[jhb_airlines] Re: Please refresh these old brain cells

  • From: "Bones" <bones@xxxxxxx>
  • To: <jhb_airlines@xxxxxxxxxxxxx>
  • Date: Wed, 24 Sep 2008 19:22:30 +0100

The Mode S codes started off being issued on request but the CAA didn't
realise that uptake would be so fast and they got rather snowed under. After
18 months they suddenly did what the USA did and allocate codes to every
registration regardless of whether one was asked for - or even if it is
feasible to fit Mode S to the aircraft. The result is that every aircraft in
their database (and on G-INFO) now has a Mode S code allocated -you can
check this on the G-INFO page.

The actual unit is set via dip switches on the back. Some are Octal and some
binary so that is why all the code blocks are published:

Binary: 0100_00_000_010_10_0110010001
Hex: 402991
Octal: 20024621

Many are binary and have the full set of 24 dip switches on the unit. Here's
a diagram of a 737 module:


I honestly don't know about a full ADSB fit as the only light aircraft I've
seen with it is G-BRZS - although I know there are several others around. I
don't even know what unit they are using as I am sure the Garmin GTX328 is
pure Mode S only. Whatever he's using it looks like he has a GPS feed going
to the transponder and the data is being fired out by the extended squitter.

I've only found one box from a Google search -
http://www.trig-avionics.com/latest.html - which seems to be about 1800 UKP.
Also read http://forums.flyer.co.uk/viewtopic.php?t=48269&highlight=trig 

I you are curious enough to enquire the owner of G-BRZS is:



-----Original Message-----
From: jhb_airlines-bounce@xxxxxxxxxxxxx
[mailto:jhb_airlines-bounce@xxxxxxxxxxxxx] On Behalf Of Peter Dodds
Sent: 24 September 2008 18:15
To: jhb_airlines@xxxxxxxxxxxxx
Cc: pdodds@xxxxxxxxxxxxx
Subject: [jhb_airlines] Re: Please refresh these old brain cells

> Peter's
> C172 G-GYAV may not yet be fitted with Mode S but it has already 
> been
> allocated a code of 402991.

Bloomin' 'eck! I'd better tell all the members we're bein' watched.

Can I copy that post to Cix VFR Club - I'm sure they'd be as fascinated as

We have discussed fitting mode S in Alpha Victor recently, but we need a
new engine first.  It's coming up to 2400 hours in about 12 months.  We are
already running "on condition" under the new rules, but prudence has been
whispering that we didn't ought to leave it too long, even though
compressions are A1 and the oil clean.

How much is an ADSB fit in ballpark figures Mode S is about £1500 we think,
although we haven't enquired properly yet.


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