[ARC5] R-23/ARC-5

[CARL HUETHER]

On March 2, 2019 at 11:11 AM CARL HUETHER <k1uhy at comcast.net> wrote:
 
 
50-60 years ago most hams didnt understand the concept of useable sensitivity versus frequency.
 
The hottest octal tube setup while still having good AGC on the RF amp was the 6/12SG7 and 6SB7Y mixer/converter. Some preferred the 717A which negated the usual AGC circuit. It was a 6AK5 laid over on an octal base. For 7 pin miniatures the 6GM6 and 6BY6 is the hot setup.
 
I converted a 1947 NC-240D about 25 years ago to the 6SG7/6SB7Y and it is still a hot performer on 20-30 MHz and used mostly on 10M AM.

I never felt the need to do any ARC-5 tube mods due to the low frequencies involved.

Carl 

 
> > On March 1, 2019 at 1:59 AM Robert Downs via ARC5 <arc5 at mailman.qth.net> wrote:
> > 
> > 
> > The 12SG7 (equivalent to a 12BA6 except for base and envelope) might have
> > helped the performance of the 10-meter conversion a little bit, but only if
> > some other component values were also changed.
> > 
> > Robert Downs
> > 
> > 
> > -----Original Message-----
> > From: arc5-bounces at mailman.qth.net [mailto:arc5-bounces at mailman.qth.net] On
> > Behalf Of Kenneth G. Gordon
> > Sent: Thursday, February 28, 2019 19:20
> > To: Arc5 at mailman.qth.net
> > Subject: Re: [ARC5] R-23/ARC-5
> > 
> > On 28 Feb 2019 at 20:01, Mike Morrow wrote:
> > 
> > >     current balancing resistor.  However, there should 
> > >     have been little motivation for increased RF stage 
> > >     gain in an R-23.
> > 
> > This is absolutely correct. My rebuilt BC-453B can "hear" a 0.1 microvolt CW
> > signal with all 
> > stock original tubes.
> > 
> > https://www.youtube.com/watch?v=vlz83QXM66A
> > 
> > I also have a BC-454 which someone attempted to modify, back in the 1950s,
> > to cover 10 
> > meters. After I did some work on it to finish the original owner's project,
> > with the original 
> > 12SK7 RF amp, it easily copies a 1 microvolt CW signal.
> > 
> > I can think of no good reason to change the RF amp to any other tube.
> > 
> > Ken W7EKB
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