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Moonraker
Intermediate Member
Username: Moonraker
Post Number: 234
Registered: 3-2005
| | Posted on Saturday, July 15, 2006 - 8:25 pm: | 
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OK, Radio set-up #1 DK= 125 watts, RMS swing= 250 watts PEP=500 watts.
Set-up #2 DK=200 watts, RMS swing= 125 watts (back-swing from 200), PEP=800 watts.
Would the one with the higher pep be louder and the one with the higher rms get out more? Or would the higher pep make up for the lost rms power?
Not sure which way to go on this one. |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 3091
Registered: 7-2004
| | Posted on Saturday, July 15, 2006 - 9:17 pm: |
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set up #1 is the better setup. too many times i'll help somebody get their amp setup correctly, & they get upset when they see as much as a 50% decrease in measured output. when they notice a 200% increase in ability to talk DX or LONG distance, they realize forcing a # is NOT helping them.
if it was on a reflect reading meter, you'd probably notice a drastic increase in reflected power, due to overdriving the heck out of it, so forward power would be more on the lesser PEP.
backswing is never a good thing. find the transistors rated output, multiply times quantity of transistors, then divide by 4. that is the dead key you are looking for. adjust radio output, so with no modulation, the amp now keys that #. then, turn up mic gain til you get PEP near the # you got when you multiplied output X qty.
example-2 x 2sc2879 amp:
1. transistors are rated at 120 watts PEP
2. 2 transistors X 120 watts = 240 watts PEP
3. divide 240 by 4, equals 60 watts...dead key. adjust the radio so amp dead keys 60 watts.
4. then turn up mic gain til you get 240 PEP, more or less. more realistically, turn up mic gain with meter in RMS/AVG mode, & adjust for max swing in that mode. should be from 1/2 to 2/3 of rated PEP. in this case 120-180 watts. you have little control (at this point) of where RMS swing will max out. then, wherever PEP falls is it. by turning mic gain up more, you may still be able to increase PEP, but it is harmonics, bleedover & other garbage, doing nothing for you, so leave it where RMS swing maxes.
these #'s are approximate, & a very good starting point. watch heat, you can probably increase the dead key a bit, but only do so until RMS swing begins to drop off.
audio power/carrier power are like horsepower/torque. when you have a set 'piece' to work with, increasing one decreases the other. you want the perfect compromise for the fastest speed over a distance, or talkpower in this case. you wanna go faster increase the motor. you want more talkpower, increase the (# of) transistors. |
Moonraker
Intermediate Member
Username: Moonraker
Post Number: 235
Registered: 3-2005
| | Posted on Sunday, July 16, 2006 - 12:12 pm: |
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That is exactly what I found. I,m back to using setup #1 as I was extremely disappointed with setup #2.
Are you ready for the funny part? Both setups were with the same amp (the amp was not being over driven by either radio) but different radios, Radio #1 was a MAGNUM S9 and #2 just happened to be...a Galaxy 95t.
I could not get any forward rms swing out of the galaxy (it has not been clipped or butchered). Now if both radios were barefoot I could turn up the dead key on the 95t and it would out talk the S9, but it I set the DK's on both radios at around 10 watts...I think the 95t would get smoked.
It was not only the #'s on the meter, I talked to a station from the same location I usually do and lost 2 s units.
The only way I will ever buy another galaxy radio is if I get it at a good price and can make some $$$ on it. |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 3104
Registered: 7-2004
| | Posted on Sunday, July 16, 2006 - 9:52 pm: |
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equal wattage from an S9 & another radio, galaxy included(especially ), with the magnum topgun on & functioning properly, yup, it SHOULD outtalk the non-compressor radio, as much as 3db is possible. at 40 watts PEP, that could make it equal to a radio actually doing 80 PEP.
as for buying a galaxy.....
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Cdn_superpower
Member
Username: Cdn_superpower
Post Number: 70
Registered: 6-2005
| | Posted on Monday, July 17, 2006 - 3:57 am: |
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back swing is bad, very bad.
It's like the timming on your car, too much is not good, it has to be just on the downside of the peak. |
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