[Elecraft] VCO voltages for 160m band??

G3VVT at aol.com G3VVT at aol.com
Tue Sep 14 10:42:10 EDT 2004


 
I needed to open up my K2 serial no. 4168 to tinker with the AGC threshold  
setting so took the time to measure what the VCO voltages at R30 were on  160m.
The results are:
                        1800kHz  = 1.68V
                        2000kHz  = 3.83V
 
On my particular K2 on initial testing the lowest reading VCO voltage  
reading came out on 7000kHz rather than 3500kHz so made that the reference  setting 
at 1.50V. This shifted up 3500KHz to 2.40V and 4000kHz to 6.85V. All  still 
within the stated goal posts.
 
As a side issue the optimum AGC threshold seemed to be at 3.70V rather than  
the initial 3.80V on this K2. Another item noticed during testing was that 
even  with the S LO and S HI correctly adjusted for the new threshold the signal 
level  required for S9 reduced with lower threshold settings. On this K2 with 
the  preamp off the settings for S9 came out as follows:
 
AGC threshold V.    uV PD for S9.
3.80V                        63uV  (-71dBm)
3.70V                        40uV  (-75dBm)
3.60V                        25uV  (-79dBm)
 
With the new setting of 3.70V the audible low level band noise  from AGC on 
to AGC off is just reached the point of no change. This compares  with the 
initial AGC threshold setting of 3.80v, where there was  a small increase in noise 
when the AGC was switched off.
 
Bob, G3VVT
K2 #4168



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