Contesters don't need S Meters everyone's 59!!
73, Gator N5RZ -----------------------------------;--;<< N5RZ@aol.com
>From jreid@aloha.net (Jim Reid) Mon Aug 21 20:53:44 1995
From: jreid@aloha.net (Jim Reid) (Jim Reid)
Subject: SSB Minimum Usable Signal Level
Message-ID: <199508211950.JAA26618@hookomo.aloha.net>
Hi Larry,
Yes, ON4UN"s data must be based on a transceiver
with an MDS of about -137 dBm. Recall that the thermal
noise power in the 50 ohm system at 500 Hz bandwidth is
-147 dBm (after I was corrected!). Opening up the bandwidth
to ON4UN"S 3 kHz for SSB reception is a 6 times increase in
bandwidth, or 7.78 dB; call it 8dB.
So, yes, he probably did have the FT-1000D in mind when
developing his numbers, as the 1000D, as reported by
by the ARRL, apparently with 500 Hz bandwidth, does have
a noise floor (MDS level) of -137 dBm at their 20 meter test
frequency, whatever it was. So, -137 dBm + 8dB = -129 dBm.
This also means that the 1000D, at that frequency on 20 meters,
has a front end noise figure of 10 dB (since the theoretic
thermal noise floor should be down at -147 dBm, and in their
1000D test sample of one, they measured it to be 10 dB higher at
-137 dBm). BTW. 10 dB NF at 20 meters has got to be very
close to the "state-of-the-art. "
Also, keep in mind that there will be variations unit
to unit among rigs coming from the production line for any
manufacturer. The FET's in the front-end RF gain stage are
going to vary in the added thermal noise at the gate junction
and the gain of the stage will also vary from unit to unit; this
gain variation will vary the amount of noise contributed to the
MDS level from circuitry following the first preamp gain stage.
The higher the front end gain, the less noise contribution
by following circuitry.
Also remember that ON4UN's numbers assume a very
quiet, QRN wise, 20 meter band. which it can be at times.
He also assumes the operator needs a 10 dB signal- to- noise
ratio to make a valid contest or DX contact; an experienced,
golden eared operator may not need that much S/N at all!
Hope this info helps, Larry.
73, Jim, AH6NB
>From jreid@aloha.net (Jim Reid) Mon Aug 21 20:53:54 1995
From: jreid@aloha.net (Jim Reid) (Jim Reid)
Subject: S-Meters, Piece Corrections
Message-ID: <199508211950.JAA26633@hookomo.aloha.net>
Hi All,
I have received many comments re: my bit
on using dBm as an S-meter unit. Also has
been pointed out that I typed 500 kHz
when I intended 500 Hz as the bandwidth used
by many (most?) CW ops when S&P contest
operating or digging out DX. Also managed to
cross-modulate hte 50 ohm source impedance
1/2 microvolt power level of -113 dBm with the
1 mHz thermal energy in 50 ohms of -114 dBm.
So the noise in a 500 Hz bandwidth 50 ohm system
is -147 dBm. All other numbers seem to be ok
as sent out: the S-unit to dBm numbers are
correct, as are the ARRL lab numbers reported
and ON4UN"s data.
Sorry about my errors.
Mahalo and 73, Jim, AH6NB
>From Steve Sacco <0006901972@mcimail.com> Mon Aug 21 21:41:00 1995
From: Steve Sacco <0006901972@mcimail.com> (Steve Sacco)
Subject: MultiTasking
Message-ID: <62950821204126/0006901972DC1EM@MCIMAIL.COM>
> Please help me understand this. With virtual memory I can >run programs
much larger than the physical RAM, yet don't >have a performance hit?
> Pray tell, where is the code if it is not in swap space on the disk?
Hmmm...I'm sure this all has SOMETHING to do with Contesting.
There's an old saying that says "A little knowledge is a dangerous thing"
It's obvious that somewhere, you've heard a little about virtual memory and
swap space.
Sometimes, if you don't know a whole lot about something, it's better to do
a little quiet research on the side to learn about it, rather than "go off"
in public, and expose what you don't know.
Howie, WB2CPU, is 100% correct in his statement: "Modern O/S's (OS/2, NT,
Win 95, Unix, Mac Sys 7, etc.) use virtual memory schemes where you can run
programs much larger than the machine's physical RAM size and without a
significant performance penalty."
This is accomplished by the design and inclusion of highly sophisticated
memory management schemes, and of even more elegant statistical algorithms
which support those schemes. Examples of this functionality inlcude keeping
track of each loaded page - which pages are being used the most, which are
"LRU" (Least Recently Used) memory pages, "Dirty Pages" (pages of memory
whereby the contents have changed) and on and on. There's an alphbet soup
of initials to describe each of the different types!
The basic concept is extremely simple, although the details are far beyond
my level of knowledge: the O/S tries to "guess", via statistical methods,
which pages of memory you are going to need NEXT. It attempts to keep them
in RAM, and, if there's not enough physical room, it then tries to pick the
page or pages which it thinks you WILL NOT need right away, and swaps them
out to disk. While it's doing this, it's also trying to optimize its
performance by keeping disk WRITES to a minimum - it will refrain from
writing a "Dirty Page" to disk until there is some quiet time, unless it's
forced to to make room for a chunk of memory which is statistically more
likely to be needed.
If it is a good O/S, it will "guess" right a vast majority of the time; the
pages you need will be in memory when you need them, your performance will
be top-notch, and you'll never have known that some of your memory resided
in a swap file. If it doesn't guess right, then you've got a little
heartburn in your life, and probably some "tweaking" of some tunable
parameters of the O/S in you future.
Class dismissed.
73,
Steve KC2X
ssacco@mcimail.com
>From biss@epg.nist.gov (Robert Biss) Mon Aug 21 16:43:26 1995
From: biss@epg.nist.gov (Robert Biss) (Robert Biss)
Subject: Grounding again
Message-ID: <Q038E1DF@washer.NIST.GOV>
----------
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Hi All, I've been reading all of this grounding info and something occured
to me about this new CONTEST station that I am building in WV....
I have 390" of well casing going down into the earth on a well that is 486'
deep. I have a ground lead from the casing to the ground rod at the
electric meter, (some 35'away) is that at all good or bad??? Should I not
tie them together?
Secondly, has anyone ever tried or had any success at using the well casing
as a counterpoise for a top band vertical? or any other band....
Many thanks in advance for your thoughts and input.
73's....bob K3ZNV
BISS@EPG.NIST.GOV
>From n6ig@netcom.com (Jim Pratt) Mon Aug 21 21:47:37 1995
From: n6ig@netcom.com (Jim Pratt) (Jim Pratt)
Subject: S-Meters, Piece Corrections
Message-ID: <199508212047.NAA14406@netcom5.netcom.com>
> on using dBm as an S-meter unit. Also has
> been pointed out that I typed 500 kHz
> when I intended 500 Hz as the bandwidth used
> by many (most?) CW ops when S&P contest
> operating or digging out DX. Also managed to
>
> Mahalo and 73, Jim, AH6NB
>
>
Rumor has it that K3ZO uses the 500 kHz mode... :.)
73, N6IG
>From ironsp@fox.nstn.ns.ca (Phil Irons) Sun Aug 20 00:25:26 1995
From: ironsp@fox.nstn.ns.ca (Phil Irons) (Phil Irons)
Subject: Msg from TF3KX
Message-ID: <199508212225.TAA25151@Fox.NSTN.Ca>
The following message appeared in my mailbox...I don't know if it was given
circulation to the entire reflector. If not, here it is...if it was, I
apologize for the repetition.
>From: owner-cq-contest@tgv.com
>Apparently-To: <ironsp@FOX.NSTN.NS.CA>
>
>I need one of those maps that has my QTH in the center and shows=
propagation
>directions as straight lines - the one where Australia ends up encircling
>the earth and beyond that you fall off into the black hole!! Sorry, but I
>don=B4t recall what the proper term is (...centric something?).
>
>Anyway, I know there are some programs around that can custom print this. =
I
>would like to copy such a program through the internet or, if someone can
>make me a map, I would like to copy it through the net. This would do in
>the short term. In the long term, if someone knows who sells such=
software,
>please let me know.
>
>My location is just south of Reykjavik, Iceland. Lat: 64N, Long: 22W
>(approximately).
>
>Thanks and 73 de Kristinn, TF3KX (kiddi@marel.is)
>
>
Phil Irons VE1BVD
Sydney, NS Canada
B1P 1Y6
One of these days my ship will come in...
with my luck I'll be waiting at the airport!
>From n1jm@future.dreamscape.com (John Merrill) Tue Aug 22 00:16:07 1995
From: n1jm@future.dreamscape.com (John Merrill) (John Merrill)
Subject: CQWW Results
Message-ID: <199508212311.TAA21900@future.dreamscape.com>
Congratulations to K1AR. I wonder if an employee of CQ operating in a CQ contest
would be considered a conflict of interest. HI. Only kidding.
John N1JM
>From Frank Donovan <donovanf@sgate.com> Tue Aug 22 00:29:22 1995
From: Frank Donovan <donovanf@sgate.com> (Frank Donovan)
Subject: Silent Beverages
Message-ID: <Pine.OSF.3.91.950821191723.7613B-100000@jekyll.sgate.com>
Hello Mario!
I haven't tried to develop a physical explanation of why certain Beverage
lengths produce a "cone of silence" at specific frequencies! The lengths
result from computer-based optimization! A velocity factor of 0.89 was
used for the optimization, which is typical for Beverage antennas.
Beverage antennas used in non-amateur applications really cannot take
advantage of the cone of silence property, because the phenomenon occurs
over a relatively narrow bandwidth, which is inconsistent with
non-amateur applications for the most part.
73!
Frank
W3LPL
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