[Heath] SB-610 monitor scope technical assist

[G3OOU at aol.com]

Hi Dick
 
Are you measuring/assessing the vertical sensitivity using a signal  
generator or a rig?
 
The resonant frequency of the tuned circuit using inductor L1 is  dependant 
on the capacitance of the coax cable connecting the SB610 to the rig  plus 
any coax inside that rig and the small coupling capacitor to the receiver  
last IF amplifier. If I recall correctly Heathkit recommended the use of high 
 impedance (93ohms) cable because it has a lower capacitance per unit  
length than conventional 50 ohm type. You need to get that tuned circuit to  
show resonance at the correct frequency in order to get the correct  
sensitivity.
 
Check the resonance with a GDO to see where it is currently located.
 
If you connect a signal generator to the vertical input the resonance of L1 
 will not be apparent because of loading by the generator output impedance, 
 typically 50 ohms.
 
73

Bob

Bob F Burns
C Eng,  FIET, MSE
Amateur Radio Callsign: G3OOU
Registered RSGB  Instructor
G-QRP Member No: 6907; Zone: 14, QRA: IO91WH; WAB:  TQ25
Secretary of Crystal Palace Radio & Electronics Club: _www.g3oou.co.uk_ 
(http://www.g3oou.co.uk/) 
Technical web site: _www.qsl.net/g3oou_ (http://www.qsl.net/g3oou) 
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