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The RF environment at stadiums

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tggzzz:

--- Quote from: pdenisowski on March 30, 2023, 03:44:28 pm ---
--- Quote from: tggzzz on March 30, 2023, 02:34:31 pm ---The "rusty bolt" problem is unpredictable and can be severe.

Certainly HMS Sheffield was sunk partly because it had turned off its primary radar in order to use comms equipment. Whether that was because/i] of "rusty bolts" is unknown to me.

--- End quote ---

Passive intermodulation (PIM, a.k.a. the rusty bolt effect) is a serious enough issue that many major test and measurement instrument manufacturers offer a PIM tester that transmits two high power CW signals (tones) and then looks for intermod products at the expected (calculated) frequency.  In my field experience, almost all PIM issues are (unsurprisingly) associated with high power transmitters, usually either broadcasters or cellular base stations.

My understanding is that the Sheffield's radar was turned off due to interference caused by (co-channel) SATCOM, not PIM.  Whatever the cause, the sinking of the Sheffield created a lot of interest in EMC MIL-STD testing that continues to this day:  I can't count how many EMC presentations I've listened to that started with the story of the Sheffield.

--- End quote ---

I initially heard SATCOMs, but the relatively recent https://www.theguardian.com/uk-news/2017/oct/15/revealed-full-story-behind-sinking-of-falklands-warship-hms-sheffield mentions the more ambiguous "The radar on board the ship that could have detected incoming Super Étendard fighter aircraft had been blanked out by a transmission being made to another vessel.". Hence my weaker statement.

Terry Bites:
We do need to be warned when coldplay might untintentionally heard.

LaserSteve:
One of the additional hazards is front end overload.

A security guard standing next to your gear with a 5 watt handietalkie can wreak havoc.  I have a friend who lost a laser show projector from a HT keyed right next to the galvo scanners.  At the time the scanners used RF
at a few Mhz in capacitive position sensors. 


Steve

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