[Boatanchors] Using a SG-230 tuner on AM
J. Forster
jfor at quik.com
Mon Aug 10 16:05:14 EDT 2009
A table that shows 0 dBm = .006 Watts is WRONG.
dB is a power RATIO and is dimensionless. It is NOT Volts, Amps, Watts or
any other physical unit (except when measuring sound pressure level, where
a reference level is assumed by convention).
dBm is a power LEVEL referred to 1 milliWatt
dBW is a power LEVEL referred to 1 Watt
dBM is a power LEVEL referred to 1 MegaWatt
To say "my transmitter puts out +13 dB is meaningless"
To say it puts out +13 dBW has meaning, it equals 20 Watts.
To say "my antenna has +10 dBm of gain" is meaningless.
To say "my antenna has +10 dB of gain" makes sense.
So, a station that has a transmitter output of +13 dBW and an antenna with
+10 dB of gain, will put out an EIRP of +23 dBW or 200 Watts. (A big RADAR
can put out EIRPs of many dBMs)
-John
===============
> 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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>> >>>
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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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>> >> 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----------------------------+
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