Today's Message Index:
----------------------
1. 04:20 AM - Grey code for altitude encoders (Bill Reed)
2. 06:48 AM - Re: Grey code for altitude encoders (Finn Lassen)
3. 07:18 AM - Re: Grey code for altitude encoders (Finn Lassen)
4. 09:52 PM - Radio transmission problem...help! (Tom)
Message 1
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| Subject: | Grey code for altitude encoders |
--> Avionics-List message posted by: Bill Reed <bill@ncf.ca>
Does anyone on this list have the table/algorithm to translate the grey
code generated by the altitude encoders to Pressure altitude? There are
only three octal digits to translate so it should not be difficult once
the key is known.
Have a good day,
Bill
Message 2
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| Subject: | Re: Grey code for altitude encoders |
--> Avionics-List message posted by: Finn Lassen <finnlassen@netzero.net>
Funny you should ask.
Here's a link to get you started:
http://www.nist.gov/dads/HTML/graycode.html
Gray-to-Bin:
B(i) Binary (bit i)
G(i) Gray (bit i)
MSBit just copied to output. ( B(n) = G(n) )
Subsequent bits: B(i) = B(i+1) XOR G(i) (i = n -1 to 0)
Altitude encoder output to Binary:
1) Invert all 9 bits
2) Get checksum of upper 6 bits
3) Convert upper 6 bits to gray and multiply by 10
4) Lower 3 bits:
5) Change 100 to 111
6) Convert to bin to Gray
7) If checksum was 0 then add to previous result (upper * 10) and subtract 1
else subtract from previous result
9) Subtract 12 from result and display, appending 2 zeroes or just
display in x100's feet
Only have a hard copy of table.
Search for:
MODE A AND MODE C CODES
The Full List
by
Darryl Phillips
THE AIRSPORT CORPORATION
Affordable Avionics.
I assume he still has this posted somewhere.
Finn
Bill Reed wrote:
>--> Avionics-List message posted by: Bill Reed <bill@ncf.ca>
>
>Does anyone on this list have the table/algorithm to translate the grey
>code generated by the altitude encoders to Pressure altitude? There are
>only three octal digits to translate so it should not be difficult once
>the key is known.
>
>Have a good day,
>Bill
>
>
>
>
Message 3
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| Subject: | Re: Grey code for altitude encoders |
--> Avionics-List message posted by: Finn Lassen <finnlassen@netzero.net>
Here the table:
http://www.airsport-corp.com/modecascii.txt
http://www.airsport-corp.com/modec.htm
Finn
Bill Reed wrote:
>--> Avionics-List message posted by: Bill Reed <bill@ncf.ca>
>
>Does anyone on this list have the table/algorithm to translate the grey
>code generated by the altitude encoders to Pressure altitude? There are
>only three octal digits to translate so it should not be difficult once
>the key is known.
>
>Have a good day,
>Bill
>
>
>
>
Message 4
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| Subject: | Radio transmission problem...help! |
--> Avionics-List message posted by: "Tom" <tomrv8@gvtc.com>
Hi all,
I'm having a transmitting problem with the radio in my RV-4. Here's the
background;
16 year old Terra TX 720 dinosaur radio with pushbutton frequency change
RST intercom, built by my amatuer hands 16 years ago
Push to talk button on control stick
Reception/ transmission has always been fine, never any grief
Problem;
Other planes I fly with report they are not receiving my voice
transmissions (it is actually intermittent, occasionally they will
"hear" me at good volume)
Factors to consider;
I am receiving full volume sidetone in my headset (I assume that means
the microphone is OK)
Happens whether I'm using the pilot or passenger jacks
Changing headsets has no effect
Ever since the first time I used the radio, it has a very distictive
"ping" when I press the push to talk switch. It is audible both
in my headset, as well as being received by the planes I fly with. Even
now, with the inability of others to hear my voice transmission, the
"ping" is still very audible to them. (I assume that means the antennae is
OK)
When I've tested the unit on the ground using my handheld radio to
listen to the transmission, I clearly hear the "ping", and actually
can hear my voice transmission at a "very" low level.
I would really like you guys to tell me to just throw away the radio and get
a real one and all my troubles will be over , but I'd better make sure the
radio is the culprit before I go to that extreme.
Thanks for the help,
Tom Chapman
RV-4 N153TK
1020 hours of fun
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