[ARC5] Harmonic question

[Richard Knoppow]

     I was aware of this circuit but had not seen this paper. Thanks for 
posting the link.
     As far as modulation of harmonics is concerned. I think it depends 
on where the modulation is applied. I mean if the carrier is modulated 
at a low level and amplified by an amplifier which produces harmonics it 
seems to me the modulation sidebands will be multiplied in the same way 
as the carrier. If the modulation takes place in the final amplifier the 
harmonics will be modulated as though they were secondary carriers and 
modulation will be the same as the carrier. I am not quite sure of the 
theory and not quite sure where to look it up.
    If we consider broadcast transmitters the use of plain linear 
amplifiers ended around the late 1930s. After than most transmitters 
were either plate modulated or Doherty type. The Doherty is, in fact, a 
linear amplifier.  So, what happens to the modulation of the harmonic 
output of these two types or of a plain linear as used for SSB?
    The effect on SSB should be the same as for AM, i.e., if a harmonic 
is generated by the linear it should multiply all components of the 
signal. That would result in doubling the bandwidth of the second 
harmonic or tripling it for the third harmonic.
     Does this make sense?

On 4/16/2017 11:37 AM, Sheldon Daitch wrote:
> Neil,
>
>
> Sure, as all transmitters develop some level of harmonic emissions.
>
> Most modern commercial transmitters have near negligible harmonic
> emissions, but near negligible doesn't mean they don't exist.
>
> As to audio quality, here is what I just found on a quick and dirty test
> for the second harmonic of 690 kHz, WOKV (the old WAPE).
>
> Why this one?
>
> Their day-time transmitter site is about 1228 smoots or 6860 feet from
> my house and the second harmonic very  easy to receive.   Audio quality,
> not so great, although it was perfectly understandable, with maybe 10%
> distortion.  What was interesting was the amount of "buzz" associated
> with the second harmonic, no doubt a product of the digital type
> transmitter.  I also noted nothing heard 10 kHz on either side of the
> second harmonic, the resolution of a digital tuned automotive receiver.
>
> On the specifics of the third harmonic, RCA utilized the third harmonic
> energy of a tube amplifier to increase the plate efficiency in the 5kW
> BTA-5T.
>
> One technical document on this transmitter is at:
>
> http://www.nrcdxas.org/articles/bta5t/
>
>
> 73
>
>
> Sheldon
>
> WA4MZZ
>
>
>
>
> ------------------------------------------------------------------------
> *From:* ARC5 <arc5-bounces at mailman.qth.net> on behalf of AKLDGUY .
> <neilb0627 at gmail.com>
> *Sent:* Sunday, April 16, 2017 4:52 AM
> *To:* ARC-5 List; milsurplus
> *Subject:* [ARC5] Harmonic question
>
> Suppose I have a properly adjusted AM transmitter and am operating it.
>
> What would a nearby listener hear at say, the third or fifth harmonic,
> assuming a good strength carrier at that frequency is present at his
> receiver?
>
> Is the bandwidth of the sidebands 3x or 5x, so all that's heard is
> incomprehensible splatter?
>
> This is not a trick question. The textbooks don't address this at all.
>
> 73 de Neil ZL1ANM
>
>
>
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-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL