RE: [amsat-bb] AO-7

["Dr Tom Clark" <w3iwi@xxxxxxxx>]

W8ZCF asked:

> At 15:05 UTC was able to get a weak  voice return signal from AO-7 145.953
> up 29.498 dn.  Does anyone know the sequence of Mode A and Mode B turn on?

The concept of a "sequence" doesn't really apply. First of all, remember
that AO-7 was launched 6 months before Intel introduced the original
microprocessor "sequencer", the 4004.

The entire command "sequence" is generated by some latching flip-flops that
hold the last "command" sent from earth until a new command is loaded. The
assumption was that these latches would hold their state because power is
applied continuously.

Many of these states are exclusive of each other -- like: Only one of 20wpm
OR 10wpm OR RTTY OR no telemetry. Only one of the transponder transmitters
(2M or 10M) can be on at a time. etcetera.

>From all indications, these flip-flop registers are initializing randomly on
power-up each time  (each orbit, 12.5 times per day) the satellite sees the
sun.

AO-7's rebirth took us all by surprise. Scrounging thru the junk boxes,
files and brains of W3GEY (the AO-7 project manager), W4PUJ (who built much
of the hardware) and me (who was a flunky on the project), aided by
recollections from VA3LK (who was VE3QB when the satellite was launched), we
have managed to dig up a command uplink encoder, command list, uplink
frequency info, etcetera.

One of our enthusiastic satellite users has been attempting to regain some
measure of control this week, but so far hasn't found the magic gold ring
yet.

So, to answer your question, there is no "sequence" -- it is a random
number. I believe that any attempts to predict the "sequence" is akin to
predicting the sequence of wheels on a slot machine or the winning slot on a
roulette wheel.

73 de Tom, W3IWI

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