[Elecraft] XG1 Observations

Thu Jan 29 17:01:20 2004

Hi Vic.  I didn't - and - probably should have!  I think you are on to
something here!  Could be that the 20 meter results could better be
expressed as -138.8 (-131.8 - 7) and -130 (-123 - 7) because we are using
the 2nd harmonic which is about 7 dB down from the 1 microvolt at 7040 and
the "formula" is based on a 1 microvolt signal.

Just as a side note, I put it on my old trusty KWM-2 (born Sept 1961) and
the S meter was right on at 50 microvolts for S9 on 40 and showed S8 on 20
(about the 7 dB down as predicted - the Collins supposedly runs a nominal 6
dB per S unit).  Have not done the MDS on it yet but can tell you that it
"hears" the 1 microvolt signal about the same as the K2 does on both 40 and
20. 'Course, the K2 is way better at close strong signals, etc! - that young
whippersnapper!

Bet those that who knowledgeable about measuring MDS will chime in and hope
they do!  (Actually, as I understand it we are not actually "measuring" the
MDS but "predicting" or "inferring" it from the "formula" - how else to
explain subtracting from -107 dBm (wondered where that came from).  In
addition, we are multiplying the ratio by 20 to get it in dB at 1 microvolt.

By the way - the spreadsheets that Dave (K9FZJ) put together for both the
DL1 and the XG1 work very well.  I did run separate calculations for each
and it looks like his formula interpretation for both is right on!  Thanks
Dave - good job!  You can email Dave at [email protected] and he will send you
copies of each.  They really do make life easy - 'course you could always
set the formula up on a programmable calculator and save some aggravation
that way too.

In a way this could all be just an "academic" exercise since actually
hearing something depends on the noise floor to begin with.  It is
interesting to look at the K2 using Spectrum Lab (software package) and to
note that as far as I can tell, the noise floor shown there as a base line
is around -102 dB +/- or is it dBm?  (could this be where the magic "-107
dBm" used in the formula comes from??)

Could we hear from the really knowledgeable - how do we do the MDS on 20
meters?  And - anyone else have the "areas" of "staticky" noise around 14035
and 14080?  73  --don n4hh K2/100 #2028

----- Original Message ----- 
From: "Vic Rosenthal" <[email protected]>
To: "Donald Nesbitt" <[email protected]>
Cc: "Elecraft" <[email protected]>
Sent: Thursday, January 29, 2004 2:12 PM
Subject: Re: [Elecraft] XG1 Observations

> Donald Nesbitt wrote:
>
> > MDS level was measured as -142 dbm with preamp on and -138 dbm with
preamp
> > off on 7040 using the setup noted in the manual - wonder if this is
typical
> > on 40?   On 20 meters, results were a disappointing -131.8 dbm with the
> > preamp on and -123 dbm with the preamp off.
>
> How did you take the 7 db reduction in signal into account when you did
>   the calculation for 14 MHz?  Or is it unnecessary?
> Vic, K2VCO
> Fresno CA