[Boatanchors] Using a SG-230 tuner on AM
Gary Schafer
garyschafer at comcast.net
Mon Aug 10 15:19:50 EDT 2009
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.
> >>>>>>>>
> >>>>>>>>
> >>> ______________________________________________________________
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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----------------------------+
> >>
> >> ______________________________________________________________
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> >>
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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----------------------------+
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