[hpsdr] Mercury Level Cal

[K1rqg at aol.com]

Alexander
 
50 micro volts = -73 dbm (S-9) when using the XG-2 
 
73 de Joe K1RQG
 
In a message dated 2/28/2009 2:00:42 P.M. Eastern Standard Time,  
alexander.geckeler at gmx.de writes:

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Hello  Ben,

thanks for your suggestions.
I bought an Elecraft XG-2 and will  use it as a signal source.
At what what output level it should be used -  1microV or 50 microV to 
calibrate  Mercury?

Alexander



-------- Original-Nachricht  --------
Betreff:     [hpsdr] Mercury Level Cal
Datum:    Sat, 28 Feb 2009 13:42:31 -0500
Von:     W4sc  <www4sc at alltel.net>
An:     HPSDR Reflector  <hpsdr at hpsdr.org>



***** High Performance Software Defined  Radio Discussion List *****

All,

In level calibration of Mercury  RX, be aware of the following that may
leave you with a less than optimal  calibration. A good, consistant
calibration could not be obtained while  attempting on 14.2MHz at -70dbm.

If you use a signal generator  connected via a cable, make sure the
inter-connecting cable is of good  quality and condition and no longer than
required.  In the specific  case, it was determined that the interconnect
cable (RG-58)  had a bad  connector, and the shielding effectiveness was not
good enough. Leakage  into the setup from external sources (ie computer
clocks, and  general
electrical noise, external radio signals ect, ect.) should be  eliminated.
Level calibration was being attempted on 14.2 MHz, and in this  particular
case the 20M band seems rife with computer and other external  noise.
Possibly due to the 14.314MHz crystal osillator within the host  itself.

Level calibration was eventually performed at 15MHz, first at  -70dbm, then
at -90dbm.

The following is suggested to mitigate this  leakage problem:

1) Use a good quality inter connect cable, such as a  double shielded RG-142
This can give about 20db better isolation over RG-58  type cable.
2) Use the Elecraft signal generator (XG1 or XG2) connected  directly to
Mercury.. This will eliminate the interconnect. Be sure of the  SGx output
level.  This setup may also benefit from having a shield  around the
generator.
3) Find and use a "quiet" frequency.


de  Ben W4SC




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