IMD and supply voltage
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This subject keeps cropping up. Is this a serious issue ?
I have heard that IMD improves by 10db with a one volt increase in supply voltage. Is this really the case or just a measurement error? 10db is a large difference. One volt is a small variation. What is the minimum acceptable IMD? How linear does the amp need to be? If 36db is better than 26db is 100db even better or just overkill? Are other solid state amplifier products similarly effected? What is the IMD performance of the K3S at 10 watts over a supply voltage variation from 11 volts to 14.7 volts? I ask because I believe those ten watts are generated by Dmos devices as well. Do these devices only misbehave with varying supply voltage at higher (100w) power levels and lower supply voltages? Should I wait to purchase a K3S until this issue is resolved? (Assuming this is a valid issue) Back in the good old days we used to solve problems. Today we don't have problems, just issues. -- Frank - K5DKZ KX3 - 7550 PX3 - 1143 KXPA100 - 1566 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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Frank,
I think the "issue" is one of some hams wanting to make what is good already into something better. If you look closely you should discover that this is a situation common to *all* 100 watt class amplifiers that are supposed to run on a nominal '12 volt' supply. That voltage level is chosen because it is common for vehicle batteries, so most transceivers are designed around that voltage - the K3S is just one of those. Using an increased voltage power supply will drastically reduce the transmit IMD, and that is true for all those 100 watt class amplifiers. Bottom line is that I don't think it will be "fixed" in the K3S - I don't think it can be fixed in any of the 100 watt class solid state amplifiers. So the thing to do is to run the power supply voltage up to near 15 volts (but not above), and do not operate with "all knobs to the right". Many hams seen to want to squeeze all the power output that they can from a transceiver, so you will put a cleaner signal on the air if you set the power to 100 watts rather than trying to squeeze that last 20 extra watts out of an amplifier. 73, Don W3FPR On 10/29/2015 11:09 AM, frank wrote: > This subject keeps cropping up. Is this a serious issue ? > > I have heard that IMD improves by 10db with a one volt increase in supply voltage. Is this really the case or just a measurement error? 10db is a large difference. One volt is a small variation. > > What is the minimum acceptable IMD? How linear does the amp need to be? If 36db is better than 26db is 100db even better or just overkill? > > Are other solid state amplifier products similarly effected? > > What is the IMD performance of the K3S at 10 watts over a supply voltage variation from 11 volts to 14.7 volts? I ask because I believe those ten watts are generated by Dmos devices as well. Do these devices only misbehave with varying supply voltage at higher (100w) power levels and lower supply voltages? > > Should I wait to purchase a K3S until this issue is resolved? (Assuming this is a valid issue) > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by frank-2
Frank,
All radios that run from an external DC supply (to make them usable with emergency power sources, such as a 12-V car battery or solar panel) are subject to increasing TX IMD as supply voltage goes down. But such radios are virtually all specified (by the manufacturer) and tested (in QST reviews, for example) at a standard bench supply voltage of about 14 V. If you're running from lower voltages, such as from a depleted 12 V car battery, the radio is not likely to put out full power on all bands. This effect will vary with band, load impedance, and the actual voltage. You could simply crank the power all the way up and accept whatever TX IMD results from this. Instead, we recommend reducing power manually if you know the voltage is low. The K3 and K3S, like our other radios, are very popular for Field Day and other applications where a battery might be used. So we provide two ways for you to monitor the supply voltage: 1. The CONFIG:BAT MIN menu entry. This sets the voltage at which you will periodically see a BAT LOW warning on the display. 2. Voltage display: Tap DISP and rotate VFO B until you see XX.X VDC. You can also display current drain and PA temperature this way. 73, Wayne N6KR On Oct 29, 2015, at 8:09 AM, frank <[hidden email]> wrote: > This subject keeps cropping up. Is this a serious issue ? > > I have heard that IMD improves by 10db with a one volt increase in supply voltage. Is this really the case or just a measurement error? 10db is a large difference. One volt is a small variation. > > What is the minimum acceptable IMD? How linear does the amp need to be? If 36db is better than 26db is 100db even better or just overkill? > > Are other solid state amplifier products similarly effected? > > What is the IMD performance of the K3S at 10 watts over a supply voltage variation from 11 volts to 14.7 volts? I ask because I believe those ten watts are generated by Dmos devices as well. Do these devices only misbehave with varying supply voltage at higher (100w) power levels and lower supply voltages? > > Should I wait to purchase a K3S until this issue is resolved? (Assuming this is a valid issue) > > Back in the good old days we used to solve problems. Today we don't have problems, just issues. > > -- > Frank - K5DKZ > KX3 - 7550 > PX3 - 1143 > KXPA100 - 1566 > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Don Wilhelm-4
Does that imply we should all adjust our power supplies to output +15VDC?
Will that damage my 2M Rig? I recently purchased the powerwerx SS-30DV from Elecraft when I purchased my K3S kit. Thanks Jerry Moore CDXA, INDEXA, SKCC, Fists AE4PB, K3S - S.N. 010324 http://www.qrz.com/db/AE4PB An Amateur is - Considerate, Loyal, Progressive, Friendly, Balanced, and Patriotic. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Don Wilhelm-4
How about 80 watts instead.
Won't make a noticeable difference on the receive end. Even better, get rid of all the Yaesu and Icom "Clackers" with their VERY poor CW performance. You can have the best class A amplifier in the world, but garbage in will always equal garbage out. I am ashamed at our "leaders" at the ARRL for not petitioning the FCC for better specs. The technology is there, they all use it in their business radios that have a better spec. Oh, I forgot, follow the money and take the advertising monies from these clackers Jim W6AIM -----Original Message----- From: Elecraft [mailto:[hidden email]] On Behalf Of Don Wilhelm Sent: Thursday, October 29, 2015 7:41 AM To: frank; [hidden email] Subject: Re: [Elecraft] IMD and supply voltage Frank, I think the "issue" is one of some hams wanting to make what is good already into something better. If you look closely you should discover that this is a situation common to *all* 100 watt class amplifiers that are supposed to run on a nominal '12 volt' supply. That voltage level is chosen because it is common for vehicle batteries, so most transceivers are designed around that voltage - the K3S is just one of those. Using an increased voltage power supply will drastically reduce the transmit IMD, and that is true for all those 100 watt class amplifiers. Bottom line is that I don't think it will be "fixed" in the K3S - I don't think it can be fixed in any of the 100 watt class solid state amplifiers. So the thing to do is to run the power supply voltage up to near 15 volts (but not above), and do not operate with "all knobs to the right". Many hams seen to want to squeeze all the power output that they can from a transceiver, so you will put a cleaner signal on the air if you set the power to 100 watts rather than trying to squeeze that last 20 extra watts out of an amplifier. 73, Don W3FPR On 10/29/2015 11:09 AM, frank wrote: > This subject keeps cropping up. Is this a serious issue ? > > I have heard that IMD improves by 10db with a one volt increase in supply voltage. Is this really the case or just a measurement error? 10db is a large difference. One volt is a small variation. > > What is the minimum acceptable IMD? How linear does the amp need to be? If 36db is better than 26db is 100db even better or just overkill? > > Are other solid state amplifier products similarly effected? > > What is the IMD performance of the K3S at 10 watts over a supply voltage variation from 11 volts to 14.7 volts? I ask because I believe those ten watts are generated by Dmos devices as well. Do these devices only misbehave with varying supply voltage at higher (100w) power levels and lower supply voltages? > > Should I wait to purchase a K3S until this issue is resolved? (Assuming this is a valid issue) > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Don Wilhelm-4
And 120W over 100W gives you a whopping 0.8dB increase in power.
Will anyone notice? I see the "easy to measure" effect in many fields. Anything that's easy to measure becomes the only thing to optimize. In program language compilers,the speed of the optimized program is easy to measure so it is more important than robustness, which is hard to measure. In cars, horsepower is easy to measure, so it becomes more important than handling. In cameras, its pixels over lens quality. In radios, it's power over IMD. etc. 73 Bill AE6JV On 10/29/15 at 7:41 AM, [hidden email] (Don Wilhelm) wrote: >So the thing to do is to run the power supply voltage up to >near 15 volts (but not above), and do not operate with "all >knobs to the right". >Many hams seen to want to squeeze all the power output that >they can from a transceiver, so you will put a cleaner signal >on the air if you set the power to 100 watts rather than trying >to squeeze that last 20 extra watts out of an amplifier. -------------------------------------------------------------- Bill Frantz | There are now so many exceptions to the 408-356-8506 | Fourth Amendment that it operates only by www.pwpconsult.com | accident. - William Hugh Murray ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by wayne burdick
On Thu, 29 Oct 2015 07:43:24 -0700
Wayne Burdick <[hidden email]> wrote: > The K3 and K3S, like our other radios, are very popular for Field Day and other applications where a battery might be used. So we provide two ways for you to monitor the supply voltage: > > 1. The CONFIG:BAT MIN menu entry. This sets the voltage at which you will periodically see a BAT LOW warning on the display. > > 2. Voltage display: Tap DISP and rotate VFO B until you see XX.X VDC. You can also display current drain and PA temperature this way. > Verifying the obvious is sometimes helpful. Of course the battery voltage is going to drop when you are pulling enough current to power a 100 watt transceiver. I was hoping for a more pro-active suggestion to the IMD problem. My old Drake, tube type, mobile did not have an IMD problem even when run off less than 12 volts. it had a switching supply delivering 700 volts at 200ma to the finals. Today we use switching supplies to deliver 12 volts to finals that are not capable of delivering a clean signal at 12 volts. This is state of the art? Just because everyone else is building radios that produce dirty signals, does that justify doing the same? Also, you did not answer my questions. Maybe I should ask them one at a time. I > > On Oct 29, 2015, at 8:09 AM, frank <[hidden email]> wrote: > > > This subject keeps cropping up. Is this a serious issue ? > > > > I have heard that IMD improves by 10db with a one volt increase in supply voltage. Is this really the case or just a measurement error? 10db is a large difference. One volt is a small variation. > > > > What is the minimum acceptable IMD? How linear does the amp need to be? If 36db is better than 26db is 100db even better or just overkill? > > > > Are other solid state amplifier products similarly effected? > > > > What is the IMD performance of the K3S at 10 watts over a supply voltage variation from 11 volts to 14.7 volts? I ask because I believe those ten watts are generated by Dmos devices as well. Do these devices only misbehave with varying supply voltage at higher (100w) power levels and lower supply voltages? > > > > Should I wait to purchase a K3S until this issue is resolved? (Assuming this is a valid issue) > > > > Back in the good old days we used to solve problems. Today we don't have problems, just issues. > > > > -- > > Frank - K5DKZ > > KX3 - 7550 > > PX3 - 1143 > > KXPA100 - 1566 > > ______________________________________________________________ > > Elecraft mailing list > > Home: http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/mmfaq.htm > > Post: mailto:[hidden email] > > > > This list hosted by: http://www.qsl.net > > Please help support this email list: http://www.qsl.net/donate.html > > Message delivered to [hidden email] > -- Frank - K5DKZ KX3 - 7550 PX3 - 1143 KXPA100 - 1566 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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On Thu,10/29/2015 12:06 PM, frank wrote:
> Also, you did not answer my questions. Maybe I should ask them one at a time. I thought Wayne answered them quite well, but I'll try to rephrase his answers in terms that are easier to understand. 1) Contemporary ham rigs are designed to operate from automotive DC voltages as a matter of convenience. 2) The output transistors used in these rigs produce less distortion at higher supply voltages. 3) Most rigs are optimized for 13.8 - 14 VDC, and are tested at that level by ARRL. 4) Most commercial power supplies marketed to hams are regulated to 13.8 - 14.5 VDC, and that voltage is internally adjustable. 5) Most rigs will work at lower DC power supply voltages. 6) When operated at lower DC power supply voltage, their distortion will increase. 7) When operated above their design output power, distortion will increase. 8) Doing both 6 and 7 will increase distortion even more. 9) Distortion in the K3 and K3S output stage is specified for full power output at 13.8 - 14 VDC, and distortion is greatly reduced when run at lower power levels. My own comments: Distortion causes the most QRM when running high power. Many of the best power amps reach full power with drive power in the range of 50-60 W -- the KPA500 needs about 28W, my Titans (I have three) need between 40-60W, depending on condition of the tubes and the operating frequency. An ACOM 1010 needs between 50 and 70 watts, again depending on the operating frequency. > This is state of the art? How much do you want to pay for "state of the art?" How about the infamous pentagon $800 hammer? According to ARRL measurements, the K3 produces the cleanest CW signal of any current rig. See my summary of their published data in the following link k9yc.com/TXNoise.pdf See my measurements of my K3 and several other rigs in this link http://k9yc.com/P3_Spectrum_Measurements.pdf 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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On Thu, Oct 29, 2015 at 2:58 PM, Jim Brown <[hidden email]>
wrote: > According to ARRL measurements, the K3 produces the cleanest CW signal of > any current rig. See my summary of their published data in the following > link > > k9yc.com/TXNoise.pdf > > See my measurements of my K3 and several other rigs in this link > > http://k9yc.com/P3_Spectrum_Measurements.pdf > > 73, Jim K9YC > Any chance you will be able to revise those two documents by adding K3S or K3/syn3a mod, without removing the existing K3 curves in there? Think that might put the synthesizer mod in a very appropriate setting. 73, Guy K2AV ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: IMD and supply voltage
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CW is just one mode and is the easiest to "get right" as far as the PA is concerned. CW bandwidth is determined primarily by keying shape and phase noise in the synthesizer (or D to A clock jitter). The K3/K3S is far from the cleanest rig when it comes to SSB on any of the audio based digital modes. All of the rigs using 48V finals have IMD products many dB less than the K3/K3S - particularly when the K3/K3S is being run from a partially discharged battery. However, even rigs with 48V finals are notably more dirty than many of the rigs that used tube type finals (particularly the 6146) of 40 years ago. Amateur rigs need predistortion - particularly those with "12V" finals - to get SSB (and data mode) IMD below -50 dBc (-44 dB PEP) as a starting point or "12V" radios should be limited by their makers to 60-80W where the IMD is much lower than at 100-120W levels. For ARRL to have silently watched transmit IMD degrade by nearly 20 dB in the last 40 years and not raised the issue is unconscionable. Lest anyone think I'm picking on Elecraft ... the IMD issues are the same in many solid state amplifiers, they are rated for saturated conditions which drive up IMD. Most are significantly less dirty when operated at 60-75% of rated PEP output unless the designer has built in a significant amount of negative feedback. When a 1200W PEP amplifier has only 8 150W transistors or or a 600 W amplifier has only two 300 W transistors that's a good sign the amplifier can not possibly be clean at its rated output. 73, ... Joe, W4TV > On Thu, Oct 29, 2015 at 2:58 PM, Jim Brown <[hidden email]> > wrote: > >> According to ARRL measurements, the K3 produces the cleanest CW signal of >> any current rig. See my summary of their published data in the following >> link >> >> k9yc.com/TXNoise.pdf >> >> See my measurements of my K3 and several other rigs in this link >> >> http://k9yc.com/P3_Spectrum_Measurements.pdf >> >> 73, Jim K9YC >> Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Jim Brown-10
Jim,
The marine divisions of Kenwood, et.al. already have low cost, low voltage, PA solutions with better IMD specs, primarily due to channel spacing for the marine band. Jim W6AIM -----Original Message----- From: Elecraft [mailto:[hidden email]] On Behalf Of Jim Brown Sent: Thursday, October 29, 2015 11:58 AM To: [hidden email] Subject: Re: [Elecraft] IMD and supply voltage On Thu,10/29/2015 12:06 PM, frank wrote: > Also, you did not answer my questions. Maybe I should ask them one at a time. I thought Wayne answered them quite well, but I'll try to rephrase his answers in terms that are easier to understand. 1) Contemporary ham rigs are designed to operate from automotive DC voltages as a matter of convenience. 2) The output transistors used in these rigs produce less distortion at higher supply voltages. 3) Most rigs are optimized for 13.8 - 14 VDC, and are tested at that level by ARRL. 4) Most commercial power supplies marketed to hams are regulated to 13.8 - 14.5 VDC, and that voltage is internally adjustable. 5) Most rigs will work at lower DC power supply voltages. 6) When operated at lower DC power supply voltage, their distortion will increase. 7) When operated above their design output power, distortion will increase. 8) Doing both 6 and 7 will increase distortion even more. 9) Distortion in the K3 and K3S output stage is specified for full power output at 13.8 - 14 VDC, and distortion is greatly reduced when run at lower power levels. My own comments: Distortion causes the most QRM when running high power. Many of the best power amps reach full power with drive power in the range of 50-60 W -- the KPA500 needs about 28W, my Titans (I have three) need between 40-60W, depending on condition of the tubes and the operating frequency. An ACOM 1010 needs between 50 and 70 watts, again depending on the operating frequency. > This is state of the art? How much do you want to pay for "state of the art?" How about the infamous pentagon $800 hammer? According to ARRL measurements, the K3 produces the cleanest CW signal of any current rig. See my summary of their published data in the following link k9yc.com/TXNoise.pdf See my measurements of my K3 and several other rigs in this link http://k9yc.com/P3_Spectrum_Measurements.pdf 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Joe Subich, W4TV-4
My internal K3 readings of 14.3V idle and 14.0V at the 35w PEP out needed
to drive my Alpha 8410 to 1200 or 1300 watts out, probably is pretty good IMD. The idle current is ~1.3 amps. Tune at 35 watts into 1:1 SWR is 8.7 amps. That's .04 ohms in the cabling. I don't have anything to directly measure that. At that point, the tuning of the Alpha would has more to do with the over-the-air IMD than the K3. Wouldn't predistortion need to be external to the K3, dynamic based on sampling the output of the amp, and converted into some DSP friendly format fed to the K3 CPU? 73, Guy K2AV On Thu, Oct 29, 2015 at 3:52 PM, Joe Subich, W4TV <[hidden email]> wrote: > > CW is just one mode and is the easiest to "get right" as far as the PA > is concerned. CW bandwidth is determined primarily by keying shape and > phase noise in the synthesizer (or D to A clock jitter). > > The K3/K3S is far from the cleanest rig when it comes to SSB on any of > the audio based digital modes. All of the rigs using 48V finals have > IMD products many dB less than the K3/K3S - particularly when the > K3/K3S is being run from a partially discharged battery. > > However, even rigs with 48V finals are notably more dirty than many of > the rigs that used tube type finals (particularly the 6146) of 40 years > ago. > > Amateur rigs need predistortion - particularly those with "12V" finals - > to get SSB (and data mode) IMD below -50 dBc (-44 dB PEP) as a starting > point or "12V" radios should be limited by their makers to 60-80W where > the IMD is much lower than at 100-120W levels. > > For ARRL to have silently watched transmit IMD degrade by nearly 20 dB > in the last 40 years and not raised the issue is unconscionable. > > Lest anyone think I'm picking on Elecraft ... the IMD issues are the > same in many solid state amplifiers, they are rated for saturated > conditions which drive up IMD. Most are significantly less dirty when > operated at 60-75% of rated PEP output unless the designer has built in > a significant amount of negative feedback. When a 1200W PEP amplifier > has only 8 150W transistors or or a 600 W amplifier has only two 300 W > transistors that's a good sign the amplifier can not possibly be clean > at its rated output. > > 73, > > ... Joe, W4TV > > On Thu, Oct 29, 2015 at 2:58 PM, Jim Brown <[hidden email]> >> wrote: >> >> According to ARRL measurements, the K3 produces the cleanest CW signal of >>> any current rig. See my summary of their published data in the following >>> link >>> >>> k9yc.com/TXNoise.pdf >>> >>> See my measurements of my K3 and several other rigs in this link >>> >>> http://k9yc.com/P3_Spectrum_Measurements.pdf >>> >>> 73, Jim K9YC >>> >>> ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Jim Bolit
Jim,
This appears to *not* be true, at least for one radio lauded by those concerned about TX IMD. Earlier this year there was a long forum thread on Eham.net lamenting the "fact" that 12-V ham rigs were not as clean as 12-V marine rigs. One radio in particular, the Icom M802, was touted by forum participants as having far better IMD specs than any 12-V ham transceiver. We downloaded the manual for we this radio and found that Icom was using the same devices and essentially the same amplifier circuit that we were. Still, we gave them the benefit of the doubt and purchased a new Icom M802 (from Amazon, $1813) to test in our own lab. We very carefully measured transmit IMD at 100 watts on several channels, covering the full range of the HF marine band. Here is an example plot from about 12.28 MHz: http://www.elecraft.com/Icom%20M802%20100-W%20IMD.jpeg This plot shows the two 3rd-order products being down by about 27 and 30 dBc, respectively. A plot for the Elecraft K3 posted earlier on this same forum showed these tones down 33 and 36 dBc--about a 6-dB improvement over this particular marine radio. A bit on our test setup: We used a very clean 14.0 V DC power supply with short cables, a high-performance analog 2-tone generator, and a very hefty 50-ohm nonreactive dummy load. We set the top of the spectral plot at 100 W and equalized the amplitude of the tones at -6 dBc, consistent with the usual ARRL method. The tests were done by our senior RF engineer, and I'm sure he was not overdriving the spectrum analyzer :) Chances are that virtually all marine HF SSB radios being made today are using the same 100-W MOSFET PAs that we and other ham manufacturers do. As far as we can tell, there is no magic in the marine radios that is making them better. On the other hand, their marketing department may be better funded. If you have another marine radio in mind that you think is using different/better circuitry, please let me know so we can repeat this exercise if necessary. 73, Wayne N6KR On Oct 29, 2015, at 1:04 PM, jim <[hidden email]> wrote: > Jim, > > The marine divisions of Kenwood, et.al. already have low cost, low voltage, > PA solutions with better IMD specs, primarily due to channel spacing for the > marine band. > > Jim > > W6AIM ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: IMD and supply voltage
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In reply to this post by Jim Bolit
I agree Jim. Many hams do not understand what IMD values mean and how
it affects other signals on the bands. To wit, the "on frequency" signal is not affected, the IMD is not heard on frequency, so it is of little concern to the operator as they are only concerned about getting a big signal report. However, a transmitter and/or amplifier spewing garbage across the entire band affects all of us. We fight noise and QRM most aggressively with receivers. Some of this noise we must deal with is IMD from adjacent stations often some 5 kHz to 20 kHz or more. The ones I simply detest are the operators that say "my station sounds great" not realizing the amount of garbage he's spewing up and down the band for the rest of use to deal with. Signal reports heard being given today are largely "ego reports" and are of little to no value. When was the last time you heard a report indicating ones audio is distorted, or sounds like the transmitter has a bit of FM, or there's buck shot heard 10 kHz away, or there's a noise, humm or a buzz on your signal? Nope, we don't want to offend anyone and thus seemingly just roll out a meaningless, non constructive report. I suppose to many of us have forgotten what we learned; "if you can't say something nice, then don't say anything at all". We talk about the level of electronic noise which is heard today as opposed to what we heard 20 or so years ago. Well, the IMD component is part of that electronic noise. Yes I would agree the technology is available and that company's should or could design radios to attain at least a 10 dB improvement in IMD numbers. Yes, the ARRL does represent a majority of the hams in the US area. I would certainly like to see them petition the FCC for improved specs in this regard. 73 Bob, K4TAX On 10/29/2015 12:37 PM, jim wrote: > How about 80 watts instead. > > Won't make a noticeable difference on the receive end. > > Even better, get rid of all the Yaesu and Icom "Clackers" with their VERY > poor CW performance. You can have the best class A amplifier in the world, > but garbage in will always equal garbage out. > > I am ashamed at our "leaders" at the ARRL for not petitioning the FCC for > better specs. The technology is there, they all use it in their business > radios that have a better spec. > > Oh, I forgot, follow the money and take the advertising monies from these > clackers > > Jim > W6AIM ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Jim Brown-10
I personally found the recent review in QST of the ANAN 100D using
pre-distortion to lower TX distortion products to be the most exciting thing I have read in that rag in a LONG time. I DO hope they are setting a standard that others will strive for. It was so much better than any other rig they have ever tested, that is was literally "off the chart". Not sure I want a rig controlled ONLY with a computer interface, but this might sway my decision to at least try one! Greg in West Mitten, KC8HXO On Thu, Oct 29, 2015 at 2:58 PM, Jim Brown <[hidden email]> wrote: > On Thu,10/29/2015 12:06 PM, frank wrote: >> >> Also, you did not answer my questions. Maybe I should ask them one at a >> time. > > > I thought Wayne answered them quite well, but I'll try to rephrase his > answers in terms that are easier to understand. > > 1) Contemporary ham rigs are designed to operate from automotive DC voltages > as a matter of convenience. > > 2) The output transistors used in these rigs produce less distortion at > higher supply voltages. > > 3) Most rigs are optimized for 13.8 - 14 VDC, and are tested at that level > by ARRL. > > 4) Most commercial power supplies marketed to hams are regulated to 13.8 - > 14.5 VDC, and that voltage is internally adjustable. > > 5) Most rigs will work at lower DC power supply voltages. > > 6) When operated at lower DC power supply voltage, their distortion will > increase. > > 7) When operated above their design output power, distortion will increase. > > 8) Doing both 6 and 7 will increase distortion even more. > > 9) Distortion in the K3 and K3S output stage is specified for full power > output at 13.8 - 14 VDC, and distortion is greatly reduced when run at lower > power levels. > > My own comments: > > Distortion causes the most QRM when running high power. Many of the best > power amps reach full power with drive power in the range of 50-60 W -- the > KPA500 needs about 28W, my Titans (I have three) need between 40-60W, > depending on condition of the tubes and the operating frequency. An ACOM > 1010 needs between 50 and 70 watts, again depending on the operating > frequency. > >> This is state of the art? > > How much do you want to pay for "state of the art?" How about the infamous > pentagon $800 hammer? > > According to ARRL measurements, the K3 produces the cleanest CW signal of > any current rig. See my summary of their published data in the following > link > > k9yc.com/TXNoise.pdf > > See my measurements of my K3 and several other rigs in this link > > http://k9yc.com/P3_Spectrum_Measurements.pdf > > 73, Jim K9YC > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by wayne burdick
Interesting results about the Icom M-802. It is actually marketed as a "150
Watt" rig, so testing it at 100 Watts would be giving it even more "benefit of the doubt". It is also interesting to note that Icom has disabled speech compression in the M-802 by default. Apparently, when compression is enabled the transmitter doesn't meet FCC requirements for use on the marine bands. I suspect that what this means is that the M-802 is normally driven far below 150 Watts PEP or even 100 Watts PEP when used without voice compression. 73 Chip AE5KA On Thu, Oct 29, 2015 at 3:39 PM, Wayne Burdick <[hidden email]> wrote: > Jim, > > This appears to *not* be true, at least for one radio lauded by those > concerned about TX IMD. > > Earlier this year there was a long forum thread on Eham.net lamenting the > "fact" that 12-V ham rigs were not as clean as 12-V marine rigs. One radio > in particular, the Icom M802, was touted by forum participants as having > far better IMD specs than any 12-V ham transceiver. > > We downloaded the manual for we this radio and found that Icom was using > the same devices and essentially the same amplifier circuit that we were. > Still, we gave them the benefit of the doubt and purchased a new Icom M802 > (from Amazon, $1813) to test in our own lab. > > We very carefully measured transmit IMD at 100 watts on several channels, > covering the full range of the HF marine band. Here is an example plot from > about 12.28 MHz: > > http://www.elecraft.com/Icom%20M802%20100-W%20IMD.jpeg > > This plot shows the two 3rd-order products being down by about 27 and 30 > dBc, respectively. A plot for the Elecraft K3 posted earlier on this same > forum showed these tones down 33 and 36 dBc--about a 6-dB improvement over > this particular marine radio. > > A bit on our test setup: We used a very clean 14.0 V DC power supply with > short cables, a high-performance analog 2-tone generator, and a very hefty > 50-ohm nonreactive dummy load. We set the top of the spectral plot at 100 W > and equalized the amplitude of the tones at -6 dBc, consistent with the > usual ARRL method. The tests were done by our senior RF engineer, and I'm > sure he was not overdriving the spectrum analyzer :) > > Chances are that virtually all marine HF SSB radios being made today are > using the same 100-W MOSFET PAs that we and other ham manufacturers do. As > far as we can tell, there is no magic in the marine radios that is making > them better. On the other hand, their marketing department may be better > funded. > > If you have another marine radio in mind that you think is using > different/better circuitry, please let me know so we can repeat this > exercise if necessary. > > 73, > Wayne > N6KR > > > > On Oct 29, 2015, at 1:04 PM, jim <[hidden email]> wrote: > > > Jim, > > > > The marine divisions of Kenwood, et.al. already have low cost, low > voltage, > > PA solutions with better IMD specs, primarily due to channel spacing for > the > > marine band. > > > > Jim > > > > W6AIM > > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by frank-2
Bob, et. Al:
> >Signal reports heard being given today are largely "ego reports" and are >of little to no value. When was the last time you heard a report >indicating ones audio is distorted, or sounds like the transmitter has a >bit of FM, or there's buck shot heard 10 kHz away, or there's a noise, >humm or a buzz on your signal? Nope, we don't want to offend anyone >and thus seemingly just roll out a meaningless, non constructive >report. I suppose to many of us have forgotten what we learned; "if you >can't say something nice, then don't say anything at all". > Well, you obviously have not worked me :) Audio transmission quality is a subject close to my heart. While I understand all the technical issues regarding Intermodulation Distortion in 12v vs 48 volt and Tube vs Solid State amps, the proof is in the pudding: Just listen on the air! You will find folks running Class A rigs that sound horrible due to overprocessing and the belief that turning all the transmit audio knobs all the way to ELEVEN and seeing dancing meters make for great signals. Processor missadjustment is a worse culprit than IMD and, although IMD products do harm, processor knobs turned all the way to the right are the main culprit in the mess that has become our SSB subbands. There are some operators I can't understand at all. Worse, some of the "Audio VooDoo" ESSB types have so much bass that they create a phantom carrier, making their signal copyable in AM mode. On many of these, I even able to lock my WinRadio SDR to the pseudo carrier in Synchronous AM mode! In the last CQ WW SSB, I started to think that my signal was too clean and too bandwidth efficient versus my "competitors". That lovely, raspy, sharp, dense MP1000 sound (not to blame a particular radio, but I know how to make that one sound that way), while certainly "penetrating", is difficult to listen to, and, when overdone, makes it hard to understand. That means lost QSO's. Want to increase your score? Consider making better audio! Overdone processing by and large creates listener fatigue and intelligibility problems. A 10 second contest QSO, while not creating fatigue on its own, when joined by 300 of them, will. Wonder why you are tired after a short stint on 40m in WorldWide Friday night? This might be the answer! Transmitter IMD in this scenario is still there, however, exacerbating the problem. And some contesters will use their IMD "wideness" as a weapon of advantage in the competition. There is nothing we can do in our receivers to counteract this. We are at their mercy. Where is the Wouff Hong and the Rettysnich? We need you now more than ever! If we are going to campaign against anything, I would say campaign against over-processing. Once we get them to understand that issue, then we can concentrate on IMD. With some of the signals I hear on the air today, IMD is the least of our worry in a world where everybody is Fine Nine oh Five. Audio quality is a very personal thing, like your car choice, radio choice or your hair coloring chemical choices... I wish everyone had the common sense to make articulate, clear, yet punchy and "communications quality" audio by avoiding the temptation to eke out that last watt. When we all do that, then we can worry about Amplifier IMD. Processing issues heard on the air today simply make the discussion of final amplifier spectral purity moot. Respectfully Lu - W4LT K-Line ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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Walt,
Spot on. It is frustrating to operate in a contest as much as I enjoy the challenge, the vast majority of strong signals are many times, disturbing to listen to. I make a point of complimenting good audio even in the heat of battle. Gary -----Original Message----- From: "Luis V. Romero" <[hidden email]> Sent: 30/10/2015 7:54 AM To: "[hidden email]" <[hidden email]> Subject: Re: [Elecraft] IMD and supply voltage Bob, et. Al: > >Signal reports heard being given today are largely "ego reports" and are >of little to no value. When was the last time you heard a report >indicating ones audio is distorted, or sounds like the transmitter has a >bit of FM, or there's buck shot heard 10 kHz away, or there's a noise, >humm or a buzz on your signal? Nope, we don't want to offend anyone >and thus seemingly just roll out a meaningless, non constructive >report. I suppose to many of us have forgotten what we learned; "if you >can't say something nice, then don't say anything at all". > Well, you obviously have not worked me :) Audio transmission quality is a subject close to my heart. While I understand all the technical issues regarding Intermodulation Distortion in 12v vs 48 volt and Tube vs Solid State amps, the proof is in the pudding: Just listen on the air! You will find folks running Class A rigs that sound horrible due to overprocessing and the belief that turning all the transmit audio knobs all the way to ELEVEN and seeing dancing meters make for great signals. Processor missadjustment is a worse culprit than IMD and, although IMD products do harm, processor knobs turned all the way to the right are the main culprit in the mess that has become our SSB subbands. There are some operators I can't understand at all. Worse, some of the "Audio VooDoo" ESSB types have so much bass that they create a phantom carrier, making their signal copyable in AM mode. On many of these, I even able to lock my WinRadio SDR to the pseudo carrier in Synchronous AM mode! In the last CQ WW SSB, I started to think that my signal was too clean and too bandwidth efficient versus my "competitors". That lovely, raspy, sharp, dense MP1000 sound (not to blame a particular radio, but I know how to make that one sound that way), while certainly "penetrating", is difficult to listen to, and, when overdone, makes it hard to understand. That means lost QSO's. Want to increase your score? Consider making better audio! Overdone processing by and large creates listener fatigue and intelligibility problems. A 10 second contest QSO, while not creating fatigue on its own, when joined by 300 of them, will. Wonder why you are tired after a short stint on 40m in WorldWide Friday night? This might be the answer! Transmitter IMD in this scenario is still there, however, exacerbating the problem. And some contesters will use their IMD "wideness" as a weapon of advantage in the competition. There is nothing we can do in our receivers to counteract this. We are at their mercy. Where is the Wouff Hong and the Rettysnich? We need you now more than ever! If we are going to campaign against anything, I would say campaign against over-processing. Once we get them to understand that issue, then we can concentrate on IMD. With some of the signals I hear on the air today, IMD is the least of our worry in a world where everybody is Fine Nine oh Five. Audio quality is a very personal thing, like your car choice, radio choice or your hair coloring chemical choices... I wish everyone had the common sense to make articulate, clear, yet punchy and "communications quality" audio by avoiding the temptation to eke out that last watt. When we all do that, then we can worry about Amplifier IMD. Processing issues heard on the air today simply make the discussion of final amplifier spectral purity moot. Respectfully Lu - W4LT K-Line ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by ae5ka
Yes, we made sure compression was off. We gave the unit every opportunity to exhibit magic properties. Alas, it did not.
Wayne N6KR On Oct 29, 2015, at 2:10 PM, Chip Stratton <[hidden email]> wrote: > Interesting results about the Icom M-802. It is actually marketed as a "150 Watt" rig, so testing it at 100 Watts would be giving it even more "benefit of the doubt". > > It is also interesting to note that Icom has disabled speech compression in the M-802 by default. Apparently, when compression is enabled the transmitter doesn't meet FCC requirements for use on the marine bands. I suspect that what this means is that the M-802 is normally driven far below 150 Watts PEP or even 100 Watts PEP when used without voice compression. > > 73 > Chip > AE5KA ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Gregory Schippers
Greg,
Even a rig with predistortion capability will run out of steam and exhibit greater IMD when running from low supply voltages. Predistortion attempts to compensate for the compression by increasing drive, but there must be enough headroom to allow the algorithm to work. Note that the rear panel of the ANAN 100D specifies "13.8V DC". I doubt that the ARRL did any testing at lower voltages. There are other situations where inadequate headroom might come into play, too, such as when driving a somewhat reactive load that causes the transmitter to hit a current limit. While this particular radio emphasizes predistortion, there's more than that involved in keeping the bands clean. Figure 3 of the QST review for the rig (page 47) shows transmit phase noise that is about 15 dB higher than a K3+KSYN3A or a K3S at a 100-kHz offset. This 15 dB of additional wideband noise would in many situations (such as FD or multi-transmitter stations) cancel out the value obtained with predistortion. 73, Wayne N6KR On Oct 29, 2015, at 2:07 PM, Gregory Schippers <[hidden email]> wrote: > I personally found the recent review in QST of the ANAN 100D using > pre-distortion to lower TX distortion products to be the most exciting > thing I have read in that rag in a LONG time. I DO hope they are > setting a standard that others will strive for. It was so much better > than any other rig they have ever tested, that is was literally "off > the chart". Not sure I want a rig controlled ONLY with a computer > interface, but this might sway my decision to at least try one! > > Greg in West Mitten, KC8HXO > > On Thu, Oct 29, 2015 at 2:58 PM, Jim Brown <[hidden email]> wrote: >> On Thu,10/29/2015 12:06 PM, frank wrote: >>> >>> Also, you did not answer my questions. Maybe I should ask them one at a >>> time. >> >> >> I thought Wayne answered them quite well, but I'll try to rephrase his >> answers in terms that are easier to understand. >> >> 1) Contemporary ham rigs are designed to operate from automotive DC voltages >> as a matter of convenience. >> >> 2) The output transistors used in these rigs produce less distortion at >> higher supply voltages. >> >> 3) Most rigs are optimized for 13.8 - 14 VDC, and are tested at that level >> by ARRL. >> >> 4) Most commercial power supplies marketed to hams are regulated to 13.8 - >> 14.5 VDC, and that voltage is internally adjustable. >> >> 5) Most rigs will work at lower DC power supply voltages. >> >> 6) When operated at lower DC power supply voltage, their distortion will >> increase. >> >> 7) When operated above their design output power, distortion will increase. >> >> 8) Doing both 6 and 7 will increase distortion even more. >> >> 9) Distortion in the K3 and K3S output stage is specified for full power >> output at 13.8 - 14 VDC, and distortion is greatly reduced when run at lower >> power levels. >> >> My own comments: >> >> Distortion causes the most QRM when running high power. Many of the best >> power amps reach full power with drive power in the range of 50-60 W -- the >> KPA500 needs about 28W, my Titans (I have three) need between 40-60W, >> depending on condition of the tubes and the operating frequency. An ACOM >> 1010 needs between 50 and 70 watts, again depending on the operating >> frequency. >> >>> This is state of the art? >> >> How much do you want to pay for "state of the art?" How about the infamous >> pentagon $800 hammer? >> >> According to ARRL measurements, the K3 produces the cleanest CW signal of >> any current rig. See my summary of their published data in the following >> link >> >> k9yc.com/TXNoise.pdf >> >> See my measurements of my K3 and several other rigs in this link >> >> http://k9yc.com/P3_Spectrum_Measurements.pdf >> >> 73, Jim K9YC >> >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:[hidden email] >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> Message delivered to [hidden email] > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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