[AMRadio] HRO question for the day

Bernie Doran qedconsultants at embarqmail.com
Thu Dec 17 22:53:52 EST 2009

Hi John: from I can gather, it appears that National did this same thing 
with at least several other rx.   6h6s are cheap, but a fast diode would 
work fine if needed. National had to have a reason for this, s-meter zero 
can be taken care of in many other ways. 73 Bernie
----- Original Message ----- 
From: "John Coleman" <jc at pctechref.com>
To: "'Discussion of AM Radio in the Amateur Service'" 
<amradio at mailman.qth.net>
Sent: Thursday, December 17, 2009 7:15 PM
Subject: Re: [AMRadio] HRO question for the day

>I can see a small amount of contact bias being generated by the 6H6, 6AL5,
> etc.  But that would be easy to compensate with divider from the cathode
> bias of the output tubes or any small positive source.  I guess they may
> have been looking for an easy fix to get the S-meter to zero.
> This is all very interesting but why not just solder in a Germanium 1N64 
> or
> a NTE109 or Silicone NTE177 or even a NTE519 with 4 ns recovery time.  I
> pulled the 6AL5 out of my HQ170 and went to diodes. Saving 150ma of heater
> current WEEEE.
> I ask this sincerely because I really don't know.
> What would be the disadvantage of using small signal solid state diodes as
> long as the IF frequency isn't too high.
> John
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