David's comment on the direct and retransmitted signals is right on point.
You are creating a multipath environment with increased signal strength and
matching polarization. Even with no amplification between the antennas, you
are generating multipath signals for you and your neighbors.
Advocating signal repeaters is very dangerous. With out proper bandpass
filtering and path isolation you are inviting trouble from feedback
oscillation, both in-band and out of band. You may not even be aware of out
of band effects. If not done properly, including taking in account seasonal
variation of vegetation, possible effects of someone moving lawn furniture
around or even vehicular motion changing the feedback path, the results
could be disastrous. You could be the owner of an intermittent jammer,
interfere with GPS and/or other signals, and possibly receive a visit from
the authorities. Look at the problems that where caused by oscillating TV
peamplifiers radiating from a marina on the west coast. Retransmitting with
a different output frequency is a different issue and may be a better
approach.
John WA4WDL
--------------------------------------------------
From: "David McGaw" <n1...@alum.dartmouth.org>
Sent: Thursday, April 12, 2012 11:11 AM
To: "Discussion of precise time and frequency measurement"
<time-nuts@febo.com>
Subject: Re: [time-nuts] Re-radiating a GPS signal...??
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.me...@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"<mp...@clanbaker.org>
To:<time-nuts@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
----------------------
_______________________________________________
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
