[NN5I]

Originally Posted by Mr. Ham

Unfortunately today we give amateur radio exams and then we hang out to dry the new hams by not requiring them to learn anything or do anything.
Had [they] learned how to calculate power and gain ...

And, of course, had you learned it you could have avoided some of the following errors:

Originally Posted by Mr. Ham

they would learn that 100 watts is probably the most efficient use of power on the HF band.

Your logic is hard to follow. Often, it takes very little power to communicate. If you can hear me comfortably at 1 watt, how is 100 watts more efficient? Or, if you can't hear me at 100 watts but have armchair copy at 500 watts, how is 100 watts more efficient?

Originally Posted by Mr. Ham

To move the S meter needle one S unit below S-9, you would need a power increase of 6 - or 600 watts.

Well, no. A standard S-unit is nominally 6 dB, which is a power ratio of about 4, not 6. They'd need 400 watts approximately. Most receivers' S-meters are very inaccurate and not really logarithmic anyway, so the power ratio between, say, S5 and S6 on the meter might be very different from the power ratio between S6 and S7 on the meter.

The difference between 100 watts and 600 watts is about 1.3 standard S-units.

Why did I say approximately above? Many people parrot that a power ratio of 2:1 is 3 dB. I parrot it too, but actually it's about 3.0103 dB -- a negligible error that's easily within slide-rule accuracy.

Originally Posted by Mr. Ham

To move the S meter needle one S unit above S-9 you would need a power increase of 10. Hence with a 100w transceiver you would need 1000 watts to move the needle from 10/9 to 20/9 and you would need 10,000 watts to move it to 30/9 and 100,000 watts to move it to 40/9.

Sort of. There are no S-units above S9. Many S-meters are marked in tens of dB above S9, and indeed 10 dB is a power ratio of 10:1. But most S-meters are just as inaccurate above S9 as below, so the required increase might vary wildly.

Cheers!