FAA "Centers" have primary radar?

jimp wrote

Having spent more hours than I care to remember behind military air
defense radar systems, I can say with some authority that a single
fighter is tough for any radar to see at long ranges.

Yeah, and I even heard that they now make fighters nearly impossible to see
on primary radar, ON PURPOSE ! ! ! g
--
Jim in NC

On Aug 6, 12:10 pm, Eeyore
wrote:
Danny Deger wrote:
In another thread I am in a discussion on radar capability for FAA
"Centers". My recollection is that they typically have no primary radar,
thus no capability to paint weather.

There is no connection whatever between 'primary radar' and 'weather radar'.

The ability to detect storm clouds is related purely to the wavelength of the
radar transmission. A radar that was swamped by cloud returns would be utterly
useless as a primary radar !

Graham

No...the least useful measure of what kind of radar a device is is its
frequency.

the "innards" mostly are what determines what kind of radar a
particular device is.

Robert

wrote:

In rec.aviation.piloting Eeyore wrote:
Danny Deger wrote:

In another thread I am in a discussion on radar capability for FAA
"Centers". My recollection is that they typically have no primary radar,
thus no capability to paint weather.

There is no connection whatever between 'primary radar' and 'weather radar'.

The ability to detect storm clouds is related purely to the wavelength of the
radar transmission. A radar that was swamped by cloud returns would be utterly
useless as a primary radar !

Bzzzt, wrong answer.

The ablility of radar to detect weather is related to frequency, antenna
polarization, antenna sweep rate, type (as in pure pulse versus doppler)
and signal processing (if any).

Mainly frequency actually. If not ENTIRELY frequency. The effect was found by
accident during WW2 btw.

Graham

Danny Deger wrote:
I would like thank everybody for all of the information. I have made
changes to my book to reflect Centers in general have skin paint
capability. There must be something unique about Washington Center's
radar out over the Atlantic Ocean Warning Areas that prevented them from
getting a skin paint on my friend's F-4.

There is one other aspect of primary radar that does not seem to have
been discussed: Most, if not all, airspace surveillance radars use a
"Moving Target Indicator" system to filter out the returns from fixed
terrain and structures. In essence this is a very narrow notch filter
centered at the radar's transmit frequency. Only returns that are
doppler-shifted a detectable amount from the transmit frequency are
painted on the display. This makes it difficult to detect turbojet
aircraft that are moving tangentially to the radar site. Rotating
propellers, on the other hand, usually produce a nice
frequency-broadened return and are usually easy to detect.

- Bill Frensley

In rec.aviation.piloting Eeyore wrote:


wrote:

In rec.aviation.piloting Eeyore wrote:
Danny Deger wrote:

In another thread I am in a discussion on radar capability for FAA
"Centers". My recollection is that they typically have no primary radar,
thus no capability to paint weather.

There is no connection whatever between 'primary radar' and 'weather radar'.

The ability to detect storm clouds is related purely to the wavelength of the
radar transmission. A radar that was swamped by cloud returns would be utterly
useless as a primary radar !

Bzzzt, wrong answer.

The ablility of radar to detect weather is related to frequency, antenna
polarization, antenna sweep rate, type (as in pure pulse versus doppler)
and signal processing (if any).

Mainly frequency actually. If not ENTIRELY frequency. The effect was found by
accident during WW2 btw.

Nonsense.

When you have a few years with L, S, X, and Ku band radars come back
and tell me what you have learned about the real world.

While you're at it, read up on linear polarization versus circular
polarization.

--
Jim Pennino

Remove .spam.sux to reply.

On Aug 6, 1:52 pm, "William R. Frensley"
wrote:
Danny Deger wrote:
I would like thank everybody for all of the information. I have made
changes to my book to reflect Centers in general have skin paint
capability. There must be something unique about Washington Center's
radar out over the Atlantic Ocean Warning Areas that prevented them from
getting a skin paint on my friend's F-4.

There is one other aspect of primary radar that does not seem to have
been discussed: Most, if not all, airspace surveillance radars use a
"Moving Target Indicator" system to filter out the returns from fixed
terrain and structures. In essence this is a very narrow notch filter
centered at the radar's transmit frequency. Only returns that are
doppler-shifted a detectable amount from the transmit frequency are
painted on the display. This makes it difficult to detect turbojet
aircraft that are moving tangentially to the radar site. Rotating
propellers, on the other hand, usually produce a nice
frequency-broadened return and are usually easy to detect.

- Bill Frensley

Excellent point...I was trying desperatly to stay out of MTI!...

Most of the MTI's I am aware of occur in the baseband data
processing...but I suspect that the APRS 4 has a notch filter...or
did.

Robert

Eeyore wrote in
:



Danny Deger wrote:

In another thread I am in a discussion on radar capability for FAA
"Centers". My recollection is that they typically have no primary
radar, thus no capability to paint weather.

There is no connection whatever between 'primary radar' and 'weather
radar'.

The ability to detect storm clouds is related purely to the wavelength
of the radar transmission. A radar that was swamped by cloud returns
would be utterly useless as a primary radar !

Graham





Wrong


Bertie

Eeyore wrote in
:



wrote:

In rec.aviation.piloting Eeyore
wrote:
Danny Deger wrote:

In another thread I am in a discussion on radar capability for
FAA "Centers". My recollection is that they typically have no
primary radar, thus no capability to paint weather.

There is no connection whatever between 'primary radar' and
'weather radar'.

The ability to detect storm clouds is related purely to the
wavelength of the radar transmission. A radar that was swamped by
cloud returns would be utterly useless as a primary radar !

Bzzzt, wrong answer.

The ablility of radar to detect weather is related to frequency,
antenna polarization, antenna sweep rate, type (as in pure pulse
versus doppler) and signal processing (if any).

Mainly frequency actually. If not ENTIRELY frequency. The effect was
found by accident during WW2 btw.


You're sitll wrong


Bertie

Danny Deger wrote:

In another thread I am in a discussion on radar capability for FAA
"Centers". My recollection is that they typically have no primary radar,
thus no capability to paint weather. Someone is telling me they do.
Anybody out there have the answer. Maybe some do and some don't, and the
ones I used in the past don't.

The answer is "it depends." Many enroute U.S. radar sites DO have primary
radar coverage. However there are also plenty so-called "beacon only" sites
that only interogate transponders. These sites are less expensive to install,
particularly in remote areas where installations and electric is at a premium.
The long term trend of FAA was to have less and less full blown primary radar
coverage, similar to what many other countries were already doing for their
civil aviation. The FAA's strategy changed in September, 2001. Primary
coverage will be with us to stay, and may even be expanded in some areas.

Air traffic control radar is optimized and sized for finding airplanes, not
rain drops. Newer center facilities use weather radar (Nexrad) to provide
their weather information on their screens.

I highly recommend taking a tour of any local TRACON and ARTCC facilities. You
will need a pre-approved appointment and may have to provide your information
well in advance. Participating as part of a small group (such as an instrument
ground school course) may be helpful.

The new center and approach faciltiies have wonderful equipment and radar
displays. I cringe whenever I hear a politician say that we haven't invested a
penny in air traffic control for forty years. It took a long time, yes, but
the upgrades are paying dividends. Now to redesign the airspace maps......

On Aug 6, 8:49 am, Luke Skywalker wrote:
On Aug 6, 1:56 am, wrote:

Someone mentioned secondary surveillance. This is mode-s. It is also
on 1030/1090Mhz. However, the reply from the transponder is more
detailed. It contains a unique code for each aircraft. The older
transponders simply return the squawk code that was assigned by ATC
and entered by the pilot. Some mode-s can return airspace and
location.

http://mit.edu/6.933/www/Fall2000/mo...sb.tc.faa.gov/

Secondary "radar" is any type of system where the target is an active
particpant in the radio direction and ranging system. In the US civil
airways system this can be mode a/c/s and it is all the same (more or
less) technical description...

aka the main Secondary system sends out an interrogation pulse on one
frequency and the target replies on another. The times are measured
(ie time main pulse went out and secondary pulse recieved) and hence
range is achieved. Direction is based on the pointing of the primary
interrogator.

"Beacon" Antennas are commonly (but not always) co located with main
primary radar...they will generally be the "flat" rectangle on top of
the main (larger) antenna. They can stand alone...and that is common
in places like Canada and Austrailia...they require far less power
then primary or skin paint radars.

Beacon (ie secondary radar) was a US invention in WWII...It was called
"IFF" identification friend or foe".

What seperates a primary radar for ATC and one for WX are the
characteristics of the radar. Frequency is important but more so are
pulse repetition rate (PRR), polarization, and antenna rotation rate.
Most people think that there is one "echo returned" from a
target...this is not correct.

The PRR and antenna rotation rate are designed to maximise the number
of "Paints" of a target on a particular sweep.

Robert

Are you saying FAA radar determines the position from the l-band
interrogation signal? This is not the case. The primary radar is
around 2.8GHz.