[time-nuts] Re-radiating a GPS signal...??

David McGaw n1hac at Alum.Dartmouth.ORG
Thu Apr 12 15:11:40 UTC 2012


The time/position fix would be from the location of the receiving 
antenna of the repeater, degraded only by noise.

This should work if both antennas have good back-side rejection 
(choke-rings are particularly good for this but perhaps any good timing 
antenna could meet this), the re-transmitting antenna is close to being 
directly under the receiving antenna, and the system gain is low 
enough.  The problem I would see in a room that is not fully shielded is 
interference between the direct and retransmitted signals at the 
receiver under test.

David N1HAC

On 4/12/12 10:17 AM, MailLists wrote:
> GPS being extremely time-dependent, any delay introduced will affect 
> positioning precision. Also, the signal is too weak for such an 
> amplification/echo cancelling signal chain.
> Passive relaying, or using at most a simple amplifier with low enough 
> gain, and short signal delay, remain the only feasible concepts.
>
> On 4/12/2012 4:48 PM, Azelio Boriani wrote:
>> Passive UHF TV repeaters were in use in Italy too. Nowadays, for the 
>> DVB-T
>> TV, active gap-fillers are used instead. Active gap-fillers are
>> same-channel repeaters with the necessary, sophisticated echo 
>> suppression
>> technique. We have developed our echo suppression signal processor on a
>> Xilinx Virtex5 FPGA: maybe something similar may be done for the GPS 
>> CDMA.
>>
>> On Thu, Apr 12, 2012 at 3:29 PM, Alan 
>> Melia<alan.melia at btinternet.com>wrote:
>>
>>> If the isolation is good and the "clear view" signal is reasonably 
>>> strong,
>>> the passive system works well in hangers, metalclad warehouses, 
>>> ferry lorry
>>> decks.
>>> The passive system in the UK used to be refered to as the "Matlock
>>> Repeater".
>>>
>>> Alan
>>> G3NYK
>>>
>>> ----- Original Message -----
>>> From: "Michael Baker"<mpb45 at clanbaker.org>
>>> To:<time-nuts at febo.com>
>>> Sent: Thursday, April 12, 2012 2:05 PM
>>> Subject: [time-nuts] Re-radiating a GPS signal...??
>>>
>>>
>>>> Time-nutters--
>>>>
>>>> So--  How do GPS signal re-radiators work?
>>>>
>>>> How do you place a GPS antenna on top of a building,
>>>> pick up the signal with an LNA, amplify it to re-transmit
>>>> on an inside antenna without the amplified re-transmitted
>>>> signal getting back into the roof-top receiving antenna?
>>>>
>>>> I can see circumstances where a huge metal building
>>>> (aircraft hangar?) might provide enough isolation to
>>>> prevent problems, but in many cases I wonder about it...
>>>> ----------------------------
>>>>
>>>> As an aside note-- I recall seeing, many years ago, a totally
>>>> passive TV signal repeater on top of a tall hill in mountainous
>>>> territory relaying a TV station signal to some homes in a valley
>>>> just below.  The passive repeater consisted of an array of
>>>> high-gain UHF yagis pointing to the 40 mile distant TV station tower.
>>>> The yagi array was coupled to another set of high-gain yagi
>>>> antennas pointing down to the homesites in the valley.  I was
>>>> told that it worked pretty well.
>>>>
>>>> Mike Baker
>>>> ----------------------
>>>>
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