>
>That's OK.  I'm a radio amateur, even if my "operating" involves looking 
>at my HF set and thinking "I might enjoy that if I took the time to 
>string an antenna and re-learn Morse code".

Amateur Radio is expanding at the same or greater rate as the rest of
Technology. There are more hams now than ever.

If you are not familiar with PSK mode you should check it out. PSK-31
Was devised by (I think) AE4JY. While he was at it, he placed his work
in the public domain so there is a lot of development activity as well
as just contacts.  PSK-31 is Phase Shift Keying at 31 Baud. Some what
like RTTY but it takes only 31 HZ of spectrum for a contact. According
to what I have read 20 watts of   31 Hz is roughly equivalent to 2 KW
of speech. Whatever it is, I rarely run over 30 watts and I am working
the world.I have seen times when there were over 12 QSO's on a single
3000 Hz audio channel on 20 meters with minimal problems.

Best of all to me (Failing hearing) it can be done in silence with
"Waterfall" display. 

Code is not required for any US Amateur Radio License any more.
However, the CW bands are as active as ever. Radio Improvements have
not eliminated noise and crowding, but it has gone a long ways. 

Most of us believe Software Defined Radio is the way of the future.

Proficient CW operators are not pleased so far with the latency of the
system  but I expect better software/hardware will get there in time.

Thanks again for putting up with me, I am going to retreat to the
recliner for the evening. I downloaded a series of YouTube videos on
Fourier Analysis this morning. I(t is about time for me to try to read
Rick's book some more! 

John, de W8CCW

John Ferrell W8CCW

On 8/21/12 2:46 PM, Tim Wescott wrote:
> On Tue, 21 Aug 2012 14:35:52 -0400, John Ferrell wrote:
>
...
>>
>> John, W8CCW
>> John Ferrell W8CCW
>
>   I'm a radio amateur, even if my "operating" involves looking
> at my HF set and thinking "I might enjoy that if I took the time to
> string an antenna and re-learn Morse code".
>


Morse code, Schmorse code.  nowadays everything is at 2-meters or 
higher, ain't it?

i used to be a ham operator too.  back in the late '60s and early '70s.

formerly WB0CCA.

-- 

r b-j                  rbj@audioimagination.com

"Imagination is more important than knowledge."

On Tue, 21 Aug 2012 14:35:52 -0400, John Ferrell wrote:

> On Mon, 20 Aug 2012 12:19:53 -0500, Tim Wescott <tim@seemywebsite.com>
> wrote:
> 
>>On Mon, 13 Aug 2012 13:07:03 -0400, John Ferrell wrote:
>>
>>> On Sun, 12 Aug 2012 23:18:30 +0300, Tauno Voipio
>>> <tauno.voipio@notused.fi.invalid> wrote:
>>> 
>>>>On 12.8.12 11:00 , John Ferrell wrote:
>>>>>
>>>>>> 2. When comparing SSB or DSB performance to FM or AM, it is often
>>>>>> overlooked that the transmit power amplifier for SSB/DSB has to be
>>>>>> linear, whereas FM/AM amplifiers operate in efficient class C or D
>>>>>> or E mode. So, if performance is compared for the same power
>>>>>> consumption of the transmitter (and this is what matters), the
>>>>>> advantages of SSB/DSB are not so obvious if any at all.
>>>>>>
>>>>> This elderly, slow witted student is slowly beginning to understand
>>>>> the subject and then you say "FM/AM amplifiers operate in efficient
>>>>> class C or D or E mode". Tell me that was a simple miss speak and I
>>>>> can get back to the struggle!
>>>>>
>>>>> I am learning and enjoying the process but I doubt will ever be more
>>>>> than a student here. Thanks to all.
>>>>>
>>>>> John, de W8CCW
>>>>
>>>>It is possible to use a Class C (or higher) amplifier for conventional
>>>>AM, but the power of the amplifier has to be adjusted along with the
>>>>modulating waveform. There are two possibilites here:
>>>>
>>>>1. Adjust the excitation or operating point of the amplifier so that
>>>>    the output follows the desired envelope,
>>>>
>>>>2. Adjust the supply feed so that the output follows the desired
>>>>    envelope.
>>>>
>>>>The case 1 was known in the tube era as grid modulation. Both control
>>>>grid and screen grid modulation were used. Here the modulation comes
>>>>at the price that the efficiency of the amplifier is about the same as
>>>>the efficiency of a linear amplifier with the same PEP.
>>>>
>>>>The case 2 was known in the tube era as anode (or anode-screen)
>>>>modulation. Here the carrier efficiency at PEP is the classic Class C
>>>>level, but the price to be paid is the audio power needed from the
>>>>modulator, half of the RF stage input power. To have a fair
>>>>comparison, the modulator power must be calculated into the total
>>>>efficiency of the transmitter. Remember that the modulator must run in
>>>>Class B or AB, with the modest efficiency.
>>>>
>>>>Transistor power amplifiers often need an adjustment of excitation in
>>>>combination with the supply voltage modualtion, so pretty often two of
>>>>the last stages of the transmitter get modulated.
>>>>
>>>>---
>>>>
>>>>FM and PM (which are essentially the same thing) are different beasts,
>>>>as the output envelope is constant. These modulation methods are not
>>>>spectrally efficient, so their use is not a good idea on crowded
>>>>frequency bands.
>>> 
>>> Perhaps it is a matter of perspective. From my point of view you can
>>> modulate a Class C amplifier to produce an Amplitude Modulation Output
>>> in several ways. Further amplification of the AM output requires a
>>> linear amplifier.
>>> 
>>> I apologize if I am coming across as an Anal Troll, but you folks are
>>> normally very concise with your Math. If I am in error, please
>>> explain. I make many mistakes every day. I will not take offense from
>>> those who offer to teach me...
>>> John, W8CCW.
>>> John Ferrell W8CCW
>>
>>I'm still not sure where your misunderstanding arises, but I'll try.
>>
>>If you're going to make a purpose-built transmitter to operate on just
>>one modulation mode at a specific power level (or narrow range thereof),
>>and if it's a mode that'll support it, then you'll get better efficiency
>>in the RF final amplifier with class C (or E).  Adding a follow-on
>>linear amplifier isn't a consideration, because you're purpose-building
>>the thing (for instance, for an AM or FM radio station).
>>
>>You're probably used to current amateur practice where you want one
>>radio that does everything, so you get a Kenwood or Yaesu or whatever
>>that puts out 100W PEP, then if you want more punch you follow it with a
>>linear amplifier.  That makes sense in the amateur domain because (a)
>>the cost of the power that you use to operate costs a fraction of the
>>total station cost, and (b) the transciever + linear amp combination can
>>be used on any mode that the transciever is capable of, whereas a
>>station with a class-C final stage is much less flexible (you can't use
>>it on SSB, for instance).
>>
>>But if you only ever operate on CW, or AM, FM, or PSK, then you pay for
>>that linear amplifier in your monthly power bill, because it's not
>>operating with nearly the efficiency that a class C amplifier would.
> 
> Thank you,
> You spent quite a bit of time on me. I hope my dumb questions do not
> interfere with the discussions. I hope to better understand signal
> processing, especially in regard to software defined radio.
> 
> So, anything offered is appreciated but please just treat me like noise
> and filter me out when I become a nescience!
> 
> John, W8CCW
> John Ferrell W8CCW

That's OK.  I'm a radio amateur, even if my "operating" involves looking 
at my HF set and thinking "I might enjoy that if I took the time to 
string an antenna and re-learn Morse code".

-- 
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com

On Mon, 20 Aug 2012 12:19:53 -0500, Tim Wescott <tim@seemywebsite.com>
wrote:

>On Mon, 13 Aug 2012 13:07:03 -0400, John Ferrell wrote:
>
>> On Sun, 12 Aug 2012 23:18:30 +0300, Tauno Voipio
>> <tauno.voipio@notused.fi.invalid> wrote:
>> 
>>>On 12.8.12 11:00 , John Ferrell wrote:
>>>>
>>>>> 2. When comparing SSB or DSB performance to FM or AM, it is often
>>>>> overlooked that the transmit power amplifier for SSB/DSB has to be
>>>>> linear, whereas FM/AM amplifiers operate in efficient class C or D or
>>>>> E mode. So, if performance is compared for the same power consumption
>>>>> of the transmitter (and this is what matters), the advantages of
>>>>> SSB/DSB are not so obvious if any at all.
>>>>>
>>>> This elderly, slow witted student is slowly beginning to understand
>>>> the subject and then you say "FM/AM amplifiers operate in efficient
>>>> class C or D or E mode". Tell me that was a simple miss speak and I
>>>> can get back to the struggle!
>>>>
>>>> I am learning and enjoying the process but I doubt will ever be more
>>>> than a student here. Thanks to all.
>>>>
>>>> John, de W8CCW
>>>
>>>It is possible to use a Class C (or higher) amplifier for conventional
>>>AM, but the power of the amplifier has to be adjusted along with the
>>>modulating waveform. There are two possibilites here:
>>>
>>>1. Adjust the excitation or operating point of the amplifier so that
>>>    the output follows the desired envelope,
>>>
>>>2. Adjust the supply feed so that the output follows the desired
>>>    envelope.
>>>
>>>The case 1 was known in the tube era as grid modulation. Both control
>>>grid and screen grid modulation were used. Here the modulation comes at
>>>the price that the efficiency of the amplifier is about the same as the
>>>efficiency of a linear amplifier with the same PEP.
>>>
>>>The case 2 was known in the tube era as anode (or anode-screen)
>>>modulation. Here the carrier efficiency at PEP is the classic Class C
>>>level, but the price to be paid is the audio power needed from the
>>>modulator, half of the RF stage input power. To have a fair comparison,
>>>the modulator power must be calculated into the total efficiency of the
>>>transmitter. Remember that the modulator must run in Class B or AB, with
>>>the modest efficiency.
>>>
>>>Transistor power amplifiers often need an adjustment of excitation in
>>>combination with the supply voltage modualtion, so pretty often two of
>>>the last stages of the transmitter get modulated.
>>>
>>>---
>>>
>>>FM and PM (which are essentially the same thing) are different beasts,
>>>as the output envelope is constant. These modulation methods are not
>>>spectrally efficient, so their use is not a good idea on crowded
>>>frequency bands.
>> 
>> Perhaps it is a matter of perspective. From my point of view you can
>> modulate a Class C amplifier to produce an Amplitude Modulation Output
>> in several ways. Further amplification of the AM output requires a
>> linear amplifier.
>> 
>> I apologize if I am coming across as an Anal Troll, but you folks are
>> normally very concise with your Math. If I am in error, please explain.
>> I make many mistakes every day. I will not take offense from those who
>> offer to teach me...
>> John, W8CCW.
>> John Ferrell W8CCW
>
>I'm still not sure where your misunderstanding arises, but I'll try.
>
>If you're going to make a purpose-built transmitter to operate on just 
>one modulation mode at a specific power level (or narrow range thereof), 
>and if it's a mode that'll support it, then you'll get better efficiency 
>in the RF final amplifier with class C (or E).  Adding a follow-on linear 
>amplifier isn't a consideration, because you're purpose-building the 
>thing (for instance, for an AM or FM radio station).
>
>You're probably used to current amateur practice where you want one radio 
>that does everything, so you get a Kenwood or Yaesu or whatever that puts 
>out 100W PEP, then if you want more punch you follow it with a linear 
>amplifier.  That makes sense in the amateur domain because (a) the cost 
>of the power that you use to operate costs a fraction of the total 
>station cost, and (b) the transciever + linear amp combination can be 
>used on any mode that the transciever is capable of, whereas a station 
>with a class-C final stage is much less flexible (you can't use it on SSB, 
>for instance).
>
>But if you only ever operate on CW, or AM, FM, or PSK, then you pay for 
>that linear amplifier in your monthly power bill, because it's not 
>operating with nearly the efficiency that a class C amplifier would.

Thank you,
You spent quite a bit of time on me. I hope my dumb questions do not
interfere with the discussions. I hope to better understand signal
processing, especially in regard to software defined radio. 

So, anything offered is appreciated but please just treat me like
noise and filter me out when I become a nescience!

John, W8CCW
John Ferrell W8CCW

On Mon, 13 Aug 2012 13:07:03 -0400, John Ferrell wrote:

> On Sun, 12 Aug 2012 23:18:30 +0300, Tauno Voipio
> <tauno.voipio@notused.fi.invalid> wrote:
> 
>>On 12.8.12 11:00 , John Ferrell wrote:
>>>
>>>> 2. When comparing SSB or DSB performance to FM or AM, it is often
>>>> overlooked that the transmit power amplifier for SSB/DSB has to be
>>>> linear, whereas FM/AM amplifiers operate in efficient class C or D or
>>>> E mode. So, if performance is compared for the same power consumption
>>>> of the transmitter (and this is what matters), the advantages of
>>>> SSB/DSB are not so obvious if any at all.
>>>>
>>> This elderly, slow witted student is slowly beginning to understand
>>> the subject and then you say "FM/AM amplifiers operate in efficient
>>> class C or D or E mode". Tell me that was a simple miss speak and I
>>> can get back to the struggle!
>>>
>>> I am learning and enjoying the process but I doubt will ever be more
>>> than a student here. Thanks to all.
>>>
>>> John, de W8CCW
>>
>>It is possible to use a Class C (or higher) amplifier for conventional
>>AM, but the power of the amplifier has to be adjusted along with the
>>modulating waveform. There are two possibilites here:
>>
>>1. Adjust the excitation or operating point of the amplifier so that
>>    the output follows the desired envelope,
>>
>>2. Adjust the supply feed so that the output follows the desired
>>    envelope.
>>
>>The case 1 was known in the tube era as grid modulation. Both control
>>grid and screen grid modulation were used. Here the modulation comes at
>>the price that the efficiency of the amplifier is about the same as the
>>efficiency of a linear amplifier with the same PEP.
>>
>>The case 2 was known in the tube era as anode (or anode-screen)
>>modulation. Here the carrier efficiency at PEP is the classic Class C
>>level, but the price to be paid is the audio power needed from the
>>modulator, half of the RF stage input power. To have a fair comparison,
>>the modulator power must be calculated into the total efficiency of the
>>transmitter. Remember that the modulator must run in Class B or AB, with
>>the modest efficiency.
>>
>>Transistor power amplifiers often need an adjustment of excitation in
>>combination with the supply voltage modualtion, so pretty often two of
>>the last stages of the transmitter get modulated.
>>
>>---
>>
>>FM and PM (which are essentially the same thing) are different beasts,
>>as the output envelope is constant. These modulation methods are not
>>spectrally efficient, so their use is not a good idea on crowded
>>frequency bands.
> 
> Perhaps it is a matter of perspective. From my point of view you can
> modulate a Class C amplifier to produce an Amplitude Modulation Output
> in several ways. Further amplification of the AM output requires a
> linear amplifier.
> 
> I apologize if I am coming across as an Anal Troll, but you folks are
> normally very concise with your Math. If I am in error, please explain.
> I make many mistakes every day. I will not take offense from those who
> offer to teach me...
> John, W8CCW.
> John Ferrell W8CCW

I'm still not sure where your misunderstanding arises, but I'll try.

If you're going to make a purpose-built transmitter to operate on just 
one modulation mode at a specific power level (or narrow range thereof), 
and if it's a mode that'll support it, then you'll get better efficiency 
in the RF final amplifier with class C (or E).  Adding a follow-on linear 
amplifier isn't a consideration, because you're purpose-building the 
thing (for instance, for an AM or FM radio station).

You're probably used to current amateur practice where you want one radio 
that does everything, so you get a Kenwood or Yaesu or whatever that puts 
out 100W PEP, then if you want more punch you follow it with a linear 
amplifier.  That makes sense in the amateur domain because (a) the cost 
of the power that you use to operate costs a fraction of the total 
station cost, and (b) the transciever + linear amp combination can be 
used on any mode that the transciever is capable of, whereas a station 
with a class-C final stage is much less flexible (you can't use it on SSB, 
for instance).

But if you only ever operate on CW, or AM, FM, or PSK, then you pay for 
that linear amplifier in your monthly power bill, because it's not 
operating with nearly the efficiency that a class C amplifier would.

-- 
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com

On Sun, 12 Aug 2012 23:18:30 +0300, Tauno Voipio
<tauno.voipio@notused.fi.invalid> wrote:

>On 12.8.12 11:00 , John Ferrell wrote:
>>
>>> 2. When comparing SSB or DSB performance to FM or AM, it is often overlooked
>>> that the transmit power amplifier for SSB/DSB has to be linear, whereas
>>> FM/AM amplifiers operate in efficient class C or D or E mode. So, if
>>> performance is compared for the same power consumption of the transmitter
>>> (and this is what matters), the advantages of SSB/DSB are not so obvious if
>>> any at all.
>>>
>> This elderly, slow witted student is slowly beginning to understand
>> the subject and then you say "FM/AM amplifiers operate in efficient
>> class C or D or E mode". Tell me that was a simple miss speak and I
>> can get back to the struggle!
>>
>> I am learning and enjoying the process but I doubt will ever be more
>> than a student here. Thanks to all.
>>
>> John, de W8CCW
>
>It is possible to use a Class C (or higher) amplifier for conventional
>AM, but the power of the amplifier has to be adjusted along with the
>modulating waveform. There are two possibilites here:
>
>1. Adjust the excitation or operating point of the amplifier so that
>    the output follows the desired envelope,
>
>2. Adjust the supply feed so that the output follows the desired
>    envelope.
>
>The case 1 was known in the tube era as grid modulation. Both control
>grid and screen grid modulation were used. Here the modulation comes
>at the price that the efficiency of the amplifier is about the same
>as the efficiency of a linear amplifier with the same PEP.
>
>The case 2 was known in the tube era as anode (or anode-screen)
>modulation. Here the carrier efficiency at PEP is the classic Class
>C level, but the price to be paid is the audio power needed from
>the modulator, half of the RF stage input power. To have a fair
>comparison, the modulator power must be calculated into the total
>efficiency of the transmitter. Remember that the modulator must
>run in Class B or AB, with the modest efficiency.
>
>Transistor power amplifiers often need an adjustment of excitation
>in combination with the supply voltage modualtion, so pretty often
>two of the last stages of the transmitter get modulated.
>
>---
>
>FM and PM (which are essentially the same thing) are different beasts,
>as the output envelope is constant. These modulation methods are not
>spectrally efficient, so their use is not a good idea on crowded
>frequency bands.

Perhaps it is a matter of perspective. From my point of view you can
modulate a Class C amplifier to produce an Amplitude Modulation Output
in several ways. Further amplification of the AM output requires a
linear amplifier.  

I apologize if I am coming across as an Anal Troll, but you folks are
normally very concise with your Math. If I am in error, please
explain. I make many mistakes every day. I will not take offense from
those who offer to teach me...
John, W8CCW.
John Ferrell W8CCW

"Tauno Voipio" <tauno.voipio@notused.fi.invalid> wrote in message 
news:k0932n$6ic$1@dont-email.me...
> On 12.8.12 11:00 , John Ferrell wrote:
>>
> It is possible to use a Class C (or higher) amplifier for conventional
> AM, but the power of the amplifier has to be adjusted along with the
> modulating waveform. There are two possibilites here:
>
> 1. Adjust the excitation or operating point of the amplifier so that
>    the output follows the desired envelope,
>
> 2. Adjust the supply feed so that the output follows the desired
>    envelope.
>
> The case 1 was known in the tube era as grid modulation. Both control
> grid and screen grid modulation were used. Here the modulation comes
> at the price that the efficiency of the amplifier is about the same
> as the efficiency of a linear amplifier with the same PEP.
>
> The case 2 was known in the tube era as anode (or anode-screen)
> modulation. Here the carrier efficiency at PEP is the classic Class
> C level, but the price to be paid is the audio power needed from
> the modulator, half of the RF stage input power.

There are double- and tripple- anode modulations, where they regulate grid 
bias altogether with supply voltage on the output and driver stages. This 
improves linearity and efficiency, and this is substantial at power levels 
typical for broadcasting.

> To have a fair
> comparison, the modulator power must be calculated into the total
> efficiency of the transmitter. Remember that the modulator must
> run in Class B or AB, with the modest efficiency.

For that matter, modulator could operate in Class D.
The elegant solution is auto anode modulation: anode surcuit of the output 
stage is loaded on low frequency choke,  grid bias is modulated by audio 
signal.

> Transistor power amplifiers often need an adjustment of excitation
> in combination with the supply voltage modualtion, so pretty often
> two of the last stages of the transmitter get modulated.

That is done of necessity. Transistors have high reaction of the output 
circuit to the input circuit altogether with nonlinearity; other methods 
will result in distortions, low efficiency and underutilization of devices.

Vladimir Vassilevsky
DSP and Mixed Signal Consultant
www.abvolt.com

On 12.8.12 11:00 , John Ferrell wrote:
>
>> 2. When comparing SSB or DSB performance to FM or AM, it is often overlooked
>> that the transmit power amplifier for SSB/DSB has to be linear, whereas
>> FM/AM amplifiers operate in efficient class C or D or E mode. So, if
>> performance is compared for the same power consumption of the transmitter
>> (and this is what matters), the advantages of SSB/DSB are not so obvious if
>> any at all.
>>
> This elderly, slow witted student is slowly beginning to understand
> the subject and then you say "FM/AM amplifiers operate in efficient
> class C or D or E mode". Tell me that was a simple miss speak and I
> can get back to the struggle!
>
> I am learning and enjoying the process but I doubt will ever be more
> than a student here. Thanks to all.
>
> John, de W8CCW

It is possible to use a Class C (or higher) amplifier for conventional
AM, but the power of the amplifier has to be adjusted along with the
modulating waveform. There are two possibilites here:

1. Adjust the excitation or operating point of the amplifier so that
    the output follows the desired envelope,

2. Adjust the supply feed so that the output follows the desired
    envelope.

The case 1 was known in the tube era as grid modulation. Both control
grid and screen grid modulation were used. Here the modulation comes
at the price that the efficiency of the amplifier is about the same
as the efficiency of a linear amplifier with the same PEP.

The case 2 was known in the tube era as anode (or anode-screen)
modulation. Here the carrier efficiency at PEP is the classic Class
C level, but the price to be paid is the audio power needed from
the modulator, half of the RF stage input power. To have a fair
comparison, the modulator power must be calculated into the total
efficiency of the transmitter. Remember that the modulator must
run in Class B or AB, with the modest efficiency.

Transistor power amplifiers often need an adjustment of excitation
in combination with the supply voltage modualtion, so pretty often
two of the last stages of the transmitter get modulated.

---

FM and PM (which are essentially the same thing) are different beasts,
as the output envelope is constant. These modulation methods are not
spectrally efficient, so their use is not a good idea on crowded
frequency bands.

-- 

Tauno Voipio, OH2UG

On Thu, 9 Aug 2012 10:10:20 -0500, "Vladimir Vassilevsky"
<nospam@nowhere.com> wrote:

>
>"Rick Lyons" <R.Lyons@_BOGUS_ieee.org> wrote in message 
>news:hbo528d30hi5hi3ffs90c3htqbv4fr6dce@4ax.com...
>>
>> Hi guys,
>>  Some weeks ago I posted a message asking for help
>> in understanding the 'phasing method' of single
>> sideband (SSB) demodulation.
>>
>> You guys helped me out, and I learned so much that
>> I wrote a blog on that SSB demodulation method.
>> In case anyone's interested, the blog is at:
>>
>> http://www.dsprelated.com/showarticle/176.php
>
>1. When communication engineers sketch out an audio spectrum, they represent 
>it as trapezium with the fall from low to high frequencies. This is more 
>like the audio spectrum looks in reality, and this convention makes real 
>easy to see if a sideband signal is inverted in frequency or not. The author 
>draws spectrums vise versa.
>
>2. When comparing SSB or DSB performance to FM or AM, it is often overlooked 
>that the transmit power amplifier for SSB/DSB has to be linear, whereas 
>FM/AM amplifiers operate in efficient class C or D or E mode. So, if 
>performance is compared for the same power consumption of the transmitter 
>(and this is what matters), the advantages of SSB/DSB are not so obvious if 
>any at all.
>
This elderly, slow witted student is slowly beginning to understand
the subject and then you say "FM/AM amplifiers operate in efficient
class C or D or E mode". Tell me that was a simple miss speak and I
can get back to the struggle!

I am learning and enjoying the process but I doubt will ever be more
than a student here. Thanks to all.

John, de W8CCW

>3. DSB demodulator requires perfect carrier recovery in frequency and phase. 
>A practical DSB demodulator must include PLL for carrier recovery. Costas 
>loop structure is suitable for that purpose.
>
>Vladimir Vassilevsky
>DSP and Mixed Signal Consultant
>www.abvolt.com
>
>
>
John Ferrell W8CCW

On Saturday, August 11, 2012 3:46:37 PM UTC-4, Vladimir Vassilevsky wrote:
> Mark wrote in message 
> 
> >Generally linear modulations require linear amplifiers while phase 
> >modulations do not.
> 
> This statement is both wrong and irrelevant  :-)

That it is distinct from PA class of operation does not diminish its relevance.  The statement is relevant in that a PA can be, and often is operated in compression and therefore at a higher  efficiency when transmitting a constant envelope signal.  This is not true for linear modulation.  The statement, therefore, could only be wrong if this were not the case.

Further, its relevance is supported by the torrent of patents issued in the 90s for inventions aimed at improving the efficiency-linearity tradeoff for linear modulation.  Some key examples follow.

US5880633 claims a feedback linearization circuit for eliminating distortion due to operating a PA close to saturation for the purpose of increasing power efficiency.  Read the background section for a succinct statement of issues and tradeoffs relating efficiency, modulation type and their relevance to the global personal communications market.

US7164893 claims a supply modulation technique specifically designed to improve efficiency of linear amplifiers for use with linear modulation.

US6236837 claims a predistortion method for compensating nonlinearities in an RF PA in order to reduce spectral growth of linear modulation.

US5638403 claims a peak to average power ratio reduction method for improving efficiency of a linear RF PA by allowing it to operate near but not in compression for linear modulation.


> > Class D and E are less common in many RF applications because the filter 
> > is more expensive.
> 
> Huh? Refer to any book on transmitter design.

Hard to see why this statement would be challenged.  Seemingly such a challenge could only be valid if Class D and E amplifiers were as common in all RF applications as Class AB or if their filter requirements were looser.  But, on both accounts, they are not. 


> Amplification of a modulated signal is the least efficient way of power 
> amplification. Classic AM is performed by modulating power supply of the 
> transmitter output stage; this could be up to 100% efficient.

This is only one type of amplifier design, albeit a more efficient one.  Supply modulation is hardly the rule especially in lower power and lower cost designs.  See for example the RF PA designs in the ARRL Handbook for Radio Communications.  While the PA operates at a higher efficiency, supply modulating systems often utilize lower efficiency Class AB stages to amplify  the modulation to a level sufficient to drive the final stage. So although in theory the final stage can operate at close to 100% efficiency, in practice the overall system does not.


> It would be good to generate complex signals like SSB as a combination of AM 
> and PM, i.e. in polar coordinate system.

Yes, such a method is a beautiful dream.