[Heath] Heath Digest, Vol 89, Issue 9

Mon May 21 09:31:00 EDT 2018

Guys,This AM discussion is a little confusing due to the terms being used.Carrier controlled AM is a method to reduce power consumption by lowering the output of the carrier when little or no audio is present.  In broadcast AM transmission (especially when stations were producing up to 250kW) reducing the carrier resulted in considerable input power savings.  Broadcast stations use some further black magic to increase power on audio positive going peaks while reducing modulation on negative going peaks.  This prevents modulation from reducing the carrier to zero which produces significant interference out of band.  High level modulation was one method of further reducing input power by using more efficient carrier amplifiers and adding modulation power in the output stage.  This was also a little easier to maintain as RF stages did not need to adjusted to keep them linear.Additionally, audio is bandwidth limited to further reduce power consumption and protect adjacent channels.  Europe and other countries mandated 9kHz bandpass to provide more channels in the AM broadcast band.  The NAB lobbied to keep 10kHz spacing in this country but many stations now filter audio to 9kHz with a filter that has a more gentle band edge slope.
DSB is standard AM modulation with carrier.  
DSBSC is AM modulation with the carrier suppressed.  In this discussion, DSB has been used for this mode.  A carrier needs to be introduced in the receiver for demodulation to occur.SSB is one sideband with carrier.  Only one sideband is needed for audio demodulation.  This mode also reduces input power.SSBSC suppresses the carrier resulting in additional power reduction.  A carrier needs to be introduced in the receiver for demodulation to occur.  
The term 'suppressed carrier' is further misused as it can mean a reduced carrier level or no carrier.  "Reduced carrier" has fallen out of favor.
Eliminating the carrier in AM reduces the output power by 50%.
A simple method of modulating AM suppressed carrier signals is to use a balanced modulator.  When carefully adjusted, the carrier will be completely eliminated.  If the modulator is left slightly out of balance, a small amount of carrier can be present.  To make this signal SSB, one only needs to pass the signal through a filter that is just wide enough to pass one sideband.  This method is used in radios like the HW101.  The resulting sideband energy is then passed through a series of linear stages to boost power.  The output in HW101 is an AB1 linear amplifier.
AlWB9UVJBroadcast Engineer, WTTW/WFMT 

    On Sunday, May 20, 2018 9:54 AM, "heath-request at puck.nether.net" <heath-request at puck.nether.net> wrote:

 Send Heath mailing list submissions to
    heath at puck.nether.net

To subscribe or unsubscribe via the World Wide Web, visit
    https://puck.nether.net/mailman/listinfo/heath
or, via email, send a message with subject or body 'help' to
    heath-request at puck.nether.net

You can reach the person managing the list at
    heath-owner at puck.nether.net

When replying, please edit your Subject line so it is more specific
than "Re: Contents of Heath digest..."

Today's Topics:

  1. Re: SB-200 and AM (Kenneth G. Gordon)
  2. DSB... (Kenneth G. Gordon)
  3. Sales... (Mike)
  4. Re: Sales... (heathmod at centurylink.net)
  5. Re: DSB... (ChrisIwata)
  6. Re: SB-200 and AM (Kenneth G. Gordon)
  7. Re: SB-200 and AM (Glen Zook)

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

Message: 1
Date: Sat, 19 May 2018 15:48:55 -0700
From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
To: ChrisIwata via Heath <heath at puck.nether.net>
Subject: Re: [Heath] SB-200 and AM
Message-ID: <5B00A9D7.24344.ADF369F at kgordon2006.frontier.com>
Content-Type: text/plain; charset=US-ASCII

On 19 May 2018 at 14:48, ChrisIwata via Heath wrote:

> Is there any difference between carrier controlled AM and suppressed carrier DSB?

Yes. A HUGE difference. Controlled-carrier AM is, after all, true AM. It has a carrier whose 
power level follows the average level of the audio. Essentially, the audio controls the 
amount of power out of the amplifier.

DSB is not AM. I supposed one could call DSB, "AM-without-the-carrier".

But DSB is far more difficult to implement than CC-AM.

For one thing, the "simple" methods of generating DSB require two tubes in the final amp 
stage, as I remember it. 

I'll go look it up again just to make sure.

Ken W7EKB

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

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

Message: 2
Date: Sat, 19 May 2018 16:34:07 -0700
From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
To: Heath at puck.nether.net
Subject: [Heath] DSB...
Message-ID: <5B00B46F.16934.B08989E at kgordon2006.frontier.com>
Content-Type: text/plain; charset=US-ASCII

OK. I did some research: generating a DSB signal requires a balanced modulator 
somewhere in the system.

In one case I remember, the two 1625s in an "ARC-5" transmitter were used as a 
direct-to-antenna DSB transmitter.

The screens were fed push-pull audio, while the plates were parallel-connected. As I 
remember it, an oscilloscope was required to get it adjusted properly.

DSB is far more complex than the simple controlled-carrier systems in our simple 
transmitters.

If anyone here is interested, here is a link to the "Double-Sideband Junior" from GE Ham 
News of March-April 1958.

http://n4trb.com/AmateurRadio/GE_HamNews/issues/GE%20Ham%20News%20Vol%2013
%20No%202.pdf

Ken W7EKB

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

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

Message: 3
Date: Sun, 20 May 2018 01:59:21 +0000
From: Mike <MLF42 at Q.com>
To: Heath <Heath at puck.nether.net>
Subject: [Heath] Sales...
Message-ID: <em89bb9b98-554f-4bb9-8810-7b66daff0467 at mike-pc>
Content-Type: text/plain; charset="utf-8"; Format="flowed"

Not sure about the "rules"  so gotta ask...I have some items that might 
of interest to guys who own HW & SB transceivers. Am I allowed to offer 
them for sale?

---
This email has been checked for viruses by AVG.
https://www.avg.com
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://puck.nether.net/pipermail/heath/attachments/20180520/282546d3/attachment-0001.html>

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

Message: 4
Date: Sun, 20 May 2018 02:12:12 +0000 (UTC)
From: <heathmod at centurylink.net>
To: Heath <heath at puck.nether.net>
Subject: Re: [Heath] Sales...
Message-ID:
    <63478D7973B325E8.705f0ca1-678b-40e3-b63b-168d099b18be at mail.outlook.com>

Content-Type: text/plain; charset="utf-8"

Non commercial notices pertaining to for sale or wtb Heathkit or Heathkit related equipment are welcome.

Members are asked to limit for sale notices to one per week.? Multiple items can be listed in a single posting.

On Sat, May 19, 2018 at 9:06 PM -0500, "Mike" <MLF42 at Q.com> wrote:

Not sure about the "rules" ?so gotta ask...I have some items that might of interest to guys who own HW & SB transceivers. Am I allowed to offer them for sale?

        Virus-free. www.avg.com

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://puck.nether.net/pipermail/heath/attachments/20180520/d7b254ef/attachment-0001.html>

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

Message: 5
Date: Sat, 19 May 2018 22:18:50 -0700
From: ChrisIwata <chrisiwata at aol.com>
To: heath at puck.nether.net
Subject: Re: [Heath] DSB...
Message-ID: <5B01053A.70205 at aol.com>
Content-Type: text/plain; charset=windows-1252; format=flowed

I don't mean zero carrier DSB,  I mean suppressed carrier.  In modern 
day this amounts to unbalancing the balanced DSB modulator, so that some 
carrier is there even in the absence of modulation.

I'm not talking about the implementation,  I'm talking about the signal.

Yup, I agree controlled carrier AM is much easier to implement. Both on 
the transmitting end and the receiving end, compared to DSB.

Seems to me the signal generated by controlled carrier AM is the same as 
suppressed carrier DSB?  Neither one has zero carrier with no 
modulation, and the carrier increases with modulation.  I don't know, 
maybe the controlled carrier signal is not a linear representation of 
the modulation as is the case with suppressed DSB?  That is, if you 
speak twice as loud, the controlled carrier might not go up twice as much?

The one big feature of this signal is it can be detected with a simple 
envelope (AM) detector, just like plate modulated AM

When you think about it, aside from CW, modern ham radio communication 
has become very complex.  I guess this is why home-brewing is becoming a 
lost art.

Chris, KL7DM

On 5/19/2018 4:34 PM, Kenneth G. Gordon wrote:
> OK. I did some research: generating a DSB signal requires a balanced modulator
> somewhere in the system.
>
> In one case I remember, the two 1625s in an "ARC-5" transmitter were used as a
> direct-to-antenna DSB transmitter.
>
> The screens were fed push-pull audio, while the plates were parallel-connected. As I
> remember it, an oscilloscope was required to get it adjusted properly.
>
> DSB is far more complex than the simple controlled-carrier systems in our simple
> transmitters.
>
> If anyone here is interested, here is a link to the "Double-Sideband Junior" from GE Ham
> News of March-April 1958.
>
> http://n4trb.com/AmateurRadio/GE_HamNews/issues/GE%20Ham%20News%20Vol%2013
> %20No%202.pdf
>
> Ken W7EKB
>
> ---
> This email has been checked for viruses by Avast antivirus software.
> https://www.avast.com/antivirus
>
> _______________________________________________
> Heath mailing list
> Heath at puck.nether.net
> https://puck.nether.net/mailman/listinfo/heath

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

Message: 6
Date: Sat, 19 May 2018 20:04:36 -0700
From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
To: jerrylofstead at bellsouth.net
Cc: Heath at puck.nether.net
Subject: Re: [Heath] SB-200 and AM
Message-ID: <5B00E5C4.6833.BC94C58 at kgordon2006.frontier.com>
Content-Type: text/plain; charset=ISO-8859-1

On 19 May 2018 at 23:44, jerrylofstead at bellsouth.net wrote:

> Oh yes! Controlled carrier the RF level varies at a voice rate.? DSB SC(supresed carier) was 
> produced by putting two tubes in push-push...? usually push pull grids and paralell plates.

Exactly! :-)

> Audio was applied to the screen elements. I ran dsb for a few years
> since as a kid, l could not afford a ssb exciter? A Central
> Electronics SB10 OR 20Watt SB 20. 

Central Electronics 10A and 20A. :-)

>? These were the first available in the 
> mid 50s.? DSB SC workrd great.? Google tht CE exciters for early SSB.

I still have an operational 20A and 455 VFO here. Neat rig. Does 160 meters and CW too.

Audio sounds superb, BTW. Much nicer than a filter-rig.

vy 73,

Ken W7EKB

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

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

Message: 7
Date: Sun, 20 May 2018 14:52:21 +0000 (UTC)
From: Glen Zook <gzook at yahoo.com>
To: "Kenneth G. Gordon" <kgordon2006 at frontier.com>,  ChrisIwata via
    Heath <heath at puck.nether.net>
Subject: Re: [Heath] SB-200 and AM
Message-ID: <2060329906.3308404.1526827941836 at mail.yahoo.com>
Content-Type: text/plain; charset="utf-8"

The "generic" term, "AM", normally, to most amateur radio operators, refers to a signal amplitude modulated that has the carrier present.? Of course, FM and PM also have a carrier.

However, the modes referred to as SSB and DSB are also amplitude modulated signals even though the carrier is suppressed.? ACSB (amplitude companded sideband) is another signal that falls in this realm.? As such, one can say that all "AM" signals are AM but not all AM signals are "AM".? :>)

That is, all "AM" signals are amplitude modulated but not all amplitude modulated signals are "AM"!
?Glen, K9STH?
Website: http://k9sth.net

      From: Kenneth G. Gordon <kgordon2006 at frontier.com>
 To: ChrisIwata via Heath <heath at puck.nether.net> 
 Sent: Saturday, May 19, 2018 9:05 PM
 Subject: Re: [Heath] SB-200 and AM