Ian, GM3SEK wrote:
"Sure, but none of those (bedapring antenna arrays) would fly very
well."

It`s been a long time now but I believe investigation showed the army`s
new radar (earthborne) got good echos from the approaching Japanese
arircraft on December 7, 1941, but the top brass rejected the reports in
disbelief of either the new equipment or the audacity of the Japanese
Navy. That attack changed naval warfare forever. Lot more respect for
both aircraft and radar ever since.

Best regards, Richard Harrison, KB5WZI

Allison wrote:
On Fri, 2 Jun 2006 07:35:24 +0100, Ian White GM3SEK
wrote:

Sal M. Onella wrote:

"Ian White GM3SEK" wrote in message
...


Those were the phased arrays for the earlier VHF radar, and consisted of
two or four two-element yagis clustered around the nose (of a
two-engined aircraft, obviously). This gave a fairly good
forward-looking capability. Both sides did much the same, and given the
relatively long wavelength, it's hard to think how better to do it.

The huge benefit of the magnetron was that it operated at much shorter
wavelengths, which frees up the antenna design and provides much better
spatial resolution - witness the downward-looking "H2S" radar which was
the magnetron's first major deployment.

The VHF radars were still around into the late 1970's, maybe beyond. The US
Navy had them on carriers for air search. I think the nomenclature was
AN/SPS-29 and/or AN/SPS-37. The one I recall was in the 218 - 220 MHz and
it was hell on TV channel 13! The antenna was referred to as a bedspring
array; the rectangular framework for the dipole radiating elements resembled
a giant bedspring.


Sure, but none of those would fly very well. The discussion was really
about airborne radar, where there are tough limits on antenna size.

P38s, Spitfires and other aircraft setup for night attack or bombing
did have a smaller high VHF radars using smaller 8 element bedspring
arrays. They proved very effective.


As far as I know, these VHF arrays were only installed on the nose of
twin-engined or four-engined aircraft. On a single-engined aircraft like
the Spitfire, the antenna would have been behind the propeller. Did you
mean the Mosquito?

There were also some rearward-looking VHF/UHF radars using a simple
2-element antenna, to warn of aircraft approaching from anywhere within
a large rearward beamwidth.

A common feature of all these early airborne VHF/UHF systems was that
the antennas were fixed, so the view was always relative to the
direction of the aircraft.


VHF and UHF radar has a better ability to peek over the horizon and at
the time when reciever for uhf were still new tech offered the best
range/power ratios.

Hence VHF/UHF was favored for shipborne use, where the horizon range is
limited by the relatively low antenna height.

The magnetron moved effort to the milimeter bands
at high power outputs where small high gain antennas were practical
thus negating the need for high gain recievers.

Yup... and the small size eventually opened the way to steerable
antennas too.


--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

The RAF Sunderland Flying Boat had a high wing and a deep hull with 4
engines. The Radar was ASV Mk 3 or Mk 5, a sea-going version of H2S.
Sunderlands were employed on submarine hunting over the North Atlantic
and Indian Oceans. 3000 MHz, 50 kW peak pulse power, radar range =
100 miles.

A radar scanner could not be installed under the nose. It had to be
kept out of the water. Instead there were two syncronised scanners,
one hanging under each wing tip. They rotated together, one scanner
covering the port side 180 degrees and the other the starboard side.

The magnetron output was switched in the waveguide system between port
and starboard, changing over at 5 degrees away from dead ahead to
avoid spurious switching effects.

The parabolic scanners, rotating about once every two seconds, had a
habit of getting out of sychronism when the aircraft made a tight
turn. Something to do with gyroscopic, centrifugal and gravitational
forces. It took 7 or 8 seconds to regain syncronism by which time the
radar operator had got the target and other ships in the vicinity all
mixed up with each other on the radar PPI display.

Aa the radar operator over the China Sea, I was once severely cursed
(reprimanded) over the intercom by the skipper for getting ourselves
lost immediately following a tight turn. But the war was now over and
it was only a practice exercise.
----
Reg.

Reg, G4FGQ weote:
"As the radar operator over the China Sea, I was once severely cursed
(reoremanded) over the intercom by the skipper for getting ourselves
lost immediately following a tight turn."

On my ship, most of the crew was sleepless most of the time while we
were underway. We had two 4-hour watches each day at our sea detail.
Plus, we had to turn-to on our regular work details during dayrime hours
if we weren`t on watch. But, the killer was the dawn and dusk general
quarters positions we had to man every day while traveling in a war
zone. You were really lucky if your assigned watch time sometimes
cincided with work-detail time.

The result of all this sleep loss was some cat-napping on the bridge in
addition to elsewhere aboard. Our top speed was 14 knots which made us
faster than a liberty ship, so at times we got convoy escort duty. We
had antiaircraft guns, 50 ca., 20 mm, and 40 mm. My gq position was on
the latter.

Whenever the brdge awakened after a doze in convoy, someone would often
shout down through the voice tube to the radar operator:
"Geez! how close is that ship ahead? Whereupon, the operator would push
or pull himself away from a PPI tube covered with false sea return, poke
his head out a porthole, then scream his best estimate back up the voice
tube. That`s how he avoided being scolded.

Best regards, Richard Harrison, KB5WZI

Richard Harrison wrote:
Ian, GM3SEK wrote:
"Sure, but none of those (bedapring antenna arrays) would fly very
well."

It`s been a long time now but I believe investigation showed the army`s
new radar (earthborne) got good echos from the approaching Japanese
arircraft on December 7, 1941, but the top brass rejected the reports in
disbelief of either the new equipment or the audacity of the Japanese
Navy. That attack changed naval warfare forever. Lot more respect for
both aircraft and radar ever since.

Best regards, Richard Harrison, KB5WZI

as I understand the Matter the radar sighting never made past a LT to
the top brass that one of the problem that day was the still pecetime
armed forces were quick to discount anything with the number of "false
sighting" etc