MS
Mark Sims
Thu, Aug 28, 2008 5:05 PM
The Thunderbolt does not seem to be the most sensitive receiver around, but it does not seem particularly bad. Sensitivity in a time receiver can be a bad thing... more sensitivity tends to make it more susceptible to multipath, etc. These things were meant to be mounted on cell towers, etc where they have a pretty clear view of the sky. Once you have that, you don't need high sensitivity. Also their proximity to high power RF transmitters makes overly sensitive front ends a problem.
On the subject of GPS amplifiers... adding external amplification to a GPS may not improve its performance and can actually degrade it. All amplifiers amplify signal and noise, plus distort everything in the process. (fundamental laws of the universe: 1) You can't get something for nothing, 2) You can't break even, 3) You'll die trying) Ideally, you want the amplifier at the antenna and you want the amplification to match the cable loss and no more. Generally GPS receivers with poor sensitivity have poorly designed front ends or signal processing. Yelling in their ears won't make them work any better.
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The Thunderbolt does not seem to be the most sensitive receiver around, but it does not seem particularly bad. Sensitivity in a time receiver can be a bad thing... more sensitivity tends to make it more susceptible to multipath, etc. These things were meant to be mounted on cell towers, etc where they have a pretty clear view of the sky. Once you have that, you don't need high sensitivity. Also their proximity to high power RF transmitters makes overly sensitive front ends a problem.
On the subject of GPS amplifiers... adding external amplification to a GPS may not improve its performance and can actually degrade it. All amplifiers amplify signal and noise, plus distort everything in the process. (fundamental laws of the universe: 1) You can't get something for nothing, 2) You can't break even, 3) You'll die trying) Ideally, you want the amplifier at the antenna and you want the amplification to match the cable loss and no more. Generally GPS receivers with poor sensitivity have poorly designed front ends or signal processing. Yelling in their ears won't make them work any better.
----------------------------------------
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PD
Predrag Dukic
Thu, Aug 28, 2008 11:04 PM
I also had the same feeling until I changed the position of the
antenna from eastern side of the building to the southern.
At least two usable svs more on the average...
P. Dukic
At 19:05 28.8.2008, you wrote:
The Thunderbolt does not seem to be the most sensitive receiver
around, but it does not seem particularly bad. Sensitivity in a
time receiver can be a bad thing... more sensitivity tends to make
it more susceptible to multipath, etc. These things were meant to
be mounted on cell towers, etc where they have a pretty clear view
of the sky. Once you have that, you don't need high
sensitivity. Also their proximity to high power RF transmitters
makes overly sensitive front ends a problem.
On the subject of GPS amplifiers... adding external amplification
to a GPS may not improve its performance and can actually degrade
it. All amplifiers amplify signal and noise, plus distort
everything in the process. (fundamental laws of the universe: 1) You
can't get something for nothing, 2) You can't break even, 3)
You'll die trying) Ideally, you want the amplifier at the
antenna and you want the amplification to match the cable loss and
no more. Generally GPS receivers with poor sensitivity have poorly
designed front ends or signal processing. Yelling in their ears
won't make them work any better.
Get ideas on sharing photos from people like you. Find new ways to share.
http://www.windowslive.com/explore/photogallery/posts?ocid=TXT_TAGLM_WL_Photo_Gallery_082008
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I also had the same feeling until I changed the position of the
antenna from eastern side of the building to the southern.
At least two usable svs more on the average...
P. Dukic
At 19:05 28.8.2008, you wrote:
>The Thunderbolt does not seem to be the most sensitive receiver
>around, but it does not seem particularly bad. Sensitivity in a
>time receiver can be a bad thing... more sensitivity tends to make
>it more susceptible to multipath, etc. These things were meant to
>be mounted on cell towers, etc where they have a pretty clear view
>of the sky. Once you have that, you don't need high
>sensitivity. Also their proximity to high power RF transmitters
>makes overly sensitive front ends a problem.
>
>On the subject of GPS amplifiers... adding external amplification
>to a GPS may not improve its performance and can actually degrade
>it. All amplifiers amplify signal and noise, plus distort
>everything in the process. (fundamental laws of the universe: 1) You
>can't get something for nothing, 2) You can't break even, 3)
>You'll die trying) Ideally, you want the amplifier at the
>antenna and you want the amplification to match the cable loss and
>no more. Generally GPS receivers with poor sensitivity have poorly
>designed front ends or signal processing. Yelling in their ears
>won't make them work any better.
>----------------------------------------
>
>_________________________________________________________________
>Get ideas on sharing photos from people like you. Find new ways to share.
>http://www.windowslive.com/explore/photogallery/posts?ocid=TXT_TAGLM_WL_Photo_Gallery_082008
>_______________________________________________
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>To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>and follow the instructions there.
SM
Scott Mace
Thu, Aug 28, 2008 11:11 PM
Both of the thunderbolts I have usually see 7-8 satellites, SNRs from 35-50,
antenna is on the roof with about 150ft of LMR-400 and going through 2 4-port
distribution splitter/amps. I use the belden equiv of LMR-195 for all
connections between the receivers and the amps. Both thunderbolts seem to
compare well to the M12+ based Fury, and do usually better than the 6-channel VP z3801a.
Scott
Mark Sims wrote:
The Thunderbolt does not seem to be the most sensitive receiver around, but it does not seem particularly bad. Sensitivity in a time receiver can be a bad thing... more sensitivity tends to make it more susceptible to multipath, etc. These things were meant to be mounted on cell towers, etc where they have a pretty clear view of the sky. Once you have that, you don't need high sensitivity. Also their proximity to high power RF transmitters makes overly sensitive front ends a problem.
On the subject of GPS amplifiers... adding external amplification to a GPS may not improve its performance and can actually degrade it. All amplifiers amplify signal and noise, plus distort everything in the process. (fundamental laws of the universe: 1) You can't get something for nothing, 2) You can't break even, 3) You'll die trying) Ideally, you want the amplifier at the antenna and you want the amplification to match the cable loss and no more. Generally GPS receivers with poor sensitivity have poorly designed front ends or signal processing. Yelling in their ears won't make them work any better.
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Both of the thunderbolts I have usually see 7-8 satellites, SNRs from 35-50,
antenna is on the roof with about 150ft of LMR-400 and going through 2 4-port
distribution splitter/amps. I use the belden equiv of LMR-195 for all
connections between the receivers and the amps. Both thunderbolts seem to
compare well to the M12+ based Fury, and do usually better than the 6-channel VP z3801a.
Scott
Mark Sims wrote:
> The Thunderbolt does not seem to be the most sensitive receiver around, but it does not seem particularly bad. Sensitivity in a time receiver can be a bad thing... more sensitivity tends to make it more susceptible to multipath, etc. These things were meant to be mounted on cell towers, etc where they have a pretty clear view of the sky. Once you have that, you don't need high sensitivity. Also their proximity to high power RF transmitters makes overly sensitive front ends a problem.
>
> On the subject of GPS amplifiers... adding external amplification to a GPS may not improve its performance and can actually degrade it. All amplifiers amplify signal and noise, plus distort everything in the process. (fundamental laws of the universe: 1) You can't get something for nothing, 2) You can't break even, 3) You'll die trying) Ideally, you want the amplifier at the antenna and you want the amplification to match the cable loss and no more. Generally GPS receivers with poor sensitivity have poorly designed front ends or signal processing. Yelling in their ears won't make them work any better.
> ----------------------------------------
>
> _________________________________________________________________
> Get ideas on sharing photos from people like you. Find new ways to share.
> http://www.windowslive.com/explore/photogallery/posts?ocid=TXT_TAGLM_WL_Photo_Gallery_082008
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> and follow the instructions there.
>
>
BK
Brian Kirby
Fri, Aug 29, 2008 1:37 AM
My problem is I am using a Motorola antenna with 24 db of gain, looking
at Trimble they expect 35 db gain.
I am in an apartment and the management let me put up a GPS antenna on
the edge of the roof. I came down with 20 feet of RG6 and then jumped
into RG59 coax to run inside the apartment. I "guesstimate" there is 40
to 60 feet in the RG59 run.
I added a cheap DSS amplifier at the GPS splitters and its improved. I
am going to look into moving the amp to where the coax comes into the
building , the RG6/RG59 junction - but I will need to figure out a bias
tee scheme to feed 12 volts to the DSS amp, and then I need to take it
out and bias the antenna at +5 volts.
Brian - KD4FM
Mark Sims wrote:
The Thunderbolt does not seem to be the most sensitive receiver around, but it does not seem particularly bad. Sensitivity in a time receiver can be a bad thing... more sensitivity tends to make it more susceptible to multipath, etc. These things were meant to be mounted on cell towers, etc where they have a pretty clear view of the sky. Once you have that, you don't need high sensitivity. Also their proximity to high power RF transmitters makes overly sensitive front ends a problem.
On the subject of GPS amplifiers... adding external amplification to a GPS may not improve its performance and can actually degrade it. All amplifiers amplify signal and noise, plus distort everything in the process. (fundamental laws of the universe: 1) You can't get something for nothing, 2) You can't break even, 3) You'll die trying) Ideally, you want the amplifier at the antenna and you want the amplification to match the cable loss and no more. Generally GPS receivers with poor sensitivity have poorly designed front ends or signal processing. Yelling in their ears won't make them work any better.
Get ideas on sharing photos from people like you. Find new ways to share.
http://www.windowslive.com/explore/photogallery/posts?ocid=TXT_TAGLM_WL_Photo_Gallery_082008
time-nuts mailing list -- time-nuts@febo.com
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and follow the instructions there.
My problem is I am using a Motorola antenna with 24 db of gain, looking
at Trimble they expect 35 db gain.
I am in an apartment and the management let me put up a GPS antenna on
the edge of the roof. I came down with 20 feet of RG6 and then jumped
into RG59 coax to run inside the apartment. I "guesstimate" there is 40
to 60 feet in the RG59 run.
I added a cheap DSS amplifier at the GPS splitters and its improved. I
am going to look into moving the amp to where the coax comes into the
building , the RG6/RG59 junction - but I will need to figure out a bias
tee scheme to feed 12 volts to the DSS amp, and then I need to take it
out and bias the antenna at +5 volts.
Brian - KD4FM
Mark Sims wrote:
> The Thunderbolt does not seem to be the most sensitive receiver around, but it does not seem particularly bad. Sensitivity in a time receiver can be a bad thing... more sensitivity tends to make it more susceptible to multipath, etc. These things were meant to be mounted on cell towers, etc where they have a pretty clear view of the sky. Once you have that, you don't need high sensitivity. Also their proximity to high power RF transmitters makes overly sensitive front ends a problem.
>
> On the subject of GPS amplifiers... adding external amplification to a GPS may not improve its performance and can actually degrade it. All amplifiers amplify signal and noise, plus distort everything in the process. (fundamental laws of the universe: 1) You can't get something for nothing, 2) You can't break even, 3) You'll die trying) Ideally, you want the amplifier at the antenna and you want the amplification to match the cable loss and no more. Generally GPS receivers with poor sensitivity have poorly designed front ends or signal processing. Yelling in their ears won't make them work any better.
> ----------------------------------------
>
> _________________________________________________________________
> Get ideas on sharing photos from people like you. Find new ways to share.
> http://www.windowslive.com/explore/photogallery/posts?ocid=TXT_TAGLM_WL_Photo_Gallery_082008
> _______________________________________________
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> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
JL
J. L. Trantham
Fri, Aug 29, 2008 2:39 AM
When I compared the function of the Thunderbolt to my Z3816A, the number of
tracked satellites was smaller on the Thunderbolt. However, the Signal
Level Mask is set to 4.0 on the Thunderbolt. After I reset it to 1.0, they
tracked the same (and number of) satellites.
This I did with TBoltMon under 'Setup', 'GPS Receiver' which takes you to
'Receiver Configuration'. Change the Signal Level Mask (AMU) to the desired
number then 'Set Receiver'. I also hit 'Save Segment' though I do not know
if this is a required step.
Joe
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Predrag Dukic
Sent: Thursday, August 28, 2008 6:05 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Trimble Thunderbolt - Receive Sensistivity
I also had the same feeling until I changed the position of the
antenna from eastern side of the building to the southern.
At least two usable svs more on the average...
P. Dukic
At 19:05 28.8.2008, you wrote:
The Thunderbolt does not seem to be the most sensitive receiver
around, but it does not seem particularly bad. Sensitivity in a
time receiver can be a bad thing... more sensitivity tends to make
it more susceptible to multipath, etc. These things were meant to
be mounted on cell towers, etc where they have a pretty clear view
of the sky. Once you have that, you don't need high
sensitivity. Also their proximity to high power RF transmitters
makes overly sensitive front ends a problem.
On the subject of GPS amplifiers... adding external amplification
to a GPS may not improve its performance and can actually degrade
it. All amplifiers amplify signal and noise, plus distort
everything in the process. (fundamental laws of the universe: 1) You
can't get something for nothing, 2) You can't break even, 3)
You'll die trying) Ideally, you want the amplifier at the
antenna and you want the amplification to match the cable loss and
no more. Generally GPS receivers with poor sensitivity have poorly
designed front ends or signal processing. Yelling in their ears
won't make them work any better.
Get ideas on sharing photos from people like you. Find new ways to share.
http://www.windowslive.com/explore/photogallery/posts?ocid=TXT_TAGLM_WL_Pho
and follow the instructions there.
When I compared the function of the Thunderbolt to my Z3816A, the number of
tracked satellites was smaller on the Thunderbolt. However, the Signal
Level Mask is set to 4.0 on the Thunderbolt. After I reset it to 1.0, they
tracked the same (and number of) satellites.
This I did with TBoltMon under 'Setup', 'GPS Receiver' which takes you to
'Receiver Configuration'. Change the Signal Level Mask (AMU) to the desired
number then 'Set Receiver'. I also hit 'Save Segment' though I do not know
if this is a required step.
Joe
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Predrag Dukic
Sent: Thursday, August 28, 2008 6:05 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Trimble Thunderbolt - Receive Sensistivity
I also had the same feeling until I changed the position of the
antenna from eastern side of the building to the southern.
At least two usable svs more on the average...
P. Dukic
At 19:05 28.8.2008, you wrote:
>The Thunderbolt does not seem to be the most sensitive receiver
>around, but it does not seem particularly bad. Sensitivity in a
>time receiver can be a bad thing... more sensitivity tends to make
>it more susceptible to multipath, etc. These things were meant to
>be mounted on cell towers, etc where they have a pretty clear view
>of the sky. Once you have that, you don't need high
>sensitivity. Also their proximity to high power RF transmitters
>makes overly sensitive front ends a problem.
>
>On the subject of GPS amplifiers... adding external amplification
>to a GPS may not improve its performance and can actually degrade
>it. All amplifiers amplify signal and noise, plus distort
>everything in the process. (fundamental laws of the universe: 1) You
>can't get something for nothing, 2) You can't break even, 3)
>You'll die trying) Ideally, you want the amplifier at the
>antenna and you want the amplification to match the cable loss and
>no more. Generally GPS receivers with poor sensitivity have poorly
>designed front ends or signal processing. Yelling in their ears
>won't make them work any better.
>----------------------------------------
>
>_________________________________________________________________
>Get ideas on sharing photos from people like you. Find new ways to share.
>http://www.windowslive.com/explore/photogallery/posts?ocid=TXT_TAGLM_WL_Pho
to_Gallery_082008
>_______________________________________________
>time-nuts mailing list -- time-nuts@febo.com
>To unsubscribe, go to
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>and follow the instructions there.
_______________________________________________
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To unsubscribe, go to
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and follow the instructions there.
JM
John Miles
Fri, Aug 29, 2008 2:48 AM
The elevation mask might also come into play. Ordinarily you don't want to
consider input from satellites too near the horizon, as terrestrial features
can distort the signal's timing.
I think it can be stated with confidence that there's nothing wrong with a
(normally functioning) Thunderbolt's sensitivity specs, and that putting
random amplifiers, splitters, and such into the antenna lead might be
counterproductive.
-- john, KE5FX
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com]On
Behalf Of J. L. Trantham
Sent: Thursday, August 28, 2008 7:39 PM
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] Trimble Thunderbolt - Receive Sensistivity
When I compared the function of the Thunderbolt to my Z3816A, the
number of
tracked satellites was smaller on the Thunderbolt. However, the Signal
Level Mask is set to 4.0 on the Thunderbolt. After I reset it to
1.0, they
tracked the same (and number of) satellites.
This I did with TBoltMon under 'Setup', 'GPS Receiver' which takes you to
'Receiver Configuration'. Change the Signal Level Mask (AMU) to
the desired
number then 'Set Receiver'. I also hit 'Save Segment' though I
do not know
if this is a required step.
Joe
The elevation mask might also come into play. Ordinarily you don't want to
consider input from satellites too near the horizon, as terrestrial features
can distort the signal's timing.
I think it can be stated with confidence that there's nothing wrong with a
(normally functioning) Thunderbolt's sensitivity specs, and that putting
random amplifiers, splitters, and such into the antenna lead might be
counterproductive.
-- john, KE5FX
> -----Original Message-----
> From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com]On
> Behalf Of J. L. Trantham
> Sent: Thursday, August 28, 2008 7:39 PM
> To: 'Discussion of precise time and frequency measurement'
> Subject: Re: [time-nuts] Trimble Thunderbolt - Receive Sensistivity
>
>
> When I compared the function of the Thunderbolt to my Z3816A, the
> number of
> tracked satellites was smaller on the Thunderbolt. However, the Signal
> Level Mask is set to 4.0 on the Thunderbolt. After I reset it to
> 1.0, they
> tracked the same (and number of) satellites.
>
> This I did with TBoltMon under 'Setup', 'GPS Receiver' which takes you to
> 'Receiver Configuration'. Change the Signal Level Mask (AMU) to
> the desired
> number then 'Set Receiver'. I also hit 'Save Segment' though I
> do not know
> if this is a required step.
>
> Joe
JL
J. L. Trantham
Fri, Aug 29, 2008 3:39 AM
You are correct about the elevation mask and it, too, can be changed via
TBoltMon. However, the Thunderbolt and the Z3816A both had the elevation
mask set to 10 degrees. They were running off the same HP timing antenna
with 25 feet of RG-58 to a 58536A Symmetricom GPS distribution amplifier and
then a short RG-58 jumper to the respective receivers with N to BNC adapters
everywhere and BNC connectors on the RG-58. Clearly not the most ideal
cable system but it works for comparison.
Joe
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of John Miles
Sent: Thursday, August 28, 2008 9:49 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Trimble Thunderbolt - Receive Sensistivity
The elevation mask might also come into play. Ordinarily you don't want to
consider input from satellites too near the horizon, as terrestrial features
can distort the signal's timing.
I think it can be stated with confidence that there's nothing wrong with a
(normally functioning) Thunderbolt's sensitivity specs, and that putting
random amplifiers, splitters, and such into the antenna lead might be
counterproductive.
-- john, KE5FX
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com]On
Behalf Of J. L. Trantham
Sent: Thursday, August 28, 2008 7:39 PM
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] Trimble Thunderbolt - Receive Sensistivity
When I compared the function of the Thunderbolt to my Z3816A, the
number of
tracked satellites was smaller on the Thunderbolt. However, the Signal
Level Mask is set to 4.0 on the Thunderbolt. After I reset it to
1.0, they
tracked the same (and number of) satellites.
This I did with TBoltMon under 'Setup', 'GPS Receiver' which takes you to
'Receiver Configuration'. Change the Signal Level Mask (AMU) to
the desired
number then 'Set Receiver'. I also hit 'Save Segment' though I
do not know
if this is a required step.
Joe
You are correct about the elevation mask and it, too, can be changed via
TBoltMon. However, the Thunderbolt and the Z3816A both had the elevation
mask set to 10 degrees. They were running off the same HP timing antenna
with 25 feet of RG-58 to a 58536A Symmetricom GPS distribution amplifier and
then a short RG-58 jumper to the respective receivers with N to BNC adapters
everywhere and BNC connectors on the RG-58. Clearly not the most ideal
cable system but it works for comparison.
Joe
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of John Miles
Sent: Thursday, August 28, 2008 9:49 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Trimble Thunderbolt - Receive Sensistivity
The elevation mask might also come into play. Ordinarily you don't want to
consider input from satellites too near the horizon, as terrestrial features
can distort the signal's timing.
I think it can be stated with confidence that there's nothing wrong with a
(normally functioning) Thunderbolt's sensitivity specs, and that putting
random amplifiers, splitters, and such into the antenna lead might be
counterproductive.
-- john, KE5FX
> -----Original Message-----
> From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com]On
> Behalf Of J. L. Trantham
> Sent: Thursday, August 28, 2008 7:39 PM
> To: 'Discussion of precise time and frequency measurement'
> Subject: Re: [time-nuts] Trimble Thunderbolt - Receive Sensistivity
>
>
> When I compared the function of the Thunderbolt to my Z3816A, the
> number of
> tracked satellites was smaller on the Thunderbolt. However, the Signal
> Level Mask is set to 4.0 on the Thunderbolt. After I reset it to
> 1.0, they
> tracked the same (and number of) satellites.
>
> This I did with TBoltMon under 'Setup', 'GPS Receiver' which takes you to
> 'Receiver Configuration'. Change the Signal Level Mask (AMU) to
> the desired
> number then 'Set Receiver'. I also hit 'Save Segment' though I
> do not know
> if this is a required step.
>
> Joe
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