CODE 7777 24/7

[marcdeklerk]

Hi all, im getting these 2 codes:

006552
006553

and sometimes 006554 and 006551
 
these codes on the RB 24/7 with altitudes varying from 0 to 98000ft? when I disconnect the antenna they disappear? I triend with another antenna then they are back?,

any ideas?

[viking9]

Squawk codes 7776-7777 are allocated to ground based transponders.

See: http://www.caa.co.uk/docs/64/DAP_ACD_14_SSR_Transponder.pdf

Tom

[marcdeklerk]

what would someone do with ground based transponders? Surely only aircraft use them? I phoned the Area radar and nothing with this squawk desplayed on their screen? possibly blocked via the radar system.

weird?

[DaveReid]

I phoned the Area radar and nothing with this squawk desplayed on their screen? possibly blocked via the radar system.

Or else they aren't receiving Mode S data.

[OKC-Steve]

Many radar sites have a ground transponder nearby that is used as an alarm or quality control.  Without the transponder they would have to depend on the users to tell them the system was broken.  Electronics fail, so the ground transponders give them a rapid troubleshooting tool.  They are usually low power, so you are probably pretty close to the mode-s antenna.

[RodBearden]

There has been talk in the past on the forum of airside vehicles at airports using mode-s withs ADS-B. I remember that last year Oslo Gardermoen airport was giving returns that only chugged around the airport and never took off.

Perhaps Marc's spottings are in that category.

Rod

[marcdeklerk]

No I don't think is a car, I'll drive around and take a tiny antenna with low gain to try and find it... I'm 8km north of FAJS

I forgot to add, the squawk is always 7777 for these 4 codes and they are from Mozambique! Here in South Africa!? Weird test code...

[marcdeklerk]

A friend closeby to the north west of me not receiving this data Mose S at all?!

[OKC-Steve]

There's an NDB site at about 3.7 nm before RWY 21L (445 kHz Morse Code .--- .- JA) it is at S260437.38 E0281630.92 coordinates.  This would be a good place to put a remote transponder.

There's a little square building on google maps on 1st Road just off the R21 highway.

[marcdeklerk]

I'll go check it out today and report if
info back here on the forum

thanks guys!

[tarbat]

what would someone do with ground based transponders? Surely only aircraft use them?

Lots of ground vehicles have ModeS.  For example, Heathrow - see http://www.airframes.org/reg/egllground

43BFFA AOSU5 - LHR ground vehicle GY05 PKO, Mitsubishi Shogun
43BFFB AOSU6 - LHR ground vehicle BF09 LCA Land Rover
43BFFD AFS1 - LHR ground vehicle GY06 BXK, Mitsubishi Shogun
43BFF6 AOSU3 - LHR ground vehicle GY05 KWZ, Mitsubishi Shogun
43BFF8 AFS10 - LHR ground vehicle GY05 OGR, Mitsubishi Shogun
43BFFF TELS1 - LHR ground vehicle, Mitsubishi L200
43BFFC AOSU7 - LHR ground vehicle GV56 LJY, Mitsubishi 200

SBS-1 users have even designed silhouettes for these types of "aircraft" - see http://www.sbsbst.co.uk/iank/Non%20ICAO.htm