[Milsurplus] 991 neon lamp

[Mike Feher]

John -

I went downstairs into the dungeon and low and behold, in spite of the
flood, I found the box where I thought some 991s may lurk. I grabbed 4 of
them and tested just two. Those two both worked fine. One is made by Kuthe
Labs and the other by RCA. The KL one struck at about 84 volts and regulated
at 65 volts through a 20K limiting resistor. The RCA struck at about 75
volts and regulated at 55 volts through the same resistor. You are welcome
to either, but, I expect you would prefer the RCA. Send me your address and
I'll have it in Tuesday's mail. - Mike

Mike B. Feher, N4FS
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960




-----Original Message-----
From: milsurplus-bounces at mailman.qth.net
[mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of J. Forster
Sent: Saturday, January 16, 2010 1:09 PM
To: 'milsurplus'
Subject: Re: [Milsurplus] 991 neon lamp

For those intetrested in relatively current Noise measurement, there is an
AILtech Group on Yahoo.

However noisy, I'd still like a couple of NE-16 / 991s for my ARB.

-John

===============

> Of course I can see how that may well be true, as gaseous tubes have been
> used as broadband noise sources for years, especially the fluorescent
> types.
> Still, their ENR is doubtfully great enough to overcome a WWII front end
> NF
> and even the atmospheric noise prevalent there. Of course, zeners have
> been
> used as noise sources as well and the choice for state of the art noise
> sources is a solid state diode. Heck, even a tube filament or a light
> bulb,
> generates considerable ENR above kT (where T=290K). In the 70's there was
> an
> article in "Ham Radio" magazine as to how to make a noise source from an
> incandescent light bulb. I built that circuit and used it to measure the
> NF
> of some of my UHF preamps. I personally have not experienced a noise
> problem
> by the 991s in the 348s that I used in the past. I suppose this is not
> really OT in this forum. 73 - Mike
>
> Mike B. Feher, N4FS
> 89 Arnold Blvd.
> Howell, NJ, 07731
> 732-886-5960
>
>
>
> -----Original Message-----
> From: milsurplus-bounces at mailman.qth.net
> [mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of Richard Brunner
> Sent: Saturday, January 16, 2010 11:16 AM
> To: milsurplus
> Subject: Re: [Milsurplus] 991 neon lamp
>
> The 991 neon lamp is actually a voltage regulator rated 55 to 60 volts
> at 2 ma, with 87 volts striking voltage.  They recommend changing at
> 1000 hours.  My experience is they drift up in operating voltage with
> use and time.  Ones I have tested regulated between 80 to over 100
> volts.  I doubt an old one can be found in as-new condition, and would
> use a Zener.  I also read that in the BC-348 receiver the 991 is a noise
> source, and receiver performance improves when it is removed.
>
> Richard, AA1P
>
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