BC

Bob Camp

Fri, Mar 4, 2011 6:31 PM

Hi

Ok, now it's pretty obvious the RF world near your GPS will be changing a lot in the near future. Lightsquared and a bunch of similar outfits will be camping out right next door with very high power gear. They will be running 1.5KW from somewhere in town. GPS is running 30 watts from off planet.

Has anybody tossed the various HP / Symmetricom GPS splitters on a network analyzer? If so, what do the filters in them look like?

I probably should corner the market on these things before asking a question like that.

The new neighbors will be at 1525 to 1559 MHz. GPS L1 is at 1575.42 MHz. That's what we are using for timing. L2 is down at 1227.5, right now it's mainly military use. Obviously these guys are a bigger deal for civilians than the military.

So the question is - do the built in splitter filters have any real rejection 15 to 50 MHz off of center?

Probably worth checking. It would be a pleasant surprise if they turned out to be useful.

Bob

Hi Ok, now it's pretty obvious the RF world near your GPS will be changing a *lot* in the near future. Lightsquared and a bunch of similar outfits will be camping out right next door with very high power gear. They will be running 1.5KW from somewhere in town. GPS is running 30 watts from off planet. Has anybody tossed the various HP / Symmetricom GPS splitters on a network analyzer? If so, what do the filters in them look like? I probably should corner the market on these things before asking a question like that. The new neighbors will be at 1525 to 1559 MHz. GPS L1 is at 1575.42 MHz. That's what we are using for timing. L2 is down at 1227.5, right now it's mainly military use. Obviously these guys are a bigger deal for civilians than the military. So the question is - do the built in splitter filters have any real rejection 15 to 50 MHz off of center? Probably worth checking. It would be a pleasant surprise if they turned out to be useful. Bob

CA

Chris Albertson

Fri, Mar 4, 2011 8:20 PM

On Fri, Mar 4, 2011 at 10:31 AM, Bob Camp lists@rtty.us wrote:
now it's mainly military use. Obviously these guys are a bigger deal
for civilians than the military.

So the question is - do the built in splitter filters have any real rejection 15 to 50 MHz off of center?

Most GPS antenna are active. I'm a bit more worried about the preamps
built into the antenna. A filter external to the antenna will not
protect the built-in preamp.

But there are all kinds of designs for home built GPS antenna. A
helix antenna is not hard to make. Timing GPSes at fixed sites can
use antenna that have a deep null aimed at the nearby transmitter
(which is also fixed) People at fixed sites will have it easy.
Mobile GPS users will not be able use antenna design.

--

Chris Albertson
Redondo Beach, California

On Fri, Mar 4, 2011 at 10:31 AM, Bob Camp <lists@rtty.us> wrote: now it's mainly military use. Obviously these guys are a bigger deal for civilians than the military. > > So the question is - do the built in splitter filters have any real rejection 15 to 50 MHz off of center? Most GPS antenna are active. I'm a bit more worried about the preamps built into the antenna. A filter external to the antenna will not protect the built-in preamp. But there are all kinds of designs for home built GPS antenna. A helix antenna is not hard to make. Timing GPSes at fixed sites can use antenna that have a deep null aimed at the nearby transmitter (which is also fixed) People at fixed sites will have it easy. Mobile GPS users will not be able use antenna design. -- ===== Chris Albertson Redondo Beach, California

JA

John Ackermann N8UR

Fri, Mar 4, 2011 8:31 PM

Here's a measurement we did a few years ago on the HP 58535A:
http://www.febo.com/pages/hp_gps_splitter/port_1_hp_58535a_two_port_amp.png

John

On 3/4/2011 1:31 PM, Bob Camp wrote:

Hi

Ok, now it's pretty obvious the RF world near your GPS will be changing a lot in the near future. Lightsquared and a bunch of similar outfits will be camping out right next door with very high power gear. They will be running 1.5KW from somewhere in town. GPS is running 30 watts from off planet.

Has anybody tossed the various HP / Symmetricom GPS splitters on a network analyzer? If so, what do the filters in them look like?

I probably should corner the market on these things before asking a question like that.

The new neighbors will be at 1525 to 1559 MHz. GPS L1 is at 1575.42 MHz. That's what we are using for timing. L2 is down at 1227.5, right now it's mainly military use. Obviously these guys are a bigger deal for civilians than the military.

So the question is - do the built in splitter filters have any real rejection 15 to 50 MHz off of center?

Probably worth checking. It would be a pleasant surprise if they turned out to be useful.

Bob

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.

Here's a measurement we did a few years ago on the HP 58535A: http://www.febo.com/pages/hp_gps_splitter/port_1_hp_58535a_two_port_amp.png John ---- On 3/4/2011 1:31 PM, Bob Camp wrote: > Hi > > Ok, now it's pretty obvious the RF world near your GPS will be changing a *lot* in the near future. Lightsquared and a bunch of similar outfits will be camping out right next door with very high power gear. They will be running 1.5KW from somewhere in town. GPS is running 30 watts from off planet. > > Has anybody tossed the various HP / Symmetricom GPS splitters on a network analyzer? If so, what do the filters in them look like? > > I probably should corner the market on these things before asking a question like that. > > The new neighbors will be at 1525 to 1559 MHz. GPS L1 is at 1575.42 MHz. That's what we are using for timing. L2 is down at 1227.5, right now it's mainly military use. Obviously these guys are a bigger deal for civilians than the military. > > So the question is - do the built in splitter filters have any real rejection 15 to 50 MHz off of center? > > Probably worth checking. It would be a pleasant surprise if they turned out to be useful. > > Bob > > > > _______________________________________________ > 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.

Z

Ziggy

Sat, Mar 5, 2011 12:47 AM

The discussion got me to thinking about how we used to filter out nearby
interference on amateur TV - namely by using interdigital filters. This
led to a search for GPS interdigital filters which i did indeed find.
See Alison Microwave website at
http://www.amlant.co.uk/DetailsAD430.htm for one example of an
integrated antenna/filter/preamp. (I'm sure these aren't cheap, but I
haven't asked.) As for retrofitting, you could add a filter after the
antenna/amplifier assembly but I might be concerned that the amplified
GPS antenna is pretty wide and may have trouble with a Lightsquared
transmitter nearby. There are passive antennas though, and there are
in-line amps - you'd need to add the filter in between. We made these
ourselves for 439 and 1296 MHz - GPS L1 isn't much above that so with
some care it should be doable. The tuning can be finicky though :\

Ziggy

On 03/04/2011 03:31 PM, John Ackermann N8UR wrote:

Here's a measurement we did a few years ago on the HP 58535A:
http://www.febo.com/pages/hp_gps_splitter/port_1_hp_58535a_two_port_amp.png

John

On 3/4/2011 1:31 PM, Bob Camp wrote:

Hi

Ok, now it's pretty obvious the RF world near your GPS will be
changing a lot in the near future. Lightsquared and a bunch of
similar outfits will be camping out right next door with very high
power gear. They will be running 1.5KW from somewhere in town. GPS is
running 30 watts from off planet.

Has anybody tossed the various HP / Symmetricom GPS splitters on a
network analyzer? If so, what do the filters in them look like?

I probably should corner the market on these things before asking a
question like that.

The new neighbors will be at 1525 to 1559 MHz. GPS L1 is at 1575.42
MHz. That's what we are using for timing. L2 is down at 1227.5,
right now it's mainly military use. Obviously these guys are a bigger
deal for civilians than the military.

So the question is - do the built in splitter filters have any real
rejection 15 to 50 MHz off of center?

Probably worth checking. It would be a pleasant surprise if they
turned out to be useful.

Bob

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.

The discussion got me to thinking about how we used to filter out nearby interference on amateur TV - namely by using interdigital filters. This led to a search for GPS interdigital filters which i did indeed find. See Alison Microwave website at <http://www.amlant.co.uk/DetailsAD430.htm> for one example of an integrated antenna/filter/preamp. (I'm sure these aren't cheap, but I haven't asked.) As for retrofitting, you could add a filter after the antenna/amplifier assembly but I might be concerned that the amplified GPS antenna is pretty wide and may have trouble with a Lightsquared transmitter nearby. There are passive antennas though, and there are in-line amps - you'd need to add the filter in between. We made these ourselves for 439 and 1296 MHz - GPS L1 isn't much above that so with some care it should be doable. The tuning can be finicky though :\ Ziggy On 03/04/2011 03:31 PM, John Ackermann N8UR wrote: > Here's a measurement we did a few years ago on the HP 58535A: > http://www.febo.com/pages/hp_gps_splitter/port_1_hp_58535a_two_port_amp.png > > > John > ---- > On 3/4/2011 1:31 PM, Bob Camp wrote: >> Hi >> >> Ok, now it's pretty obvious the RF world near your GPS will be >> changing a *lot* in the near future. Lightsquared and a bunch of >> similar outfits will be camping out right next door with very high >> power gear. They will be running 1.5KW from somewhere in town. GPS is >> running 30 watts from off planet. >> >> Has anybody tossed the various HP / Symmetricom GPS splitters on a >> network analyzer? If so, what do the filters in them look like? >> >> I probably should corner the market on these things before asking a >> question like that. >> >> The new neighbors will be at 1525 to 1559 MHz. GPS L1 is at 1575.42 >> MHz. That's what we are using for timing. L2 is down at 1227.5, >> right now it's mainly military use. Obviously these guys are a bigger >> deal for civilians than the military. >> >> So the question is - do the built in splitter filters have any real >> rejection 15 to 50 MHz off of center? >> >> Probably worth checking. It would be a pleasant surprise if they >> turned out to be useful. >> >> Bob >> >> >> >> _______________________________________________ >> 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. >

MF

Mike Feher

Sat, Mar 5, 2011 1:36 AM

I used to make some interdigital filters and amplifiers in the early 80's
for MDS TV reception in the 2.3 GHz range. One can easily fabricate a low
loss narrow band filter at 1.5 GHz if need be, and as mentioned before,
antennas should be easy as well. If this really becomes an issue, I am sure
there will be a lot of solutions offered and anyone with some RF experience
will also be able to handle it themselves. Regards - Mike

Mike B. Feher, EOZ Inc.
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960 office
908-902-3831 cell

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Ziggy
Sent: Friday, March 04, 2011 7:47 PM
To: time-nuts@febo.com
Subject: Re: [time-nuts] GPS Filter

The discussion got me to thinking about how we used to filter out nearby
interference on amateur TV - namely by using interdigital filters. This
led to a search for GPS interdigital filters which i did indeed find.
See Alison Microwave website at
http://www.amlant.co.uk/DetailsAD430.htm for one example of an
integrated antenna/filter/preamp. (I'm sure these aren't cheap, but I
haven't asked.) As for retrofitting, you could add a filter after the
antenna/amplifier assembly but I might be concerned that the amplified
GPS antenna is pretty wide and may have trouble with a Lightsquared
transmitter nearby. There are passive antennas though, and there are
in-line amps - you'd need to add the filter in between. We made these
ourselves for 439 and 1296 MHz - GPS L1 isn't much above that so with
some care it should be doable. The tuning can be finicky though :\

Ziggy

On 03/04/2011 03:31 PM, John Ackermann N8UR wrote:

Here's a measurement we did a few years ago on the HP 58535A:

http://www.febo.com/pages/hp_gps_splitter/port_1_hp_58535a_two_port_amp.png

John

On 3/4/2011 1:31 PM, Bob Camp wrote:

Hi

Ok, now it's pretty obvious the RF world near your GPS will be
changing a lot in the near future. Lightsquared and a bunch of
similar outfits will be camping out right next door with very high
power gear. They will be running 1.5KW from somewhere in town. GPS is
running 30 watts from off planet.

Has anybody tossed the various HP / Symmetricom GPS splitters on a
network analyzer? If so, what do the filters in them look like?

I probably should corner the market on these things before asking a
question like that.

The new neighbors will be at 1525 to 1559 MHz. GPS L1 is at 1575.42
MHz. That's what we are using for timing. L2 is down at 1227.5,
right now it's mainly military use. Obviously these guys are a bigger
deal for civilians than the military.

So the question is - do the built in splitter filters have any real
rejection 15 to 50 MHz off of center?

Probably worth checking. It would be a pleasant surprise if they
turned out to be useful.

Bob

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.

I used to make some interdigital filters and amplifiers in the early 80's for MDS TV reception in the 2.3 GHz range. One can easily fabricate a low loss narrow band filter at 1.5 GHz if need be, and as mentioned before, antennas should be easy as well. If this really becomes an issue, I am sure there will be a lot of solutions offered and anyone with some RF experience will also be able to handle it themselves. Regards - Mike Mike B. Feher, EOZ Inc. 89 Arnold Blvd. Howell, NJ, 07731 732-886-5960 office 908-902-3831 cell -----Original Message----- From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On Behalf Of Ziggy Sent: Friday, March 04, 2011 7:47 PM To: time-nuts@febo.com Subject: Re: [time-nuts] GPS Filter The discussion got me to thinking about how we used to filter out nearby interference on amateur TV - namely by using interdigital filters. This led to a search for GPS interdigital filters which i did indeed find. See Alison Microwave website at <http://www.amlant.co.uk/DetailsAD430.htm> for one example of an integrated antenna/filter/preamp. (I'm sure these aren't cheap, but I haven't asked.) As for retrofitting, you could add a filter after the antenna/amplifier assembly but I might be concerned that the amplified GPS antenna is pretty wide and may have trouble with a Lightsquared transmitter nearby. There are passive antennas though, and there are in-line amps - you'd need to add the filter in between. We made these ourselves for 439 and 1296 MHz - GPS L1 isn't much above that so with some care it should be doable. The tuning can be finicky though :\ Ziggy On 03/04/2011 03:31 PM, John Ackermann N8UR wrote: > Here's a measurement we did a few years ago on the HP 58535A: > http://www.febo.com/pages/hp_gps_splitter/port_1_hp_58535a_two_port_amp.png > > > John > ---- > On 3/4/2011 1:31 PM, Bob Camp wrote: >> Hi >> >> Ok, now it's pretty obvious the RF world near your GPS will be >> changing a *lot* in the near future. Lightsquared and a bunch of >> similar outfits will be camping out right next door with very high >> power gear. They will be running 1.5KW from somewhere in town. GPS is >> running 30 watts from off planet. >> >> Has anybody tossed the various HP / Symmetricom GPS splitters on a >> network analyzer? If so, what do the filters in them look like? >> >> I probably should corner the market on these things before asking a >> question like that. >> >> The new neighbors will be at 1525 to 1559 MHz. GPS L1 is at 1575.42 >> MHz. That's what we are using for timing. L2 is down at 1227.5, >> right now it's mainly military use. Obviously these guys are a bigger >> deal for civilians than the military. >> >> So the question is - do the built in splitter filters have any real >> rejection 15 to 50 MHz off of center? >> >> Probably worth checking. It would be a pleasant surprise if they >> turned out to be useful. >> >> Bob >> >> >> >> _______________________________________________ >> 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.

JF

J. Forster

Sat, Mar 5, 2011 1:46 AM

I'm not so sure.

A filter ahead of a preamp significantly increases the system Noise
Temperature.

GPS signals are weak and link margins are small. The receiver preamps are
already very low noise.

I'd think that a narrow filter might well drive up the systen NF to the
point it'd be useless.

FWIW,

-John

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

I used to make some interdigital filters and amplifiers in the early 80's
for MDS TV reception in the 2.3 GHz range. One can easily fabricate a low
loss narrow band filter at 1.5 GHz if need be, and as mentioned before,
antennas should be easy as well. If this really becomes an issue, I am
sure
there will be a lot of solutions offered and anyone with some RF
experience
will also be able to handle it themselves. Regards - Mike

Mike B. Feher, EOZ Inc.
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960 office
908-902-3831 cell

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Ziggy
Sent: Friday, March 04, 2011 7:47 PM
To: time-nuts@febo.com
Subject: Re: [time-nuts] GPS Filter

The discussion got me to thinking about how we used to filter out nearby
interference on amateur TV - namely by using interdigital filters. This
led to a search for GPS interdigital filters which i did indeed find.
See Alison Microwave website at
http://www.amlant.co.uk/DetailsAD430.htm for one example of an
integrated antenna/filter/preamp. (I'm sure these aren't cheap, but I
haven't asked.) As for retrofitting, you could add a filter after the
antenna/amplifier assembly but I might be concerned that the amplified
GPS antenna is pretty wide and may have trouble with a Lightsquared
transmitter nearby. There are passive antennas though, and there are
in-line amps - you'd need to add the filter in between. We made these
ourselves for 439 and 1296 MHz - GPS L1 isn't much above that so with
some care it should be doable. The tuning can be finicky though :\

Ziggy

On 03/04/2011 03:31 PM, John Ackermann N8UR wrote:

Here's a measurement we did a few years ago on the HP 58535A:

http://www.febo.com/pages/hp_gps_splitter/port_1_hp_58535a_two_port_amp.png

John

On 3/4/2011 1:31 PM, Bob Camp wrote:

Hi

Ok, now it's pretty obvious the RF world near your GPS will be
changing a lot in the near future. Lightsquared and a bunch of
similar outfits will be camping out right next door with very high
power gear. They will be running 1.5KW from somewhere in town. GPS is
running 30 watts from off planet.

Has anybody tossed the various HP / Symmetricom GPS splitters on a
network analyzer? If so, what do the filters in them look like?

I probably should corner the market on these things before asking a
question like that.

The new neighbors will be at 1525 to 1559 MHz. GPS L1 is at 1575.42
MHz. That's what we are using for timing. L2 is down at 1227.5,
right now it's mainly military use. Obviously these guys are a bigger
deal for civilians than the military.

So the question is - do the built in splitter filters have any real
rejection 15 to 50 MHz off of center?

Probably worth checking. It would be a pleasant surprise if they
turned out to be useful.

Bob

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.

I'm not so sure. A filter ahead of a preamp significantly increases the system Noise Temperature. GPS signals are weak and link margins are small. The receiver preamps are already very low noise. I'd think that a narrow filter might well drive up the systen NF to the point it'd be useless. FWIW, -John ============= > I used to make some interdigital filters and amplifiers in the early 80's > for MDS TV reception in the 2.3 GHz range. One can easily fabricate a low > loss narrow band filter at 1.5 GHz if need be, and as mentioned before, > antennas should be easy as well. If this really becomes an issue, I am > sure > there will be a lot of solutions offered and anyone with some RF > experience > will also be able to handle it themselves. Regards - Mike > > Mike B. Feher, EOZ Inc. > 89 Arnold Blvd. > Howell, NJ, 07731 > 732-886-5960 office > 908-902-3831 cell > > > -----Original Message----- > From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On > Behalf Of Ziggy > Sent: Friday, March 04, 2011 7:47 PM > To: time-nuts@febo.com > Subject: Re: [time-nuts] GPS Filter > > The discussion got me to thinking about how we used to filter out nearby > interference on amateur TV - namely by using interdigital filters. This > led to a search for GPS interdigital filters which i did indeed find. > See Alison Microwave website at > <http://www.amlant.co.uk/DetailsAD430.htm> for one example of an > integrated antenna/filter/preamp. (I'm sure these aren't cheap, but I > haven't asked.) As for retrofitting, you could add a filter after the > antenna/amplifier assembly but I might be concerned that the amplified > GPS antenna is pretty wide and may have trouble with a Lightsquared > transmitter nearby. There are passive antennas though, and there are > in-line amps - you'd need to add the filter in between. We made these > ourselves for 439 and 1296 MHz - GPS L1 isn't much above that so with > some care it should be doable. The tuning can be finicky though :\ > > Ziggy > > On 03/04/2011 03:31 PM, John Ackermann N8UR wrote: >> Here's a measurement we did a few years ago on the HP 58535A: >> > http://www.febo.com/pages/hp_gps_splitter/port_1_hp_58535a_two_port_amp.png >> >> >> John >> ---- >> On 3/4/2011 1:31 PM, Bob Camp wrote: >>> Hi >>> >>> Ok, now it's pretty obvious the RF world near your GPS will be >>> changing a *lot* in the near future. Lightsquared and a bunch of >>> similar outfits will be camping out right next door with very high >>> power gear. They will be running 1.5KW from somewhere in town. GPS is >>> running 30 watts from off planet. >>> >>> Has anybody tossed the various HP / Symmetricom GPS splitters on a >>> network analyzer? If so, what do the filters in them look like? >>> >>> I probably should corner the market on these things before asking a >>> question like that. >>> >>> The new neighbors will be at 1525 to 1559 MHz. GPS L1 is at 1575.42 >>> MHz. That's what we are using for timing. L2 is down at 1227.5, >>> right now it's mainly military use. Obviously these guys are a bigger >>> deal for civilians than the military. >>> >>> So the question is - do the built in splitter filters have any real >>> rejection 15 to 50 MHz off of center? >>> >>> Probably worth checking. It would be a pleasant surprise if they >>> turned out to be useful. >>> >>> Bob >>> >>> >>> >>> _______________________________________________ >>> 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. > >

MF

Mike Feher

Sat, Mar 5, 2011 1:59 AM

Well, as you said John, for FWIW. In this case not much. As said low loss,
so increase in noise temp would be minimal, and, if it makes a difference
between an overloaded front end or a 0.5 dB loss in NF, it will be welcome.
Heck, we use filters in front of most of our Satcom LNBs at 21 GHz with
minimal effect. Been there and done that, as the saying goes. If necessary
the small increase in noise temp can easily be overcome by a slightly larger
aperture, especially since a view of the full sky is not really necessary
and birds below certain elevation angles are typically ignored by software
settings of one's own choosing. And again, I was talking about people who
have done this and can do it again. It would not be an issue for me. Regards

Mike

Mike B. Feher, EOZ Inc.
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960 office
908-902-3831 cell

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of J. Forster
Sent: Friday, March 04, 2011 8:47 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] GPS Filter

I'm not so sure.

A filter ahead of a preamp significantly increases the system Noise
Temperature.

GPS signals are weak and link margins are small. The receiver preamps are
already very low noise.

I'd think that a narrow filter might well drive up the systen NF to the
point it'd be useless.

FWIW,

-John

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

I used to make some interdigital filters and amplifiers in the early 80's
for MDS TV reception in the 2.3 GHz range. One can easily fabricate a low
loss narrow band filter at 1.5 GHz if need be, and as mentioned before,
antennas should be easy as well. If this really becomes an issue, I am
sure
there will be a lot of solutions offered and anyone with some RF
experience
will also be able to handle it themselves. Regards - Mike

Mike B. Feher, EOZ Inc.
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960 office
908-902-3831 cell

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Ziggy
Sent: Friday, March 04, 2011 7:47 PM
To: time-nuts@febo.com
Subject: Re: [time-nuts] GPS Filter

The discussion got me to thinking about how we used to filter out nearby
interference on amateur TV - namely by using interdigital filters. This
led to a search for GPS interdigital filters which i did indeed find.
See Alison Microwave website at
http://www.amlant.co.uk/DetailsAD430.htm for one example of an
integrated antenna/filter/preamp. (I'm sure these aren't cheap, but I
haven't asked.) As for retrofitting, you could add a filter after the
antenna/amplifier assembly but I might be concerned that the amplified
GPS antenna is pretty wide and may have trouble with a Lightsquared
transmitter nearby. There are passive antennas though, and there are
in-line amps - you'd need to add the filter in between. We made these
ourselves for 439 and 1296 MHz - GPS L1 isn't much above that so with
some care it should be doable. The tuning can be finicky though :\

Ziggy

On 03/04/2011 03:31 PM, John Ackermann N8UR wrote:

Here's a measurement we did a few years ago on the HP 58535A:

http://www.febo.com/pages/hp_gps_splitter/port_1_hp_58535a_two_port_amp.png

John

On 3/4/2011 1:31 PM, Bob Camp wrote:

Hi

Ok, now it's pretty obvious the RF world near your GPS will be
changing a lot in the near future. Lightsquared and a bunch of
similar outfits will be camping out right next door with very high
power gear. They will be running 1.5KW from somewhere in town. GPS is
running 30 watts from off planet.

Has anybody tossed the various HP / Symmetricom GPS splitters on a
network analyzer? If so, what do the filters in them look like?

I probably should corner the market on these things before asking a
question like that.

The new neighbors will be at 1525 to 1559 MHz. GPS L1 is at 1575.42
MHz. That's what we are using for timing. L2 is down at 1227.5,
right now it's mainly military use. Obviously these guys are a bigger
deal for civilians than the military.

So the question is - do the built in splitter filters have any real
rejection 15 to 50 MHz off of center?

Probably worth checking. It would be a pleasant surprise if they
turned out to be useful.

Bob

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.

Well, as you said John, for FWIW. In this case not much. As said low loss, so increase in noise temp would be minimal, and, if it makes a difference between an overloaded front end or a 0.5 dB loss in NF, it will be welcome. Heck, we use filters in front of most of our Satcom LNBs at 21 GHz with minimal effect. Been there and done that, as the saying goes. If necessary the small increase in noise temp can easily be overcome by a slightly larger aperture, especially since a view of the full sky is not really necessary and birds below certain elevation angles are typically ignored by software settings of one's own choosing. And again, I was talking about people who have done this and can do it again. It would not be an issue for me. Regards - Mike Mike B. Feher, EOZ Inc. 89 Arnold Blvd. Howell, NJ, 07731 732-886-5960 office 908-902-3831 cell -----Original Message----- From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On Behalf Of J. Forster Sent: Friday, March 04, 2011 8:47 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] GPS Filter I'm not so sure. A filter ahead of a preamp significantly increases the system Noise Temperature. GPS signals are weak and link margins are small. The receiver preamps are already very low noise. I'd think that a narrow filter might well drive up the systen NF to the point it'd be useless. FWIW, -John ============= > I used to make some interdigital filters and amplifiers in the early 80's > for MDS TV reception in the 2.3 GHz range. One can easily fabricate a low > loss narrow band filter at 1.5 GHz if need be, and as mentioned before, > antennas should be easy as well. If this really becomes an issue, I am > sure > there will be a lot of solutions offered and anyone with some RF > experience > will also be able to handle it themselves. Regards - Mike > > Mike B. Feher, EOZ Inc. > 89 Arnold Blvd. > Howell, NJ, 07731 > 732-886-5960 office > 908-902-3831 cell > > > -----Original Message----- > From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On > Behalf Of Ziggy > Sent: Friday, March 04, 2011 7:47 PM > To: time-nuts@febo.com > Subject: Re: [time-nuts] GPS Filter > > The discussion got me to thinking about how we used to filter out nearby > interference on amateur TV - namely by using interdigital filters. This > led to a search for GPS interdigital filters which i did indeed find. > See Alison Microwave website at > <http://www.amlant.co.uk/DetailsAD430.htm> for one example of an > integrated antenna/filter/preamp. (I'm sure these aren't cheap, but I > haven't asked.) As for retrofitting, you could add a filter after the > antenna/amplifier assembly but I might be concerned that the amplified > GPS antenna is pretty wide and may have trouble with a Lightsquared > transmitter nearby. There are passive antennas though, and there are > in-line amps - you'd need to add the filter in between. We made these > ourselves for 439 and 1296 MHz - GPS L1 isn't much above that so with > some care it should be doable. The tuning can be finicky though :\ > > Ziggy > > On 03/04/2011 03:31 PM, John Ackermann N8UR wrote: >> Here's a measurement we did a few years ago on the HP 58535A: >> > http://www.febo.com/pages/hp_gps_splitter/port_1_hp_58535a_two_port_amp.png >> >> >> John >> ---- >> On 3/4/2011 1:31 PM, Bob Camp wrote: >>> Hi >>> >>> Ok, now it's pretty obvious the RF world near your GPS will be >>> changing a *lot* in the near future. Lightsquared and a bunch of >>> similar outfits will be camping out right next door with very high >>> power gear. They will be running 1.5KW from somewhere in town. GPS is >>> running 30 watts from off planet. >>> >>> Has anybody tossed the various HP / Symmetricom GPS splitters on a >>> network analyzer? If so, what do the filters in them look like? >>> >>> I probably should corner the market on these things before asking a >>> question like that. >>> >>> The new neighbors will be at 1525 to 1559 MHz. GPS L1 is at 1575.42 >>> MHz. That's what we are using for timing. L2 is down at 1227.5, >>> right now it's mainly military use. Obviously these guys are a bigger >>> deal for civilians than the military. >>> >>> So the question is - do the built in splitter filters have any real >>> rejection 15 to 50 MHz off of center? >>> >>> Probably worth checking. It would be a pleasant surprise if they >>> turned out to be useful. >>> >>> Bob >>> >>> >>> >>> _______________________________________________ >>> 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.

JF

J. Forster

Sat, Mar 5, 2011 2:08 AM

Preamps with NFs under 0.5 dB are available for the 1.5 GHz region. IMO a
doubling of system noise temperature is non-trivial.

-John

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

Well, as you said John, for FWIW. In this case not much. As said low loss,
so increase in noise temp would be minimal, and, if it makes a difference
between an overloaded front end or a 0.5 dB loss in NF, it will be
welcome.
Heck, we use filters in front of most of our Satcom LNBs at 21 GHz with
minimal effect. Been there and done that, as the saying goes. If necessary
the small increase in noise temp can easily be overcome by a slightly
larger
aperture, especially since a view of the full sky is not really necessary
and birds below certain elevation angles are typically ignored by software
settings of one's own choosing. And again, I was talking about people who
have done this and can do it again. It would not be an issue for me.
Regards

Mike

Mike B. Feher, EOZ Inc.
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960 office
908-902-3831 cell

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of J. Forster
Sent: Friday, March 04, 2011 8:47 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] GPS Filter

I'm not so sure.

A filter ahead of a preamp significantly increases the system Noise
Temperature.

GPS signals are weak and link margins are small. The receiver preamps are
already very low noise.

I'd think that a narrow filter might well drive up the systen NF to the
point it'd be useless.

FWIW,

-John

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

I used to make some interdigital filters and amplifiers in the early
80's
for MDS TV reception in the 2.3 GHz range. One can easily fabricate a
low
loss narrow band filter at 1.5 GHz if need be, and as mentioned before,
antennas should be easy as well. If this really becomes an issue, I am
sure
there will be a lot of solutions offered and anyone with some RF
experience
will also be able to handle it themselves. Regards - Mike

Mike B. Feher, EOZ Inc.
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960 office
908-902-3831 cell

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Ziggy
Sent: Friday, March 04, 2011 7:47 PM
To: time-nuts@febo.com
Subject: Re: [time-nuts] GPS Filter

The discussion got me to thinking about how we used to filter out nearby
interference on amateur TV - namely by using interdigital filters. This
led to a search for GPS interdigital filters which i did indeed find.
See Alison Microwave website at
http://www.amlant.co.uk/DetailsAD430.htm for one example of an
integrated antenna/filter/preamp. (I'm sure these aren't cheap, but I
haven't asked.) As for retrofitting, you could add a filter after the
antenna/amplifier assembly but I might be concerned that the amplified
GPS antenna is pretty wide and may have trouble with a Lightsquared
transmitter nearby. There are passive antennas though, and there are
in-line amps - you'd need to add the filter in between. We made these
ourselves for 439 and 1296 MHz - GPS L1 isn't much above that so with
some care it should be doable. The tuning can be finicky though :\

Ziggy

On 03/04/2011 03:31 PM, John Ackermann N8UR wrote:

Here's a measurement we did a few years ago on the HP 58535A:

http://www.febo.com/pages/hp_gps_splitter/port_1_hp_58535a_two_port_amp.png

John

On 3/4/2011 1:31 PM, Bob Camp wrote:

Hi

Ok, now it's pretty obvious the RF world near your GPS will be
changing a lot in the near future. Lightsquared and a bunch of
similar outfits will be camping out right next door with very high
power gear. They will be running 1.5KW from somewhere in town. GPS is
running 30 watts from off planet.

Has anybody tossed the various HP / Symmetricom GPS splitters on a
network analyzer? If so, what do the filters in them look like?

I probably should corner the market on these things before asking a
question like that.

The new neighbors will be at 1525 to 1559 MHz. GPS L1 is at 1575.42
MHz. That's what we are using for timing. L2 is down at 1227.5,
right now it's mainly military use. Obviously these guys are a bigger
deal for civilians than the military.

So the question is - do the built in splitter filters have any real
rejection 15 to 50 MHz off of center?

Probably worth checking. It would be a pleasant surprise if they
turned out to be useful.

Bob

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.

Preamps with NFs under 0.5 dB are available for the 1.5 GHz region. IMO a doubling of system noise temperature is non-trivial. -John =============== > Well, as you said John, for FWIW. In this case not much. As said low loss, > so increase in noise temp would be minimal, and, if it makes a difference > between an overloaded front end or a 0.5 dB loss in NF, it will be > welcome. > Heck, we use filters in front of most of our Satcom LNBs at 21 GHz with > minimal effect. Been there and done that, as the saying goes. If necessary > the small increase in noise temp can easily be overcome by a slightly > larger > aperture, especially since a view of the full sky is not really necessary > and birds below certain elevation angles are typically ignored by software > settings of one's own choosing. And again, I was talking about people who > have done this and can do it again. It would not be an issue for me. > Regards > - Mike > > Mike B. Feher, EOZ Inc. > 89 Arnold Blvd. > Howell, NJ, 07731 > 732-886-5960 office > 908-902-3831 cell > > > -----Original Message----- > From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On > Behalf Of J. Forster > Sent: Friday, March 04, 2011 8:47 PM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] GPS Filter > > I'm not so sure. > > A filter ahead of a preamp significantly increases the system Noise > Temperature. > > GPS signals are weak and link margins are small. The receiver preamps are > already very low noise. > > I'd think that a narrow filter might well drive up the systen NF to the > point it'd be useless. > > FWIW, > > -John > > ============= > > >> I used to make some interdigital filters and amplifiers in the early >> 80's >> for MDS TV reception in the 2.3 GHz range. One can easily fabricate a >> low >> loss narrow band filter at 1.5 GHz if need be, and as mentioned before, >> antennas should be easy as well. If this really becomes an issue, I am >> sure >> there will be a lot of solutions offered and anyone with some RF >> experience >> will also be able to handle it themselves. Regards - Mike >> >> Mike B. Feher, EOZ Inc. >> 89 Arnold Blvd. >> Howell, NJ, 07731 >> 732-886-5960 office >> 908-902-3831 cell >> >> >> -----Original Message----- >> From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On >> Behalf Of Ziggy >> Sent: Friday, March 04, 2011 7:47 PM >> To: time-nuts@febo.com >> Subject: Re: [time-nuts] GPS Filter >> >> The discussion got me to thinking about how we used to filter out nearby >> interference on amateur TV - namely by using interdigital filters. This >> led to a search for GPS interdigital filters which i did indeed find. >> See Alison Microwave website at >> <http://www.amlant.co.uk/DetailsAD430.htm> for one example of an >> integrated antenna/filter/preamp. (I'm sure these aren't cheap, but I >> haven't asked.) As for retrofitting, you could add a filter after the >> antenna/amplifier assembly but I might be concerned that the amplified >> GPS antenna is pretty wide and may have trouble with a Lightsquared >> transmitter nearby. There are passive antennas though, and there are >> in-line amps - you'd need to add the filter in between. We made these >> ourselves for 439 and 1296 MHz - GPS L1 isn't much above that so with >> some care it should be doable. The tuning can be finicky though :\ >> >> Ziggy >> >> On 03/04/2011 03:31 PM, John Ackermann N8UR wrote: >>> Here's a measurement we did a few years ago on the HP 58535A: >>> >> > http://www.febo.com/pages/hp_gps_splitter/port_1_hp_58535a_two_port_amp.png >>> >>> >>> John >>> ---- >>> On 3/4/2011 1:31 PM, Bob Camp wrote: >>>> Hi >>>> >>>> Ok, now it's pretty obvious the RF world near your GPS will be >>>> changing a *lot* in the near future. Lightsquared and a bunch of >>>> similar outfits will be camping out right next door with very high >>>> power gear. They will be running 1.5KW from somewhere in town. GPS is >>>> running 30 watts from off planet. >>>> >>>> Has anybody tossed the various HP / Symmetricom GPS splitters on a >>>> network analyzer? If so, what do the filters in them look like? >>>> >>>> I probably should corner the market on these things before asking a >>>> question like that. >>>> >>>> The new neighbors will be at 1525 to 1559 MHz. GPS L1 is at 1575.42 >>>> MHz. That's what we are using for timing. L2 is down at 1227.5, >>>> right now it's mainly military use. Obviously these guys are a bigger >>>> deal for civilians than the military. >>>> >>>> So the question is - do the built in splitter filters have any real >>>> rejection 15 to 50 MHz off of center? >>>> >>>> Probably worth checking. It would be a pleasant surprise if they >>>> turned out to be useful. >>>> >>>> Bob >>>> >>>> >>>> >>>> _______________________________________________ >>>> 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. > >

MF

Mike Feher

Sat, Mar 5, 2011 2:38 AM

I used the 0.5 dB number for loss as a worst case. Of course they are
available. They are available even lower, and even at higher frequencies.
Whether or not is trivial is not relevant. What is required is relevant.
This would of course be relevant in small handheld disadvantaged GPS
receivers, but, for roof mounted time-nuts use it should not be a problem.
Even some indoor use it would be fine. If you really feel that you need less
than 0.5 dB of NF, get the numbers. What is the typical RIP from the various
birds at various locations? Then knowing Ga and NF you can calculate C/N and
Eb/No required for the processors to work with acceptable error. Anyway,
enough on this. This is something I can personally handle and am not
worried. Besides, imagine if all of the sudden millions of Cell phones
became useless. Just not going to happen. - Mike

Mike B. Feher, EOZ Inc.
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960 office
908-902-3831 cell

-----Original Message-----
From: J. Forster [mailto:jfor@quik.com]
Sent: Friday, March 04, 2011 9:09 PM
To: Mike Feher
Cc: 'Discussion of precise time and frequency measurement'
Subject: RE: [time-nuts] GPS Filter

Preamps with NFs under 0.5 dB are available for the 1.5 GHz region. IMO a
doubling of system noise temperature is non-trivial.

-John

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

Well, as you said John, for FWIW. In this case not much. As said low loss,
so increase in noise temp would be minimal, and, if it makes a difference
between an overloaded front end or a 0.5 dB loss in NF, it will be
welcome.
Heck, we use filters in front of most of our Satcom LNBs at 21 GHz with
minimal effect. Been there and done that, as the saying goes. If necessary
the small increase in noise temp can easily be overcome by a slightly
larger
aperture, especially since a view of the full sky is not really necessary
and birds below certain elevation angles are typically ignored by software
settings of one's own choosing. And again, I was talking about people who
have done this and can do it again. It would not be an issue for me.
Regards

Mike

Mike B. Feher, EOZ Inc.
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960 office
908-902-3831 cell

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of J. Forster
Sent: Friday, March 04, 2011 8:47 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] GPS Filter

I'm not so sure.

A filter ahead of a preamp significantly increases the system Noise
Temperature.

GPS signals are weak and link margins are small. The receiver preamps are
already very low noise.

I'd think that a narrow filter might well drive up the systen NF to the
point it'd be useless.

FWIW,

-John

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

I used to make some interdigital filters and amplifiers in the early
80's
for MDS TV reception in the 2.3 GHz range. One can easily fabricate a
low
loss narrow band filter at 1.5 GHz if need be, and as mentioned before,
antennas should be easy as well. If this really becomes an issue, I am
sure
there will be a lot of solutions offered and anyone with some RF
experience
will also be able to handle it themselves. Regards - Mike

Mike B. Feher, EOZ Inc.
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960 office
908-902-3831 cell

I used the 0.5 dB number for loss as a worst case. Of course they are available. They are available even lower, and even at higher frequencies. Whether or not is trivial is not relevant. What is required is relevant. This would of course be relevant in small handheld disadvantaged GPS receivers, but, for roof mounted time-nuts use it should not be a problem. Even some indoor use it would be fine. If you really feel that you need less than 0.5 dB of NF, get the numbers. What is the typical RIP from the various birds at various locations? Then knowing Ga and NF you can calculate C/N and Eb/No required for the processors to work with acceptable error. Anyway, enough on this. This is something I can personally handle and am not worried. Besides, imagine if all of the sudden millions of Cell phones became useless. Just not going to happen. - Mike Mike B. Feher, EOZ Inc. 89 Arnold Blvd. Howell, NJ, 07731 732-886-5960 office 908-902-3831 cell -----Original Message----- From: J. Forster [mailto:jfor@quik.com] Sent: Friday, March 04, 2011 9:09 PM To: Mike Feher Cc: 'Discussion of precise time and frequency measurement' Subject: RE: [time-nuts] GPS Filter Preamps with NFs under 0.5 dB are available for the 1.5 GHz region. IMO a doubling of system noise temperature is non-trivial. -John =============== > Well, as you said John, for FWIW. In this case not much. As said low loss, > so increase in noise temp would be minimal, and, if it makes a difference > between an overloaded front end or a 0.5 dB loss in NF, it will be > welcome. > Heck, we use filters in front of most of our Satcom LNBs at 21 GHz with > minimal effect. Been there and done that, as the saying goes. If necessary > the small increase in noise temp can easily be overcome by a slightly > larger > aperture, especially since a view of the full sky is not really necessary > and birds below certain elevation angles are typically ignored by software > settings of one's own choosing. And again, I was talking about people who > have done this and can do it again. It would not be an issue for me. > Regards > - Mike > > Mike B. Feher, EOZ Inc. > 89 Arnold Blvd. > Howell, NJ, 07731 > 732-886-5960 office > 908-902-3831 cell > > > -----Original Message----- > From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On > Behalf Of J. Forster > Sent: Friday, March 04, 2011 8:47 PM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] GPS Filter > > I'm not so sure. > > A filter ahead of a preamp significantly increases the system Noise > Temperature. > > GPS signals are weak and link margins are small. The receiver preamps are > already very low noise. > > I'd think that a narrow filter might well drive up the systen NF to the > point it'd be useless. > > FWIW, > > -John > > ============= > > >> I used to make some interdigital filters and amplifiers in the early >> 80's >> for MDS TV reception in the 2.3 GHz range. One can easily fabricate a >> low >> loss narrow band filter at 1.5 GHz if need be, and as mentioned before, >> antennas should be easy as well. If this really becomes an issue, I am >> sure >> there will be a lot of solutions offered and anyone with some RF >> experience >> will also be able to handle it themselves. Regards - Mike >> >> Mike B. Feher, EOZ Inc. >> 89 Arnold Blvd. >> Howell, NJ, 07731 >> 732-886-5960 office >> 908-902-3831 cell

JF

J. Forster

Sat, Mar 5, 2011 2:41 AM

There are far more portable GPS units than fixed, timing units.
Furthermore, the consequences of a position error are far greater.

Hence, a filter option may well not get rid of LightSquared issues for the
majority of users users.

-John

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

I used the 0.5 dB number for loss as a worst case. Of course they are
available. They are available even lower, and even at higher frequencies.
Whether or not is trivial is not relevant. What is required is relevant.
This would of course be relevant in small handheld disadvantaged GPS
receivers, but, for roof mounted time-nuts use it should not be a problem.
Even some indoor use it would be fine. If you really feel that you need
less
than 0.5 dB of NF, get the numbers. What is the typical RIP from the
various
birds at various locations? Then knowing Ga and NF you can calculate C/N
and
Eb/No required for the processors to work with acceptable error. Anyway,
enough on this. This is something I can personally handle and am not
worried. Besides, imagine if all of the sudden millions of Cell phones
became useless. Just not going to happen. - Mike

Mike B. Feher, EOZ Inc.
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960 office
908-902-3831 cell

-----Original Message-----
From: J. Forster [mailto:jfor@quik.com]
Sent: Friday, March 04, 2011 9:09 PM
To: Mike Feher
Cc: 'Discussion of precise time and frequency measurement'
Subject: RE: [time-nuts] GPS Filter

Preamps with NFs under 0.5 dB are available for the 1.5 GHz region. IMO a
doubling of system noise temperature is non-trivial.

-John

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

Well, as you said John, for FWIW. In this case not much. As said low
loss,
so increase in noise temp would be minimal, and, if it makes a
difference
between an overloaded front end or a 0.5 dB loss in NF, it will be
welcome.
Heck, we use filters in front of most of our Satcom LNBs at 21 GHz with
minimal effect. Been there and done that, as the saying goes. If
necessary
the small increase in noise temp can easily be overcome by a slightly
larger
aperture, especially since a view of the full sky is not really
necessary
and birds below certain elevation angles are typically ignored by
software
settings of one's own choosing. And again, I was talking about people
who
have done this and can do it again. It would not be an issue for me.
Regards

Mike

Mike B. Feher, EOZ Inc.
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960 office
908-902-3831 cell

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of J. Forster
Sent: Friday, March 04, 2011 8:47 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] GPS Filter

I'm not so sure.

A filter ahead of a preamp significantly increases the system Noise
Temperature.

GPS signals are weak and link margins are small. The receiver preamps
are
already very low noise.

I'd think that a narrow filter might well drive up the systen NF to the
point it'd be useless.

FWIW,

-John

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

I used to make some interdigital filters and amplifiers in the early
80's
for MDS TV reception in the 2.3 GHz range. One can easily fabricate a
low
loss narrow band filter at 1.5 GHz if need be, and as mentioned before,
antennas should be easy as well. If this really becomes an issue, I am
sure
there will be a lot of solutions offered and anyone with some RF
experience
will also be able to handle it themselves. Regards - Mike

Mike B. Feher, EOZ Inc.
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960 office
908-902-3831 cell

There are far more portable GPS units than fixed, timing units. Furthermore, the consequences of a position error are far greater. Hence, a filter option may well not get rid of LightSquared issues for the majority of users users. -John =============== > I used the 0.5 dB number for loss as a worst case. Of course they are > available. They are available even lower, and even at higher frequencies. > Whether or not is trivial is not relevant. What is required is relevant. > This would of course be relevant in small handheld disadvantaged GPS > receivers, but, for roof mounted time-nuts use it should not be a problem. > Even some indoor use it would be fine. If you really feel that you need > less > than 0.5 dB of NF, get the numbers. What is the typical RIP from the > various > birds at various locations? Then knowing Ga and NF you can calculate C/N > and > Eb/No required for the processors to work with acceptable error. Anyway, > enough on this. This is something I can personally handle and am not > worried. Besides, imagine if all of the sudden millions of Cell phones > became useless. Just not going to happen. - Mike > > Mike B. Feher, EOZ Inc. > 89 Arnold Blvd. > Howell, NJ, 07731 > 732-886-5960 office > 908-902-3831 cell > > > -----Original Message----- > From: J. Forster [mailto:jfor@quik.com] > Sent: Friday, March 04, 2011 9:09 PM > To: Mike Feher > Cc: 'Discussion of precise time and frequency measurement' > Subject: RE: [time-nuts] GPS Filter > > Preamps with NFs under 0.5 dB are available for the 1.5 GHz region. IMO a > doubling of system noise temperature is non-trivial. > > -John > > =============== > > >> Well, as you said John, for FWIW. In this case not much. As said low >> loss, >> so increase in noise temp would be minimal, and, if it makes a >> difference >> between an overloaded front end or a 0.5 dB loss in NF, it will be >> welcome. >> Heck, we use filters in front of most of our Satcom LNBs at 21 GHz with >> minimal effect. Been there and done that, as the saying goes. If >> necessary >> the small increase in noise temp can easily be overcome by a slightly >> larger >> aperture, especially since a view of the full sky is not really >> necessary >> and birds below certain elevation angles are typically ignored by >> software >> settings of one's own choosing. And again, I was talking about people >> who >> have done this and can do it again. It would not be an issue for me. >> Regards >> - Mike >> >> Mike B. Feher, EOZ Inc. >> 89 Arnold Blvd. >> Howell, NJ, 07731 >> 732-886-5960 office >> 908-902-3831 cell >> >> >> -----Original Message----- >> From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On >> Behalf Of J. Forster >> Sent: Friday, March 04, 2011 8:47 PM >> To: Discussion of precise time and frequency measurement >> Subject: Re: [time-nuts] GPS Filter >> >> I'm not so sure. >> >> A filter ahead of a preamp significantly increases the system Noise >> Temperature. >> >> GPS signals are weak and link margins are small. The receiver preamps >> are >> already very low noise. >> >> I'd think that a narrow filter might well drive up the systen NF to the >> point it'd be useless. >> >> FWIW, >> >> -John >> >> ============= >> >> >>> I used to make some interdigital filters and amplifiers in the early >>> 80's >>> for MDS TV reception in the 2.3 GHz range. One can easily fabricate a >>> low >>> loss narrow band filter at 1.5 GHz if need be, and as mentioned before, >>> antennas should be easy as well. If this really becomes an issue, I am >>> sure >>> there will be a lot of solutions offered and anyone with some RF >>> experience >>> will also be able to handle it themselves. Regards - Mike >>> >>> Mike B. Feher, EOZ Inc. >>> 89 Arnold Blvd. >>> Howell, NJ, 07731 >>> 732-886-5960 office >>> 908-902-3831 cell > > >

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GPS Filter

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