Re: [Elecraft] Elecraft gear relative IMD

[Barry N1EU]

Pre-distortion dsp processing on the tx signal makes a DRAMATIC
improvement.  Check out the tx spectrum and waterfall outside the filter
passband on this video before and after W1AEX switches in pre-distortion at
34 seconds in:  https://www.youtube.com/watch?v=MCm3mKHyuAo

73/HNY,
Barry N1EU

On Thu, Dec 31, 2015 at 7:34 AM, Kevin Stover 
wrote:

> Two different animals.
> Harmonics and spurs are regulated by the FCC to be at least -43dB down on
> HF and -60dB down on 6 meters.
> The K3(s) meets those specs easily as evidenced by a couple of QST reviews.
> IMD is not regulated I think because most hams don't have the test
> equipment to pull it off accurately.
>
> All of this IMD hullabaloo would quickly go away if the manufacturers
> would switch from 12V finals to 50V finals or used pre-distortion of some
> sort. How much will Ham's pay to clean up the IMD problem when the FCC
> doesn't regulate it?
>
>
> On 12/30/2015 9:09 PM, a...@sbcglobal.net wrote:
>
>> Who has some measured 2 tone IMD test figures for an actual  K3/K3S at
>> full and reduced power levels and at supply voltage levels between 12-15
>> volts?Must assume the Harmonic and Spurious Outputs exceed 50dB below
>> carrier @ 100W within ham bands as per Elecraft manual specs.  HOW  much
>> better than 50dB with above variables is the question?   Can someone share
>> these figures?
>> 73,Mike  AC5P
>>
>>
>
> --
> R. Kevin Stover
> AC0H
> ARRL
> FISTS #11993
> SKCC #215
> NAQCC #3441
>
>
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Re: [Elecraft] Elecraft gear relative IMD

[Kevin Stover]

Two different animals.
Harmonics and spurs are regulated by the FCC to be at least -43dB down 
on HF and -60dB down on 6 meters.

The K3(s) meets those specs easily as evidenced by a couple of QST reviews.
IMD is not regulated I think because most hams don't have the test 
equipment to pull it off accurately.


All of this IMD hullabaloo would quickly go away if the manufacturers 
would switch from 12V finals to 50V finals or used pre-distortion of 
some sort. How much will Ham's pay to clean up the IMD problem when the 
FCC doesn't regulate it?



On 12/30/2015 9:09 PM, a...@sbcglobal.net wrote:

Who has some measured 2 tone IMD test figures for an actual  K3/K3S at full and 
reduced power levels and at supply voltage levels between 12-15 volts?Must 
assume the Harmonic and Spurious Outputs exceed 50dB below carrier @ 100W 
within ham bands as per Elecraft manual specs.  HOW  much better than 50dB with 
above variables is the question?   Can someone share these figures?
73,Mike  AC5P




--
R. Kevin Stover
AC0H
ARRL
FISTS #11993
SKCC #215
NAQCC #3441


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Re: [Elecraft] Elecraft gear relative IMD

[Jim Brown]

On Thu,12/31/2015 4:34 AM, Kevin Stover wrote:
IMD is not regulated 


It is, as part of the wording of regulation of transmitted bandwidth, 
but the wording doesn't include numbers. The regulation states (I'm 
paraphrasing from memory) that the bandwidth of the transmitted signal 
shall be no greater than required for the means of transmission. I've 
served on the AES Standard Committee, and that's the sort of language 
used to say that the signal should be as narrow as possible, but that it 
is understood that through the years, it will be possible to make 
narrower rigs, so it leaves out the number, which is a moving target.


Elecraft has pretty well set the standard for the bandwidth of a CW 
signal, thanks to the careful control of the keying waveform, pretty low 
IMD, and a design architecture that produces very low phase noise. In my 
tests, I see the K3 as no cleaner than other rigs I've tested on SSB, 
but significantly cleaner on CW, RTTY, and digital modes.


Important note: IMD strongly affects the bandwidth of a CW signal, 
because CW is 100% amplitude modulation of a carrier by a square wave. 
Square waves have an infinite number of harmonics, the strength of which 
are related to the rise time of the CW keying (and NOT to CW SPEED). The 
IMD of a gain stage that amplifies that signal WILL produce sidebands 
(clicks). CW keying bandwidth can easily be measured using a spectrum 
analyzer that has low enough resolution bandwidth. A P3 can do it, and a 
P3 with SVGA has even lower resolution bandwidth. Likewise, an SDR with 
suitable software can do it, and I'm planning to buy an ANAN 10E for 
measurement only.


But the FCC Rules make the operator responsible for occupying the 
minimum spectrum. So that means buying a rig that's clean in the first 
place, giving the rig enough DC voltage, and not overdriving audio 
stages and power amps.


73, Jim K9YC
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Re: [Elecraft] Elecraft gear relative IMD

[Don Wilhelm]

Being New Years Eve, it is nostalgia time, and I think it appropriate to 
discuss those antique stations.


If you want to hear how bad some of those antique transmitters were, do 
listen tonight for SKN.
Bad chirps, bad keyclicks and lots of phase noise that spread the 
signals out over a large portion of the band.
The bands today are more crowded than they were back then, and while it 
is legal to use those antique transmitters and receivers, I do not think 
it should be an everyday event.


Yes, I know several hams who are into 'boat anchors', particularly those 
old AM transmitters.  Fortunately, that crowd concentrates on 80 meters 
when the band is not full of signals, but listening with today's more 
selective receivers and hearing signals in a 'net' so spread out and off 
frequency, it amazes me that we were able to communicate easily back 
then.  BUT we did, and had fun doing it.


I would not advocate using those transmitters and receivers in a contest 
today, but they did work for us back then.  BTW, I was first licensed in 
1955, so you can perhaps understand the advances in technology that I 
have seen over the years.  There has been a LOT.


I have often considered building again my Novice transmitter which I 
assembled from the article in the 1955 ARRL handbook (a 6CL6 xtal 
oscillator and a 6146 final), but obtaining the parts is almost 
impossible.  Can you find 1 1/4 inch diameter, 4 pin coil forms these 
days?  Maybe, but they are prohibitively expensive, and the power 
transformer is almost impossible to find although back then, they were 
quite common because they were used in TV designs.


I pass by the flea market areas at hamfests and get enough of my 
nostalgia satisfied by looking at those old transmitters and receivers 
that I drooled over 'way back then' knowing that as a teen with limited 
income I could never afford them.  I don't have time nor energy to 
restore any of those 70 pound radios, nor does my hamshack have space 
for them, so I look and marvel, but do not take any of them home with me.


I do have my homebrew receiver, a version of the HBR-16 and an old NC100 
receiver that I may someday bring out of the attic and bring back to 
operational status, but that is pretty far down on the priority list for me.


Enjoy SKN and listen to those old transmitters (and even listen on your 
vintage receiver).  It is a telling story of the history of ham radio 
and the gear available in the years gone by.


Happy New Year.

73,
Don W3FPR

On 12/31/2015 7:30 PM, Ron D'Eau Claire wrote:

Sure the rules apply, and rules for spectrum bandwidth provide no numbers,
saying only "... in accordance with good amateur practice."

Right now, New Year's eve, there is an on air event taking place, Straight
Key Night, that encourages the use of antique rigs on the air and is
sponsored by the largest association of Radio Amateurs in the USA, the ARRL.





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Re: [Elecraft] Elecraft gear relative IMD

[Jim Brown]

On Thu,12/31/2015 3:07 PM, Ron D'Eau Claire wrote:

The same is true for Ham rigs. It's perfectly okay to run an old Heathkit
AT-1 or a 1930's homebrew rig with cathode keying today as it was back then,
even though the keying bandwidth will be substantially greater than modern
rigs.


WRONG!  The rule about bandwidth governs.


The bottom line is to make sure the rig you have is being operated to
produce the cleanest signal its design allows in the mode of operation being
used.


The rule says NOTHING about the design of the rig. It speaks ONLY about 
the means of transmission, which refers to the communications mode (CW, 
SSB, FM, RTTY, PSK, etc.)



That's why double-sideband amplitude modulation is still legal even though
it requires more than twice the spectrum of an SSB signal and CW is still
allowed even though SSB and the various digital modes provide the same
information in yet smaller bandwidths.


WRONG. Double-sideband AM with a carrier is legal because it is a 
DIFFERENT mode permitted by the FCC Rules.  (A3 is the FCC designator). 
SSB is J3 if the carrier is suppressed. CW is A1.


73, Jim K9YC
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Re: [Elecraft] Elecraft gear relative IMD

[Ron D'Eau Claire]

The FCC here in the USA does not require having a rig that meets state of
the art specs, either for Amateur or many commercial applications. 

When checking shipboard radio installations in preparation for their annual
FCC inspections, I used a variety of different specs the gear had to meet
based on its year of manufacture. Older gear had a lot looser specs than the
newer stuff. 

The same is true for Ham rigs. It's perfectly okay to run an old Heathkit
AT-1 or a 1930's homebrew rig with cathode keying today as it was back then,
even though the keying bandwidth will be substantially greater than modern
rigs. 

The bottom line is to make sure the rig you have is being operated to
produce the cleanest signal its design allows in the mode of operation being
used.

That's why double-sideband amplitude modulation is still legal even though
it requires more than twice the spectrum of an SSB signal and CW is still
allowed even though SSB and the various digital modes provide the same
information in yet smaller bandwidths.   

73, Ron AC7AC


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Re: [Elecraft] Elecraft gear relative IMD

[Ron D'Eau Claire]

Sure the rules apply, and rules for spectrum bandwidth provide no numbers,
saying only "... in accordance with good amateur practice."

Right now, New Year's eve, there is an on air event taking place, Straight
Key Night, that encourages the use of antique rigs on the air and is
sponsored by the largest association of Radio Amateurs in the USA, the ARRL.


Amateur radio is still a homebrewer's hobby, encouraging Hams to design,
build and maintain their own rigs frequently without access to modern
equipment to evaluate their performance. I believe it is for that reason the
rules are very loose about things like spectrum bandwidth. 

73, Ron AC7AC

-Original Message-
From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Jim
Brown
Sent: Thursday, December 31, 2015 3:27 PM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] Elecraft gear relative IMD

On Thu,12/31/2015 3:07 PM, Ron D'Eau Claire wrote:
> The same is true for Ham rigs. It's perfectly okay to run an old 
> Heathkit
> AT-1 or a 1930's homebrew rig with cathode keying today as it was back 
> then, even though the keying bandwidth will be substantially greater 
> than modern rigs.

WRONG!  The rule about bandwidth governs.

> The bottom line is to make sure the rig you have is being operated to 
> produce the cleanest signal its design allows in the mode of operation 
> being used.

The rule says NOTHING about the design of the rig. It speaks ONLY about the
means of transmission, which refers to the communications mode (CW, SSB, FM,
RTTY, PSK, etc.)

> That's why double-sideband amplitude modulation is still legal even 
> though it requires more than twice the spectrum of an SSB signal and 
> CW is still allowed even though SSB and the various digital modes 
> provide the same information in yet smaller bandwidths.

WRONG. Double-sideband AM with a carrier is legal because it is a DIFFERENT
mode permitted by the FCC Rules.  (A3 is the FCC designator). 
SSB is J3 if the carrier is suppressed. CW is A1.

73, Jim K9YC

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Re: [Elecraft] Elecraft gear relative IMD

[Grant Youngman]

I honestly don't understand why this keeps coming up, or what it has to do with 
Elecraft. 

I'll operate my DX-40, or Viking II, or 100V or other vintage rig anytime and 
anywhere I please, thank you. These radios don't generally chirp wildly or have 
substantial phase noise. If phase noise is a concern, be concerned about some 
of the infamous 80's import all mode solid state, with a hundred tiny knobs, 
impressive looking expensive radios that could well clear out a band. 
Fortunately that junk doesn't show up very often. 

A well built tube transmitter, vintage or not, is a good thing. A modern 
receiver is a great tool and we wail when it's S-meter reading is off by .01dB 
or it drifts 2 HZ or there's something wrong with a Windows driver or whatever. 
  A vintage one with a pair of 6V6s driving a large loudspeaker and an 
operating manual that doesn't require a search engine has character, soul, and 
audio that has to be heard to be believed, even if it can't read freq out to a 
few milli-hertz :)

And other than contest weekends, I keep searching and searching for crowded 
bands ...

Grant NQ5T

Sent from my iPhone

> On Dec 31, 2015, at 8:22 PM, Don Wilhelm  wrote:
> 
> Being New Years Eve, it is nostalgia time, and I think it appropriate to 
> discuss those antique stations.
> 
> If you want to hear how bad some of those antique transmitters were, do 
> listen tonight for SKN.
> Bad chirps, bad keyclicks and lots of phase noise that spread the signals out 
> over a large portion of the band.
> The bands today are more crowded than they were back then, and while it is 
> legal to use those antique transmitters and receivers, I do not think it 
> should be an everyday event.
> 
> Yes, I know several hams who are into 'boat anchors', particularly those old 
> AM transmitters.  Fortunately, that crowd concentrates on 80 meters when the 
> band is not full of signals, but listening with today's more selective 
> receivers and hearing signals in a 'net' so spread out and off frequency, it 
> amazes me that we were able to communicate easily back then.  BUT we did, and 
> had fun doing it.
> 
> I would not advocate using those transmitters and receivers in a contest 
> today, but they did work for us back then.  BTW, I was first licensed in 
> 1955, so you can perhaps understand the advances in technology that I have 
> seen over the years.  There has been a LOT.
> 
> I have often considered building again my Novice transmitter which I 
> assembled from the article in the 1955 ARRL handbook (a 6CL6 xtal oscillator 
> and a 6146 final), but obtaining the parts is almost impossible.  Can you 
> find 1 1/4 inch diameter, 4 pin coil forms these days?  Maybe, but they are 
> prohibitively expensive, and the power transformer is almost impossible to 
> find although back then, they were quite common because they were used in TV 
> designs.
> 
> I pass by the flea market areas at hamfests and get enough of my nostalgia 
> satisfied by looking at those old transmitters and receivers that I drooled 
> over 'way back then' knowing that as a teen with limited income I could never 
> afford them.  I don't have time nor energy to restore any of those 70 pound 
> radios, nor does my hamshack have space for them, so I look and marvel, but 
> do not take any of them home with me.
> 
> I do have my homebrew receiver, a version of the HBR-16 and an old NC100 
> receiver that I may someday bring out of the attic and bring back to 
> operational status, but that is pretty far down on the priority list for me.
> 
> Enjoy SKN and listen to those old transmitters (and even listen on your 
> vintage receiver).  It is a telling story of the history of ham radio and the 
> gear available in the years gone by.
> 
> Happy New Year.
> 
> 73,
> Don W3FPR
> 
>> On 12/31/2015 7:30 PM, Ron D'Eau Claire wrote:
>> Sure the rules apply, and rules for spectrum bandwidth provide no numbers,
>> saying only "... in accordance with good amateur practice."
>> 
>> Right now, New Year's eve, there is an on air event taking place, Straight
>> Key Night, that encourages the use of antique rigs on the air and is
>> sponsored by the largest association of Radio Amateurs in the USA, the ARRL.
> 
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Re: [Elecraft] Elecraft gear relative IMD

[Wes (N7WS)]

I have some of those data, but not all.  This conversation had already given me 
the idea that I should remeasure the two radios' IMD at different voltages, as 
well as vs power vs. frequency.


But you are asking for two different things, IMD and spurious signals.  With a 
nominal "12 V" radio, absent some fancy feedback, IMD products will never be 
down 50 dB in this lifetime, even when using the "cheating" (IMHO) 
dB-relative-to-PEP method.


Looking for and measuring spurs, other than harmonics, is a job for a spectrum 
analyzer, something I lack.



On 12/30/2015 8:09 PM, a...@sbcglobal.net wrote:

Who has some measured 2 tone IMD test figures for an actual  K3/K3S at full and 
reduced power levels and at supply voltage levels between 12-15 volts?Must 
assume the Harmonic and Spurious Outputs exceed 50dB below carrier @ 100W 
within ham bands as per Elecraft manual specs.  HOW  much better than 50dB with 
above variables is the question?   Can someone share these figures?
73,Mike  AC5P
  


 On Wednesday, December 30, 2015 6:39 PM, Don Wilhelm 
 wrote:
  


  I think it is time to change the subject line (and I did).  The original
question was about increased IMD with lower power supply voltages.
It has now morphed into the relative IMD at different power levels with
higher (normal) power supply voltages.

Whatever the actual IMD of the K3/K3S at any power level, the
information I have heard from contesters and DXers is that the Elecraft
gear is has lower IMD than most other transceivers.  We have heard
testimony to that repeatedly from Field Day setups and DXpeditions where
there are multiple transceivers operating in close proximity to other
stations.  When station A cannot hear anything interfering when station
B transmits, that is a good thing. Elecraft gear can do that while many
other manufacturer's transceivers cannot say the same thing.

What we do know is that higher power supply voltages provide better IMD
figures, and since the Elecraft gear is rated for up to 15 volts, we
will achieve better IMD performance if the power supply is cranked up to
provide a voltage just a bit below 15 volts.

73,
Don W3FPR

On 12/30/2015 6:52 PM, Fred Jensen wrote:

Ummm ... I don't think that was what was suggested at all.  I read the
post to be an observation of a *relative* condition.  All amplifiers
[at least that I've ever encountered] exhibit increasing distortion
near their rated power limits.  I've always assumed that's why
distortion numbers are almost always accompanied by the power when the
measurements were taken.

My K3/100 is a K3/10 below about 15 watts ... the 100 W amplifier
switches out of the circuit.  I think all that the post was trying to
point out is that, from 100 W downward, the distortion will decrease
*until* the KPA3 cuts out.  At that point, the LP amplifier/exciter is
near it's max power, and it's distortion will probably be higher than
the values from the KPA3 operating just above that power.  In any
case, absolute distortion from a K3/ is still among the
lowest in the marketplace.


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Re: [Elecraft] Elecraft gear relative IMD

[ac5p]

Who has some measured 2 tone IMD test figures for an actual  K3/K3S at full and 
reduced power levels and at supply voltage levels between 12-15 volts?Must 
assume the Harmonic and Spurious Outputs exceed 50dB below carrier @ 100W 
within ham bands as per Elecraft manual specs.  HOW  much better than 50dB with 
above variables is the question?   Can someone share these figures?  
73,Mike  AC5P   
 

On Wednesday, December 30, 2015 6:39 PM, Don Wilhelm  
wrote:
 

 I think it is time to change the subject line (and I did).  The original 
question was about increased IMD with lower power supply voltages.
It has now morphed into the relative IMD at different power levels with 
higher (normal) power supply voltages.

Whatever the actual IMD of the K3/K3S at any power level, the 
information I have heard from contesters and DXers is that the Elecraft 
gear is has lower IMD than most other transceivers.  We have heard 
testimony to that repeatedly from Field Day setups and DXpeditions where 
there are multiple transceivers operating in close proximity to other 
stations.  When station A cannot hear anything interfering when station 
B transmits, that is a good thing. Elecraft gear can do that while many 
other manufacturer's transceivers cannot say the same thing.

What we do know is that higher power supply voltages provide better IMD 
figures, and since the Elecraft gear is rated for up to 15 volts, we 
will achieve better IMD performance if the power supply is cranked up to 
provide a voltage just a bit below 15 volts.

73,
Don W3FPR

On 12/30/2015 6:52 PM, Fred Jensen wrote:
> Ummm ... I don't think that was what was suggested at all.  I read the 
> post to be an observation of a *relative* condition.  All amplifiers 
> [at least that I've ever encountered] exhibit increasing distortion 
> near their rated power limits.  I've always assumed that's why 
> distortion numbers are almost always accompanied by the power when the 
> measurements were taken.
>
> My K3/100 is a K3/10 below about 15 watts ... the 100 W amplifier 
> switches out of the circuit.  I think all that the post was trying to 
> point out is that, from 100 W downward, the distortion will decrease 
> *until* the KPA3 cuts out.  At that point, the LP amplifier/exciter is 
> near it's max power, and it's distortion will probably be higher than 
> the values from the KPA3 operating just above that power.  In any 
> case, absolute distortion from a K3/ is still among the 
> lowest in the marketplace.
>

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Re: [Elecraft] Elecraft gear relative IMD

[Don Wilhelm]

I think it is time to change the subject line (and I did).  The original 
question was about increased IMD with lower power supply voltages.
It has now morphed into the relative IMD at different power levels with 
higher (normal) power supply voltages.


Whatever the actual IMD of the K3/K3S at any power level, the 
information I have heard from contesters and DXers is that the Elecraft 
gear is has lower IMD than most other transceivers.  We have heard 
testimony to that repeatedly from Field Day setups and DXpeditions where 
there are multiple transceivers operating in close proximity to other 
stations.  When station A cannot hear anything interfering when station 
B transmits, that is a good thing. Elecraft gear can do that while many 
other manufacturer's transceivers cannot say the same thing.


What we do know is that higher power supply voltages provide better IMD 
figures, and since the Elecraft gear is rated for up to 15 volts, we 
will achieve better IMD performance if the power supply is cranked up to 
provide a voltage just a bit below 15 volts.


73,
Don W3FPR

On 12/30/2015 6:52 PM, Fred Jensen wrote:
Ummm ... I don't think that was what was suggested at all.  I read the 
post to be an observation of a *relative* condition.  All amplifiers 
[at least that I've ever encountered] exhibit increasing distortion 
near their rated power limits.  I've always assumed that's why 
distortion numbers are almost always accompanied by the power when the 
measurements were taken.


My K3/100 is a K3/10 below about 15 watts ... the 100 W amplifier 
switches out of the circuit.  I think all that the post was trying to 
point out is that, from 100 W downward, the distortion will decrease 
*until* the KPA3 cuts out.  At that point, the LP amplifier/exciter is 
near it's max power, and it's distortion will probably be higher than 
the values from the KPA3 operating just above that power.  In any 
case, absolute distortion from a K3/ is still among the 
lowest in the marketplace.




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