Finally a radio technician that actually knows what he is doing!!!!!!

[rabbiporkchop]

Like the title says....
https://www.youtube.com/watch?v=XJDtYDqYsIA

https://www.facebook.com/finetune.cb

 

[unseenone]

My hands are never leaving your sight. Next frame, hands out of sight... LOL.. Aren't amps illegal on CB's?

He may know what he is doing, but it wasn't particularly informative. It was also a pain to go through the whole youtube video, with no contact info, and finally the facebook page to finally find his URL to see what the heck he does.... and then the page has no useful information, including contact information of any way. So how did you determine that? With the three video's on the u tube channel, or actual experience?

 

[Tennmogger]

What was he striving to show? What was his test setup? Is he trying to sell his magic cables? What was 'magic' was how the modulation level changed so the Bird showed higher power. Bah humbug.

 

[4x4junkie]

Yeah I don't buy that nothing else was changed or that the other cables were purposely defective or something. He also seems to have a pompous holier than thou attitude.

If everything is grounded well, all shields properly terminated, cable is of good quality, etc., length of the cable is infact irrelevant.
I've done exactly what he does on equipment of my own, never seen a change occur outside of whatever difference in cable loss there was for various length jumpers (same for cables going out to the antenna as well).

What the waveform on his scope does clearly demonstrate is that his amp is very non-linear (probably uses a class-C circuit like a lot of poorly-built CB amps do). It's actually comical the way those amps sound when people try to use them on SSB lol.

 

[AlbanyTom]

4x4 is, of course, correct. As long as the antenna system is good, adding or removing good feed line only changes loss a little.

More importantly, the reverse is true - if changing lengths of good feed line changes SWR at the radio, then it mean, absolutely, that something is wrong with your antenna. So if you put in some length of coax, and things change, the thought should be "hey, time to fix the broken antenna!" not "I wonder how I can make a jumper that's just the right length to make it look like my antenna actually works right". The reason is simple physics...if the antenna isn't tuned or installed correctly, the impedance won't match the coax. Impedance mismatches cause reflections. The electrical length of the mismatch from the transmitter determines what the reflection looks like to the transmitter...but it doesn't make it go away.

 

[rabbiporkchop]

My hands are never leaving your sight. Next frame, hands out of sight... LOL.. Aren't amps illegal on CB's?
Yes they are illegal.

He may know what he is doing, but it wasn't particularly informative. It was also a pain to go through the whole youtube video, with no contact info, and finally the facebook page to finally find his URL to see what the heck he does.... and then the page has no useful information, including contact information of any way. So how did you determine that? With the three video's on the u tube channel, or actual experience?

He wasn't trying to inform technicians on how to duplicate his work. He was trying to educate consumers on how to spot a scam artist posing as a radio technician. If they don't understand class C amplification and how to make it work properly, they need to find a new line of work.

What was he striving to show? What was his test setup? Is he trying to sell his magic cables? What was 'magic' was how the modulation level changed so the Bird showed higher power. Bah humbug.

If you didn't recognize the first waveform then you can't say humbug about things that went over your head. First waveform @ phase angle of 180° @ 27.205mhz which is what was used in the tuning process. Second waveform @ phase angle of 90° @ 27.205mhz created spurious emissions and screwed up waveform along with higher watts and lots of harmonics. Third waveform @ approximate phase angle of 45° @ 27.205mhz created spurious emissions and screwed up waveform along with higher watts and lots of harmonics. 4th waveform @ phase angle of 180° @ 27.205mhz shows a perfectly modulated carrier. Imagine if I sold the radio and amp to your next door neighbor without telling him the importance of the jumper cable length. It would work great for me, but he would be scratching his head wondering why it doesn't work for him, and he would be wondering why I don't bleed over onto your tv set but using the same equipment minus the correct length jumper, he is bleeding all over your tv set. The first cable is the only cable that should be used in the installation otherwise Harmonics will be the result. Understanding how the speed of light relates to frequency, you could always do the math and use a cable of any kind as long as the phase angle is 180° @ 27.205mhz.

Yeah I don't buy that nothing else was changed or that the other cables were purposely defective or something. He also seems to have a pompous holier than thou attitude.

If everything is grounded well, all shields properly terminated, cable is of good quality, etc., length of the cable is infact irrelevant.
I've done exactly what he does on equipment of my own, never seen a change occur outside of whatever difference in cable loss there was for various length jumpers (same for cables going out to the antenna as well).

What the waveform on his scope does clearly demonstrate is that his amp is very non-linear (probably uses a class-C circuit like a lot of poorly-built CB amps do). It's actually comical the way those amps sound when people try to use them on SSB lol.

You are assuming a purely resistive load which doesn't exist in the real world. Since current and voltage are 90° out of phase, and due to the reactance of the load, the feedpoint impedance will only be repeated every 180°.

4x4 is, of course, correct. As long as the antenna system is good, adding or removing good feed line only changes loss a little.

More importantly, the reverse is true - if changing lengths of good feed line changes SWR at the radio, then it mean, absolutely, that something is wrong with your antenna. So if you put in some length of coax, and things change, the thought should be "hey, time to fix the broken antenna!" not "I wonder how I can make a jumper that's just the right length to make it look like my antenna actually works right". The reason is simple physics...if the antenna isn't tuned or installed correctly, the impedance won't match the coax. Impedance mismatches cause reflections. The electrical length of the mismatch from the transmitter determines what the reflection looks like to the transmitter...but it doesn't make it go away.

IT is a class C amplifier for AM only and if installed in the customers vehicle using the correct length cable will perform exactly the same as the first and last waveform, but following a "hams advice" by choosing a random length cable would yield awful results, overmodulated and distorted audio, as well as causing harmful interference to others across a huge spectrum. He is "holier than thou" because no other technician in the country can achieve results like his, and he makes a living cleaning up the airwaves by retuning other techs work with Class C amps. While illegal, his work is the best in the country for taking cheap cb stuff and making it sound like commercial broadcast stations without causing interference to others. Due to inductance and reactance impedance changes with cable length which alters the output of the radio which completely screws up the output of the amp. The jumper cable is part of the "tune" , and by changing the cable length the tune has been destroyed.

 

[4x4junkie]

Are you the person in the video trying to toot your own horn here while pretending to not be him? You sure seem to know a lot about many details that are not mentioned in the video....
I think this post is what has "Scam" written on it.

You clearly don't know what class-C amplification is or how it works if you think you can reduce what you are incorrectly calling "harmonics" and "spurious emissions" to acceptable levels when using a class-C amp on AM (especially if you think it's best done by changing the length of a piece of coax).

 

[rabbiporkchop]

Are you the person in the video trying to toot your own horn here while pretending to not be him? You sure seem to know a lot about many details that are not mentioned in the video....
I think this post is what has "Scam" written on it.

You clearly don't know what class-C amplification is or how it works if you think you can reduce what you are incorrectly calling "harmonics" and "spurious emissions" to acceptable levels when using a class-C amp on AM (especially if you think it's best done by changing the length of a piece of coax).

I am simply one of his happy customers in search of the worlds greatest technician. If you think class c is synonymous with spurious emissions then you clearly don't have a clue about the physics involved. The difference between class ab and class c is simply a biasing issue. Just because 999/1000 operators that use class c amps are generating a dirty signal with their equipment doesn't mean it isn't possible to generate a clean one. This simply demonstrates a lack of knowledge on the subject, and a lack of technicians able to do so. Every station that leaves my technicians bench is spectrally pure regardless of biasing scheme. Most commercial broadcast stations use some form of class c amplification at levels of up to 125% positive modulation with the negative peaks at no greater than 100% with no spurious emissions. His customers dominate the 11 meter world from coast to coast without any spurious emissions. His scope and spectrum analyzer tell everything you need to know. No harmonics and crystal clean audio are his specialty. If anybody claims to be a better technician than this guy I would be the first in line to test his work. 4 watt radios that leave his bench outperform many 1000 watt radios in the real world. Watts mean absolutely nothing unless they are on the fundamental frequency without spurious emissions, and that is why it is called Fine Tune CB Shop.
This wasn't meant to be a dicussion with closed minded hams who have already allowed their opinions to cripple their minds ability to understand things which RF engineers take for granted on a daily basis, it was simply a post to alert others interested in running a cb radio that there is at least one radio technician in the country that outshines all the others in the work he does. For thousands of years, mainstream science thought the earth was flat, and people who stated the obvious as they saw ships sink below the horizon were persecuted for going against the mainstream who thought the earth was flat. RF engineers don't seem to enjoy correcting those less informed for some reason, although that doesn't make their work any less relevant in todays world.
Non Linear is not synonymous with spurious emissions or harmonics under ideal laboratory conditions. I will concede all of those conditions must be met for this biasing scheme to function within acceptable parameters, and when it stays within these parameters it is a very efficient mode of amplification for AM and FM only.

 

[Finlay]

I
This wasn't meant to be a dicussion with closed minded hams who have already allowed their opinions to cripple their minds ability to understand things which RF engineers take for granted on a daily basis,

I don't consider myself a closed minded HAM, and I'm totally open to admitting I am wrong - I am happily married and all that.

But, this YouTube Technician says he designs his cables based off of a calculation that "isn't really online" - which seems odd, but whatever.

However, I did keep all of my textbooks from 4(!) semesters of Fields and Waves (PDF. Calculus) while I was doing my Electrical Engineering degree (Go Badgers!) and I can't find anywhere in there that says transmission cable length matters at all. I mean, there are lots of variables - skin conductance, axial distance, dielectric constant, and so on and on and on, but for exactly zero equations are there considerations for wire length. Similarly, I have 2 different versions of the ARRL Antenna Book (a very handy resource if you're into radio stuff!) and there is zero consideration given to feedline length there, as well.

I mean, yeah, the wire matters - shorter is better (i.e. don't coil it). Get a good dielectric. That sort of thing. But length ? Never a factor.

But, whatever. Math can be wrong. Newton's motion equations are good enough to put a man on the moon, but Einstein demonstrated that they are fundamentally broken. And my first two semesters of Physics were all based on Newton, so you know Universities are happy to teach things of limited usefulness. Empirically, I know that I don't have the change the feedline on my radio when I switch bands I am operating on - it performs well across the spectrum on the same wire. Which seems contrary to what you are saying - you are saying I need a different length feedline at 6m than I do at 80m or at .7m. That is completely contrary to my education and experience.

Anyway, all of that is to say, show me the math. Show me actual math that demonstrates why you are right, and the dozens of extremely smart and very accomplished people* who taught me are wrong.

I promise, I will buy you lunch with the money from my Nobel Prize.


*one of whom worked on the team that designed the antenna and feed array for the voyager 2 space probe. It talks to us, intelligibly, from billions of miles away on ~20watts of power. Neat guy. And an actual RF engineer.

 

[rabbiporkchop]

I don't consider myself a closed minded HAM, and I'm totally open to admitting I am wrong - I am happily married and all that.

But, this YouTube Technician says he designs his cables based off of a calculation that "isn't really online" - which seems odd, but whatever.

However, I did keep all of my textbooks from 4(!) semesters of Fields and Waves (PDF. Calculus) while I was doing my Electrical Engineering degree (Go Badgers!) and I can't find anywhere in there that says transmission cable length matters at all. I mean, there are lots of variables - skin conductance, axial distance, dielectric constant, and so on and on and on, but for exactly zero equations are there considerations for wire length. Similarly, I have 2 different versions of the ARRL Antenna Book (a very handy resource if you're into radio stuff!) and there is zero consideration given to feedline length there, as well.

I mean, yeah, the wire matters - shorter is better (i.e. don't coil it). Get a good dielectric. That sort of thing. But length ? Never a factor.

But, whatever. Math can be wrong. Newton's motion equations are good enough to put a man on the moon, but Einstein demonstrated that they are fundamentally broken. And my first two semesters of Physics were all based on Newton, so you know Universities are happy to teach things of limited usefulness. Empirically, I know that I don't have the change the feedline on my radio when I switch bands I am operating on - it performs well across the spectrum on the same wire. Which seems contrary to what you are saying - you are saying I need a different length feedline at 6m than I do at 80m or at .7m. That is completely contrary to my education and experience.

Anyway, all of that is to say, show me the math. Show me actual math that demonstrates why you are right, and the dozens of extremely smart and very accomplished people* who taught me are wrong.

I promise, I will buy you lunch with the money from my Nobel Prize.


*one of whom worked on the team that designed the antenna and feed array for the voyager 2 space probe. It talks to us, intelligibly, from billions of miles away on ~20watts of power. Neat guy. And an actual RF engineer.

I'm assuming you have one of these, and I'm assuming you understand the basics of using it like I do.

I'm assuming at one time or another you have found a use for a 1/4 wave impedance transformer aka a 90 degree cable.
assuming you have witnessed the obvious, can you honestly say impedance remains constant at any random frequency through an entire cable with a straight face? keep in mind, imedance changes with frequency. We are not talking about dc ohms, this is rf. By the way, feedline was never mentioned. Phase angle between components was the only thing mentioned. feedline is a completely different topic.

 

[Finlay]

can you honestly say impedance remains constant through an entire cable with a straight face?

So, no math then. I thought as much.

It is a property of transmission lines in general that if it is terminated at both ends by its characteristic impedance, then the current and voltage measured anywhere along it will be the same. As long as this is remains true it doesn't matter what the actual length of the line is; its properties won't vary. This applies to jumpers, etc.

Yes, yes, this is not true across the entire spectrum, different cables have different impedances at different frequencies, and it is important to choose cable that has the desired impedance at the desired frequencies. Insert the usual engineering "It Depends" blah blah stuff here. Point is, as long as all of the impedances match, the line/jumper length does not matter.

If the impedances do not match, then... well, you get what you see here. He's got cables that don't have the same impedance as his radio and his amp for whatever reason, so he gets some reflectance and harmonics as a result.

It's great that he is smart enough to discover the problem. It's bad that he is not smart enough to correctly diagnose it.

 

[rabbiporkchop]

So, no math then. I thought as much.

It is a property of transmission lines in general that if it is terminated at both ends by its characteristic impedance, then the current and voltage measured anywhere along it will be the same. As long as this is remains true it doesn't matter what the actual length of the line is; its properties won't vary. This applies to jumpers, etc.

Yes, yes, this is not true across the entire spectrum, different cables have different impedances at different frequencies, and it is important to choose cable that has the desired impedance at the desired frequencies. Insert the usual engineering "It Depends" blah blah stuff here. Point is, as long as all of the impedances match, the line/jumper length does not matter.

If the impedances do not match, then... well, you get what you see here. He's got cables that don't have the same impedance as his radio and his amp for whatever reason, so he gets some reflectance and harmonics as a result.

It's great that he is smart enough to discover the problem. It's bad that he is not smart enough to correctly diagnose it.

speed of light divided by frequency = wavelength in meters multiplied by the velocity of propagation equals electrical wavelength as your ARRL handbook should tell you as mine does. Divided by two equals 180 degrees which serves as an impedance repeater at one frequency only. He has no problems. He fixes problems. He is simply showing off problems other people have. None of his customers have any of those problems because they do exactly as they are told and follow his instructions to the letter. There is no confusion on his part. He knows exactly what he is doing, and every station that leaves his bench looks exactly like the waveform below.

By the way, if you terminate 50 ohm coax with a 50 ohm load, assuming it is purely resistive then hypothetcically you would be correct, but since reactance is involved, and current and voltage are only equal every 180 degrees, impedance varies depending on the length of the cable. This is why we use 90 degree pieces of 75 ohm cable for building phased arrays to match multiple elements and bring the whole thing back to 50 ohms as I'm sure you already know.

 

[4x4junkie]

I am simply one of his happy customers in search of the worlds greatest technician. If you think class c is synonymous with spurious emissions then you clearly don't have a clue about the physics involved. The difference between class ab and class c is simply a biasing issue. Just because 999/1000 operators that use class c amps are generating a dirty signal with their equipment doesn't mean it isn't possible to generate a clean one. This simply demonstrates a lack of knowledge on the subject, and a lack of technicians able to do so. Every station that leaves my technicians bench is spectrally pure regardless of biasing scheme. Most commercial broadcast stations use some form of class c amplification at levels of up to 125% positive modulation with the negative peaks at no greater than 100% with no spurious emissions. His customers dominate the 11 meter world from coast to coast without any spurious emissions. His scope and spectrum analyzer tell everything you need to know. No harmonics and crystal clean audio are his specialty. If anybody claims to be a better technician than this guy I would be the first in line to test his work. 4 watt radios that leave his bench outperform many 1000 watt radios in the real world. Watts mean absolutely nothing unless they are on the fundamental frequency without spurious emissions, and that is why it is called Fine Tune CB Shop.
This wasn't meant to be a dicussion with closed minded hams who have already allowed their opinions to cripple their minds ability to understand things which RF engineers take for granted on a daily basis, it was simply a post to alert others interested in running a cb radio that there is at least one radio technician in the country that outshines all the others in the work he does. For thousands of years, mainstream science thought the earth was flat, and people who stated the obvious as they saw ships sink below the horizon were persecuted for going against the mainstream who thought the earth was flat. RF engineers don't seem to enjoy correcting those less informed for some reason, although that doesn't make their work any less relevant in todays world.
Non Linear is not synonymous with spurious emissions or harmonics under ideal laboratory conditions. I will concede all of those conditions must be met for this biasing scheme to function within acceptable parameters, and when it stays within these parameters it is a very efficient mode of amplification for AM and FM only.

Interesting the flopping back & forth there, and the way how you word your posts oh-so-similar to the video...


I never said a word about class-c = harmonics and spurious emissions. What is displayed on that scope is NOT harmonics or spurious. That is very clearly the amp's cutting off the modulation waveform because it drops into the amp's non-linear or "cutoff" region at the waveform's minimum.
A class-C amp by it's nature is very non-linear because there is zero bias voltage going to the output transistors, they are well below their cutoff point. This means the RF input signal itself has to bring them above cutoff and into conduction. If the signal isn't strong enough to bring them into conduction, then the output remains at zero. Sure, many people do use class-C amps on AM (unaware of the effects it creates on their modulation), but it's far from ideal, and only creates more adjacent-channel bleed-over (on SSB you typically can barely even understand the person). A class-C amp can only be ideal for FM work (to include FSK), nothing else (technically not CW either). Nothing you can do will change that other than to change the amp's bias to class A or class AB (greater than 180° conduction angle). What you might want to do is brush yourself up on "Intermodulation Distortion". This isn't about harmonics or spurious emissions, it is the distortion of an AM waveform created by non-linearities in an amplifier (maybe you could call the spectral products of the IMD "spurious emissions", though that's not the typical use of the word).

And commercial broadcast stations purposely use modulation techniques that do not require linear final amplification stages. Commercial stations (if not FM) either directly modulate the actual supply voltage going to the transmitter final output stage (often known as "plate", or "high-level" modulation), or in some cases they phase modulate two separate fixed-amplitude transmitters, the carriers of which are then summed together in a combiner to create the final output signal (called "Ampliphase" modulation, I believe).
So by comparing them to your CB hooked to an external amp you've shown you know nothing about commercial broadcast transmitters as well.

But, this YouTube Technician says he designs his cables based off of a calculation that "isn't really online" - which seems odd, but whatever.

I was gonna comment on that also. Certainly if it was so important to have specific length cables for each frequency one operates on, there'd be a heck of a lot of info about it out there. But it's not (and HF guys often use the same piece of cable for 10 different bands that span 4 octaves without issue), so that is why there "isn't really [anything] online".

 

[rabbiporkchop]

Interesting the flopping back & forth there, and the way how you word your posts oh-so-similar to the video...


I never said a word about class-c = harmonics and spurious emissions. What is displayed on that scope is NOT harmonics or spurious. That is very clearly the amp's cutting off the modulation waveform because it drops into the amp's non-linear or "cutoff" region at the waveform's minimum.
A class-C amp by it's nature is very non-linear because there is zero bias voltage going to the output transistors, they are well below their cutoff point. This means the RF input signal itself has to bring them above cutoff and into conduction. If the signal isn't strong enough to bring them into conduction, then the output remains at zero. Sure, many people do use class-C amps on AM (unaware of the effects it creates on their modulation), but it's far from ideal, and only creates more adjacent-channel bleed-over (on SSB you typically can barely even understand the person). A class-C amp can only be ideal for FM work (to include FSK), nothing else (technically not CW either). Nothing you can do will change that other than to change the amp's bias to class A or class AB (greater than 180° conduction angle). What you might want to do is brush yourself up on "Intermodulation Distortion". This isn't about harmonics or spurious emissions, it is the distortion of an AM waveform created by non-linearities in an amplifier (maybe you could call the spectral products of the IMD "spurious emissions", though that's not the typical use of the word).

And commercial broadcast stations purposely use modulation techniques that do not require linear final amplification stages. Commercial stations (if not FM) either directly modulate the actual supply voltage going to the transmitter final output stage (often known as "plate", or "high-level" modulation), or in some cases they phase modulate two separate fixed-amplitude transmitters, the carriers of which are then summed together in a combiner to create the final output signal (called "Ampliphase" modulation, I believe).
So by comparing them to your CB hooked to an external amp you've shown you know nothing about commercial broadcast transmitters as well.




I was gonna comment on that also. Certainly if it was so important to have specific length cables for each frequency one operates on, there'd be a heck of a lot of info about it out there. But it's not (and HF guys often use the same piece of cable for 10 different bands that span 4 octaves without issue), so that is why there "isn't really [anything] online".

The reason the calculation he uses isn't available online, is because he disputes the commonly estimated speed of light which puts his numbers slightly different than the ones you would arrive at should you do the calculation. As far as IMD, during the tuning process there would be some visible on the scope until the tuning is complete, at which point IMD is not visible. Until a technician can surpass the work this guy does, I will have to recommend his work above all others. Remember this is the 11 meter world, and 99% of his customers stay on 27.185 mhz 24 hours a day unlike most hams who like to use antenna matchers to allow various bands which is less efficient than a system optimized for a single frequency to put it politely. You are right, I am not a technician, hence improper terminology, but after 10 years on one frequency 24 hours a day in all 48 states plus Canada, I can honestly say I have experienced things no ham could have ever experienced due to the amount of time spent on one frequency.
By recommending this guys work, I speak from experience. No technician anywhere in the country achieves the results he achieves. I've spent 10 years asking people who their technician is. I ask relevent questions and get valuable information over a 10 year period on one channel one has a tendency to familiarize themselves with every voice on the air. the best performing radios were either untouched from the factory or tuned by this guy. hams might not feel a compulsion to tamper with their ICOMS and Kenwoods, but as you know, "stupid truck drivers" like to pay "technicians" to hack up their radios so they can talk on all 40 channels at the same time.:sombrero: I'm being facetious, but you get the idea. I hate splatterboxes, and unfortunately in my world that is all I hear unless the rig is stock or tuned by one of 5 people. It's pretty sad the state of the 11 meter world has sunk but cb radios are a tool to help me do my job so until truck drivers decide to start using the same commercial vhf or uhf radios to communicate I'll help this guy clean up the airwaves one radio at a time.

 

[rabbiporkchop]

Here is a video of a rig he worked on after the tune was complete demonstrating frequency response after modifications to rig.
https://www.youtube.com/watch?v=ZyRARy0EoYw

Look closely at spectrum analyzer. Keep in mind, he purposely doesn't show what he does to eliminate harmonics, but he does show what you would look for in a prospective technician.
https://www.youtube.com/watch?v=6ROf6j8G7Dg

His receiver sensitivity
https://www.youtube.com/watch?v=VnH_oJgpNP4

He drops the noise floor on these rigs so low, his generator can usually drop to 1/1000th of a microvolt and still produce an audible tone in the receiver which equates to hearing a walkie talkie with rubber duckie antenna 20 miles away.:wings:

This one shows flat topping simply by adding an extra 3 foot of rg58 to the feedline. By removing the extra 3 feet, the waveform is as it should be....
https://www.youtube.com/watch?v=HeWrIt2-kiY