audio lessons. Way too much muddy lows. The 30KHz is intentional to keep SSB from getting close, but also limits other AM QSO's in the getto. That entire group's goal it to use as much spectrum as possible, crank up the positive peaks on those Flex rigs, and be frequency hogs. An Apache Lab owner joined in a while back and I had to open the IF bandwidth on the R390/A to 16KC before that rig started to sound half way decent.

On this point, I agree with you 100%.  Rigs operated this way may sound full-throated and good if you're close, but get out a ways, and they're mud.  Like someone talking with a banana in their throat.    I've listened to many such transmissions and usually just move on.  Still, quibbling over 4-5 KHz audio bandwidth, tailored to intelligibility, is a different thing altogether.  And that's all this was about .. :-)

[N1BCG]

It's no longer the 1960s and there are no F.C.C. mandated bandwidths just like there's no more "AM Window". It's 2020...

What DOES govern bandwidth is common sense. If a band is lightly populated with signals then there's no issue with spreading out and letting other ops enjoy good sounding audio. Conversely, if a band is crowded with signals then it's prudent to narrow things up just like everyone is doing with their receivers. There's no sense in transmitting a HiFi signal if others in your QSO have their receive filters tightened up.

Need an analogy?

You can park across spaces in a vacant lot without anyone complaining. Pull that maneuver in a full parking lot where cars are circling to find even one spot and you'll surely attract some criticism, or worse.



Common sense and neighborliness go hand in hand in life, both on and off the air.

[K1JJ]

Need an analogy?
You can park across spaces in a vacant lot without anyone complaining. Pull that maneuver in a full parking lot where cars are circling to find even one spot and you'll surely attract some criticism, or worse.

Good analogy!


Another good observant statement made by Rick/KHK:  

"Sibilance is SO important in understanding!  If the bandwidth is available, we should use it.  When we are through, someone else can have it.  Fully renewable resource!"


And another:  "When the band gets crowded and we stay wide, the people we are QRMing up and down the band are probably our own friends."


*BTW, today I heard and talked with possibly one of the very best hi-fi AM signals on the band. Look for Skip WT1H from MA.  He has a broadcast quality voice and was running his e-rig, on a quiet band. His high end was so transparent and clear it sounded like he was in the room. The room ambience was like being in an auditorium. And just a hint of reverb. Amazing sound. Full dynamic range.  He said he was feeding the e-rig directly with a high end BC mic and preamp. Wow.

T

[KK4YY]

Common sense and neighborliness go hand in hand in life, both on and off the air.

Would that it were so simple.

[KA3EKH]

All this talk of bandwidth makes my head hurt! People talking about stations being 30 kHz or wider.
Back when I was a pup we were told that in AM if you modulate a carrier with a 3 kHz signal you would get three things, the carrier, a upper side band 3 kHz out from the carrier and a lower sideband 3 kHz from the carrier. Would assume that is a total occupied bandwidth of 6 kHz? A SSB transmitter suppresses the carrier and one sideband leaving a signal side band for an occupied bandwidth of just under 3 kHz. For a AM transmitter to have an occupied bandwidth of 30 kHz it would have to be modulated with a signal of around 15 kHz.
Most people who are over the hill like me have a hard time hearing anything above 8 or so kHz, myself I am limited to not hearing much above 6 kHz or so. When I see all this talk about high fidelity audio I have to wonder just what people are talking about? From much of what I hear on the air it sounds to me like people are going for the “punchy” full sound that as best in my limited understanding I can describe as pumping up the low to mid-range audio in the spectrum between 200 Hz to around 3.5 kHz, the audio above 5 or 6 kHz is just about useless in a communications circuit.
Ok, so the full audio Ham station may be running an occupied bandwidth of around 7 or maybe 8 kHz but beyond 8 kHz what do you get?

[WA5VGO]

There aren’t any bandwidth limits in the rules yet. Keep putting 30kc signals on the bands and there will be.

[WD8KDG]

There aren’t any bandwidth limits in the rules yet. Keep putting 30kc signals on the bands and there will be.

This is where the AM mode is today The quest for Hi-Fi, broadcast announcer audio, is crazy. Next door to the transmitting station it might sound ok, but after several hundred miles that quest sounds like the operator has an used dirty condom rolled down their tongue. Please spit it out!

In our proclaimed 75 meter AM getto…...…..3.870 to 3.885 MHz there isn't room for Hi-Fi audio. As the decades have passed the use of broadcast transmitters have increased along with the audio processing. Hogging of that spectrum is common and little regard for low power AM stations is the norm.

Hiding the results are no longer possible. Entry level transceivers with a spectrum scope make the evidence clear.

The "O..F..F" function is used more often in my shack rather than listening to hogs.

Regards,
Craig

  

[KK4YY]

We have met the enemy and he is us.

[KA3EKH]

Their must obviously be something wrong with my brain, I still don’t see how people are generating these wide bandwidth signals? If you had a perfectly flat audio response out to 50 kHz and a ideal modulator that that was capable of modulating out that far and an antenna that was flat across the channel so your radiated signal equally so what, most of the energy in voice transmission is still below 5 kHz or so with only a small component extending above that so the amount of power that’s developed above 5 to10 kHz is minimal.
But yet people talk about these super wide band signals? Ok, if we were talking about FM I can get it but with AM what is the information that’s living out above maybe 7 or 8 kHz? Can see where a great audio response out to 8 kHz is going to come back with an occupied bandwidth of around 16 kHz.
I just can’t see how all this wide band stuff is happening. Not that a 15 or 16 kHz occupied bandwidth would not be a problem on the bands, can see where that would be evil to someone 4 kHz or so from your carrier frequency and can imagine a world where two wide AM signals within a couple kHz of each other can produce spurious products but somehow I think maybe the problems are not the occupied bandwidth of the signals but perhaps bad thing occurring from people over driving there negative peaks into clipping the carrier and causing splatter or running crazy positive peaks that exceed the linearity of there output tanks and developing wide band noise that way?
In the last couple years have been playing around with linearity and power levels in amplifiers with both SSB and AM and can see many ways to overdrive and produce wide band noise, spurious noise and splatter and is it possible that’s this is the real problem as opposed to some form of super wide band audio that for the life of me cannot see people producing?

[N1BCG]

I agree that the majority of normal vocal energy is under 5kc but there are numerous factors that can extend sidebands far beyond that. Non-linear modulation and IMD are common. Another is the excessive boost of high frequencies. This artificially expands the width of sidebands as does the use of multi band processors.

In the latter case, the higher bands will ensure that energy in this passbands will always be maxed out even if it brings up non-vocal energy such as hiss, harmonic energy, or shack noise.

AM broadcast processors are designed to deliver maximum modulation out to 9kc (18kc bandwidth), so users of such equipment need to take particular care when setting them up for use on the amateur bands.

[Opcom]

Bandwidth, meaning bandpass, including pre-emphasis and slope at filter cutoff, should be tailored to each individual because all voices are different.

I favor a selection of HF and LF cutoffs to be used as the situation may require.
I never 'chase away' other stations by using wide signals but I don't give in to encROACHers either..

If some tinpot is going to report me for my audio signal being >3Khz then let him.
To have any traction he will need data from calibrated equipment, not ham gear.
Scientific data is measured at the transmitter, not 100 miles away.
Nonetheless, I will be happy to receive informal 'distance check' test data for free.
I will even send him a QSL card because I am courteous.

 

[Steve - K4HX]

My AM broadcast processors work all the way to 15 kHz. 

People have been P&Ming about wide signals since the 1930s. Nothing that is going on today is going to result in bandwidth limitations. The 75 meter band is FAR less crowded than it was even 15 years ago and almost a completely different band than it was in the 1980s. Most any evening here on the east coast, I can tune and find multiple 20-30 kHz chunks where there are no QSOs. None. If someone is too wide, use your VFO and find a quiet spot. P&Ming about it is like peeing yourself when wearing dark pants. It might make you feel good, but no one else cares.

[WA5VGO]

I guess severe over modulation and audio parasitics are also okay. After all, all they do is occupy bandwidth and there’s plenty of it available.

[KK4YY]

Last time I checked, this was the final word on the subject.

Title 47, Chapter I, Subchapter D, Part 97, Subpart D, §97.307
https://ecfr.io/Title-47/se47.5.97_1307

[Steve - K4HX]

Your words, not mine.

I guess severe over modulation and audio parasitics are also okay. After all, all they do is occupy bandwidth and there’s plenty of it available.

[Opcom]

Your words, not mine.

I guess severe over modulation and audio parasitics are also okay. After all, all they do is occupy bandwidth and there’s plenty of it available.

There's always plenty of bandwidth available in my dummy load! Anything goes in there.