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RM Italy Amp harmonics to 11th Harmonic at 2 watts input!
- Thread starter Onelasttime
- Start date
Cool. But he should have hooked up the low pass filter - as he suggested to do - and show the difference on the spectrum analyzer to make his point better.
Seems that amp users are afraid that their watt meters won't swing as much with that filter in place. And they would be both right and wrong. The wattmeter will sum all of the watts out of the amp - especially and including the bad watts of the harmonics making a greater reading. But the wattmeter doesn't let one know that this extra watts aren't even on the channel they are talking on. They would be better off by using low pass filters just to have an honest evaluation of what their radio is really doing w/o the the crap
Even worse to toss into the mix, is to use a radio with an amp that wasn't aligned properly with some crappy swing mod - and the amp spews out even more harmonic watts - since the radio is now generating even more crap harmonics. This leads to the amp overheating and failing prematurely. It also skews their SWR reading. But those in the know are well aware of all those facts. The trouble is getting thru bullet proof heads that insist they know what they are doing - that is so hard to do.
Seems that amp users are afraid that their watt meters won't swing as much with that filter in place. And they would be both right and wrong. The wattmeter will sum all of the watts out of the amp - especially and including the bad watts of the harmonics making a greater reading. But the wattmeter doesn't let one know that this extra watts aren't even on the channel they are talking on. They would be better off by using low pass filters just to have an honest evaluation of what their radio is really doing w/o the the crap
Even worse to toss into the mix, is to use a radio with an amp that wasn't aligned properly with some crappy swing mod - and the amp spews out even more harmonic watts - since the radio is now generating even more crap harmonics. This leads to the amp overheating and failing prematurely. It also skews their SWR reading. But those in the know are well aware of all those facts. The trouble is getting thru bullet proof heads that insist they know what they are doing - that is so hard to do.
Try it with the covers installed on the radio! It does make a difference. Were any of the coils spread in the finals area? Station grounds are important on the test bench too, all test equipment, power supplies, amps, and radios need them.
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I doubt cover's on or off would matter since it was clean covers off into the scope and spectrum analyzer. That is an unmodified modern radio. Even with the carrier turned down to 1 1/4 watt it had harmonics out to the 10th harmonic. Those harmonics where not 40db down or 60 db down they where insanely high! How lower does he need to go 1/4 of watt to get the harmonics to acceptable levels! LOL I have never used anything made by RM Italy. That said I have used a RF Limited amp before which is prob. not much better! I was 18 though so I am giving myself a pass! LOL
I have always told people to filter the radio output due to wide band hifi supressed carrier nonsense. I had no idea a clean stock radio even with carrier turned down to 1 1/4 watt with 1000cps test tone would have that level of harmonics!
I have always told people to filter the radio output due to wide band hifi supressed carrier nonsense. I had no idea a clean stock radio even with carrier turned down to 1 1/4 watt with 1000cps test tone would have that level of harmonics!
A low pass filter is always a good idea. One should be on the back of every broad band transistor amplifier.
I had a Stryker 955 that worked fine with the bottom cover off but had an oscillation issue with the covers installed. With the amplifier sitting right next to the radio it might be a good idea to put the cover on.
This video is more you tube smear campaign from someone that doesn't know how to use his analyzer or is trying to mislead his customers with it. The analyzer isn't adjusted properly. When barefoot the fundamental freq is already 20 db down. Of course you don't see any harmonics.
With the amp on the fundamental freq is around 10 db down. Why can't he just adjust the damn thing and put the cover on the radio? RF from the amplifier getting back into the radio could certainly be making this look worse than it really is.Look at how many db down some of the harmonics are on the analyzer. We have to estimate because the analyzer isn't adjusted so that the fundamental freq is at 0 db. The second harmonic is -30db 3rd is -20db It's hard to give exact numbers because the analyzer isn't set properly but the rest of the harmonics are roughly below -43 which is the fcc limit for HF. Why make such a big deal out of them?
If the 2nd and 3rd harmonic measurements are true we need to do something about that. Since he didn't give us a proper measurement of the barefoot radio, left the cover off and set an amplifier next to it this is all BS. We can tell that the amplifier has about 10db gain at 2 watts input so his 2 watts are amplified to 20 watts. 30 db down from 20 watts is .02 watts.....Oh my god the sky is falling! How much damage are you going to do with .02 watts into an antenna system that isn't tuned for it?
BAREFOOT
AMP ON
Where I did the math.
https://www.pasternack.com/t-calculator-ratio-conv.aspx
Continuing to lower the power does not guarantee an improvement. When you operate equipment below the power output it was designed for you can make matters worse. There's a reason for the low power spec in service manuals.
The radio was not all that clean. I saw the 11th harmonic peak with the 203 off. Mind you I am not disagreeing with you about the low pass filters, I always have advised people to run two filters, one right behind the radio before the amp and one after the amp.
I always say "Garbage in = Louder Garbage out"
The covers are an EMI shield and with feedback radiated from the coax, power supply, and from the KL-203 itself. All of the KL-203's I have seen have a plastic cover on the bottom of the amp.
I do wonder about the presence of the 11th harmonic that I saw with the amp off at low power level. Leave the 203 off and turn the power up on the radio and check it again. Some of those harmonics could be "Birds" from the power supply.
I also not disagreeing about the 203 being a splatter box. It is a linear amplifier and that gets you "Garbage in = Louder Garbage out."
I always say "Garbage in = Louder Garbage out"
The covers are an EMI shield and with feedback radiated from the coax, power supply, and from the KL-203 itself. All of the KL-203's I have seen have a plastic cover on the bottom of the amp.
I do wonder about the presence of the 11th harmonic that I saw with the amp off at low power level. Leave the 203 off and turn the power up on the radio and check it again. Some of those harmonics could be "Birds" from the power supply.
I also not disagreeing about the 203 being a splatter box. It is a linear amplifier and that gets you "Garbage in = Louder Garbage out."
I think he might have been overdriving the amplifer from the very start of the video. The RF power on the McKinley wasn't down all the way. Even when he was trying to set it to minimum it was flashing and you still have to save the level before unkeying, perhaps that's why the levels didn't change at all.
I don't doubt that the amp is putting out harmonics but it would be interesting to see if the harmonics vary with the input and how they change with the level of input.
Would have been nice to see a test done with a ham radio with 1/4 watt or 1/2 output to show the harmonics at that level of input. Those amps don't do we'll with high drive, I've never run one with more than 1 watt input. If it produces those harmonics regardless of input then definitely it could use some filtering.
Probably unlikely to cause interference to anyone at that power level unless they are pretty close and most CBer's wouldn't care anyway.
I don't doubt that the amp is putting out harmonics but it would be interesting to see if the harmonics vary with the input and how they change with the level of input.
Would have been nice to see a test done with a ham radio with 1/4 watt or 1/2 output to show the harmonics at that level of input. Those amps don't do we'll with high drive, I've never run one with more than 1 watt input. If it produces those harmonics regardless of input then definitely it could use some filtering.
Probably unlikely to cause interference to anyone at that power level unless they are pretty close and most CBer's wouldn't care anyway.
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Well that is a problem. The harmonics end up in the six meter band. If you piss a ham operator off because you just crapped all over a record setting QSO with your harmonics they might not be sympathetic to any trouble you brought to yourself. The six meter band is often referred to as the magic band, 100 watts is considered a big signal.
My first six meter contact I ever made was with only 20 watts and they heard me quite well down in Georgia.
I hear ya, the interference would definitely upset a 6 meter operator, however, as you mentioned it's the magic band and you know why
Which is why a CB operator with a little amp and a ham operator on 6 meters don't tangle that often. Not saying it doesn't happen, just not a major daily concern.
True enough, but what if the shoe was on the other foot? What if ham operators invaded the CB band with High Wattage amplifiers calling CQ on CH19, 28,37,38 and the free band area? Those signals would be SSB and loaded with power.I hear ya, the interference would definitely upset a 6 meter operator, however, as you mentioned it's the magic band and you know why
I don't know that I can put any of this to rest but I will at least inject some perspective. First I want it known that I like Mikes videos and if you don't agree with the results that is fine as well, I like Mike. I think Mike may have gotten his description of what is happening out of context a bit when he elated to the idea that mabe the amp was at fault for generating these at least it sounded that way in his video, But the end result is still the same it should have been described as trash in and trash amplified out! Anyway the image below I think puts it in perspective.
Image shows "radio harmonics" fall nearly perfect in line with "amplified harmonics." and it simply means what you see here.
1 bottom line on spectrum scope is simple ground noise
The 2-second line up from the bottom is radio harmonics
3 third line at the top is radio harmonics amplified by the linear.
I don't agree with the idea that the amp is generating all these harmonics and It may be that Mike just misspoke to put it in political noise and he may rethink that at some point. I can tell you that after bench testing literally thousands of radios and amps the image above is not the exception but was often the RULE.
Image shows "radio harmonics" fall nearly perfect in line with "amplified harmonics." and it simply means what you see here.
1 bottom line on spectrum scope is simple ground noise
The 2-second line up from the bottom is radio harmonics
3 third line at the top is radio harmonics amplified by the linear.
I don't agree with the idea that the amp is generating all these harmonics and It may be that Mike just misspoke to put it in political noise and he may rethink that at some point. I can tell you that after bench testing literally thousands of radios and amps the image above is not the exception but was often the RULE.
You made some really good points.A low pass filter is always a good idea. One should be on the back of every broad band transistor amplifier.
I had a Stryker 955 that worked fine with the bottom cover off but had an oscillation issue with the covers installed. With the amplifier sitting right next to the radio it might be a good idea to put the cover on.
This video is more you tube smear campaign from someone that doesn't know how to use his analyzer or is trying to mislead his customers with it. The analyzer isn't adjusted properly. When barefoot the fundamental freq is already 20 db down. Of course you don't see any harmonics.
Look at how many db down some of the harmonics are on the analyzer. We have to estimate because the analyzer isn't adjusted so that the fundamental freq is at 0 db. The second harmonic is -30db 3rd is -20db It's hard to give exact numbers because the analyzer isn't set properly but the rest of the harmonics are roughly below -43 which is the fcc limit for HF. Why make such a big deal out of them?
If the 2nd and 3rd harmonic measurements are true we need to do something about that. Since he didn't give us a proper measurement of the barefoot radio, left the cover off and set an amplifier next to it this is all BS. We can tell that the amplifier has about 10db gain at 2 watts input so his 2 watts are amplified to 20 watts. 30 db down from 20 watts is .02 watts.....Oh my god the sky is falling! How much damage are you going to do with .02 watts into an antenna system that isn't tuned for it?
BAREFOOT
View attachment 22779
AMP ON
View attachment 22780
Where I did the math.
https://www.pasternack.com/t-calculator-ratio-conv.aspx