[time-nuts] Thunderbolt GPS rollover

Javier Herrero jherrero at hvsistemas.es
Thu Jun 7 20:42:54 UTC 2012


Hello,

There was a competitor, long ago, AIR (Atmospheric Instrumentation 
Research Inc.) that produced something similar. As usual, Vaisala bought 
that company in order to make it dissapear, like a lot others, but this 
is another history.

I never had the details of how it worked (it was kept quite as a secret 
then), but the radiosonde GPS section was very very simple, without any 
digital signal processing. I remember something like an LNA and one or 
two mixers. I think that real sonde position was never calculated, only 
speed (probably 2D, since the sonde also had a pressure sensor for 
providing the height), by comparison of satellite doppler as received by 
the sonde and as received on ground, but as I said, it was never 
disclosed to me then, but I've found that Dave B. Call (then owner of 
AIR) did patented it, US patent nr 5347285, so perhaps it worths to read 
it (I will do as soon as I get a time slot available for it :) ).

Of course, operating principle for Vaisala sondes can be different.

Perhaps I've somewhere one of those sondes... but most surely I've lost 
it quite long ago.

Best regards,

Javier

El 07/06/2012 22:08, EB4APL escribió:
> Maybe you can avoid COCOM limits:  Vaisala radiosondes (the most used 
> type here in Europe, see www.vaisala.com) include  "half" GPS receiver 
> on it and the other "half" is in the ground tracking program.  The 
> balloons go up to about 30 Km and while the speed is very low this 
> height is above the limit.  Maybe you can get a recovered sonde and 
> use it either directly or modulating its telemetry on your radio.  The 
> receiving program SondeMonitor is licensed to amateurs by a small fee 
> and can be downloaded  free for evaluation.
>
> Ignacio, EB4APL
>
>
>
> On 07/06/2012 5:35, Robert Watzlavick.com wrote:
>> Onboard gps units tend to drop out at high altitude and/or high 
>> velocities due to COCOM limits. Some will re-acquire at apogee but it 
>> doesn't always work.  I'm planning for onboard telemetry but a 
>> multilateration system is the backup.
>>
>> I correspond with others on aRocket and unrestricted gps units still 
>> aren't available to the average person without a lot of paperwork and 
>> $$$.
>>
>> -Bob
>>
>> On Jun 6, 2012, at 22:13, Chris Albertson<albertson.chris at gmail.com>  
>> wrote:
>>
>>> Why not fly a tiny GPS inside the rocket?  Either modulated the 
>>> beacon with
>>> the GPS serial data or record it to a micro SD card.
>>>
>>>
>>> On Wed, Jun 6, 2012 at 7:33 PM, Robert 
>>> Watzlavick<rocket at watzlavick.com>wrote:
>>>
>>>> Sorry to resurrect an old thread but I also have a question about 
>>>> using
>>>> the Thunderbolt in the future.  I'm considering using 4 of them in a
>>>> multilateration setup to track an amateur rocket with an onboard 
>>>> beacon.
>>> Chris Albertson
>>> Redondo Beach, California
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-- 
------------------------------------------------------------------------
Javier Herrero
Chief Technology Officer                  EMAIL: jherrero at hvsistemas.com
HV Sistemas S.L.                          PHONE:         +34 949 336 806
Los Charcones, 17                         FAX:           +34 949 336 792
19170 El Casar - Guadalajara - Spain      WEB: http://www.hvsistemas.com




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