msg hath wroth:

Jeff Liebermann wrote:

snip
I have a fluorescent lamp calibrated noise source that's quite noisy
well into the GHz range.

Sounds interesting.

Would you please post some details or pointers to references about
constructing and calibrating such an instrument?

Groan. I built it myself from an article in some long lost magazine
perhaps 30 years ago. It's just a 5watt fluorescent tube, with a few
turns of wire wrapped around it going to a broadband CATV amplifier.
One end of the wire coil is terminated at 50 ohms. The other end goes
to the broadband amp. The lamp is powered by a heavily filtered
isolation xformer. Calibration consisted of taking a scope photo of
the output on a spectrum analyzer. Just about any gas discharge tube
will work. Neon, fluorescent, blue or green gas discharge display,
the new compact fluorescent tubes, plasma tube TV, etc.

Most older microwave noise sources use argon filled gas discharge
tubes, but fluorescent will sorta work. The HP 346A (3-18GHz) and
349A (0.4 to 4GHz) noise sources are examples of such gas discharge
tube test noise sources. The manual for the 342A NF test system,
which includes the 349A noise source is at:
ftp://bama.sbc.edu/downloads/hp/342a/342a_349a_service_6.pdf
See section 5.

Some minor notes around Fig 9.24 on Page 207 at:
http://books.google.com/books?id=sNLQmi3ymTYC&pg=PA206&lpg=PA206

I could post some photos, but I really don't want to tear it apart to
take pictures of the guts.

These daze, microwave noise sources use avalanche diodes although just
about any diode with a sharp knee will work. Diodes are more stable,
less fragile, and easier to produce than gas discharge tubes.
http://www.ham-radio.com/sbms/sd/nfsource.htm
http://www.atmmicrowave.com/coax-noise.html

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann wrote:

snip

I have a fluorescent lamp calibrated noise source that's quite noisy
well into the GHz range.

snip
I built it myself from an article in some long lost magazine
perhaps 30 years ago. It's just a 5watt fluorescent tube, with a few
turns of wire wrapped around it going to a broadband CATV amplifier.

I was quite excited by the acquisition of a CATV distrib. amp as a
giveaway at a local hamfest earlier this spring; I modified it to
accept external power and use BNC connectors and produced a hand-
drawn schematic which I will 'capture' when time permits and post
together with photos. I have used it as a front end to a freq.
counter and an oscilloscope and without it I could not have completed
several projects.

These units are so handy it is a wonder that (at least on the Web) there
has been little mention of their experimental uses.

BTW, which of the numerous newsgroups in this miserably cross-posted thread do
you regularly read?

Regards,

Michael

msg hath wroth:

I built it myself from an article in some long lost magazine
perhaps 30 years ago. It's just a 5watt fluorescent tube, with a few
turns of wire wrapped around it going to a broadband CATV amplifier.

I was quite excited by the acquisition of a CATV distrib. amp as a
giveaway at a local hamfest earlier this spring; I modified it to
accept external power and use BNC connectors and produced a hand-
drawn schematic which I will 'capture' when time permits and post
together with photos. I have used it as a front end to a freq.
counter and an oscilloscope and without it I could not have completed
several projects.

Good idea. I use a 5-1000MHz CATV amplifier as an output "booster"
for my various RF signal generators. It's especially handy if I want
to talk on a repeater using my signal generator or service monitor.

These units are so handy it is a wonder that (at least on the Web) there
has been little mention of their experimental uses.

Oh, they've been around. I've seen articles on how to use them as HF
AM and SSB power amplifiers. Many HF radios use CATV amplifiers for
broadband drivers. You don't see them called CATV amps much because
they are 75 ohms in and out, while just about everything else is 50
ohms.

BTW, which of the numerous newsgroups in this miserably cross-posted thread do
you regularly read?

Read? I don't read anything, I just post answers and rants.
http://groups.google.com/groups/profile?enc_user=tWGMphwAAAAGTj9X4k0U7wKkGyU8QhaBh axMG2M1PWkMtCZAt5tdxQ&hl=en
See "Recent Activity".
19,520 messages. Methinks I need a vacation, project, or something.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558