[R-390] Nuvistaplug?

[Mark Huss]

FOOOD...FIGHT!!!!

rbethman at comcast.net wrote:

> Poor SP-600 owner?  Mine works on par with my R-390A.
>  
> Bob - N0DGN
>  
>
>     -------------- Original message --------------
>     From: Mark Huss <mhuss1 at bellatlantic.net>
>
>     > In that case, the 6DS4 or 7963 may well work. Now, if Anybody runs
>     > across a Nuvista-Plug, Stock number 5960-H00-9058, grab it so we
>     can
>     > drop it into an R-390A and see how much improvement we get. I'm
>     betting
>     > there will not be that much, but would be interested to find
>     out. And
>     > if not, then one can always sell it to a poor SP-600 owner so
>     that he
>     > can get reasonable performance out of his receiver;)
>     >
>     > Michael Murphy wrote:
>     >
>     > >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"
>     > >To: "pete wokoun, sr." ; "r390 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
>     > >>>>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?
>     > >>>>_____________________________________________________________
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>     > >>>>
>     > >>>
>     > >>>
>     > >>>
>     > >>>
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>     > >
>     > >
>     >
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