Transponder code with an 8 or 9

DanWilkins

DanWilkins

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I just learned that the numbers 8 and 9 are not used in squak codes. My transponder won’t register those anyway. I post this just in case some other readers don’t know this. I was ready to have my Garmin checked.
 
Probably explains why 7500, 7600 and 7700 were chosen.
 
Capt. Geoffrey Thorpe said:
If they had used hexadecimal we would only need to punch in 3 digits for the same number of bits.
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If they had used base 64, one digit would give more bits. It’s actually better to have more digits and less twisting per digit.
 
I stopped flying from 1974-2011 and when I returned transponders, TFRs and a bunch of other stuff were new to me.
Actually several pilots in my circle didn’t now about 8 and 9.
 
The entire concept of needing to enter a number at all is fairly silly with ADS-B OUT and IN. The transponder is already sending the tail number even when the code is set to 1200.

If the system had been designed right, controller tags up the aircraft, ground computer sends a packet up, sets the code for backward compatibility with the old ground radar gear, indicator turns on on the device, transponder acknowledges, and pilot confirms they saw the indicator light up and the code change (controller got the right aircraft).

But that would require ADS-B data comm to have been designed right and not as a spray and pray data system.
 
WannFly said:
I am definitely not common and didn’t know this. And people say u don’t learn anything on POA
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You never realized that the digits on your transponder don’t go beyond 7?
 
Ryanb said:
You never realized that the digits on your transponder don’t go beyond 7?
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Lots of people are not going to know that with the new push button ones. 0-9... they won’t realize 8-9 don’t work for the first two digits.
 
denverpilot said:
Lots of people are not going to know that with the new push button ones. 0-9... they won’t realize 8-9 don’t work for the first two digits.
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Maybe, but this stuff should be basic knowledge. Even with a digital transponder, it shouldn’t take long to figure out that 8 & 9 serve no purpose in regard to beacon codes. If ATC issues a code with those two digits, you better check and see if it’s April fools day.
 
Chuck Norris uses 8888 for a beacon code if he wants to do so.
 
Ryanb said:
Maybe, but this stuff should be basic knowledge for most folks. Even with a digital transponder, it shouldn’t take long to figure out that 8 & 9 serve no purpose in regard to beacon codes. If ATC issues a code with those two digits, you better check and see if it’s April fools day.
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It wouldn’t be basic knowledge for most folks. They probably read it once out of a book during their Private study 20 years ago and immediately forgot it after the checkride.

Not information they’ll really ever need again, either.

Unless they’re avionics buffs and dig in and figure out how BCD and grey code and all that stuff work, they’ll never know it ever again. If they even did on their checkride.

Most wont know 1201 is used by gliders and aircraft nearby LAX, or that most of the 1200 series is assigned by FSS to DVFR aircraft only...

That 1000 is how an ADS-B Out equipped aircraft is supposed to inhibit Mode 3A when altitude encoding isn’t working right... (most controllers don’t know that one either)...

1255 is firefighting

1277 is SAR...

4400-4477 are reserved for aircraft that operate above FL600. (Which as far as we officially know means the U-2 has 77 discreet transponder codes all to itself now, unless that USAF returnable spaceplanes thingy has a transponder on it.)

The list goes on. And then changes drastically in some other countries. Canada has sole fun stuff.

It’s mostly aero-nerd drunken trivia fodder.
 
I've trained controllers, and had them attempt to issue a code with those numbers. Fun with newbie controllers.
 
This helped me understand a bit about the octal system.
 
In an effort to reduce frequency congestion, the FAA plans to add special transponder codes for specific operational situations, supplementing familiar codes such as 1200, 7600 and 7700. Among those under consideration are the following:

1313: Just not having any luck today at all

0666: I have no idea what this airplane is doing now. It must be demon-possessed (Airbus pilots only)

3333: Flying over a large forest

4422: Flying over a steam locomotive

4321: Ready for blast-off

1776: Canceling IFR (... as in “Declaration of Independence”)

0000: Do Not Disturb (Mile High Club initiation in progress)

1225: Merry Christmas!

:D
 
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denverpilot said:
It wouldn’t be basic knowledge for most folks. They probably read it once out of a book during their Private study 20 years ago and immediately forgot it after the checkride.

Not information they’ll really ever need again, either.
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It really is information they’ll need. Even if they read about it 20 years ago in their ground school book, anyone who flies under radar coverage regularly should know this.

The rest of that like you say is ‘mostly aero-nerd drunken trivia fodder.’ :)
 
Ryanb said:
Interesting..

How often do you fly in controlled airspace?
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Always. Busy Delta and then flight following wherever I go. While entering squawk I use the one on GNS and push buttons
 
Ryanb said:
It really is information they’ll need. Even if they read about it 20 years ago in their ground school book, anyone who flies under radar coverage regularly should know this.

The rest of that like you say is ‘mostly aero-nerd drunken trivia fodder.’ :)
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Why? Be specific. ATC isn’t going to give them codes that do not exist in their computer.
 
Clark1961 said:
Chuck Norris uses 8888 for a beacon code if he wants to do so.
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29aruk.jpg
 
denverpilot said:
Why? Be specific. ATC isn’t going to give them codes that do not exist in their computer.
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I know they won’t, hence my joke in the above post:
Ryanb said:
If ATC issues a code with those two digits, you better check and see if it’s April fools day.
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I certainly don’t mean to make this into a boxing match, but as I’ve said, knowing how the transponder functions is a basic need that all pilots should know.

I understand your point that the new digital transponders tend to make this not as easily known as previous generation models.
 
Ryanb said:
I certainly don’t mean to make this into a boxing match, but as I’ve said, knowing how the transponder functions is a basic need that all pilots should know.
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I get it. Unfortunately it’s one of those technologies that is so ubiquitous now that unless you own the aircraft and have to troubleshoot it, or you’re a working pilot and need to know how your transponder affects RVSM, etc etc etc... most people just need to know how to punch numbers in “the box”.

Knowing more is certainly good, but it doesn’t help most folks these days. They can’t work on it and touch the static system anyway.

That said, knowing how it’s connected to other things in the aircraft and a particular aircraft’s systems can be helpful.

I got an error from my system that altitude information had been lost... yup, connector from the blind encoder to the 345 had literally just fallen off. The little clip wasn’t fully engaged. No big deal.

Knowing the blind encoder only sends altitude in 100’ increments makes the altitude alert feature make more sense too, when you’re off by 10’ and it says 100’. ;) The fancy new Garmin encoder that we don’t have sends a more accurate number over the serial bus instead of via grey. Mo’ bits. :)
 
Hey man, the reason for that is the guy that designed only had 4 fingers on each hand (that's 8 total), and also he numbered the first one zero man, not one so its way cool, counting from 0 just like they do in Unix and C man. Dig?
:)
 
coloradobluesky said:
Hey man, the reason for that is the guy that designed only had 4 fingers on each hand (that's 8 total), and also he numbered the first one zero man, not one so its way cool, counting from 0 just like they do in Unix and C man. Dig?
:)
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I believe all modern number systems have zero in them. And I’m pretty sure you start counting from zero in all of them. The first number before you begin counting is always zero. When you add the first one you have one, not two.

You’re thinking of array addressing, which is zero based in Unix and c (which is the correct way). The other languages do it the wrong way starting at one.
 
Way back when transponders were developed a "bit" cost a lot of $$$. Anyone remember when 4KB (K as in KiloByte) of computer memory was "More than you would ever use!" Design engineers did everything they could to squeeze a program into the minimum number of bytes of memory. So they only allocated 3 bits to the transponder code register "More than you would ever use!"
 
coloradobluesky said:
Hey man, the reason for that is the guy that designed only had 4 fingers on each hand (that's 8 total), and also he numbered the first one zero man, not one so its way cool, counting from 0 just like they do in Unix and C man. Dig?
:)
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E014A47E-0DF4-421E-B549-F1D7CD86C760.jpeg
His cousin with 6 fingers must have designed military transponders with modes 1 & 3 combined. ;)
 
Best to remember...

...we’re all ignorant...

...about some things.

This is the kind of thing that could easily escape one’s attention until pointed out.

Especially now with digital frequency selection. On the old analog ones, it usually didn’t take long to realize if you went past 7 it went back to 0.

Anyway, best not to mock these little lapses in knowledge, lest ye yourself be mocked for yours!
 
denverpilot said:
The entire concept of needing to enter a number at all is fairly silly with ADS-B OUT and IN. The transponder is already sending the tail number even when the code is set to 1200.
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Except with certain UAT boxes when in anonymous mode.
Garmin GDL 82 Overview said:
For inflight privacy, an Anonymous mode can be set to mask your aircraft ID from displaying on other aircraft’s ADS-B “In” traffic display
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https://buy.garmin.com/en-US/US/p/540911
Garmin GDL 82 Overview said:
Want to fly with anonymity?
There are private pilots. And then there are extra-private pilots who want to keep their identities off the traffic screens of other ADS-B “In” equipped aircraft (containing business competitors, perhaps?). GDL 82 and its UAT technology can allow for this extra measure of identity security with “Anonymous mode.” Most conventional ADS-B devices are designed to transmit your aircraft’s ICAO number — a discrete “hex code” assigned by FAA as part of your aircraft’s certificate of registration. If you’re flying VFR, however, you can have GDL 82 set to mask your aircraft’s ID from being transmitted to other receivers whenever your transponder’s squawk code is set to 1200. ATC can still track you with ADS-B precision. But your GDL 82 simply won’t transmit your aircraft’s N-number to other pilots in the airspace.
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denverpilot said:
Lots of people are not going to know that with the new push button ones. 0-9... they won’t realize 8-9 don’t work for the first two digits.
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Or the last two. The 8 and 9 are only for ancillary functions like the timer.

And all mode S transponders send a model S serial number which is mappable to the N number. In addition they have an interrogation that will return the actual N number or flight number if so entered. This predates ADSB.
 
Had this sign on my cubicle: There are 10 kinds of people in the world, those who understand binary and those who don't
 
14CFR91.215(b)

"...aircraft is equipped with an operable coded radar beacon transponder having either Mode 3/A 4096 code capability..."

Never crossed anyone's mind that 4096 doesn't divide evenly by 10 (digits 0-9) ?
Never noticed it's a power of 8 (digits 0-7) ?
 
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