[Milsurplus] 991 neon lamp

[jcoward5452 at aol.com]

Arn't 2 of  these also used in the LM? Most people build a regulated supply thus they would be redundant and could be liberated for other use.
Jay





-----Original Message-----
From: J. Forster <jfor at quik.com>
To: 'milsurplus' <milsurplus at mailman.qth.net>
Sent: Sat, Jan 16, 2010 10:08 am
Subject: Re: [Milsurplus] 991 neon lamp


For those intetrested in relatively current Noise measurement, there is an
ILtech 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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