S units
bill.lumnitzer at paonline.com
bill.lumnitzer at paonline.com
Tue Apr 2 13:24:54 EST 1996
>I beg to differ. I believe that S-meter circuits are calibrated in terms
>of VOLTAGE rather than power. That would make the difference between 1.5KW
>and 5KW equal to 10.45dB(V) or 1.74 S-units.
W8> That's a common misconception Bill. Beg all you want, one dB of
W8> voltage change is 1 dB of power change, look at the formulas! A 3 dB
W8> pad provides a 3 dB voltage, current and power loss.
I'm well aware of the formulas but apparently YOU aren't! Let me refresh
your memory: for POWER changes, a numerical ratio of 2 is 3dB, 4 is 6dB,
10 is 10dB, etc. Considering VOLTAGE changes, a numerical ratio of 2 is
6dB, 4 is 12dB, 10 is 20dB. I know this since the dB formula for a POWER
ratio is 10 Log(P2/P1), while the number of dB corresponding to a VOLTAGE
(or current) ratio is given by 20 Log (V2/V1). I think this has something
to do with P = V*V/R.
W8> S meters show larger than expected increases because 6 dB is NOT an S
W8> unit. That figure never was an industry wide standard, and certainly
W8> isn't today. Almost every rig is 3 to four dB per S unit when properly
W8> aligned. And even the dB end of their scales are usually wrong.
The last time I tried to check my S-meter was in 1959 when I had a
Hallicrafters SX-99. I believe the ARRL Handbook used to suggest
that S9 be made equivalent to a signal level of 50uV and each S-unit
equal to a 6dB change. Wouldn't this mean that 25uV=S8, 12.5uV=S7, etc.?
Those dopes! I feel like burning all my old Handbooks and cancelling my QST!
I guess this never caught on for various reasons but it makes more sense
than 3-4 dB per S-unit. Actually, the real beauty of using exactly 6dB is
that you don't even need a slide rule to figure the input levels!
W8> Remember three dB is three dB, with either voltage, current or power.
W8> It's one of those rules that work funny but save headaches.
W8> 73 Tom
Huh? Which other rules? Never mind - I'm confused enough!
All I wanted to do is disagree with the statement that 5** would not offer
a significant advantage over 1.5** anyhow. More than TRIPLING
your POWER is NOT an insignificant change (whatever the effect on your
S-meter) and has to give an advantage in a contest.
NOTE: ** can be replaced by your choice of mW, W, KW, MW
73 Bill
N6CQ at paonline.com
>From David B Curtis <David_B_Curtis at ccm11.sc.intel.com> Tue Apr 2 18:12:00 1996
From: David B Curtis <David_B_Curtis at ccm11.sc.intel.com> (David B Curtis)
Date: Tue, 02 Apr 96 10:12:00 PST
Subject: 3rd party traffic and contests - solution
Message-ID: <Tue, 02 Apr 96 10:57:17 PST_4 at ccm.hf.intel.com>
OK, so Tad did a wonderful thing and inadvertantly stepped into the 3rd
party trap. He isn't the first, and won't be the last. But he is right
that DX contests can be a lot of fun for prospective hams.
There is a simple solution: It would be easy for the logging programs to
display a 3rd party traffic warning message as calls are entered. I see
this working as an option to the "operator sign-on" command. After a
3rd party op signs on, the logging program can display a warning if a
callsign for a country with no 3rd party agreement is entered.
73, Dave NG0X
>From George Cutsogeorge <0006354141 at mcimail.com> Tue Apr 2 18:56:00 1996
From: George Cutsogeorge <0006354141 at mcimail.com> (George Cutsogeorge)
Date: Tue, 2 Apr 96 13:56 EST
Subject: A dB is a dB.
Message-ID: <81960402185618/0006354141PK5EM at MCIMAIL.COM>
Sorry, I can't take it any more.
A 6 dB change in voltage IS a 6 dB change in power. If the
voltage is doubled then dB(voltage)=20 log 2=6.02.
And since power is proportional to voltage squared it goes
up by 4 times and dB(power)=10 log 4=6.02.
George, W2VJN.
>From Skelton, Tom" <skeltt at mmsmtp2.ColumbiaSC.ATTGIS.COM Tue Apr 2 16:48:00 1996
From: Skelton, Tom" <skeltt at mmsmtp2.ColumbiaSC.ATTGIS.COM (Skelton, Tom)
Date: Tue, 02 Apr 96 08:48:00 PST
Subject: FW: BEWARE: WR6R/KH7 NOT ON KURE
Message-ID: <3161A533 at mmsmtp.columbiasc.attgis.com>
_____COMMENTS FROM WB4iUX BELOW_____
From: Jim Hollenback
<del>
On Apr 1, 2:38pm, Joseph M. O'Brien wrote:
> Subject: Re: BEWARE: WR6R/KH7 NOT ON KURE
>
> WR6R/KH7 did not jump the gun.
>
> >From the FCC website (www.fcc.gov), effective as of November 1995:
>
> 13. Hawaii and Pacific Insular areas.
<DEL>
> 73,
> Joe, WI2E
> jobrien at minerva.cis.yale.edu
>
> On Mon, 1 Apr 1996, Edward W. Sleight wrote:
>
<DEL>
> > 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
> >
Thanks, Joe. I knew KH7 was Hawaii and didn't have time to get the
info off the net.
<DEL>
73, Jim, WA6SDM
jholly at cup.hp.com
----------------------------------------------------------------------------
----------------
HELLO??????????? HELLO??????????????????
AREN'T WE FORGETTING SOMETHING??????
Yes, I can understand some of our newer contesters/dx'ers got
upset because they thought they had snagged a new one. I
am certain that I would have also been frustrated. BUT I see a
lot of experienced calls on this thread....... doesn't my foggy
memory seem to recall some of our own reflectorites using the
KP3 or WP3 prefix from Puerto Rico last year???? I didn't see a
rash of carping about that last year.
Presuming my memory hasn't completely failed me, and my
family is certain that it has :-), someone please 'splain the difference.
I'd like to understand.
Thanks!!
Cheers...73, tom WB4iUX
Tom.Skelton at ColumbiaSC.ATTGIS.COM
or
WB4iUX at AOL.COM
>From Jeff Tucker <jefft at atlanta.com> Tue Apr 2 14:21:00 1996
From: Jeff Tucker <jefft at atlanta.com> (Jeff Tucker)
Date: Tue, 2 Apr 1996 14:21:00
Subject: power, voltage, and the decibel scale
Message-ID: <199604021918.OAA27880 at atlanta.com>
Hello, folks.
I'm sure 99% of the people here already know this. But, there have been
some errors propagated and I just wanted to share a few formulas, in
case there are people who would like this info, but don't want to ask.
(By the way, the abbreviation is dB. The scale was named for a man named
Bel, and therefore the B is capitalized. We're talking about a tenth of a Bel, and
SI says deci should be a small d. So, we end up with dB.)
First of all, there's some confusion about the decibel scale and how
it relates to voltage, power, and the like. The decibel scale is a RELATIVE
scale. It indicates the ratio between two values, often a measured value
and some type of reference value. So, while you can have an absolute
number like 2 Volts, it makes no sense to ask how many dB 2 Volts is.
You CAN ask how many dB 2 Volts is compared to 1 Volt. (6 dB).
Now, a couple formulas.
For things like Voltage, acoustic pressure, etc. the formula for dB is:
dB = 20 * log(V1/V0)
Note the fraction. There's always a reference, referred to here as V0. Also,
on your calculator, that's the log key (base 10 logarithm), not the ln key
(natural logarithm). When you see a dB with another letter, they're telling you
what they used for the reference. For instance, dBV means the reference is
1 Volt. There are several of these, and they're not always clear exactly what
they are.
For things that go up as the square of the first terms (electrical power, acoustic
power, others), the formula is:
dB = 10 * log(P1/P0)
Now, for a constant, resistive load, power is something like:
P = V^2 / R
So, you see that power is related to the square of Voltage. If you remember your
rules of logarithms, you can figure out that this means a dB of change in Voltage
causes a dB of change in power. Or, a 3dB change in Voltage, all other things
being equal, causes a 3dB change in power. That's right, they're equivalent!
There's been some confusion about this recently.
OK, a couple handy rules. If you don't believe me, plug the number into the
formulas above:
For Voltage:
6dB per octave (doubling of Voltage, so V1/V0 = 2)
20dB per decade (Voltage goes up by a factor of 10, i.e. V1/V0 = 10)
For Power:
3dB per octave
10 dB per decade
Now, the last little confusing thing. You can use these rules to quickly figure dB
change in your head. Figure out what factors you need and then add up the
dB numbers that go with those factors. (It's a logarithm thing).
Example:
How many dB change if you kick on your amp, going from 100W to 2000W.
(Only legal for ON4UN and his compatriots).
That is a factor of 10 (100 to 1000) and a factor of 2 (1000 to 2000). 10dB
for the decade and 3 dB for the octave and he has gained 13dB output power.
My amp will do 10,000W. How many more dB do I have than a 200W radio.
This is minus an octave and then plus two decades (200->100->10000).
So, -3 + 10 + 10 = 17dB gain.
Anyway, so ends Decibels 101. I hope you enjoyed it.
73 de Jeff N9HZQ
--
Jeff Tucker, N9HZQ
jefft at atlanta.com
Williams Consulting, Inc. http://www.crl.com/~wci
>From K0RC - Robert Chudek <K0RC at pclink.com> Tue Apr 2 19:48:21 1996
From: K0RC - Robert Chudek <K0RC at pclink.com> (K0RC - Robert Chudek)
Date: Tue, 02 Apr 1996 19:48:21 +0000
Subject: CW will go next
Message-ID: <199604021948.NAA30588 at pclink.com>
CW tests and adjustments to the theory tests will not alter the
phenomenon we are experiencing. IMO, you will need to implement a
sociological test to screen the deviates from becoming licensed.
Like this is going to happen!
73 de Bob - K0RC
k0rc at pclink.com
At 10:03 AM 4/2/96 PST, Jim, AH6NB wrote:
>
>
>> Only hope is
>> CW tests will be replaced by some technical tests with real teeth to act as
>> a way to keep our bands from becoming as did the CB bands, completely lawless
>> and world wide, as in Indonesia now.
>>
>>Jim, AH6NB
>>jreid at aloha.net
>
>
>Yes, Jim! I've been saying this for a long time. I've never bought into the
>"CW will keep out the riff-raff" argument. I'm teaching a license class now,
>and CW is not causing fear among any of my students. If we truly want the
tests
>to do a "gate keeping" function (and for reasons of political impact some may
>argue that we do not, in order to increase our numbers)... but if we want to
>erect a suitable barrier to entry into "the club" then it ought to be in the
>form of a theory exam with meaningful content, along with periodic
retesting on
>state-of-the-art technology. I would be happy to submit a few DSP
questions to
>the question pool.
>
>BTW - I am not kidding - this is my real opinion - the above is not a joke.
>
>*** flame shields up ***
>
>73, Dave NG0X
>NCCC CM87xi
>david_b_curtis at ccm.sc.intel.com
>
>
>From jbmitch at vt.edu (John Mitchell) Mon Apr 1 20:14:56 1996
From: jbmitch at vt.edu (John Mitchell) (John Mitchell)
Date: Mon, 01 Apr 1996 15:14:56 -0500
Subject: CW will go next
Message-ID: <199604022019.PAA15479 at sable.cc.vt.edu>
At 10:03 AM 4/2/96 PST, David_B_Curtis at ccm11.sc.intel.com wrote:
>
>
>> Only hope is
>> CW tests will be replaced by some technical tests with real teeth to act as
>> a way to keep our bands from becoming as did the CB bands, completely lawless
>> and world wide, as in Indonesia now.
>>
>>Jim, AH6NB
>>jreid at aloha.net
>
>
>Yes, Jim! I've been saying this for a long time. I've never bought into the
>"CW will keep out the riff-raff" argument. I'm teaching a license class now,
>and CW is not causing fear among any of my students. If we truly want the
tests
>to do a "gate keeping" function (and for reasons of political impact some may
>argue that we do not, in order to increase our numbers)... but if we want to
>erect a suitable barrier to entry into "the club" then it ought to be in the
>form of a theory exam with meaningful content, along with periodic
retesting on
>state-of-the-art technology. I would be happy to submit a few DSP
questions to
>the question pool.
>
Well guys,
I've got to disagree. CW is the ONLY thing keeping back the hordes of
absolute barbarians, imho. This is not to say that there aren't plenty of
really bad actors out there with extra class licenses, but there does seem
to be a great correlation between one being willing to learn a second
language (morse) and that one acting as if they value the privileges that
are granted. As far as the technical exam goes, as long as we have the
volunteer examination program (which I'm not against, by the way) we will
have tech exams which can either be cheated on, answers published for, or
watered down technically. This has already been occurring, and I can't see
anyone being able to reverse this trend. Let's keep CW as the final barrier
between total chaos and what we have now, which is, at times, pretty
chaotic. If we do lose CW, as we probably will, then Katy bar the door. I
am in favor of retesting, as I've seen direct on-air results of certain old
Conditional Class licensees who without a doubt could not pass even the
present exams, and whose behavior should have gotten them many pink slips.
This is another point; we've got to somehow get enforcement on some of the
really bad actors, particularly on 20 and 75.
What I'd really like to see are more frequencies just for the two top
classes, to encourage study and professionalism. We also need more, bigger,
and better HF bands from WARC, although it seems unlikely we'll get them.
(I've heard of new allocations around 5 Mhz, and we certainly need to
restructure 40 M.)
73,
John WD4MUR
>From Joseph M. O'Brien" <jobrien at minerva.cis.yale.edu Tue Apr 2 20:49:15 1996
From: Joseph M. O'Brien" <jobrien at minerva.cis.yale.edu (Joseph M. O'Brien)
Date: Tue, 2 Apr 1996 15:49:15 -0500 (EST)
Subject: FW: BEWARE: WR6R/KH7 NOT ON KURE
Message-ID: <Pine.SOL.3.91.960402154141.10486C-100000 at morpheus>
> Yes, I can understand some of our newer contesters/dx'ers got
> upset because they thought they had snagged a new one. I
> am certain that I would have also been frustrated. BUT I see a
> lot of experienced calls on this thread....... doesn't my foggy
> memory seem to recall some of our own reflectorites using the
> KP3 or WP3 prefix from Puerto Rico last year???? I didn't see a
> rash of carping about that last year.
> I'd like to understand.
> Thanks!!
>
> Cheers...73, tom WB4iUX
> Tom.Skelton at ColumbiaSC.ATTGIS.COM
Tom,
I imagine the reason behind the different reactions to /KH7 in
the WPX and /WP3 previously is that prior to November 1995, KH7
represented a rare DX locale while /WP3 didn't exist. Hence when people
heard WR6R they got all excited about Kure I. and were disappointed when
they found out prefix allocations had changed. A WP3 on the other hand,
certainly attracted attention from those who weren't up-to-date with the
FCC announcement, but being that it didn't exist previously, people had
to find out what it was before they could get their hopes up.
Anyway, that's one possible explanation.
73,
Joe, WI2E
jobrien at minerva.cis.yale.edu
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