[AMRadio] HRO question for the day

Bernie Doran qedconsultants at embarqmail.com
Thu Dec 17 16:32:59 EST 2009

----- Original Message ----- 
From: <k4kyv at charter.net>
To: <amradio at mailman.qth.net>
Cc: <amradio-request at mailman.qth.net>
Sent: Thursday, December 17, 2009 2:43 PM
Subject: Re: [AMRadio] HRO question for the day

>> 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
> I vaguely recall having the same question years ago when I was helping 
> Roger, N4IBF(SK) with his, and learning that the resistor was there for a 
> good reason, but I don't have a clue what it was now.  Hopefully someone 
> will have the info.
> Don
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