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Message |
    
Wolverine
Intermediate Member
Username: Wolverine
Post Number: 421
Registered: 2-2003
| | Posted on Friday, August 12, 2005 - 8:37 am: | 
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I originally thought, that to gain a 1/2 of an S- Unit on a radio's Rx, you must double your power. Example, going from 400 watts to 800 watts. After looking at other forums, other opinions state that the doubling of power will result in 1 full S-unit. I don't agree. Am I right or wrong??.
Also am I right to assume that this applies to the doubling of RMS (Bird watts)only, and not peak/pep watts??
Wolverine. |
Hibuckhobby
New member
Username: Hibuckhobby
Post Number: 1
Registered: 7-2005
| | Posted on Friday, August 12, 2005 - 9:34 am: |
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I would agree with your first statement...as long as the S-meter is calibrated to the standard 6db per S-unit. If it is, and it takes twice as much power to increase signal by 3db...then that would be 1/2 and S-unit. |
Tech808
Moderator
Username: Tech808
Post Number: 6638
Registered: 8-2002
| | Posted on Friday, August 12, 2005 - 11:49 am: |
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Wolverine,
Read the TOPIC/POST titled:
DO YOU KNOW?
Below this topic in the OPEN Area here.
Hope this helps,
Lon
Tech808
CEF808
N9OSN  |
Chainsawiowa
Junior Member
Username: Chainsawiowa
Post Number: 45
Registered: 1-2005
| | Posted on Friday, August 12, 2005 - 6:47 pm: |
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Here's the deal !! To get a gain of 3 DB you have to double your watt Output or you have to double the area of your antenna in gain in DB. |
Wolverine
Intermediate Member
Username: Wolverine
Post Number: 426
Registered: 2-2003
| | Posted on Saturday, August 13, 2005 - 4:47 am: |
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Thanks, Tech 808. |
Hollowpoint445
Advanced Member
Username: Hollowpoint445
Post Number: 652
Registered: 6-2004
| | Posted on Saturday, August 13, 2005 - 7:25 am: |
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6dB is supposed to equal one S-unit, but it depends entirely on the design of the radio's receiver, the way the S-meter is driven, and how it's calibrated. Some will show a full S-unit with only a doubling of power and some will show considerably less.
The only way to truely have an accurate S-meter is to make calibration marks on a blank meter movement while feeding the output of an RF signal generator to the receiver. Unless that's been done then you are just viewing a relative signal strength - and that's just fine for me. |
Wolverine
Intermediate Member
Username: Wolverine
Post Number: 428
Registered: 2-2003
| | Posted on Saturday, August 13, 2005 - 9:56 am: |
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Okay, I get it. 1 S-unit = 6db. 1/2 S-unit = 3db.
So the doubling of power, can be either(Less or more) depending on the meter movement's calibration.
Wolverine. |
Kb9umt_don_123
Junior Member
Username: Kb9umt_don_123
Post Number: 13
Registered: 3-2004
| | Posted on Sunday, August 14, 2005 - 10:40 pm: |
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The formula to calculate this correctly is below and the link I provided might help (btw, there are also other things to consider such as the calibration of s-meter, proper measurement of wattage, taking into consideration losses as power increases etc).
http://members.djcafe.com/djmapy/basics3.html
dB = 10 X log (P1 ¸ P2)
To calculate dB using a calculator, first divide the 2 levels out (P1 ¸ P2), then hit LOG & lastly multiply the value by 10.
ie: 10 X log (2 ¸ 1)
= 10 X log 2 (on the calculator hit 2, then LOG, then multiply by 10)
= 3.01
= 3 dB
It is extremely important to understand that the decibel is a comparison between two levels rather than the power value itself. If you are using ‘Windows’ for your OS then click the ‘Start’ on the bottom left of your screen, then the ‘Programs’ then the ‘Accessories’ and then finally your window ‘Calculator’….on the calculator use the ‘View’ of ‘Scientific’….now you have the ‘log’ feature to actually calculate and use this formula.
Taking the x2 factors using a starting signal of an s4 signal:
4w x 2= 8w = s4.5
8w x 2= 16w = s5.0
16w x 2= 32w = s5.5
32w x 2= 64w = s6.0
64w x 2= 128w = s6.5 ** 2 s-unit gain
128w x 2= 256w = s7.0
256w x 2= 512w = s7.5
512w x 2= 1,024w = s8.0
1,024w x 2= 2,048w = s8.5 ** next 2 s-unit gain
2,048w x 2 = 4,096w = s9.0
(as you can see even using x2 your first 100w has the first 2 s-unit jump, then you really have to put some power or money out to get to the next 2 s-unit jump)
Taking from the formula (10*log (P1/P2)) Thus, a 10x increase in power yields a 10 dB increase in signal strength. A 2x increase in power yields a 3 dB increase; a 4x increase in power yields a 6 dB increase; a 20x increase in power yields a 13 dB increase, etc, etc, etc:
Comparing 4 or 5 watts (QRP power) going to 100 watts = 14db increase or just over 2 s-units
Now 100 watts to 400 watts = 6db increase or 1 s-unit
From 100 watts to 800 watts = 9db increase or about 1 ½ s-units
From 100 watts to 1,500 watts = 12db increase or about 2 s-units
What is the next level of wattage that you would have to use to increase your signal another 2 s-units if you were using 1,500 watts (if it were legal to run over 1,500 watts)? Would you believe 25,000 watts just for another 12db or 2 s-unit increase?
If given the choice between higher power or a better (higher gain) antenna, I’d go with the better antenna every time! ANTENNA, ANTENNA, ANTENNA…added antenna gain increases not only the transmit side of the equation BUT also the RECEIVE! Couple other things to add are the narrower radiated lobes of the directional antenna can greatly reduce interference. Here are some tables proving this point also:
Relative Scale of Approximate Power and S-Meter Signal Strength For Various SSB Transmitting Systems at Low Takeoff Angles on 14MHz (HF-DX)
S9:1kW + beam = 4kW ERP
S8: 1kW + dipole = 1kW ERP
S7: 100W + beam = 400W ERP
S6: 50W + beam = 200W ERP
S6: 100W + dipole = 100W ERP
S5: 50W + high dipole = 50W ERP
S5: 12W + beam = 50W ERP
S4: 50W + low dipole = 25W ERP
S4: 12W + high dipole = 12W ERP
S3: 12W + low dipole = 3W ERP
S3: 50W + backpack whip = 12W ERP
S2: 5W + high dipole = 5W ERP
S2: 12W + backpack whip = 3W ERP
S1: 2.5W + high dipole = 2.5W ERP
S1: 5W + low dipole = 2.5W ERP
S1: 5W + backpack whip = ~1W ERP
S0: 2.5W + low dipole = ~1W ERP
S0: 2.5W + backpack whip = ~600mW ERP
NOTE: Comparison is approximate, based upon about 6dB for each S-Unit, and starting with a kilowatt into a 6dB gain triband yagi. Low dipole is considered to be about 3dB loss, and a loaded backpack whip is considered to be about 6dB loss as compared to a high dipole. 73---Bonnie KQ6XA
Breakdown by Wattage only:
S9:1kW + beam = 4kW ERP
S8: 1kW + dipole = 1kW ERP
S7: 100W + beam = 400W ERP
S6: 100W + dipole = 100W ERP
S6: 50W + beam = 200W ERP
S5: 50W + high dipole = 50W ERP
S4: 50W + low dipole = 25W ERP
S3: 50W + backpack whip = 12W ERP
S5: 12W + beam = 50W ERP
S4: 12W + high dipole = 12W ERP
S3: 12W + low dipole = 3W ERP
S2: 12W + backpack whip = 3W ERP
S2: 5W + high dipole = 5W ERP
S1: 5W + low dipole = 2.5W ERP
S1: 5W + backpack whip = ~1W ERP
S1: 2.5W + high dipole = 2.5W ERP
S0: 2.5W + low dipole = ~1W ERP
S0: 2.5W + backpack whip = ~600mW ERP
Breakdown by ERP only:
S9:1kW + beam = 4kW ERP
S8: 1kW + dipole = 1kW ERP
S7: 100W + beam = 400W ERP
S6: 50W + beam = 200W ERP
S6: 100W + dipole = 100W ERP
S5: 50W + high dipole = 50W ERP
S5: 12W + beam = 50W ERP
S4: 50W + low dipole = 25W ERP
S4: 12W + high dipole = 12W ERP
S3: 50W + backpack whip = 12W ERP
S2: 5W + high dipole = 5W ERP
S2: 12W + backpack whip = 3W ERP
S3: 12W + low dipole = 3W ERP
S1: 2.5W + high dipole = 2.5W ERP
S1: 5W + low dipole = 2.5W ERP
S1: 5W + backpack whip = ~1W ERP
S0: 2.5W + low dipole = ~1W ERP
S0: 2.5W + backpack whip = ~600mW ERP
Breakdown by Antenna only:
S9:1kW + beam = 4kW ERP
S7: 100W + beam = 400W ERP
S6: 50W + beam = 200W ERP
S5: 12W + beam = 50W ERP
S8: 1kW + dipole = 1kW ERP
S6: 100W + dipole = 100W ERP
S5: 50W + high dipole = 50W ERP
S4: 50W + low dipole = 25W ERP
S4: 12W + high dipole = 12W ERP
S3: 12W + low dipole = 3W ERP
S2: 5W + high dipole = 5W ERP
S1: 2.5W + high dipole = 2.5W ERP
S1: 5W + low dipole = 2.5W ERP
S0: 2.5W + low dipole = ~1W ERP
S3: 50W + backpack whip = 12W ERP
S2: 12W + backpack whip = 3W ERP
S1: 5W + backpack whip = ~1W ERP
S0: 2.5W + backpack whip = ~600mW ERP
Hope some of this helped. I think now you can see why most Ham rigs use around 100 watts…it really is the best ‘bang’ for signal increase for the money! The more the wattage of an amp the more the money but not always more db gain for the money spent. Also, please note that the antenna system (the whole system: antenna/gain/height, feedline (loss), connector (loss) etc). The next time you think about putting up an easy no gain vertical on a 20 ft pole and wonder why your low height antenna doesn’t work all that well or being so close to the ground close to your and your neighbors electrical equipment that causes RF problems please think about getting those antenna at least 1 wave length or 36 feet above the ground (higher better) and adding even a simple 2 or 3 element directional yagi/beam that will add from 6db (smaller yagi/beam to add 1 s-unit) to 12db (larger yagi/beam to add 2 s-units)…..this might be cheaper than an amp and help you with both transmit and receive BOTH.
De kb9umt Don
http://www.HamRadioHelp.com
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Wolverine
Intermediate Member
Username: Wolverine
Post Number: 434
Registered: 2-2003
| | Posted on Tuesday, August 16, 2005 - 5:30 am: |
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kb9umt don 123, that was a vey informative post. It explains a lot. Thanks.
Wolverine. |
Rover
Intermediate Member
Username: Rover
Post Number: 245
Registered: 2-2004
| | Posted on Tuesday, August 16, 2005 - 11:37 am: |
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Excellent post! It also proves that "power" isn't always the answer. The uninformed operator likens it to the gas pedal: the harder you push the gas, the faster the car goes. (that's where the "all knobs to the right" comes from). But with radio, it doesn't work quite like that. For example, with a 4 watt CB, normally 3db isn't even going to be noticed--one S-unit. barely. So spending bookoos of money is really a waste of $$! |
Crafter
Senior Member
Username: Crafter
Post Number: 1071
Registered: 12-2002
| | Posted on Tuesday, August 16, 2005 - 1:49 pm: |
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Excellent post Don. |
Kid_vicious
Advanced Member
Username: Kid_vicious
Post Number: 504
Registered: 9-2004
| | Posted on Tuesday, August 16, 2005 - 11:42 pm: |
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don, thank you very much for taking the time and effort to make that post so informative.
this is one post that will be referrenced far into the future. |
Kb9umt_don_123
Junior Member
Username: Kb9umt_don_123
Post Number: 19
Registered: 3-2004
| | Posted on Wednesday, August 17, 2005 - 12:39 am: |
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Thanks Woverine (Darryl),Rover(Jerry),Crafter(Johnny), and Kid Vicious (Matt)...much appreciated and glad it might have helped.
de kb9umt Don123
ps..hope you don't mind me using your first names but I always used my first name on CB even when it wasn't proper to do so (to me just more CB friendly)...Don 123 on the Hill |
Bigbob
Senior Member
Username: Bigbob
Post Number: 2135
Registered: 12-2001
| | Posted on Wednesday, August 17, 2005 - 10:55 pm: |
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Man I think my eyes are going bonkers,lol.Bigbob |
Wolverine
Intermediate Member
Username: Wolverine
Post Number: 436
Registered: 2-2003
| | Posted on Thursday, August 18, 2005 - 3:38 am: |
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No problem Don. What's in a name?, or for that matter, a call sign?. LOL. Thanks a bunch.
Wolverine. |
Wolverine
Intermediate Member
Username: Wolverine
Post Number: 437
Registered: 2-2003
| | Posted on Thursday, August 18, 2005 - 3:55 am: |
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One other thing Don, since no one answered the 2nd part of my question, I'm going to assume that I was right when I asked that the doubling of power to gain S-units refers to RMS average talking carrier watts, and not peak, pep, ghost, harnonic, or fantasy watts, that most CBer's measure with Dosey or Astatic meters. Hooray for me!!!.
Wolverine. |
Hollowpoint445
Advanced Member
Username: Hollowpoint445
Post Number: 677
Registered: 6-2004
| | Posted on Thursday, August 18, 2005 - 7:37 pm: |
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It's always about peak envelope power. |
Wolverine
Intermediate Member
Username: Wolverine
Post Number: 439
Registered: 2-2003
| | Posted on Friday, August 19, 2005 - 2:19 am: |
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Rats!!, lost another one Di-tech. Okay hollowpoint, then peak envelope power it is, and rms is "Not" the correct answer (sigh), live and learn. |
Kb9umt_don_123
Junior Member
Username: Kb9umt_don_123
Post Number: 22
Registered: 3-2004
| | Posted on Friday, August 19, 2005 - 8:22 am: |
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Yes and NO, you could be right but.....Depends on Mode (AM,SSB,CW etc) and Meter....
The truth is that the elusive "Watt" is not as definitive as the average enthusiast would like it to be. Your amplifier is not doing X number of watts, it's just not that simple. RF wave propagation and the voltage/current ratio at a certain frequency gets just a little confusing for your average electronic technician, it can get completely confusing for one not already skilled in electronics. Technically it would require a perfect current reading and a voltage sample, and then one with a degree in electronic engineering would sit down in front of a computer and work out the math.
Power is measured in 'watts'. Power or 'wattage', it can be measured in a number of different ways, just as distance can. Distance can be measured in inches, yards, meters, or miles. Power can be measured in RMS, Peak, or PEP. Just as a distance seems 'bigger' if measured in feet rather than miles, 5280 feet still equal 1 mile. The same with power, 70.7 watts RMS, is a still 100 watts Peak. To talk about distance, everyone should use the same measurement unit (feet/yards/miles) or there can be a very big misunderstanding about the distance your talking about. The same holds true for talking about RF power. If you don't know what 'kind' of watts your talking about, you can have a rather large misunderstanding of how much power you are actually talking about. Power meters do not always measure in the same 'kind' of power units (RMS, Peak, Pep [peak to peak]). The meters in the lower price ranges 'usually' measure watts in RMS. That's because these meters are not as complicated or expensive to make. The Bird model 43-watt meter measures watts in RMS, or 'average' power, so just because a wattmeter measures in RMS doesn't mean it's a 'cheap' meter. The Bird Model 4300-400 measures true peak power, but it is a more expensive unit. Why are there so many different ways of 'measuring' power? Because different modes of radio transmissions are measured using different power units, or that the additional wattage units provide more needed information about the radio signal. A 'Peak' reading meter can be thought of as being more 'advanced' than a RMS reading meter and a 'Pep' meter more advanced than a 'Peak' meter. They all measure the same thing, power. They just measure it in different 'units'. If you were measuring a CW signal (used for Morse Code), all of the different types of meters would read the same thing. But, when you change modes to SSB, you will get a different reading on each different 'type' of meter. It isn't because the power is different. It's because of 'how' a SSB signal has to be measured. For SSB you should use a Peak, or Pep meter. A RMS meter won't give you an accurate reading. One reason it won't read accurately is because a RMS meter is basically too slow, the needle in your basic analog meter is coil and magnet assembly, much likea speaker. The coil simply can not charge fully before dissipating it's charge, as the actual power of the coil is physically moving the needle. In a Peak Reading meter the power is sampled, and then a separate power source is used to move the needle, or to light the LED's. In most cases a true peak meter uses a battery or some other power source to work. A RMS reading meter doesn't need any additional power source to work. When a manufacturer or dealer refers to power, they are usually referring to Peak-to-Peak power. We do this because it is the most accurate we to identify a power level with as much information as possible.
Hope this helped.
de kb9umt Don123 |
Wolverine
Intermediate Member
Username: Wolverine
Post Number: 441
Registered: 2-2003
| | Posted on Friday, August 19, 2005 - 9:56 am: |
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I guess it's like comparing apples to oranges, both are fruit, but the simarlarity ends there. I guess the same thing can apply to RMS and PEP meters measuring the all elusive "Watt". Brilliant answers Don.
Wolverine. |
Hollowpoint445
Advanced Member
Username: Hollowpoint445
Post Number: 679
Registered: 6-2004
| | Posted on Friday, August 19, 2005 - 11:51 am: |
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All PEP meters are worthless if you're using them to measure power output with speech input. Analog movements are just too slow - whether they are powered or not. Even if the movement was fast enough - and they aren't - the time constant of the sampling circuit won't allow it to follow the changes in speech at a rate of up to 3000Hz.
If you use a constant tone then you can get a ballpark measurement, and the powered PEP meters are okay for that, but they're still not what I'd call accurate.
The only way to accurately measure PEP is with an oscilloscope - period. It's fast enough to follow speech, but you should still probably use a constant tone just to take away a variable.
Meters in general are just something to watch while chatting on the radio. They're all pretty good at showing relative output of your equipment so you can detect changes which might indicate a problem, but expecting them to be test equipment is expecting too much. |
Magnetron
New member
Username: Magnetron
Post Number: 4
Registered: 6-2005
| | Posted on Friday, August 19, 2005 - 12:08 pm: |
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I think 70.7 volts rms across a 50 ohm load and 1:1 swr equals 100 watts peak
Power equals voltage squared divided by resistance
or
P = ( V x V ) / R
P = ( 70.7 x 70.7 ) / 50
P = 4999 / 50 = 100 watts
ohm's law
All meters work off voltage. The meter scales are just calibrated to display something else depending on what we want to measure(volts amps ohms watts temperature "S"units...etc)
more fuel to the fire |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 1276
Registered: 7-2004
| | Posted on Sunday, August 21, 2005 - 10:09 am: |
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wolverine-if you can't 'get out', buy an amplifier with twice as many transistors. keep upgrading til you can 'get out'. at that point, it won't matter what the wattage is PEP, peak, RMS, average, horse & buggy, etc |
Bigbob
Senior Member
Username: Bigbob
Post Number: 2144
Registered: 12-2001
| | Posted on Sunday, August 21, 2005 - 11:08 am: |
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I used a conversion factor a while back that converted watts to horsepower,you would be surprized at how puny our transmiters are in relation to horsepower,even 50kw is puny.Bigbob |
Bigbob
Senior Member
Username: Bigbob
Post Number: 2145
Registered: 12-2001
| | Posted on Sunday, August 21, 2005 - 11:20 am: |
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Conversion factor watts to horsepower multiply watts by .001341,horsepower to watts multply horsepower by 745.7,so to a motorhead a 100 watt txer is so PUNY,compared to his street racer that produces 352,850 watts.Bigbob |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 1282
Registered: 7-2004
| | Posted on Sunday, August 21, 2005 - 3:44 pm: |
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COOL! my durango does OVER 18,000 watts!!! of course, less then 1.3 horsepower leaves my antenna! |
Wolverine
Intermediate Member
Username: Wolverine
Post Number: 442
Registered: 2-2003
| | Posted on Sunday, August 21, 2005 - 6:54 pm: |
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Patzerozero, it was my understanding that pep applies to measuring SSB signal strength, and peak measurements apply to the AM mode of Xmission. Now what they measure CW with, your guess is as good as mine. I have no problem getting out at all. My asking the question was meant to find out when a CBer reaches a point of diminishing,when it comes down to dollars invested in amps, and getting a fair return in power and value. It appears that going over a primary 256 watts, or even a secondary 512 watts, the buck stops there (According to Don's chart). Additional watts would be a waste of money, where propagation is concerned, unless you are using a beam with great ERP (Focused direction), as opposed to a "Scatter stick" radiating 360 degrees around. At least I did find out the truth about S-units represents 6 db, and what it takes to move a meter 1/2 of an S-unit.
Wolverine. |
Bigbob
Senior Member
Username: Bigbob
Post Number: 2157
Registered: 12-2001
| | Posted on Monday, August 22, 2005 - 5:52 am: |
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PEP refers to all modes except fm,fm has a different wave form,peak and peak envelope power are synonamus,from what I understand root mean square is the unit to measure your base line it includes some of the modulation,average power is not as technical and is aproximately half,but a little more because it is the average of many peaks,and peak or pep is the absolute highest point your modulation achieves,which is about 3% of the time,that is why most hobbiests use average,because it can be measured as accurate nearly 100% of the time.There are so many factors that affect output,this is merely accademic.Bigbob |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 1290
Registered: 7-2004
| | Posted on Monday, August 22, 2005 - 12:42 pm: |
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'There are so many factors that affect output,this is merely accademic'-that's why, bigbob, i said, 'if you can't get out-keep doubling transistors til ya can'!
at that point wattage #'s are unimportant! |
Wolverine
Intermediate Member
Username: Wolverine
Post Number: 448
Registered: 2-2003
| | Posted on Tuesday, August 23, 2005 - 2:24 am: |
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10-fur |
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