[AMRadio] HRO question for the day

Bernie Doran qedconsultants at embarqmail.com
Mon Dec 14 10:08:52 EST 2009

National decided in the HRO50 design to use a 4.3 Ohm resister in series 
with the fil of both 6H6  dual diodes, ( noise blanker and detector) 
dropping the fil to about 5 v.   In the Hro 50-1 the noise blanker 6h6 
operates at normal Volts and the detector still at reduced voltage. I see no 
reason for this and the tube data sheets do not address lower volt 
operation. only effect I notice is that it takes several minutes for the 
detector to warm up and produce audio. It can not be for life as when this 
was designed and built 6h6s were cheap, still are.  certainly not to save 
energy or battery operation.  perhaps it fools the detector into something 
other that a square law detector due to low emission.  tube life would be 
extended, but so what, this is not a transmitting valve and the only one I 
have seen where reduced voltage is recommended for standby is the 813, data 
recommends 8 volt when on standby and I have never done that or seen one 
used that way.  So does anyone KNOW why national did this?    I have never 
seen this in Collins so it must be wrong!!!! HI   Bernie W8RPW 

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