I wasnt going to interject here with this one because Ive been on this race track before. Ive operated radio for a very longtime and yeah I know so have alot of people but what Im going to say is imple and not what most think about but here it goes and you can research what I share with you for yourself just so you dont think I have no clue what Im talking about I always thought big big big power is better better better this is only true to a certain extent. This info is what we on the amater bands speak of as best comoon sense bang for the buck. You have to remember the rule of thumb that after a certain point the person on the receiving end will not see or even hear the difference Ive talked all over the world on different bands with a simple 100 watts out of a mobile and that is the honest truth There is lots of different sources for this information
Power, dB’s, S-Units
I am doing this page because a lot of friends seem to confused about the relationship between the amount of power their radio transmits and the s-unit reading on the other end. Unlike Tool Time’s Tim Taylor, “More Power”, isn’t always necessary. If we remember the rules we are only supposed to use the minimum amount of power to make a contact; we are not supposed to be alligators, all mouth and no ears. How many times have you heard a station calling CQ and they are a good strong signal, stations are trying to answer the CQ and no one is coming back to them. One of two things could be going on, one way propagation or the transmitting station is transmitting beyond the range that they can hear, unless the station on the other end is pumping a lot of power as well. It is far better to have good antennas to pick up the signals, a good receiver to be able to pull out and amplify the tiny signals picked up off the antenna and a good set of ears listening to the receiver. If you have all this stuff then buy your amplifier to enhance your station; you will then have a better chance of picking up the distance no-amplifier stations wanting to make contact with you. .vrz6{position:absolute;clip:rect(441px,auto,auto,483px);}
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So what is all this power, dB and S-unit talk we commonly hear. What does it mean in real terms and what does 1.5kW of transmitting power mean compared to say 100 watts?
dB is a ratio of power, it is expressed by the following formula:
Here is a table of ratios using this formula, you can see that a power ration of 1.25:1 is 1 dB. The S-Meter on most, not all, but most radios is 1 S-Unit for each 6dB. Looking at the chart below we can see that a power ratio of 4:1 is 6dB. So in real terms that means that if a station is transmitting at 25 Watts to raise the S-Meter on the other end by one unit and increase in power by a factor of 4 will do the trick. So you dial up the power to (25*4) 100 Watts and the S-Meter on the other end, will go up one S-Unit or 6bB
Power Ratio
dB
Power Ratio
dB
1.25:1112.6:1 111.58:1215.8:1 122:1320:1 132.5:1425.1:1 143.15:1531.6:1 154:16100:1 205:171,000:1 306.3:1810,000:1 407.9:19100,000:1 5010:1101,000,000:1 60So your friend calls you on the radio and you give him a signal report of 30 dB over 9. You ask him what power he is running and the friend boast 1.5kWatts. Well your friend is throwing away a lot of money for nothing really. 30dB is a power ratio of 1,000:1. So you can tell your friend that 1.5Watts will give you an S-9 reading!
Let’s look at another example, QRP. How many times do I hear people get really excited about a 5 Watt contact, lots of times! It is exciting and a lot of fun but what is the difference between a 5 Watt and 100 Watt signal? If the station receiving the 5 Watt signal is getting it at S-5 what would the station get the QRP signal at if they went to 100 Watts?
Well first look at the power ratio:
therefore
The stations S-Unit reading will only increase to an S-7. The normal human ear can only detect a change in sound volume after 12dBs increase or decrease. So you would only just notice the difference in in the 100 Watts compared to 5 Watts!
For those interested tune your radio to any of the
NCDXF/IARU Beacon Project and listen for the beacons from around the world. They transmit on a time schedule so you can monitor them without really knowing CW. There are Beacon tracking programs out there that show you which beacon is currently transmitting. All you have to do then is listen and watch the computer. It is better to learn CW though, go on give it a go! The beacons transmit at 22 WPM 100 Watts followed by four tones each tone is a the following power level: 100W, 10W, 1W, 100mW. You will be amazed at the number of times you can actually hear the 100 milli Watt signal for a far away land.