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Measuring received signal strength: "the Scrot" (also dBs)




 
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Author Topic: Measuring received signal strength: "the Scrot" (also dBs)  (Read 6865 times)
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AB2EZ
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« on: March 26, 2006, 06:47:24 AM »

In the scientific community, there occasionally comes a time when old units of measurement need to be refined or redefined (e.g., to make the measurements more accurately reproducible), or when new units of measurement need to be defined.

It is time that the AM community adopt a unit of measurement of received signal strength... which more accurately aligns with the goals of real AM operators; and which aligns more closely with the measurement capabilities of the receivers used by real AM operators.

I propose that such a unit is the "Scrot", named after the legendary 12th century AM operator: Manly Scrot. [Rhymes with "boat"]

One (1) Scrot will correspond, objectively, to a received signal level that pins the signal stength meter on a typical, unmodified R-390 receiver. This signal level has been empirically determined to be somewhere around 10 millivolts. However, in day-to-day use, 1 Scrot will be defined as the signal level that just barely pins the received signal strength meter on a given receiver.

Since it is the objective of every AMer to consistently produce a received signal level of 1 Scrot or greater, at all times, on all receivers... received signal levels less than 1 Scrot will be characterized and reported as: decibels below 1 Scrot (-dBs). A signal that produces a reading on a received signal strength meter that is 10dB below the level required to pin the meter on that receiver will be reported as a received signal level of -10 dBs ("minus ten dee bee ess").

Comments?

Stu
AB2EZ
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W1UX
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« Reply #1 on: March 26, 2006, 10:36:19 AM »

A good application on your part of this new unit of measurement, Stu, on this morning's AM Carrier Net.

A signal that actually achieves one scrot (note: should be pronounced "SCROAT" - do you agree?) should set off an AVC voltage derived relay controlled bell in the receiving station's shack.A LOUD one. Should be easy enough for an engineer or bona fide AM amchur to do.

I have one R390A with the meter calibrated to NEVER achieve one scroat. The response curve is asymptotic; doubling the TX power output, generating a 3db increase at the receiving end, barely moves the S meter once it's up in the S9_45 db equivalent range. Doubling it again, moves the meter even less, and so on.

Another 390A is set up to give ALMOST everyone a one scroat response. This is a touchy-feel-good kinda thing useful on Sundays especially when Good Will Towards Men prevails, except of course on parts of 75 meters....

Both receivers incidentally are equally sensitive and are capable of producing Q5 signal reception with only 0.005 nanovolts at the antenna terminal.

73
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Al "Al" (Al)  W1UX..... over, OVER!!! anyone OUT THERE? hi hi ha ha hee hee ho ho haw haw DAMMIT! Where'd that FLY come from?!?!?
KB2WIG
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« Reply #2 on: March 26, 2006, 11:57:54 AM »

received signal levels less than 1 Scrot will be characterized and reported as: decibels below 1 Scrot (-dBs). A signal that produces a reading on a received signal strength meter that is 10dB below the level required to pin the meter on that receiver will be reported as a received signal level of -10 dBs ("minus ten dee bee ess").

Comments?

 While the  signal level of one Scrot is a gud point for the reference level, I think the lower levels, being that it (they) is less than 1 Scrot, should be termed Scrot-less ie, 10 dB Scrot  less.....        klc
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KL7OF
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« Reply #3 on: March 26, 2006, 12:29:51 PM »

SCROT?......SCROAT....or SCROTE?..(Rhymes with boat)
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K1JJ
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« Reply #4 on: March 26, 2006, 01:34:23 PM »


Tuning across the band might become a lively experience if the S-meter relay controlled a pair of 600V clips that snapped across the sack.

T
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Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed. 

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« Reply #5 on: March 26, 2006, 09:15:46 PM »

The scrote indication device should be designed to hang lower with increasing age of the receiver.
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W1UX
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« Reply #6 on: March 27, 2006, 09:25:54 AM »

Anyone who achieves ONE SCROAT is entitled to receive, absolutely free of charge (except for a $12.95 shipping and handling fee) one of these:

http://www.bullsballs.com/real/big/truck/balls5.html

If you act NOW, you'll also receive, ABSOLUTELY FREE, one set of RADIO CONDOMS for your Cod! Remember, practice SAFE RADIO!
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Al "Al" (Al)  W1UX..... over, OVER!!! anyone OUT THERE? hi hi ha ha hee hee ho ho haw haw DAMMIT! Where'd that FLY come from?!?!?
WA1GFZ
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« Reply #7 on: March 27, 2006, 09:30:24 AM »

does it count if you monitor yourself and you hit 1 scrot.
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