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A UFO in the radalt?

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A UFO in the radalt?

Old 15th Oct 2021, 16:20
  #21 (permalink)  
Join Date: Jan 2011
Location: Seattle
Posts: 678
Originally Posted by HUTCHP View Post
First transmit pulse echo would appear in the quite time of the 2nd or 3rd transmit pulse and be interpreted as much closer distance ?
It's a distinct possibility. RAs use a system of frequency modulated continuous wave radar. A CW signal is ramped up in frequency and the reflected return signal differs in frequency based upon the travel time. So the system isn't range gated, where subsequent pulses can be spread out to avoid such misinterpretation. The failure modes would be something that a radar expert (which I am not) could expand upon.
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Old 15th Oct 2021, 16:25
  #22 (permalink)  
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I refer my honourable friend to my previous answer.

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Old 15th Oct 2021, 17:00
  #23 (permalink)  
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Originally Posted by RMK View Post
I'd get that dodgy RadAlt sorted.

In mapping UFO sightings, you’ll see a positive correlation between low levels of education/IQs and higher levels of UFO sightings.

Radalt is a tranceiver there can be an emitter in the vicinity which “fools” your radalt. I heard even 5G cellphone communications might cause these kind of issues!

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Old 16th Oct 2021, 07:33
  #24 (permalink)  
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Most rad alts I have flown with have a top of scale, beyond which the needle is hidden and an off or unlock flag when it is above its maximum height.
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Old 16th Oct 2021, 17:20
  #25 (permalink)  
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I dont think I have seen a helicopter radalt thats works above 2000' AGL. I am guessing because they are subject to error above this sort of value. Radalt unreliability is not uncommon for all sorts of reasons - eg it doesnt like wavy long grass. UFOs are likely to be rather a long way down the list.
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Old 16th Oct 2021, 18:37
  #26 (permalink)  
Join Date: Apr 2010
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Assuming the original poster is at all serious, this brings to mind a saying common in the medical profession: "When you hear hoofbeats think horses not zebras."

As the OP has hopefully learned from this thread, there are an awful lot of common reasons ("horses") for radar altimeters to read spuriously or erroneously, all of them clearly explainable by the laws of physics, and such events occur often enough, at all altitudes, to make extraterrestrial causes ("zebras") extremely unlikely.

At the risk of writing the glaringly obvious, it should also go without saying that "reality" TV producers and directors are exceeding good at, and quite in the habit of, making mountains out of molehills.
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Old 16th Oct 2021, 18:58
  #27 (permalink)  
Join Date: Dec 2005
Location: England
Posts: 1,332
Originally Posted by [email protected] View Post
Hmm, tricky decision when the rad alt starts to misbehave - do you :

A. Check the connections, the T/R and the aerial or

B. Assume it is alien interference.................

Ask an avionics engineer. He will confirm alien interference as there is nothing wrong with the equipment.
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Old 17th Oct 2021, 11:48
  #28 (permalink)  
Join Date: Apr 1998
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It would be pretty cool if the aliens made the rad-alt play the Doctor Who theme like a theremin.

It would also be cool if when starting up a helicopter it made the sound of VWORP! VWORP!
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Old 22nd Oct 2021, 19:23
  #29 (permalink)  
Join Date: Aug 2009
Location: Nova Scotia Canada
Age: 75
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There is nothing wrong with equipment and it definitely is NOT alien interference.
Most Radio Altimeters are design limited for height range. Most will flag and remove the height indication when beyond design limits, but not all. Some use different FMCW processing techniques to provide limited “look ahead” features.
Some Radio Altimeters designed for special applications such as guided weapons and military aircraft use PCM instead of FMCW. These can also have different range design features. These are by definition much more expensive and PCM altimeters are not common in civil aircraft although I have seen them installed for special operational applications.
Many are unreliable overwater particularly if the surface is flat calm, the same can happen over reflective sand based terrain. Antenna position and in particular antenna spacing and surface induced discontinuities are optimised for individual aircraft and are or should be in compliance with the equipment manufacturer installation specifications. There should be FM Supplements and or operating instructions for individual aircraft.
Sincerely, Avionics Design and Systems Integration Engineer.
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Old 22nd Oct 2021, 23:13
  #30 (permalink)  
Join Date: Dec 2017
Location: Yakima
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I've ruled out Yetis, due to the altitude involved.
Too high or too low?
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Old 5th Nov 2021, 07:21
  #31 (permalink)  
Join Date: Dec 2014
Location: Africa
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FAA Warns Of 5G Effects On Radio Altimeters

Originally Posted by casper64 View Post

Radalt is a tranceiver there can be an emitter in the vicinity which “fools” your radalt. I heard even 5G cellphone communications might cause these kind of issues!

And here

The FAA has issued a Special Airworthiness Information Bulletin (SAIB) alerting aviation manufacturers, operators and pilots to the potential adverse effects of new 5G wireless networks on radio altimeters. Released on Nov. 2, the bulletin—AIR-21-18—recommends that aircraft and avionics...
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