[R-390] Nuvistaplug? Other possible tubes.

[Mark Huss]

I thought about 7963's as well, but for two factors.  First is that I 
don't know of a good way of reducing the 150 volt B+ to under 100 
volts.  The second is personal experence.  Two receivers, part of the 
TRQ-23, that I worked on in the Army, used peanut tubes like the 7963.  
Every time I pulled them in for annual maintenance, I always had to 
replace several of the peanut tubes for low gain.  It is like they don't 
last as long when you run them for any length of time.  It could have 
been the receivr circuits were designed too critical.  I don't know.

Kenneth G. Gordon wrote:

>Mark Huss wrote:
>
>  
>
>>The installation 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.
>>    
>>
>
>I am thinking that a better, much lower-noise, Nuvistaplug could be 
>made using a single 7963 submini dual triode instead of the Nuvistors.
>
>The 7963 has far higher transconductance, 13000, than either of the 
>two Nuvistors mentioned. However, its maximum rated plate voltage is 
>only 100 VDC, so allowances would have to be made for that.
>
>Go here:
>
>http://pw2.netcom.com/~wa2ise/radios/penciltubes.html
>
>for details on submini tubes.
>
>And thanks for the plug to the Glowbugs web site. I administer that.
>
>Ken Gordon W7EKB
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