Toggle sidebar Toggle sidebar
  • You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
  • The Retevis Holidays giveaway winner has been selected! Check Here to see who won!

SINE WAVES AND CB RADIOS ?

Switch Kit

Switch Kit

Well-Known Member
Apr 6, 2005
3,615
170
63
OK , I do understand that the big strappers look for a certain sine wave from radios for driving there goodies. Can this be explained to me ? Sine Wave ? OK , Lets say I have a radio (will use a 25 GTL 1978) that will do 1 watt into say 2 x 455s and I get 35 watt DK to about 150 pep........now I can take that same radio down to a 1/2 watt and get zero from the box but 150 watt pep audio out of the box now , if I take another much newer radio and I give the box 1 watt from it now it's keying 60 watts with the same reading ? and almost 1/4 watt from the newer radio just to get down to say 25 watt DK ........this is really hard for me to explain here .......Does this all have to do with a Sine Wave ? I would really like to understand this Sine wave jazz. thanks
 

I understand what you are trying to explain. I just wonder what is causing it like you. You have me confuzzled how 1 watt from both radios yields different deadkeys.
 
sorry here guys , as I said , I don't think I was explaining it very well . sigh wave / sine wave . Once I get a better idea about what IM asking , I'll try again..........and that was what I tried to explain that one radio doing the same thing as another radio would show different readings from the box.
 
SK,
maybe try running both those radios through a good low pass filter, into the amp, and comparing the output from the amp.

this would, at least eliminate the possibility that one radio is putting out some sort of spurious emissions, thereby causing the different wattage readings.

just a thought...
loosecannon
 
some sort of spurious emissions ? That's interesting , what would cause something like that ? thanks
 
spurious emissions...........isnt that usually assocated with splatter/harmonics ? ive seen many post about the 1 to 4 ratio of dead key to modulated power providing %100 modilation . but i also see many post of radios DK 2-3 watts and MODing 30 or more watts not to mention swing kits on pimped out radios DK 1 watt and swinging 50 or more . its also my understanding that going beyond %100 modulation starts to invite harmonics/splatter . i believe the GOOD/REAL techs look for rounded peaks and valleys on thier O-scopes and that square tops or bottoms are cliping/distortion . i think this is kind of related to what Switch Kit is talking about if im wrong switch it wasnt my intention to hijack your thread........i think its related and figgured it was a good time/place to ask .
 
All joking aside, the simple fact is that if an amplifier produces different outputs when driven by different radios, then the radios are not driving the amplifier in the same way. The signal from the two radios are not the same and produce different amplifier outputs, power levels, percentages of modulation, possible spurious and harmonic components.

Harmonic components are related to frequency, multiples of a frequency. Spurious components are unwanted/undesired variations not related to frequency, just some 'freaky' product of a transmitter. Neither are related to modulation although a modulated signal, having more frequency variations than an unmodulated one, can certainly produce unwanted harmonics. The use of a sine wave as an input gives you the ability to 'see' any harmonics because of it's predictable 'shape' if you are using a scope to test with (a super good 'ear' can/could also distinguish a difference in it's sound, sometimes, but not as accurately).
It also helps if the same 'unit' of measurement is used. Changing between units of measurement introduces another possible variation in accuracy from the inaccuracy of that 'unit' conversion. Huh? Which means if you start with 'average' or 'RMS' watts, stick with that till you get through. Don't try converting to 'Pep' in the middle, see what I mean? Just an added hassle in remembering which 'unit' you are dealing with, and where/when.
Also remember that you are dealing with things that are mass produced and have variations in their itty-bitty components/parts, even the same parts. So, there will be some variation in how they all work together, which also means that two exact same radios can have different outputs. Not a huge difference, but still some. One of them 'ballpark' thingys, and there are always different sized ball parks. If there's a huge difference in how far away that outfield fence is, then you know you're in the wrong ball park, sort of. Make sense?
- 'Doc

Then there's always that mysterious 'thing' that always crops up in most testing, the difference you just can't explain away. Usually nothing really exotic, just means you haven't thought of what the problem can be... yet. That's the real head thumper! "Why..'thump'..didn't I..'thump'..think of..'thump'..that!?..'thump' ", ('thump' = head on table)...
 
if the output impedance of one radio is closer to the input impedance of the amp wouldnt that allow the amp to work more efficently with it ?
 
BOOTY MONSTER said:
if the output impedance of one radio is closer to the input impedance of the amp wouldnt that allow the amp to work more efficently with it ?
Click to expand...

That's why most commercial amateur radio amplifiers have tuned inputs: to allow the best power transfer from the driver to the input of the amplifier.
 
I really wasn't to sure where to place this question in the first place but it looks like IM getting some excellent (things to think about) answers here. Thank you . I will try the Low Pass filter once I get around to it just to see what the differances may be if any . Now unless I miss understood ? (which wouldn't be the first time) I've heard this sign/sine way thing mentioned in the past , and IM not exactly sure why ? but it usually had something to do with the radios that many of these comp amp users would rather use compared to other radios ? This was kind of my way of thinking here with the older 1978 radio to the 2002 radios being used at the same wattage into the amplifier in question but yet seeing different readings from both , but after what Doc said , that kind of goes out the door. If we were talking about a 4 to 1 ratio in power from radio to box , the older radio surely seemed to give the more sensable numbers. I surely apprecate the feedback on this one , I usually try not to get to deep on these kinds of things if I don't have to. But only with my own lack of technical experiance and basically only having a ton of experiance , keeping it simple one more time would only lead me to believe that some radios are just better then others or it's just a formula thing ? Thanks
 
some people are built to just work the knobs, some are built to tweak the pods...

You might be thinking of high-level vs. low-level modulation.

It seems to me that a 1W dead key out of a radio is a 1W 'pure' sine wave no matter what radio makes it.

Of course, there is spectral purity, harmonics, and phase noise to consider...

But in the context of CB radios, a watt is a watt. So the question is why does your amp not DK the same from the same 1W drive? How do you know that the drive is the same 1W?
 

dxChat
Help Users
  • No one is chatting at the moment.


      Top Bottom