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:
If you're thinking of impulse noise, you're mostly correct. However,
there are plenty of other sources of AM noise available. For example,
the typical VHF aircraft radio requires substantial filtering of the
magneto to avoid hash. Same with any onboard motor. If you've ever
tried to install a TV (VSB is a form of AM) in a vehicle, you'll also
find that ignition and motor noise can be a problem.

Dang it...my memory is slipping. What did Motorola call their noise
filtering circuit on their old low band Motracs. Extenders[tm]? As I recall
it was a simple noise blanker.

DTC hath wroth:

Jeff Liebermann wrote:
If you're thinking of impulse noise, you're mostly correct. However,
there are plenty of other sources of AM noise available. For example,
the typical VHF aircraft radio requires substantial filtering of the
magneto to avoid hash. Same with any onboard motor. If you've ever
tried to install a TV (VSB is a form of AM) in a vehicle, you'll also
find that ignition and motor noise can be a problem.

Dang it...my memory is slipping. What did Motorola call their noise
filtering circuit on their old low band Motracs. Extenders[tm]? As I recall
it was a simple noise blanker.

"Extender". It was a 2nd almost identical receiver, tuned to a nearby
empty frequency. If there was any impulse (ignition) noise, both
receivers would detect the pulses. The 2nd (Extender) receiver would
block the IF signal in the main receiver for the duration of the
pulse. This resulted in a "hole" in the receive IF and audio, but it
was far less noticeable than if the pulse were allowed to be heard.
The tricky part of the design was getting the delays nearly identical
in the two receivers. It also made the 80D/140D/Motrac/Motran radios
rather huge and heavy. Extenders were considered a "standard option"
on most Low Band (30-50Mhz) radios as this is where the ignition noise
is the worst.

The more generic term "noise blanker" applies to this scheme, as well
as a mess of others that detect in a single receiver or blank in the
IF or audio. GE decided that "extender" was a good name for their
mobile repeater, and called it a "mobile extender" or more commonly
just "extender".
http://www.mbay.net/~wb6nvh/chpradio.htm
Egads. I'm cleaning house and found a large box of 40 year old
Motrash control heads and cables. Want some junk?

There was also a scheme to eliminate ignition noise that involved
running a wire to the points on the distributor. The assumption was
that there was a substantial delay between when the points opened, and
when the spark jumped in the spark plug. This allowed the receiver to
be blanked before the noise pulse arrived, which really improved the
noise blanker performance. I was working on the design when marketing
decided that it should tilt at other windmills. Only a few prototypes
were built, were never patented or produced, and worked really quite
well. Cheaper too. That was all just fine because cars were begining
to use electronic ignition systems, which didn't have easily
accessible ignition points.


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

On 7/15/07 1:24 PM, in article
, "Radium"
wrote:

On Jul 1, 7:24 am, wrote in
http://groups.google.com/group/sci.e...bf90c8ed13?hl=
en&
:

how would u like to change the cell phone industry?

Analog cells phones should stop using FM and should start using AM
with SHF frequencies - at least 3 GHz and at most 30 GHz.

http://en.wikipedia.org/wiki/Super_high_frequency

I choose SHF frequencies because SHF seems to be the sweet spot
between frequencies that are high-enough to rip through charged
particles & provide large amounts of bandwidth, yet low-enough to be
wireless and long-distance. At EHF and above, it starts to get into
the IR range where long-distance wireless reception is not possible
and atmospheric opacity begins to dominate.

Equally important, SHF frequencies can efficiently transmit signals
using extremely small transmitters. Longer wavelengths require larger
transmitters.

Obviously there are frequencies lower than SHF -- VHF and above --
that can easily penetrate charged particles [e.g. anything resembling
the ionosphere or heliosphere]. However, lower-frequencies tend to
result in less bandwidth, so it is better to use higher-frequencies
when the application requires significant bandwidth.

I choose AM because it requires less bandwidth than FM. In addition,
AM tends to retain reception of rather weak signals, while FM
"considers" such signals to be absent.


Too much time on your hands again?

On Jul 15, 2:24 pm, Don Bowey wrote:
On 7/15/07 1:24 PM, in article
. com, "Radium"





wrote:
On Jul 1, 7:24 am, wrote in
http://groups.google.com/group/sci.e...sg/696d6abf90c...
en&
:

how would u like to change the cell phone industry?

Analog cells phones should stop using FM and should start using AM
with SHF frequencies - at least 3 GHz and at most 30 GHz.

http://en.wikipedia.org/wiki/Super_high_frequency

I choose SHF frequencies because SHF seems to be the sweet spot
between frequencies that are high-enough to rip through charged
particles & provide large amounts of bandwidth, yet low-enough to be
wireless and long-distance. At EHF and above, it starts to get into
the IR range where long-distance wireless reception is not possible
and atmospheric opacity begins to dominate.

Equally important, SHF frequencies can efficiently transmit signals
using extremely small transmitters. Longer wavelengths require larger
transmitters.

Obviously there are frequencies lower than SHF -- VHF and above --
that can easily penetrate charged particles [e.g. anything resembling
the ionosphere or heliosphere]. However, lower-frequencies tend to
result in less bandwidth, so it is better to use higher-frequencies
when the application requires significant bandwidth.

I choose AM because it requires less bandwidth than FM. In addition,
AM tends to retain reception of rather weak signals, while FM
"considers" such signals to be absent.

Too much time on your hands again?- Hide quoted text -

- Show quoted text -

.. . .

On Jul 15, 1:24 pm, Radium wrote:
On Jul 1, 7:24 am, wrote inhttp://groups.google.com/group/sci.electronics.basics/msg/696d6abf90c...
:

how would u like to change the cell phone industry?

Analog cells phones should stop using FM and should start using AM
with SHF frequencies - at least 3 GHz and at most 30 GHz.

http://en.wikipedia.org/wiki/Super_high_frequency

I choose SHF frequencies because SHF seems to be the sweet spot
between frequencies that are high-enough to rip through charged
particles & provide large amounts of bandwidth, yet low-enough to be
wireless and long-distance. At EHF and above, it starts to get into
the IR range where long-distance wireless reception is not possible
and atmospheric opacity begins to dominate.

Equally important, SHF frequencies can efficiently transmit signals
using extremely small transmitters. Longer wavelengths require larger
transmitters.

Obviously there are frequencies lower than SHF -- VHF and above --
that can easily penetrate charged particles [e.g. anything resembling
the ionosphere or heliosphere]. However, lower-frequencies tend to
result in less bandwidth, so it is better to use higher-frequencies
when the application requires significant bandwidth.

I choose AM because it requires less bandwidth than FM. In addition,
AM tends to retain reception of rather weak signals, while FM
"considers" such signals to be absent.

.. . .

"Radium" wrote in message
oups.com...
On Jul 1, 7:24 am, wrote in
http://groups.google.com/group/sci.e...0c8ed13?hl=en&
:

how would u like to change the cell phone industry?

Analog cells phones should stop using FM and should start using AM
with SHF frequencies - at least 3 GHz and at most 30 GHz.

Before making such a recommendation, I suggest you read up on a couple of
topics.

I'd suggest at least topics including:

Near and far antenna performance.
Path loss calculations
Signal penetration
Fading types
Interleaving
SAR
Eb/No
C/I
Frequency stability and accuracy
Component and radio design
Modem methods
Modulation methods.
Vocoders
Digital modulation
General history of modulation techniques, AM, FM and digital
Maybe others as they come up in your reading.

and then study.
Manufacturers and manufacturing history
Company pioneering status
IPR
Regulatory compliance
Government rule making processes (Nat'l and Intl)
Spectrum use (bits / Hz)
Standards setting
Getting vendors to make components for you.
Lead times
Protecting customer's investment
Security
testing methods

Engineering solutions requires you to keep you arms around all of this.

If you are serious about your request and do not at least have a casual
working knowledge of all these, you are wasting everyone's time. If your
goal is to created fruitless discussion, you are right on track.

No insult intended...just trying to tell it like it is.

Bob F.

"Radium" wrote in message
oups.com...
On Jul 1, 7:24 am, wrote in
http://groups.google.com/group/sci.e...0c8ed13?hl=en&
:

how would u like to change the cell phone industry?

Analog cells phones should stop using FM and should start using AM
with SHF frequencies - at least 3 GHz and at most 30 GHz.

Maybe you should spend more time reading up on Radio systems, RF
propagation, Modulation techniques, and a whole range of other RF and
electronic related material, before you once again make a fool of yourself.

Radium wrote:
how would u like to change the cell phone industry?

Analog cells phones should stop using FM and should start using AM
with SHF frequencies - at least 3 GHz and at most 30 GHz.

I was not aware there was a compelling reason for analog cell phones to
stop using FM. Sounds like a solution looking for a problem.

On Jul 16, 9:15 am, DTC wrote:

I was not aware there was a compelling reason for analog cell phones to
stop using FM. Sounds like a solution looking for a problem.

FM audio is boring -- no entertaining high-pitched tones from solar
prominences which would definitely be heard on AM audio.

OTOH, AM video is boring. FM video is better. As I said before, the Y
[luminance] signal should be carried on an FM wave rather than an AM
wave.

Analog radio-frequency audio devices should use AM.

Analog radio-frequency video devices should use FM.