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Author Topic: Mathematical correlation between Continuous and PEP  (Read 4199 times)
K6BRN
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« Reply #75 on: February 25, 2019, 07:59:25 PM »

Yes.  Do tell.  Smiley
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G3RZP
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« Reply #76 on: February 26, 2019, 01:23:28 AM »

Bell - as in Alexander Graham.
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W9FIB
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« Reply #77 on: February 26, 2019, 03:02:39 AM »

This gets funnier by the post!
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73, Stan
Wisdom is knowledge you gain after you know it all.
G8HQP
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« Reply #78 on: February 26, 2019, 04:06:12 AM »

Just to add to the general mirth about units, the normal convention is that a unit derived from a person's name has a capital letter for the unit symbol but not for the unit name. Examples:

W watts, named after James Watt
F farad, named after Michael Faraday
B bel, named after Bell - not clear why they dropped the second 'l'

Getting it right reduces confusion: s is seconds, S is siemens, f is femto, F is farads. Context will often help if someone gets it wrong, but this is not an excuse to get it wrong. Confusingly, m is both metres and milli; M is mega.
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WB6BYU
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« Reply #79 on: February 26, 2019, 06:09:13 AM »

One Bel is a power ratio of 10, with a logarithmic scale.

Smaller units are often more convenient, so we use decibels, abbreviated "dB".

Or, if relative to a milliwatt (mW) or an isotropic source, "dBm" and "dBi", respectively.


Not sure why Watt kept the double letter but Bel did not...
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G3RZP
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« Reply #80 on: February 26, 2019, 06:49:33 AM »

At one time, 'dBm0'  was used in telephone technology to denote dBm in 600 ohms and so '0dBm0' meant 1 mW in 600 ohms. Every time one gets used to a unit, it seems to change - like millibars are hectopascalls! While Siemens and seconds business is asking for confusion......
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G0HZU
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Posts: 163




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« Reply #81 on: February 26, 2019, 07:28:49 AM »

Quote
Getting it right reduces confusion: s is seconds, S is siemens, f is femto, F is farads. Context will often help if someone gets it wrong, but this is not an excuse to get it wrong. Confusingly, m is both metres and milli; M is mega.

On my old HP431C power meter, the milliwatt scale has MW on it rather than mW which has always amused me a little. However, someone at worked advised me that it might have been OK when the meter was new. So maybe the rules changed? I think the meter is older than me so all this was before my time...
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WA7PRC
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« Reply #82 on: February 26, 2019, 09:56:52 AM »

Quote
Getting it right reduces confusion: s is seconds, S is siemens, f is femto, F is farads. Context will often help if someone gets it wrong, but this is not an excuse to get it wrong. Confusingly, m is both metres and milli; M is mega.
On my old HP431C power meter, the milliwatt scale has MW on it rather than mW which has always amused me a little. However, someone at worked advised me that it might have been OK when the meter was new. So maybe the rules changed? I think the meter is older than me so all this was before my time...
It would be interesting to have (hypothetically) a 1MF capacitor. You might need a crane or fork lift to move it.  Grin

In the real world, I once took a tour of US Naval Radio Station, Jim Creek (link). Though the VLF transmitter has been known to be run as much as 2MW output, when I was there, they were running a bit soft (1296A into 0.456Ω). That's "only" 0.766 MW.   Grin
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G0HZU
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« Reply #83 on: February 26, 2019, 10:25:03 AM »

I just had a quick look at the old HP431C meter and it says MW on the dial but mW on the range selector! It also says DBM instead of dBm in two places. I also have a couple of the classic HP432A power meters and they both (correctly) have mW and dBm on the front panel and dial. So even HP can mix this stuff up.


« Last Edit: February 26, 2019, 10:27:26 AM by G0HZU » Logged
K6BRN
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« Reply #84 on: February 26, 2019, 12:10:26 PM »

Well... if we REALLY want to have fun, I'm using a Boonton lab wattmeter & probe labelled "RMS Watts" and a friend has a Reed handheld "True RMS Wattmeter".  In fact, Boonton has a nice appnote discussing measurements of "Watts RMS".

Everyone who has used the Boonton realizes it reads "average power" and that's what Boonton means, so no big deal.  Slang is slang and the work must go on.  Drives some people crazy, though (mainly on the ham forums).

Brian - K6BRN
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G0HZU
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Posts: 163




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« Reply #85 on: February 26, 2019, 01:46:39 PM »

Quote
Slang is slang and the work must go on.

Agreed.

However I definitely draw the line when it comes to kHz. I start to twitch and the stress hormones kick in when I see it written as KHz or Khz Smiley
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G3RZP
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« Reply #86 on: February 26, 2019, 01:52:53 PM »

Quaere:

Is it 'milliamps'  or 'milliAmps'? But it is mA.....

If 'milliAmps' why?
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K5WLR
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Posts: 313




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« Reply #87 on: February 26, 2019, 02:11:52 PM »

Quaere:

Is it 'milliamps'  or 'milliAmps'? But it is mA.....

If 'milliAmps' why?

Named after Mr. Ampere....
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G3RZP
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« Reply #88 on: February 26, 2019, 03:47:23 PM »

But which is 'correct' when spelt out -  'milliAmps' or 'milliamps' Then, what is general usage??

Plus, there are major language differences in places between 'English' and 'American'..........
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VK6HP
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Posts: 549




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« Reply #89 on: February 26, 2019, 06:02:34 PM »

When the unit is written in full, there is no capitalization, even if it is derived from a person's name.  But in the case of a unit derived from a name, write the abbreviation as a capital. So, write 10 amperes or 10 A. (Note the the spaces, by the way).

I don't know why you'd write milliamps rather than milliamperes or mA, since you are introducing a colloquialism and saving no or few keystrokes. I doubt there's a strict guideline if you do go down that path but if you do I'd write milliamps, extrapolating from the SI convention.

There are a couple of curly cases but, in general, these conventions take about half an hour to learn in high school.  I'm fascinated by the meal people seem to make of them.

By the way, apologies to M. Ampere and the francophones reading: I don't know how to get the correct accent showing but, in any case, in written English SI usage the accent is not used; it is in French I've observed (with no surprise).
« Last Edit: February 26, 2019, 06:06:39 PM by VK6HP » Logged
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