S Units

[W8JITom at aol.com]

Hi All,

I received about ten E-mails saying 3 dB of voltage change is twice the
voltage, but that is absolutely incorrect. If the posters would just lok in
the ARRL Handbooh they will see that what I said is exactly correct.

The formulas are 20 log ratio for voltage or current, and 10 log ratio for
power.

Double the voltage is +6 dB, not +3 dB.  
log of 2= .3.01 times 20 is 6.02 dB!
Double the power is log of 2= .301 times 10 is 3.01 dB!

Double the power and 1.414 times the voltage are approximately the same.
Three dB of power change IS EXACTLY 3 dB of voltage change. 

3dB voltage attenuation is exactly 3 dB power reduction. That's WHY they
don't sell  3Db pads as voltage or current pads!!!!!!

Anyone in doubt of this can confirm what I'm saying by looking in any
electronics textbook. It's a only a popular Amateur radio misconception that
3dB of voltage change is twice the voltage.

If the S meter was calibrated accurately in dB volts it would also be exactly
correct for dB watts.

73 Tom 




   

>From WX9E" <WX9E at sbbs.net   Tue Apr  2 16:14:36 1996
From: WX9E" <WX9E at sbbs.net  (WX9E)
Date: Tue, 02 Apr 96 16:14:36
Subject: KH7...  Who's the jerk????
Message-ID: <9603028284.AA828490476 at sbbs.SBBS.NET>


     >>Well, technically, he has jumped the gun, 
     >>and I agree with you entirely.
     
     Before you guys go slamming WR6R, you oughta do your homework.
     
     >>WHEN the FCC starts the Vanity program, part of 
     >>it will make KH7 a legal KH6 call. Same with KL7s.
     
     Just who exactly told you this?  Did you call the FCC or the League??  
     Is that what they told you?  If so, they told us two different things 
     and I appologize for what I am about to say.
     
     Using KH7, KL0, WP3 is not "jumping the gun."  It is perfectly legal.  
     The FCC passed the new docket last April (or something like that) 
     allocating those prefix blocks to HI, AK and PR.  The only reason they 
     are not handing out calls with those prefixes is that their computers 
     aren't updated yet.   N6VI signed /NH7 in last years WPX CW contest, 
     and I went to Puerto Rico and signed WP3/, AA3BG also went to Puerto 
     Rico and signed KP3/ and I think there was a KL9 or something like 
     that also.  Why wasn't I slammed last year?  I got nothing but thanks 
     from all the prefix hunters.
     
     Before I went off on this adventure, I called the ARRL and FCC to make 
     sure all was all right to use these newly allocated prefixes.  Both 
     offices sent me the same news release that said it was fine to do.
     
     So, bottom line....   If you go to HI, PR or AK. it is perfectly legal 
     to sign /KH7, /KP3, /KL8 
     
     >>Always some jerk....let him live in his own misery. 
     
     Jerk huh....  Well Ed, it appears as though you are the jerk in this 
     case.  You ought to be ashamed of yourself...  and you owe WR6R a 
     public apology!!
     
     >>I think I can guarantee if he submits 
     >>his log, it's going to be tossed.
     
     Did you check with Steve Bolia before you made this bold statement? 
     Well Mr. Ed, I wouldn't count on that.  If you want make a little 
     wager on that, I'll give you 10 to 1 odds.  Be sure not to bet more 
     than you can afford, because you are going to lose it!
     
     Let this be a lesson to those of you who want to slam people...  do 
     your homework first, or you could end up like N0DH and K4SB.
     
     Paul  WX9E
     


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     ----------------------------------------------
     
     K4SB wrote:
     
     Well, technically, he has jumped the gun, and I agree with you 
     entirely.
     
     WHEN the FCC starts the Vanity program, part of it will make KH7 a 
     legal KH6 call. Same with KL7s.
     
     Always some jerk....let him live in his own misery. I think I can 
     guarantee if he submits his log, it's going to be tossed.
     
     73, Ed