On Mar 27, 10:37*am, raypsi wrote:
On Mar 27, 8:22*am, JIMMIE wrote:





On Mar 27, 3:59*am, JIMMIE wrote:

On Mar 18, 10:50*pm, RFI-EMI-GUY wrote:

JIMMIE wrote:
I have 3 mast mounted nuvistor pre amps less power supplies. I was
looking for information on these to convert them to use on the 6 and 2
meter *and 70cm ham bands. I may still have a power supply around but
as of yet I havent been able to find it. The pre amps are mount in a
somewhat egg shaped plastic container with twin lead connections on
them. Im not sure of the manufacturer. Schematics on the amplifiers
and power supplies would be nice. Directions on doing the mod would be
great. There are plans for ham band nuvistor preamps around so if I
could figure out what I have it shouldnt be that difficult to conver
it to what I want. Besides that it will give me something to do with
these old 6cw4s.

Jimmie

You would do good to find a 70's or earlier ARRL handbook. There were
many articles about Nuvistors.

--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"©

"Use only Genuine Interocitor Parts" Tom Servo *;-P

Well I got a little 2M nuvistor pre-amp put together last night. Im
not sure of the noise figure of the amp but according to my S meter it
must have about at least 20 db of gain, maybe 30.

I will have to take it into work were I have the *test equipment to
check it out better.

Jimmie- Hide quoted text -

- Show quoted text -

Anyone know what kind of noise figure I could expect out of a 6cw4
nuvistor preamp. I only saw one reference and it mentioned 3db but
mostly all the other references just talked about gain.

Jimmie

Hey OM

The reason you see those high noise figures: Carbon comp resistors
being used in tube circuits. The gain of the preamp amplifies the
noise of the carbon comp resistors. Best is to use metal film
resistors much lower noise.
And squeezing 20db out of a 6cw4 that has only gain of around 64 or
about 14 db is quite the feat.

73 OM
de n8zu- Hide quoted text -

- Show quoted text -

Yeah I used metal film on my preamp. I tossed all of my carbon
resistors a few years ago after I fixed a guitar amp for a friend and
he brought it back telling me how noisy it was. I traced the problem
back to the NOS(40 years) resistors I had used.

Like I said those were S meter db. )

Jimmie