[Elecraft] Anne Marie Sullivan and Logs (XG-1 Question) - Update

Wed Jan 28 21:16:00 2004

Hi again,
 Well maybe its -138 which looks like I'm ok (and -198 wouldn't have been
stinky, but perhaps something for the K2 hall of fame).

Anyway if someone could double check me I'd appreciate it -- I'm off to the
phone book to track down, you-know-who

Tom

-----Original Message-----
From: Tom Mc <[email protected]>
To: [email protected] <[email protected]>
Date: Wednesday, January 28, 2004 8:40 PM
Subject: [Elecraft] Anne Marie Sullivan and Logs (XG-1 Question)

Hi guys,

  Well I'm trying to determine the MDS of my K2 and it seems that during
High School trig I spent more time daydreaming over Annemarie Sullivan than
learning logarithms.

So could someone please help me out.

The readings I'm getting from the K2 are N (Noise only no XG1 ) about .016
Vrms.  and S+N (Signal and noise with the XG1 on at 1 uV) of .590 Vrms.

I can't even follow the instruction sin the XG1 manual, but here they are:

A) Divide S+N by; call the resulting ratio R  ( I come up with 39.33 - so
far I think I'm OK)

B) Take the base-10 logarithm  of R ("log" key on most calculators)

C) Multiply the result by 20 to obtain the S+N/N at 1 microvolt in dB.

D) If the S+N/N is greater than 10 dB then the MDS is approximately equal to
result from (C) subtracted from -107 dBm.

Well I do all of this and I come out with an MDS of -198, which is pretty
stinky, I think.

I should also admit, that the example in the manual is totally mystifying to
me as it seems to be using numbers that just appear out of thin air (e.g.
if Step "B" says log(30) = 1.52, then why are they using 1.48 in step "C"?
And what the heck is the 30 in "log(30)".) -- OK I know, I should have paid
attention in class, but ohhh you should have seen Annmarie.

Before I go pulling everything apart, cam somebody please tell me if my math
is OK?

Thanks for your help.

Tom

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