EXPORT RADIOS AND THE SWING OF THINGS ?

[Switch Kit]

I'll just use a Magnum S-9 for an exsample. Let say I hit my little switch or variable on one of these radios and it drops down to 2 watts but yet still swings 50 watts , is the audio still at 100% or did it go out the window ? Or is this basically like a swing kit kind of deal ? I personally don't know why I would ever need that much swing out of any radio especially if IM running power to begin with. IM sure I must be missing something here and I hope this can be explained to me . Thanks

 

[Switch Kit]

Still hoping for some kind of answer on this one ? Thanks

 

[paws264]

I'll just use a Magnum S-9 for an exsample. Let say I hit my little switch or variable on one of these radios and it drops down to 2 watts but yet still swings 50 watts , is the audio still at 100% or did it go out the window ? Or is this basically like a swing kit kind of deal ? I personally don't know why I would ever need that much swing out of any radio especially if IM running power to begin with. IM sure I must be missing something here and I hope this can be explained to me . Thanks

Well Switch Kit, I am going to try to answer this question for you.

If you have a 4 watt RF carrier, you need 4 watts of audio to achieve 100% modulation of the AM signal ("100% modulation" was the measurement of the amplitude of the dual sidebands generated.

Back in the old days (pre 40 channel radios), radios used push-pull tube and transistors circuits and modulation transformers to combine the audio signal with the RF carrier; they were able to achieve 100% modulation. On a scope, a four watt fully modulated signal will show 16 watts on an O-scope.

If you were to take a standard "type accepted" CB radio keying 4 watts and check the Mod percentage with your PDC 600 (after setting the CAL at the 4 watt level you should see 100% or less.

However, if you then drop the carrier down to 2 watts (with 4 watts of audio power), you will see 200% modulation based on the CAL level.

Now, lets take this in the other direction keeping in mind that it take an equal amounts of audio power and RF carrier to achieve 100% modulation of the given signal (if your radio puts out 50 watts, you need 50 watts of audio to modulate the carrier), set you 50 watt export radio at 50 watts carrier and measure the amplitude on an O-scope; you will not see a 200 watt peak-to-peak signal because the IC audio chip is not capable of supplying 50 watts of audio out to modulate the carrier to the 100% level.

So, what do you do when you don't have enough audio to modulate the carrier 100%? Somebody who knew that a fully modulated AM signal is 4 times that of an un-modulated signal came up with the idea that you should only run 25% of your carrier so that when you swing the carrier with the less-than-fully modulated signal you still sound loud.

So, to answer your question, if you radio has an equal amount of audio power compared to the maximum dead key carrier you can get 100% modulation (enough to spread your audio 3 Kc above and below the carrier frequency).

Yo-yo modulation; 2 watts swinging 50 is bad news, I don't care how good those guys on 19 think they sound because they see the wattmeter gyrate from left to right.

.

 

[bob85]

im with paws on this, having heared them i would say they are well overmodulated swinging like that, kinda raspy sounding and then ya turn on the topgun distorter board and it all goes pearshaped but it seems loud or is that just the distortion fooling your ears

 

[Switch Kit]

well if I do my math right , I guess I was pretty close at what I was thinking about these radios , swing kit is a swing kit anyway I look at it or how they do it. It's the correct math that never seems to go away and it always seems to add up the same way everytime. 4 times the carrier at 100% modulation, Thanks Paws