[Hammarlund] NuvistaPlug & more

[jeremy-ca]

The 6BA6 was later followed by the 6BZ6 and Collins liked the 6DC6. All 
provided improvements over the 6BA6.

For ultimate NF improvement a FET with associated circuitry can be mounted 
on an adaptaplug or similar and require no receiver changes.

Carl
KM1H
----- Original Message ----- 
From: <rrkrr at comcast.net>
To: "ChasW3KC" <w3kc at verizon.net>; "hammarlund" <hammarlund at mailman.qth.net>
Cc: <glowbugs at piobaire.mines.uidaho.edu>; "ChasW3KC" <w3kc at verizon.net>
Sent: Friday, November 09, 2007 11:00 AM
Subject: Re: [Hammarlund] NuvistaPlug & more


> The stock 1st RF amplifier tube in the SP-600 was a 6BA6 - a remote cutoff 
> pentode.  The 6BA6 has a relatively high noise figure which becomes a very 
> significant limitation to receiver MDS above 20 MHz or so.  The 
> "Nuvistaplug" used two 6DS4 remote cutoff Nuvistor triodes connected in 
> cascode, which gave good gain, much improved noise figure, and high 
> reverse isolation for the 1st RF amplifier.  The Nuvistaplug was sold as a 
> tube socket plug-in replacement for a number of 7 pin tubes.  The tube 
> socket connections of the Nuvistaplug must have been adaptable to the 
> particular device to be replaced.
>
> The British companies Racal and Eddystone liked to use cascoded triodes 
> for 1st RF stages in their receivers.  They used the ECC189 (American type 
> 6ES8) which is a single 9-pin miniature tube containing two triodes that 
> are designed to be connected in cascode.  In order to use this tube in an 
> SP-600, the 7-pin 1st RF amp tube socket would have to be replaced with a 
> 9-pin, and the resulting noise figure would probably not be as good as 
> that for the Nuvistor.
>
> The 2nd RF amp in the SP-600 is also a 6BA6, but with the gain of the 1st 
> RF amp in front of it, the noise of the 1st RF amp dominates, so it's not 
> worth replacing the 2nd RF amp with a lower noise device.
>
> Bob K4ERR
>
>
> -------------- Original message ----------------------
> From: "ChasW3KC" <w3kc at verizon.net>
>> For the SP-600, what tube type did the NuvistaPlug replace?
>> Was it ever used in radios other than the SP-600?
>> As I recall,  Ameco used to make a preamp that used
>> nuvistors
>> (the Ameco preamp I have is solid state and I think it came
>> out later).
>> TNX/73 de Chas W3KC
>>
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