[R-390] Nuvistaplug?

[Michael Murphy]

Mark,

I don't know if anyone talked about the voltage situation.
As far as voltage goes, the cascode circuit can be done in a parallel or
series bias configuration with good results. In the parallel, the stages are
usually cap coupled and each tube is given the full B+ voltage through a
choke or tuned circuit. In the somewhat simpler series cascode
configuration, sometimes preferred in VHF and UHF circuits, each stage gets
around half of the B+. The series circuit is commonly used with bipolar and
J-FET circuits as well.

Mike WU2D


----- Original Message ----- 
From: "Mark Huss" <mhuss1 at bellatlantic.net>
To: "pete wokoun, sr." <pwokoun at hotmail.com>; "r390 net"
<r-390 at mailman.qth.net>
Sent: Friday, December 23, 2005 8:22 AM
Subject: Re: [R-390] Nuvistaplug?


> The instalation manual and schematic is here:
> http://www.mines.uidaho.edu/~glowbugs/receivers.htm see item number 7.
> I figure you can either use it unmodified (will have to substitute
> 6CW4's for the 6DS4's, because the 6DS4's won't handle the higher B+
> voltage) and sacrifice AGC control of the first RF Amp, or you can
> rewire pin 8 of the first 6DS4/6CW4 to connect to the unused pin 2 of
> the seven-pin plug to restore some AGC operation.
>  In 2004, W3CRR was going to build one, and wondered if there was any
> interest in copies.
> Now, the 6CW4 has a higher noise than the 6DS4, but the 6DS4 is rated
> for only 135VDC plate voltage.  Can any tube gurus out there tell us if
> using a 6DS4 as the first tube and a 6CW4 as the second would be safe?
> This might give a better noise figure than two 6CW4's.
> Further thought tells me that most receiver locations would have an
> ambient noise at their location to make this no real improvement except
> above 20 MHz.
>
> pete wokoun, sr. wrote:
>
> > Never heard of this one.  Any chance you could scan the circuit and
> > make it available?
> >
> > pete
> >
> >
> >
> >> From: Mark Huss <mhuss1 at bellatlantic.net>
> >> To: R-390 at mailman.qth.net
> >> Subject: [R-390] Nuvistaplug?
> >> Date: Thu, 22 Dec 2005 21:21:08 -0500
> >>
> >> Here is one for all the experts.  A plug-in modification for SP-600's
> >> was the Nuvistaplug.  This was a replacement for the first RF
> >> amplifier in SP-600 that substituted a pair of 6DS4's in a cascode
> >> circuit.  The resulting 6 to 9 dB increase in Signal to Noise level
> >> made the SP-600 sound like a new receiver.  My brother recalls that
> >> there was a similar modification using a 6CW4 for the R-390A, popular
> >> with MARS operators.  I happened across the schematic today, and it
> >> looks like with changing one pin in the Nuvistaplug, you could drop
> >> in the replacement for the 6DC6.  This should increase the signal to
> >> noise level of the first RF Amp.  So has anybody even heard of this
> >> being attempted?
> >> _____________________________________________________________
> >> R-390 mailing list
> >> Home: http://mailman.qth.net/mailman/listinfo/r-390
> >> Help: http://mailman.qth.net/faq.htm
> >> Post: mailto:R-390 at mailman.qth.net
> >> Unsubscribe: http://mailman.qth.net/mailman/options/r-390
> >
> >
> >
> >
>
> _____________________________________________________________
> R-390 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/r-390
> Help: http://mailman.qth.net/faq.htm
> Post: mailto:R-390 at mailman.qth.net
> Unsubscribe: http://mailman.qth.net/mailman/options/r-390