[amsat-bb] Re: AO-07 Healthy CW]

Bob McGwier n4hy at idaccr.org
Wed Nov 29 08:08:38 PST 2006

Tom Clark, K3IO wrote:
> W9GB noted
>> I can identify the lab equipment on the bench (looks like my high
>> school & college labs - 1970s) with the NiCad battery pak, EXCEPT for
>> the rectangular box with metal handles to the right of the NiCads. 
>> NiCad battery charger?   Homwbrew power supply?
> Greg -- the high-priced hardware (HP+Tek) show NASA Goddard property
> labels. The cheaper power supplies in the back are Heathkits with AMSAT
> stickers.
> The box you are asking about has a yellow Goddard tag. I'm trying to
> recognize it, and to the best of my recollection it is a Coulomb-meter
> that measured (on the mechanical counter you see on its panel) the
> integrated charge/discharge current. Also my fuzzy memory tells me that
> the heatsink device on clip leads was a prototype BCR.
There is nothing wrong with your memory!   Notice that it is in series 
with the batteries,   it has a large transistor being heat sunk and I 
can make out two high wattage resistors and an electrolytic 
capacitor.    I think you are right.

> Sil asked:
>> I guess there's a special "satellite design" reason that double wires
>> are used (instead of one thicker one) for the current carrying battery
>> leads?
> The twin wires go to a pair of pins on the DA-9 connector, with two pins
> providing greater current handling ability and redundancy. It also
> appears that the V/2 telemetry tap has a pair of whit wires even though
> it provided zero current. BTW -- the V/2 telemetry would be on 3B.
>> Leaving aside Geoff's (vk2tfg) point that the telemetry may be
>> irrelevant because of the doggy value in channel 6D, it would seem that
>> the five top cells (between half volt point and +12V - numbers 2,3,4,5,6
>> counting clockwise) are being charged with a current of 80mA and have
>> reached a terminal voltage of 6.4 volts (8.8 - 2.4). This represents a
>> voltage of 1.28 per cell (6.4/5) and is thoroughly reasonable. This idea
>> is supported by the temperature of cell number 5 at 60.28 C. 
> The top 5 cells are fed by the black wire and are the LOW voltage side.
> The 5 "high side" batteries terminate in the orange wire on the bottom,
> The thermistor on cell #5 is on the low voltage side.
> The thermal design of the s/c ended up with internal temps ~20°-30°C
> range (i.e. TLM values in the 40-50 range). I find it hard to believe
> that a valid interior temperature would ever be in the 60°C range.
> Regarding all the telemetry speculation -- AFAIK, there is no indication
> that the A/D converter is showing ANY valid data at all -- see also
> Jan's comments at http://www.amsat.org/amsat/sats/n7hpr/ao7_tlm.html.
> FYI -- the TLM and its associate Morse encoder system was built with
> discrete CMOS logic by John Goode, W5CAY in Texas. Memory fails me, but
> I believe that the TLM/Morse board is on the "back wall" in the
> photograph at http://www.amsat.org/amsat/sats/ao7/slideset/slide09.html
> even thought the photo only identifies the module as the command
> encoder. All the white IC's a early RCA ceramic 4000-series parts.
> AFAIK, Oscar-6 & -7 were the first CMOS users in space. AO-7, with much
> of this logic still functioning after 32 years and 2 weeks, certainly
> holds the longevity record!
Jan told me that no reasonable data was found during the times Mike 
Seguin and I were attempting to command the spacecraft on the two 
possible command channels.     That was the last time I really looked at 
this data in detail.  I wrote a python program to decode it all and it 
was all crap.

> [In case you forgot, Nov.15th was AO=7's 32nd birthday -- my favorite
> picture of the launch is the "7-UP" contrail left by the Delta booster
> http://www.amsat.org/amsat/sats/ao7/slideset/slide18.html]
> 73, Tom

Nice job on the memory for an OF like you!  (what are friends for after 


Robert W. McGwier, Ph.D.
Center for Communications Research
805 Bunn Drive
Princeton, NJ 08540
(sig required by employer)

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