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

Bob Camp lists at rtty.us
Fri Jun 10 16:42:49 UTC 2011


Hi

The FCC (like most US agencies) has a mission to promote as well as
regulate. The promotion side is what drives them to allocate frequencies in
a way that you can reasonably produce gear. They have always come back years
later and tried to change things around. Every time, the same issues get
hashed over. Sometimes a change actually gets made, sometimes not. 

What's surprising with the GPS impact here is that the usual conversations
are taking place a bit late in the process. The impact on legacy timing gear
is one part of a much larger issue here. Hopefully it does not get lost in
the back and forth. There's an enormous amount of gear out there that gets
timing off of GPS. 

Bob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of William H. Fite
Sent: Friday, June 10, 2011 9:47 AM
To: shalimr9 at gmail.com; Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] GPS interference and history...

You folks are all far more knowledgeable than I on these issues so I have a
question:

To what extent, from both an engineering perspective and from the standpoint
of public policy, should it be the obligation of transmitter and receiver
manufacturers to design and build devices with sufficient filtering, et
alia, to avoid or at least vastly minimize problems such as those described
below by Didier?

I suppose from an engineering standpoint the issue is one of do-ability and
from the public policy perspective, how much it is reasonable to expect both
those who transmit and those who receive to pay for equipment that will
minimize interference problems, given that we are running out of spectrum
and demands for chunks of it will continue to pour in.

Both technical information and philosophical ramblings will be appreciated.

Bill

On Fri, Jun 10, 2011 at 9:16 AM, <shalimr9 at gmail.com> wrote:

> The problem is that many FM receivers leak LO signal, so if 2 receivers
are
> next to each others and set 10.7 MHz apart, one will be receiving the LO
of
> the oter.
>
> Didier KO4BB
>
> Sent from my BlackBerry Wireless thingy while I do other things...
>
> -----Original Message-----
> From: Chuck Forsberg WA7KGX N2469R <caf at omen.com>
> Sender: time-nuts-bounces at febo.com
> Date: Thu, 09 Jun 2011 12:16:48
> To: <ehydra at arcor.de>; Discussion of precise time and frequency
> measurement<time-nuts at febo.com>
> Reply-To: Discussion of precise time and frequency measurement
>        <time-nuts at febo.com>
> Subject: Re: [time-nuts] GPS interference and history...
>
>  The image frequency for an FM receiver with a 10.7 mHz IF
> is 21.4 mHz above or below.  Perhaps they were worried about
> receivers with IFs in the 5 mHz range?
>
> --
> Chuck Forsberg WA7KGX N2469R     caf at omen.com   www.omen.com
> Developer of Industrial ZMODEM(Tm) for Embedded Applications
>   Omen Technology Inc      "The High Reliability Software"
> 10255 NW Old Cornelius Pass Portland OR 97231   503-614-0430
>
>
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