which way???

[Wire Weasel]

Me retarkles with snorts over you brainiacs telling this beginning CBer (elsewise he wouldn't be asking this question) to put his radio on an oscilloscope and check it out.

You're telling a skateboarder how to repair the space shuttle.

Please stop it. My sides hurt from the laughing.

YES YOU GUYS ARE RIGHT !!! But you're not helping.

All you OScope guys need to move over to the ham forum and leave the poor CBer's alone.

 

[BOOTY MONSTER]

Lets Explode a Few CB Myths

Numbers 4 and 5 apply to thisop:

4 is wrong

"Let's say you have a 4 watt AM carrier and 2 watts of forward audio swing. 4 watts plus 2 watts equals 6 watts. Ok that works. Now the audio swings 2 watts in the negative direction, so the 4 watt carrier minus the negative 2 watts of audio swing equals 2 watts of carrier at the most negative portion of the "swing". Ok that works too.

Now lets suppose you have a 4 watt carrier and 6 watts of audio "swing". On the forward portion of the "swing" 4 watts plus 6 watts equals 10 watts so that works. Now the audio attempts to swing negative by 6 watts. Well you only have 4 watts of carrier, so it is impossible for the audio to swing negative 6 watts because 4 watts of carrier minus 6 watts of audio swing equals negative 2 watts. You can't put out less that zero watts much less two watts less than zero watts, so the negative portion of the swing gets chopped off after the carrier reachs zero. The chopping off of the negative swing of the audio translates in to distortion of your voice over the air."

wtf LOL . there is no negative swing . the power rises and falls in response to modulation .

some of his comments are right , some are just stupid and show he doesn't have a clue what he'e talking about ...... here's a good example

"** The Antron 99 claims to be a 1/2 wave over a 1/4 wave antenna, and it is. What they do not tell you is the bottom 1/4 wave section is for matching purposes only, and only the top 1/2 wave section radiates any appreciable power. For gain comparisons consider it a 1/2 wave antenna."

what a dumb ass thing to say .

 

[GnG8d]

You're telling a skateboarder how to repair the space shuttle.

That doesn't seem so far fetched in this day and age :blink:

 

[eagle1911]

Double the carrier? I thought distortion had more to do with clipping either positive or negative peaks than any strict "rule of thumb" carrier/modulated carrier ratio.

Actually, RatsoW8 is right. You can only have 100% modulation of a carrier, which means that the carrier's amplitude is doubled at modulation peaks and reduced to exactly zero amplitude at the absolute lowest point.. Anything more results in clipping, and thus distortion. Any time you increase something by 100%, you're doubling it. A 50% increase is NOT doubling. This is a concrete "rule of thumb" and applies 100% of the time.

 

[BOOTY MONSTER]

A.M. TUTORIAL

"You'll notice that the peak envelope voltage doubled, and that the peak envelope power quadrupled. At 100% modulation our transmitter is producing 16 peak watts at the crest of the positive modulation swings ."

the voltage doubles , but us mere mortals who only have our watt meters dont measure voltage , we measure watts . our meters showing pep @ 4 times the carrier on am is the same thing as someone else doubling voltage .

you have to stay withing the proper context of the measurement method .

 

[eagle1911]

A.M. TUTORIAL

"You'll notice that the peak envelope voltage doubled, and that the peak envelope power quadrupled. At 100% modulation our transmitter is producing 16 peak watts at the crest of the positive modulation swings ."

the voltage doubles , but us mere mortals who only have our watt meters dont measure voltage , we measure watts . our meters showing pep @ 4 times the carrier on am is the same thing as someone else doubling voltage .

you have to stay withing the proper context of the measurement method .

True. I'm referring to voltage. I'm used to viewing modulation on a scope like the MacLeod-esque immortal being that I am.

Also, just for everyone's info, oscilloscopes can be had on ebay for less than many good wattmeters.. and you can do more with them, including calculating wattage.

Examples: http://shop.ebay.com/i.html?_from=R...20MHz+oscilloscope&_sacat=See-All-Categories\

A 20MHz scope will do 90% of everything you need it to when dealing with HF, but you could go with 30MHz if you can afford it. As far as measuring modulation and observing the quality of a modulated AM or SSB signal, a 20MHz scope works fine. For FM work you'd need greater than 30MHz minimum to cover all HF bands.

 

[GnG8d]

Actually, RatsoW8 is right. You can only have 100% modulation of a carrier, which means that the carrier's amplitude is doubled at modulation peaks and reduced to exactly zero amplitude at the absolute lowest point.. Anything more results in clipping, and thus distortion. Any time you increase something by 100%, you're doubling it. A 50% increase is NOT doubling. This is a concrete "rule of thumb" and applies 100% of the time.

That's only true of you are talking volts, but he's talking watts, which is incorrect.

Also, 125% positive and 95% negative modulation is not unherad of, and again, if no clipping is happening, no distortion is either.

 

[BOOTY MONSTER]

considering the quality (or lack of) of most cb speakers a fair amount of over modulation distortion will probably go unnoticed . there's a big difference going from a good external cb speaker to a set of quality headphones .

 

[eagle1911]

That's only true of you are talking volts, but he's talking watts, which is incorrect.

Also, 125% positive and 95% negative modulation is not unherad of, and again, if no clipping is happening, no distortion is either.

You are correct. Refer to my response in post 21.

 

[C2]

Also, 125% positive and 95% negative modulation is not unherad of, and again, if no clipping is happening, no distortion is either.

I thought that if the demodulated signal is not an exact copy of the original, then there was distortion. Perhaps you meant harmonic distortion?

 

[GnG8d]

I thought that if the demodulated signal is not an exact copy of the original, then there was distortion. Perhaps you meant harmonic distortion?

Correct, anything other than an exact duplicate is distorted. But an exact duplicate is theoretical as well, right?

 

[eagle1911]

Correct, anything other than an exact duplicate is distorted. But an exact duplicate is theoretical as well, right?

Not necessarily - but it does depend on how many decimal places you want to take into account when determining accuracy. A correctly driven class A amplifier should give a faithful representation of the input waveform.

 

[GnG8d]

A correctly driven class A amplifier should give a faithful representation of the input waveform.

While resistors, inductors or capacitors won't distort a sine wave, transistors, FETs and tubes will. So some distortion is pretty much unavoidable, but I'll buy "faithful representation".

 

[wavrider]

Me retarkles with snorts over you brainiacs telling this beginning CBer (elsewise he wouldn't be asking this question) to put his radio on an oscilloscope and check it out.

You're telling a skateboarder how to repair the space shuttle.

Please stop it. My sides hurt from the laughing.

YES YOU GUYS ARE RIGHT !!! But you're not helping.

All you OScope guys need to move over to the ham forum and leave the poor CBer's alone.

I use the scope to set up the cb radios also

Rule of thumb as 359 said is 4 times the dead key,on a PEP watt meter. no argument there unless the dead key is 1/2 watt, the low dead key max swing mod really sounds like junk on the air.

I have two 959s laying around the shack, so I did the mod to lower the dead key and obtain max smoke out of it.

I did back to back comparisons to see which sounded better "on the air"
The clearer, better sounding radio was the one with out the "swing mod" performed. Of course I can see that on the scope into a dummy load without having to get an on the air check.

That experiment was to show some friends what the difference is on the air quality. After hearing the difference between the two radios they started changing the way of setting up their stations. Clear and loud is better than distorted and loud any day.

For those who like to watch the watt meter swing the mod makes them happy, low drive amp, low dead key, max swing blowing smoke now, who cares what it sounds like.

To answer the question of the thread. To many variables unknown, amplifier? no amplifier?. If an amplifier what type, tube , solid state, FET finals????

What type of radio? Will the power supply handle the tuning up of the radio if it is a base etc etc etc .

 

[1iwilly]

I use the scope to set up the cb radios also

To answer the question of the thread. To many variables unknown, amplifier? no amplifier?. If an amplifier what type, tube , solid state, FET finals????

What type of radio? Will the power supply handle the tuning up of the radio if it is a base etc etc etc .

radio=29 ltd classic,with stock mike radio has the 2030 final mod. D-11 is on a off&on switch
amp=2x8
set up on a mobile at 14.50 volts