JIMMIE wrote:
On Mar 27, 12:43 pm, Joerg
wrote:
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.
From vague memory I think Geloso used them a lot and got a little under
4dB out of those on 144MHz. In case anyone needs a datasheet:

http://www.r-type.org/pdfs/6cw4.pdf

--
73, Joerg- Hide quoted text -

- Show quoted text -

Thanks, I was just trrying to finish up a project I started years ago,
my wife had been getting on to me about not completing what I start.


Somehow this sounds quite familiar :-)


Tinkering with the nuvistors also sounded like fun. Well I now realize
why you dont see projects based on them and noone is scouring the
tables at the hamfest looking for nuvistors. There are better/easier
of ways of skinning this cat. A DC to Daylight preamp using a MMIC
may well have better NF and gain.


True, but tubes and even those tiny ones do have one distinct advantage.
When a thunderstorm rolls through town or you accidentally transmit into
your pre-amp their chance of survival is orders of magnitude higher.
Just imagine, when placing a hard 50V spike onto the grid a tube won't
even flinch. A GaAs-FET or MMIC? Tsssk ... *BANG*.

I realized this early on after getting my license. The transistor in the
pre-amp on the roof had died for the umpteenth time during a
thunderstorm. But this time the moss on the roof was quite thick and I
almost slid down. Whew! That did it. Built one with a tube (army
surplus, NOS, long lifetime version), and it never died again. Oh yeah,
and more than once did I accidentally transmit into the back of it. Left
it completely unfazed. Losing a dB or two in noise figure for the sake
of not having to scale that roof was well worth it :-)

I have seen Russians offer cartons full of nuvistors on auction sites,
they almost look like bonbon boxes. They must have a sizeable stash of
those over there.

--
73, Joerg