[time-nuts] GPS interference and history...

J. Forster jfor at quik.com
Thu Jun 9 20:41:14 UTC 2011


The cold side can be cooled by radiation. It's been done. The View Factor
to the 3 K of space is nearly 1.0, and the heat transfer rate goes up as
the radiator temp EXP 4.

-John

============

> I don't think it is feasible... for a cooling reason :)
>
> Regards,
>
> Javier
>
> El 09/06/2011 22:18, William H. Fite escribió:
>> I well recall the furor over Cassini-Huygens in 1997 but approval was
>> ultimately granted and, of course, the launch was without incident.
>> Since
>> then, New Horizons, Galileo, and Ulysses have been launched with far
>> less
>> public outcry, despite the fact that all are powered by RTGs.  Arguably,
>> well-designed reactors could be even safer.
>>
>> While I appreciate that sensitivity to nuclear power for earth orbit
>> satellites could be greater than for deep space vehicles, we may have to
>> agree to disagree on the feasibility of nuclear powered satellites.
>>
>> On Thu, Jun 9, 2011 at 4:06 PM, J. Forster<jfor at quik.com>  wrote:
>>
>>> Ha!
>>>
>>> Nuclear power in space is poltically utterly impossible in the US.
>>> There
>>> is huge opposition to RTGs, never mind even the thought of reactors.
>>>
>>> Solar is not really practical either. The sun puts out about 1 KW/Sq.M
>>> in
>>> EO, and solar cell efficiency is<20%; so 10 KW needs 50 Sq.M of
>>> stabilized pointing cells.
>>>
>>> -John
>>>
>>> =============
>>>
>>>
>>>> Perhaps in the longer term (ie. next the several decades) moving away
>>> from
>>>> the
>>>> current wide band spread spectrum scheme to a higher power narrow band
>>>> scheme
>>>> might make more sense for GPS.    A previous poster mentioned the use
>>>> of
>>>> nuclear
>>>> powered satellites to achieve higher transmit powers, given the
>>>> benefits
>>>> of GPS
>>>> that option should not be entirely discoutned in my oppinion.
>>>>
>>>>
>>>> ----- Original Message ----
>>>> From: Magnus Danielson<magnus at rubidium.dyndns.org>
>>>> To: time-nuts at febo.com
>>>> Sent: Thu, June 9, 2011 12:03:45 PM
>>>> Subject: Re: [time-nuts] GPS interference and history...
>>>>
>>>> On 06/09/2011 07:29 PM, Burt I. Weiner wrote:
>>>>> For many years the FCC has not allowed FM broadcast stations within
>>>>> certain distances of each other where a 10.7 MHz frequency difference
>>>>> existed. Not exactly the same thing, but did show an understanding of
>>>>> what can go wrong as a result of good receiver front end selectivity.
>>>>> In
>>>>> AM and FM broadcasting there has also been required distances between
>>>>> 1st and 2nd adjacent channels, only partially because of overload
>>>>> issues
>>>>> but more so because of occupied bandwidth and overlapping. I'm not
>>>>> sure
>>>>> how much more it would cost to build GPS receivers with better front
>>>>> ends, but I'm sure it would've priced GPS devices out of the hands of
>>>>> many consumer level users. The FCC under the direction of Congress
>>>>> has
>>>>> made (allowed) some pretty stupid moves in the past bunch of years.
>>>>> In
>>>>> my opinion, the FCC has forgotten what their purpose is, and being
>>>>> run
>>>>> by attorneys has made the situation that much worse as there are very
>>>>> few attorneys that understand the un-revocable physics of the
>>>>> electromagnetic spectrum.
>>>>
>>>> Regarding GPS receivers there today exist many different front-end
>>>> approaches.
>>>> In particular have single-bit and 1.5 bit samplers and direct samplers
>>>> been used
>>>> for many customer GPSes. The GPS receivers needed in E911 compatible
>>>> phones is
>>>> hardly done with lots of money, space and power-budget.
>>>>
>>>> Bringing too quick shift of requirements onto the GPS receiver market
>>>> would...
>>>> well kill it. Some degradation would be tolerated.
>>>>
>>>> Look forward to L2C and L5 capabilities to show up alongside Glonass
>>> L1...
>>>>
>>>> Cheers,
>>>> Magnus
>>>>
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>>>
>>>
>>>
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