Speech postponed on enchanced AM

Speech postponed on enchanced AM
Patent lawyers tell inventor to wait

Noted audio innovator and ham Mike Dorrough this week called off a scheduled speech at the National Association of Broadcasters convention in Las Vegas where he had planned to announce details of an enhanced technique to improve the loudness of full carrier, dual sideband AM signals.

His attorneys pursuing patent protection for the system have not yet completed their efforts and he was encouraged to delay his remarks, according to a conversation he had Tuesday with an attendee at the convention.

Dorrough, KO6NM, is a prominent member of the AM community active on the shortwave ham bands. He is often heard running one of a variety of retired broadcast transmitters he has restored and retuned to HF on 160 and 75 meters. He has been worked coast-to-coast when in California, as well as from his home in Wisconsin.

http://www.amwindow.org/audio/htm/ko6nm.htm

Mike has told fellow enthusiasts he intends to share some of his experiments on HF, and that he will invite their comments and analysis on how the system sounds with basic voice audio waveforms such as those in amateur service. The technical scheme holds promise to increase the already warm and inviting sound of AM among vintage hams, who could deploy the audio on new or old transmitters used on HF.

More than 100 retired broadcast transmitters are known to have reached private hands, with most of them now restored and operating on 160, 75 and 40 meters across the United States.



http://www.rwonline.com/referen....0.shtml

In addition, a number of homebrew buffs have constructed solid state "Class E" transmitters which offer outstanding audio quality and simple design.



http://www.netway.com/~stevec/ham/kitdesc.htm

We look forward to hearing Mike's handiwork on the ham bands as his project develops.
He calls the audio system "Advanced Modulation."

Paul/VJB
Annapolis

~ What’s Behind Dorrough’s AMS? ~
Courtesy SBE Chapter 59
Thu, 28 Nov 2002 23:54:00 -0600

excerpted from Radio magazine Currents Online
A new addition to the discussion of radio’s future holds promise for
improving the performance of AM. The Advanced Modulation System (AMS), a
project currently under patent review, is headed by Mike Dorrough,
president of Dorrough Electronics. Dorrough has been involved in audio and
broadcasting for many years and is recognized as an innovator in his field.
He is currently making rounds to various SBE chapters to talk about his
proposed improvement for AM service.

In an interview with Radio magazine technical editor John Battison,
Dorrough stated that he could not comment on the specifics of the hardware
involved until the patent process was finalized. He is, however, able to
talk about the enabling scientific principles and intended results.

Following is an excerpt from the discussion between Dorrough and Battison.

Dorrough: We know that inter-modulation-prone asymmetrical processing
schemes are capable of substantial increases in apparent loudness, but the
penalty in fidelity can be quite jarring to the listener. Digital
technology allows the manipulation of time and phase relationships to
unleash the full potential of the AM carrier as a natural platform to
support fully modulated, “interlaced” sidebands. AMS circuitry allows full,
200% sinusoidal undistorted modulation of the AM carrier without the need
for negative peak clipping or hard processing. With AMS, far greater
loudness is achieved than possible with even the most aggressive negative
peak clipping without distorting the audio wave. The system is fully
backward- and forward-compatible.

Dorrough sees AMS as having an enormous benefit to normal, stereo and IBOC
broadcasting modes.

With the increased modulation, the carrier level does not change because
the additional modulation power is provided by the new side bands. As might
be expected, the power supply to the final has to be able to handle the
increased load of the new side bands. The transmitter will require a 20kHz
passband. Although the peak power increases, current FCC rules are based on
carrier power, so there is no conflict.

With AMS, Dorrough feels that far greater loudness can be achieved,
surpassing the loudness obtained with the hardest negative peak clipping.
In addition, there is no distortion of the audio signal, and the harsh
sound of asymetrical modulation is eliminated.

-----------------

Courtesy Amateur Radio Newsline 01 Nov 2002

EMERGING TECHNOLOGY:  AM MODULATION IMPROVEMENT ANNOUNCED

A new modulation technique for AM broadcasting is being promoted  by
broadcast industry pioneer Mike Dorrough, KO6NM.  Dorrough claims the
Advanced Modulation System can increase carrier modulation to 200% while
improving the performance, range and sound quality of Amplitude Modulated
radio.

According to the CGC Communicator, KO6NM recently discussed the system at
an SBE meeting in Sacramento and plans other presentations.  

Ross du Clair, WA6VWY is the Chief Engineer for Clear Channel in
Sacramento.  He attended the Sacramento meeting and is quoted in Radio
World On-Line as saying, "This is real and it does work."  

As previously reported, Mike Dorrough was the recipient of  the National
Association of Broadcasters Radio Engineering Achievement Award in 2000.
This, for his contributions to audio processing and signal monitoring.
Details of the new Advanced Modulation System will appear in an upcoming
issue of Radio World magazine.  (CGC Communicator)

 

E N H A N C E D  AM
Typo enchanced got through and showed up in the headline, where it sticks out real FB.

 

Hi Paul
I ran Enchanced AM once.
Just need to find a friendly Enchanter, most can be found in the Bazaar off of the Nexus.
I ran into a nice fellow once, and asked him if he could enchant my old boatanchor, as it was sounding rather hyellowee (it was a Valiant).
Anyway when all was said and done the rig had +5 stat boost in Fidelity, it sounded great! almost Magical
and it only cost a few platinum

now thats Enchanced AM

seriously though, im looking foreward to reading the article on "Enhanced" AM.   It sounds interesting.
Keep up the great work.
Long live AM

Blaine N1GTU

 

I hope to hear what the "enhanced" sound really sounds like on HF. Had the experience ot working at an AM broadcast station with a very early Dorrough processor back about 30 years ago (Mike...remember KIKX/Tucson?) and the difference in audio was amazing. Maybe the new equipment will meet or exceed those ancient results. May it also succeed in pushing the broadcasters on 40m into the background..

John N7IQV

 

Wow, negative peak clipping!  That brings back memories!  When I was a kid in high school, I used to listen to nightly tirades from a Pennsylvania amateur  (call sign on request! ) who had a running battle with the FCC regarding his output power.  He insisted that since he was using negative peak clipping (with his 600 watts modulation audio) his signal was within legal limits.  I understand the FCC finally suspended his license for several years.  I happened to see his callsign in a list of Pennsylvania 2 meter repeaters a couple of years ago, so at least he's still around.  I am wondering about this new development--can we use it on 40 meters to overpower the SWBC guys who make 40 mostly a wasteland at night?  In 1958, I can't remember a single SWBC signal inside the 40 meter band.  Not so today!    

73,  Ed

 

Very, very interesting. Any chance it can be done without consuming a 6Khz wide chunk of limited spectrum?

 

only 6Kc?
sounds a little constricted to me

 

In the article, this paragraph brings me pause...

=====
With the increased modulation, the carrier level does not change because the additional modulation power is provided by the new side bands. As might be expected, the power supply to the final has to be able to handle the increased load of the new side bands.
The transmitter will require a 20kHz passband. Although the peak power increases, current FCC rules are based on carrier power, so there is no conflict.
=====

I thought the FCC rules were based on P.E.P. output power?

I was ass/u/me'ing that this discussion was for AM Radio on the Ham Bands (since it was posted by Paul/VJB) but a 20kHz wide signal?

Someone straighten me out, please.

73 = Best Regards,
-Geoff/W5OMR

 

Good question, Geoff !

I'm sure Mike will limit himself to voice quality bandwidth for the testing conducted on the ham bands, and I am also certain he will use the "PEP" power measuring standard to ensure compliance with prevailing FCC opinion on such measurements in the amateur service. (this standard is not used in other services)

Mike has made it clear, and it's obvious to hear him, that his ham station follows the much more stringent technical quality control of the broadcast industry, constrained where appropriate by lower, amateur standards.

Regards,
Paul

 

Hi Paul!

Ok.  Let's stick to Ham radio AM a sec, shall we?

In order to fully modulate a carrier with a sine-wave to 100%, keeping a cap of 1,500W of PEP output, we will realize our carrier is 375W output, unmodulated.

The problem with that is, we don't speak in "sine-wave", we speak with our good ol' male-patterned (most of us, anyway ;->) aysemetrical voices.

With our asymetrical voices, we need to realize that our voices tend to have more positive peaks than negative peaks.  

Imagine, if you will, that the ratio of those peaks are 3:1.  In order for our audio to come out nice and clean and clear (non-distorted, as much as possible) we'll need a -lot- more beef in the modulator.  At the same time, if our carrier is still maintained at 375W, we are then exceeding the 1500wPEP output level.

(here, I've -got- to say, for anyone else reading, that it's MUCH easier to measure INPUT power!  
2kVDC @ 250mA can be easily metered&#33

Natural Asymmetrical Modulation
A joint effort by John - WA5BXO, Bob - WA3WDR (Bacon) - Tim, W5TOB - Don,K4KYV

Some good discussion, and the math (of course) and can be found at:
http://www.qsl.net/wa5bxo

John has some other good AM Related articles there, too.

73 = Best Regards,
-Geoff/W5OMR

 

Yes !
Your efforts have been discussed at the AM Forum at Dayton in years passed. Hope you will be there this year. I know Don K4KYV plans to attend.

A lot of folks have been puzzled that the FCC chose a PEP measurement standard for the amateur service, partly for just the reason you've cited.

Other reasons that favored the traditional DC-input standard include its applicability to stations not using coaxial feedlines. Under the FCC's present day standard, I don't know how a field engineer would connect a conventional PEP wattmeter to, say, an open wire line.

As I understand it, the change to a PEP-based power standard in the amateur service was done administratively back in the 1970s, and a full record of the technical basis and justification for it has never been made public.

Regards

Paul/VJB

 

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (N1GTU @ April 12 2003,22:02)</td></tr><tr><td id="QUOTE">Hi Paul
I ran Enchanced AM once.
Just need to find a friendly Enchanter, most can be found in the Bazaar off of the Nexus.
I ran into a nice fellow once, and asked him if he could enchant my old boatanchor, as it was sounding rather hyellowee (it was a Valiant).
Anyway when all was said and done the rig had +5 stat boost in Fidelity, it sounded great! almost Magical
and it only cost a few platinum

now thats Enchanced AM

seriously though, im looking foreward to reading the article on "Enhanced" AM.   It sounds interesting.
Keep up the great work.
Long live AM

Blaine N1GTU[/QUOTE]<span id='postcolor'>
Sounds like someone plays EQ =)

 

For what it’s worth: although *seemingly* attractive, asymmetrical modulation (i.e. substantially more than 100% positive peaks) is not recommended or used in commercial HF broadcasting, because of the selective fading problem. An order of 200% positive will only work in ground wave situations, or maybe “first hop” scenarios, depending on the band.

Instead, the preferred approach to more punch and “loudness” on HF is advanced audio processing techniques. Check out the Orban Optimod HF 9105A or 9200 – the leading manufacturer and equipment in the field. There may even be some specific documentation about this issue on their website: www.orban.com

73+55,
Bob HB9ASQ / WA2UPQ

 

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">More than 100 retired broadcast transmitters are known to have reached private hands, with most of them now restored and operating on 160, 75 and 40 meters across the United States.
[/QUOTE]<span id='postcolor'>

Oh Boy ! I looked at that list of Hams on the AM Window page that are using retired Broadcast Band transmitters and could hardly believe my eyes! Genuine Gates BC-1T's ! It makes an old AM Broadcast Engineer all misty-eyed !

The first radio station I worked at had a BC-1T and let me tell you, the audio out of that transmitter was so good that you could switch the monitor from "Program" to "Air", and hardly hear the difference! Just a bit "softer" on the top end , but that transmitter used up all of its' 10 Kcs channel ( I am using "Kcs" purposefully, here ) and still easily passed its annual "proof of performance" tests! Gates sure knew how to process audio for the AM Broadcast Band! From below 20 to above 5000 cycles, flat as can be, with very little distortion.

Just a little story about that setup. When it was first put on the air, because of FCC requirements that the control operator had to be able to physically see the meters on the transmitter, it sat in a corner of the main control-room/announcer's studio. Well, the modulation transformer's core plates vibrated so loudly that they acted like a speaker, and actually caused audio feedback when the mic was "live"! The modulation transformer, as well as the power transformer got moved to the furnace room and the wires brought into the back of the transmitter cabinet through conduit!

Well, I know this has nothing to do with AM on the Ham bands, but it sure was fun to reminisce for a minute!

73 from Jim AG3Y