[time-nuts] Best location for a GPS antenna...?

Bob Camp lists at rtty.us
Thu Apr 12 17:01:34 UTC 2012


Hi

Some of the people posting to the thread seem to be concerned about the
house burning down because they put up a GPS antenna...

Receivers can die from a lot of causes. A TBolt like GPS being killed by
input overload from a strike 100 feet away would not be very high on my list
of likely problems.

Bob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Chris Albertson
Sent: Thursday, April 12, 2012 12:50 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Best location for a GPS antenna...?

On Wed, Apr 11, 2012 at 3:08 PM, Bob Camp <lists at rtty.us> wrote:
> Hi
>
> If the antenna is no higher than your house, it's no more likely to get
hit than the house.
> If it's higher than the house by a few feet, the increase in hit
probability is vanishingly small.

Antenna do not have to be directly hit to destroy the receiver.  Let's
say that something 100 feet away is hit.  The nearby strike is
thousands of amps of current in a brief pulse.  What you have is
a strong electromagnetic field pulse.  This will induce current in any
nearby conductor, including your antenna mast, power lines, phone
lines and even the copper traces on a PCB.   The effects vary based on
the geometry.    One does not even worry about a direct hit.  It is
rare and if it happens your equipment is vaporized.  But near hits
happen all the time you can expect them and they are mostly the cause
of damaged equipment and it is actually posable to protect against a
nearby hit.

Think of lightening like a 1,000 pound bomb.  If one falls from the
sky on a city and hits you on the head you are dead.  But most of the
people effected by the bomb did NOT get hit on the head and were
varying distances from it and for most of them various protection
measures can be very effective.

Redondo Beach, California

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