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

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.
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.

Jimmie

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

On Tue, 31 Mar 2009 20:37:58 -0700, Joerg
wrote:

JIMMIE wrote:
On Mar 27, 12:43 pm, Joerg
wrote:

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

According to this page
http://www.amsat.org/amsat/archive/a.../msg00451.html
Geloso got 3.6 dB@50/144 MHz to 6.0 dB@432 MHz.

The VHF numbers are still usable at terrestrial VHF communication due
to the high band noise. For satellite and EME communication, the
performance it not very good at VHF and practically useless on UHF.


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*.

Most part of the lightning electromagnetic radiation is at quite low
frequencies (below 1 MHz) and a typical VHF/UHF antenna will have a
quite low effective height at such low frequencies, thus not much low
frequency energy should enter the preamp.

However, during thunderstorms, quite large static charges can be
accumulated in ungrounded antenna elements and if there is a DC path
to the transistor, there is a significant risk of damage.

Using a folded dipole and grounding the center point will reduce the
static build up. The folded dipole will also act as a very small
magnetic loop, reducing the LF pickup of the lightning EM pulse. A
strong DC path (such as a shorted 1/4 wavelength stub) from the
amplifier input to ground will also reduce the DC and low frequency
pickup, thus reducing the risk for dangerously large voltages at the
transistor base/gate.

Paul OH3LWR

Paul Keinanen wrote:
On Tue, 31 Mar 2009 20:37:58 -0700, Joerg
wrote:

JIMMIE wrote:
On Mar 27, 12:43 pm, Joerg
wrote:

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

According to this page
http://www.amsat.org/amsat/archive/a.../msg00451.html
Geloso got 3.6 dB@50/144 MHz to 6.0 dB@432 MHz.

The VHF numbers are still usable at terrestrial VHF communication due
to the high band noise. For satellite and EME communication, the
performance it not very good at VHF and practically useless on UHF.


Although back in those days UHF was reserved for the more well-heeled
hams. I thought the 2m performance that old John got out of the
nuvistors was pretty good.


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*.

Most part of the lightning electromagnetic radiation is at quite low
frequencies (below 1 MHz) and a typical VHF/UHF antenna will have a
quite low effective height at such low frequencies, thus not much low
frequency energy should enter the preamp.

However, during thunderstorms, quite large static charges can be
accumulated in ungrounded antenna elements and if there is a DC path
to the transistor, there is a significant risk of damage.

Using a folded dipole and grounding the center point will reduce the
static build up. The folded dipole will also act as a very small
magnetic loop, reducing the LF pickup of the lightning EM pulse. A
strong DC path (such as a shorted 1/4 wavelength stub) from the
amplifier input to ground will also reduce the DC and low frequency
pickup, thus reducing the risk for dangerously large voltages at the
transistor base/gate.


The trouble in my case was that this thing was also used for the upper
shortwave bands, when doing duplex transmissions. Similar to what is
nowadays called an active antenna. I didn't have the space for a 2nd
large antenna, the first one was already quite a stretch. This was in
Germany where properties are quite tiny.

--
73, Joerg

On Mar 31, 11:16*pm, 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.
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.

Jimmie- Hide quoted text -

- Show quoted text -

OH, what the heck,Since I got the preamp stage built I might as well
build a 2M to 10M rx converter.

Jimmie