[time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)

J. Forster jfor at quik.com
Mon Nov 16 00:51:29 UTC 2009


See my earlier post. Briefly:

Antennas do not have an infinite front-to-back ratio. (<40 dB)

The path loss from a surface jammer to a plane (10 miles) is many, many dB
less than from plane to bird (15,000 miles).

-John

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



> Considering that the GPS antenna in aircrafts is mounted on top of
> fuselage,
> and that its radiation pattern is upward, it seems that a ground jammer
> will
> have an uphill battle.
>
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
> Behalf Of J. Forster
> Sent: Sunday, November 15, 2009 6:28 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference
> oscillator accuracy)
>
>
> Or even into MP3 players, iPods, laptops, or cell phones. Then they'd
> wander all over the place too. With the latter two hosts, they could even
> be controlled remotely and even be fairly powerful. Would you notice
> having to recharge your battery a bit more often?
>
> -John
>
> ===========
>
>
>> Magnus Danielson wrote:
>>> Chuck,
>>>
>>> Chuck Harris wrote:
>>>> What makes you think it needs to be CW, and cannot be pulsed and
>>>> chirped?
>>>
>>> May I roll in a noise jammer into the debate?
>>
>> Absolutely!  They can be extremely power efficient.  Raise the noise
>> floor in the vicinity of the receiver, and it is all done.
>>
>> Probably the easiest solution would be to take a PN source and use it
>> to drive a pulser that pulses a chirp oscillator.  If you are feeling
>> really polite, you could put a bandpass filter on the thing to protect
>> other services.
>>
>>>> All it has to do is confuse the receiver enough so that you can't
>>>> trust its readings.
>>>
>>> Depends on the goal. For some strategies, blackout is the goal, for
>>> some
>>> getting the readings go haywire every once in a while suffice.
>>
>> Agreed!
>>
>> My 9V battery suggestion was for a localized blackout device.  You only
>> have to make the receiver question each satellite's signal often enough
>> for it to rule it out.  No way is CW necessary, or even desirable.
>>
>> As John suggested, someone (say the Chinese) could put these things in
>> battery operated stuffed animals, and set them up to jam a little bit
>> now and then.  After Xmas, the GPS landscape would be littered with
>> these
>> little stealth jammers, and willing supplicants to replace their
>> batteries.
>>
>> -Chuck
>>
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>
>
>
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