[Boatanchors] Using a SG-230 tuner on AM
Gary Schafer
garyschafer at comcast.net
Mon Aug 10 16:18:15 EDT 2009
That person was stating that doubling the VOLTAGE gave a 6 dB increase (4x
power) in power.
The person stating that when doubling the voltage is 4 times the power is
correct. That would be 6 dB. You can look that up on a dB table that shows
volts as a reference rather than power. Or take 20 log of the voltage rather
than 10 log for power.
Just do an easy example with ohms law. 100 volts across 50 ohms is 100
squared divided by 50 or 10000/50 = 200 watts.
Now double the 100 volts to 200 volts. 200x200 = 40000/50 = 800 watts. That
is 4 times the power. Or expressed in dB that is a 6 dB increase.
And yes when you double the voltage across a given load the current also
doubles. You can verify that with a little math too. Just another way of
expressing that power increases by a factor of 4x.
The problem with your table that you reference is that we are NOT starting
out with .006 watts as the reference.
73
Gary K4FMX
> -----Original Message-----
> From: rbethman [mailto:rbethman at comcast.net]
> Sent: Monday, August 10, 2009 2:44 PM
> To: boatanchors at mailman.qth.net
> Cc: Gary Schafer
> Subject: Re: [Boatanchors] Using a SG-230 tuner on AM
>
> What I have been trying to say is simply:
>
> Doubling of power, 2X, or two times, is a 3dB increase from the power
> referenced.
>
> There is ate LEAST one person insisting that this is four, (4), times
> since the voltage doubles therefore the current also doubles. The table
> IS about POWER not voltage separately of current.
>
> This is WHY I also posted the formula, along with the cited ref.
>
> Then you come in and tell me it is dBm. Those actually are different
> tables and have different reference levels.
>
> I don't EVEN want to go into dBm, as it is entirely a different tangent.
>
> Bob - N0DGN
>
> Gary Schafer wrote:
> > Sorry, Sorry, slip of the keyboard I did not mean to type dBm. I meant
> to
> > type just plain old dB. Now does that make sense?
> >
> > 73
> > Gary K4FMX
> >
> >
> >> -----Original Message-----
> >> From: rbethman [mailto:rbethman at comcast.net]
> >> Sent: Monday, August 10, 2009 2:23 PM
> >> To: Gary Schafer
> >> Subject: Re: [Boatanchors] Using a SG-230 tuner on AM
> >>
> >> The beef happens to be when YOU tell me I'm looking at a dBm.
> >>
> >> You aren't R-E-A-D-I-N-G!
> >>
> >> Gary Schafer wrote:
> >>
> >>> Bob,
> >>>
> >>> I don't know what you are arguing about. If the table shows 0 dBm =
> .006
> >>> watts then 3 dB above that should show 2X that or .012 watts. 6 dB
> >>>
> >> should
> >>
> >>> show 4 times that or .024 watts.
> >>>
> >>> Note that 3 dB is 2x the power and 6 dB is 4 times the power.
> >>>
> >>> It doesn't matter what reference you want to start out with. That is
> the
> >>> beauty of the dB. With a 100 watt reference 3 dB above that is 200
> >>>
> >> watts. 6
> >>
> >>> dB is 400 watts.
> >>>
> >>> If you want to reference different levels of voltage it takes 6 dB to
> >>>
> >> double
> >>
> >>> the voltage.
> >>>
> >>> Where's the beef?
> >>>
> >>> 73
> >>> Gary K4FMX
> >>>
> >>>
> >>>
> >>>> -----Original Message-----
> >>>> From: rbethman [mailto:rbethman at comcast.net]
> >>>> Sent: Monday, August 10, 2009 2:08 PM
> >>>> To: boatanchors at mailman.qth.net
> >>>> Cc: Gary Schafer; jfor at quik.com
> >>>> Subject: Re: [Boatanchors] Using a SG-230 tuner on AM
> >>>>
> >>>> Gary,
> >>>>
> >>>> The reference cited specifically states dB. No where is it a dBM
> >>>> table. I am quite aware of the differences.
> >>>>
> >>>> I gave the specific edition, title, and date. It is VERY specific
> that
> >>>> the table is based on ZERO = 0.006 Watt.
> >>>>
> >>>> The formula for this is: [ Parenthesis denotes sub ]
> >>>>
> >>>> N(dB) = 10 log X P(out)/P(reference)
> >>>>
> >>>> This is what Carl just sent.
> >>>>
> >>>> Bob N0DGN
> >>>>
> >>>> Gary Schafer wrote:
> >>>>
> >>>>
> >>>>> Ah, Bob,
> >>>>>
> >>>>> I think that you are looking at a DBM table where the reference 0
> DBM
> >>>>>
> >> is
> >>
> >>>> 1
> >>>>
> >>>>
> >>>>> milliwatt. What the rest of us are talking about is the number of DB
> >>>>>
> >>>>>
> >>>> (not
> >>>>
> >>>>
> >>>>> DBM) above some given power level. When using DB we can use any
> >>>>>
> >>>>>
> >>>> reference we
> >>>>
> >>>>
> >>>>> wish as the starting point. If expressing in DBM then you start at 1
> >>>>> milliwatt as your reference.
> >>>>>
> >>>>> 73
> >>>>> Gary K4FMX
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>> -----Original Message-----
> >>>>>> From: boatanchors-bounces at mailman.qth.net [mailto:boatanchors-
> >>>>>> bounces at mailman.qth.net] On Behalf Of rbethman
> >>>>>> Sent: Monday, August 10, 2009 1:46 PM
> >>>>>> To: boatanchors at mailman.qth.net
> >>>>>> Cc: jfor at quik.com
> >>>>>> Subject: Re: [Boatanchors] Using a SG-230 tuner on AM
> >>>>>>
> >>>>>> The dB table is ALREADY for power, page 651, "The Radio Handbook",
> >>>>>>
> >> 13th
> >>
> >>>>>> Edition, copyright 1951.
> >>>>>>
> >>>>>> Again, 2X = 3dB. The table establishes zero as 0.006 watts.
> >>>>>>
> >>>>>> Mac, you can't mix apples and oranges. That is precisely what you
> >>>>>>
> >> are
> >>
> >>>>>> trying to do in your statement.
> >>>>>>
> >>>>>> Now go back and read at least one of the Orr Handbooks. I have
> 13th,
> >>>>>> 16th, and either 20th or 21st Editions.
> >>>>>>
> >>>>>> Bob - N0DGN
> >>>>>>
> >>>>>> D C *Mac* Macdonald wrote:
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>> 2 X the voltage IS 6 dB because when voltage is doubled
> >>>>>>> into a constant load, the current will also be doubled.
> >>>>>>>
> >>>>>>> 73 - Mac, K2GKK/5
> >>>>>>> (Since 30 Nov 53)
> >>>>>>> Oklahoma City, OK
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>> Date: Mon, 10 Aug 2009 10:52:30 -0700
> >>>>>>>> From: jfor at quik.com
> >>>>>>>> To: km1h at jeremy.mv.com
> >>>>>>>> CC: boatanchors at mailman.qth.net
> >>>>>>>> Subject: Re: [Boatanchors] Using a SG-230 tuner on AM
> >>>>>>>>
> >>>>>>>> Look at my table from two posts ago, which you quoted below... I
> >>>>>>>>
> >> said
> >>
> >>>>>>>> EXACTLY that.
> >>>>>>>>
> >>>>>>>> -John
> >>>>>>>>
> >>>>>>>> ===========
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>> 4X is doubling twice so it is 3+3=6
> >>>>>>>>>
> >>>>>>>>> Carl
> >>>>>>>>> KM1H
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>> ----- Original Message -----
> >>>>>>>>> From: "rbethman" <rbethman at comcast.net>
> >>>>>>>>> To: <boatanchors at mailman.qth.net>
> >>>>>>>>> Cc: <jfor at quik.com>; "Gary Schafer" <garyschafer at comcast.net>
> >>>>>>>>> Sent: Monday, August 10, 2009 1:37 PM
> >>>>>>>>> Subject: Re: [Boatanchors] Using a SG-230 tuner on AM
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>> This will ONLY apply *IF* you read the rest of the text.
> >>>>>>>>>>
> >>>>>>>>>> "You must first agree where ZERO is at".
> >>>>>>>>>>
> >>>>>>>>>> From 13th Edition Radio Handbook. Also in Radiotron Handbook.
> >>>>>>>>>>
> >>>>>>>>>> In any event, 2X isn't 6dB in any table I've seen.
> >>>>>>>>>>
> >>>>>>>>>> Bob - N0DGN
> >>>>>>>>>>
> >>>>>>>>>> J. Forster wrote:
> >>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>>> No:
> >>>>>>>>>>>
> >>>>>>>>>>> 3 dB is 2x power
> >>>>>>>>>>> 6 dB is 4x power
> >>>>>>>>>>> 9 dB is 8x power
> >>>>>>>>>>> 10 dB is 10x power.
> >>>>>>>>>>>
> >>>>>>>>>>> -John
> >>>>>>>>>>>
> >>>>>>>>>>> ============
> >>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>>> Carl,
> >>>>>>>>>>>>
> >>>>>>>>>>>> Isn't 6dB actually a power increase 10 times the original?
> >>>>>>>>>>>>
> >>>>>>>>>>>> My understanding that 3dB is a doubling.
> >>>>>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>> ______________________________________________________________
> >>>>>>> Boatanchors mailing list
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> >>>>>>> Help: http://mailman.qth.net/mmfaq.htm
> >>>>>>> Post: mailto:Boatanchors at mailman.qth.net
> >>>>>>>
> >>>>>>> This list hosted by: http://www.qsl.net
> >>>>>>> Please help support this email list:
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> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>> --
> >>>>>> +------------------------------------------------------------------
> +
> >>>>>> | AM Amateur Radio Operator NØDGN
> |
> >>>>>> +------------------------------------------------------------------
> +
> >>>>>> | Bob Bethman \\\|/// " The absence of a danger
> |
> >>>>>> | \\ ~ ~ // signal does *NOT* mean
> |
> >>>>>> | rbethman at comcast.net (/ @ @ /) that everything is OK "
> |
> >>>>>> +-------------------------oOOo-(_)-oOOo----------------------------
> +
> >>>>>>
> >>>>>> ______________________________________________________________
> >>>>>> Boatanchors mailing list
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> >>>>>> Help: http://mailman.qth.net/mmfaq.htm
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> >>>>>>
> >>>>>> This list hosted by: http://www.qsl.net
> >>>>>> Please help support this email list: http://www.qsl.net/donate.html
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>
> >>>>>
> >>>> --
> >>>> +------------------------------------------------------------------+
> >>>> | AM Amateur Radio Operator NØDGN |
> >>>> +------------------------------------------------------------------+
> >>>> | Bob Bethman \\\|/// " The absence of a danger |
> >>>> | \\ ~ ~ // signal does *NOT* mean |
> >>>> | rbethman at comcast.net (/ @ @ /) that everything is OK " |
> >>>> +-------------------------oOOo-(_)-oOOo----------------------------+
> >>>>
> >>>>
> >>>
> >>>
> >>>
> >>>
> >> --
> >> +------------------------------------------------------------------+
> >> | AM Amateur Radio Operator NØDGN |
> >> +------------------------------------------------------------------+
> >> | Bob Bethman \\\|/// " The absence of a danger |
> >> | \\ ~ ~ // signal does *NOT* mean |
> >> | rbethman at comcast.net (/ @ @ /) that everything is OK " |
> >> +-------------------------oOOo-(_)-oOOo----------------------------+
> >>
> >
> >
> >
> >
> >
>
> --
> +------------------------------------------------------------------+
> | AM Amateur Radio Operator NØDGN |
> +------------------------------------------------------------------+
> | Bob Bethman \\\|/// " The absence of a danger |
> | \\ ~ ~ // signal does *NOT* mean |
> | rbethman at comcast.net (/ @ @ /) that everything is OK " |
> +-------------------------oOOo-(_)-oOOo----------------------------+
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