[AMRadio] HRO question for the day

[sbjohnston at aol.com]

> 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.

Could it be there to stop the formation of a parasitic diode between 
the cathode and heater?

Steve WD8DAS

sbjohnston at aol.com
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-----Original Message-----
From: k4kyv at charter.net
To: amradio at mailman.qth.net
Cc: amradio-request at mailman.qth.net
Sent: Thu, Dec 17, 2009 1:43 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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