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 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!
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.Probably unlikely to cause interference to anyone at that power level unless they are pretty close and most CBer's wouldn't care anyway.
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.
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 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.
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. 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
View attachment 22779
AMP ON
View attachment 22780
Where I did the math.
https://www.pasternack.com/t-calculator-ratio-conv.aspx
True but he did not start out that low.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.
All very valid.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."