Hi fellow time-nuts,
For those of you that isn't aware of it, using 75 Ohm antenna cables rather
than 50 Ohm cables is a bad move, as the antenna cable itself will create a
multi-path system. This article elaborate on reflections i cables:
http://tycho.usno.navy.mil/ptti/1998/Vol 30_39.pdf
Magnus Danielson wrote:
Hi fellow time-nuts,
For those of you that isn't aware of it, using 75 Ohm antenna cables rather
than 50 Ohm cables is a bad move, as the antenna cable itself will create a
multi-path system. This article elaborate on reflections i cables:
I've seen that you're right, Thunderbolt is originally supplied with
75ft of 75 ohm RG-59 cable, as indicated in the manual... So I've the
inverse problem: the GPS antennas we have in the roof both have 50ohm
cable :) So... would be good to change the impedance at the Thunderbolt
antenna port
Javier Herrero wrote:
I've seen that you're right, Thunderbolt is originally supplied with
75ft of 75 ohm RG-59 cable, as indicated in the manual... So I've the
inverse problem: the GPS antennas we have in the roof both have 50ohm
cable :) So... would be good to change the impedance at the
Javier,
According to Trimble the Thunderbolt IS 50 ohm at the antenna input.
(maybe the sole user of 50ohm F-connectors... ;-) )
See page 3-5, Section 3-4 Antenna Cables (page 39) in
http://trl.trimble.com/dscgi/ds.py/Get/File-10001/ThunderBoltBook2003.pdf
Note – RG-59 is a 75 ohm coaxial
Before you do this find out what the reflection coefficient is for the
Thunderbolt input and the active antenna output when using a 50 ohm cable.
The active antenna may not be that well matched to 50 ohm cable.
Then adjust the cable length to an odd multiple of half the signal
wavelength
- Original Message -
From: Bruce Griffiths [EMAIL PROTECTED]
To: Discussion of precise time and frequency measurement
time-nuts@febo.com
Sent: Friday, June 13, 2008 8:37 PM
Subject: Re: [time-nuts] Non-impedance matched antenna cables
Magnus Danielson wrote:
Hi fellow time-nuts,
Then, if the input is 50 ohm, at least the reflections in the other
extreme of the Thunderbolt + cable (i.e., at the antenna side) should
not be so bad... I'm afraid that since the cable is alredy routed using
the inside-building tubes (in fact it uses the tubing destinated for the
TV antenna)
Javier,
On Fri, 2008-06-13 at 12:01 +0200, Javier Herrero wrote:
Yes, I was also surprised by the use of F connectors... and that made me
suspect (with surprise) that the GPS input were 75ohm, but I must
confess that I did not read more ;).
Just opened my Thunderbolt to look at the
I don't believe the Thunderbolt is a carrier-phase receiver, is it? If it's
not, I'd be surprised if reflections make any difference.
They don't seem to have gone out of their way to match either 50 or 75 ohms
(see S11 plot of TAPR unit's antenna jack attached), unless the input Z changes
I've seen that you're right, Thunderbolt is originally supplied with 75ft
of 75 ohm RG-59 cable, as indicated in the manual... So I've the inverse
problem: the GPS antennas we have in the roof both have 50ohm cable :)
So... would be good to change the impedance at the Thunderbolt antenna
port
Chris Cheney wrote:
Before you do this find out what the reflection coefficient is for the
Thunderbolt input and the active antenna output when using a 50 ohm cable.
The active antenna may not be that well matched to 50 ohm cable.
Then adjust the cable length to an odd multiple of half the
Dave Brown wrote:
Has anyone actually measured the TBolt rx input impedance at L1?
DaveB, NZ
Dave
Unable to find specifications for Thunderbolt but some active antenas
have an SWR spec of 1.6 or even as much as 2 in a 50 ohm system.
Bruce
___
Javier Herrero wrote:
Then, if the input is 50 ohm, at least the reflections in the other
extreme of the Thunderbolt + cable (i.e., at the antenna side) should
not be so bad... I'm afraid that since the cable is alredy routed using
the inside-building tubes (in fact it uses the tubing
Chris Cheney wrote:
I've seen that you're right, Thunderbolt is originally supplied with 75ft
of 75 ohm RG-59 cable, as indicated in the manual... So I've the inverse
problem: the GPS antennas we have in the roof both have 50ohm cable :)
So... would be good to change the impedance at the
Hi Tim,
On Thu, Jun 12, 2008 at 10:05:13PM -0400, Tim Cwik wrote:
Is there a way to have gpsd use 8N1 for TSIP? The manual says teh
thunderbolt uses 8N1, the windows support program says it and the
thunderbolt are using 8N1. I can not find a way to tell the thunderbolt
to use 8O1.
as a
Also forget the complication of trying to trim the cable length... the effects
of temperature, humidity, pressure, moisture, etc in commercial TV cable
being used at microwave frequencies will rather quickly render your precise
adjustments moot.
On Fri, Jun 13, 2008 at 8:58 AM, Christian Vogel [EMAIL PROTECTED] wrote:
gpsd: GPS Time 485697.25 1483 14.00
that's encouraging
gpsd: Sat info: mode 1, satellites used 5: 18 9 28 15 26
As is this.
gpsd: Unhandled TSIP superpacket type 0xab
thar's yer problem... kinda.
yes, we
Then adjust the cable length to an odd multiple of half the signal
wavelength in the cable.
snip
Nothing to do with impedance transformation.
Just the phase shift associated with propagation down the cable and back
is then 0.
And this is also the case for a cable whose length is an even
I was referring to that :) I've not a TDR available at this moment...
However you will need to measure the in place cable length using TDR or
other suitable technique.
Bruce
___
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Tom,
Thank you very much for the information. I am using a larger PS on my
Thunderbolt, but I was looking for something smaller. Thanks again for your
input.
Bruce W1GBS
- Original Message -
From: Tom Van Baak [EMAIL PROTECTED]
To: Discussion of precise time and frequency measurement
Interesting work posted here about phase noise and how the psu affects
this, I have a couple of questions while I'm planning the supply -
First, which rail affected the noise component most?
Second, what current does the unit draw from each of the rails?
My Symetricon splitter takes the gps
Here is how I *glued* the AllElectronics power supply to the top of the
Thunderbolt and shortened the cable for a neat, compact package. I connected
the chassis wire of the power supply to the TB case.
http://www.ko4bb.com/Test_Equipment/Thunderbolt/group_buy/
The power supply is the exact same
All Electronics no longer has the 17 watt power supplies that are good for
the Thunderbolt. I checked the web site and went into the store, and they are
out.
Stuart K6YAZ
Los Angeles
**Vote for your city's best dining and nightlife. City's Best
2008.
[EMAIL PROTECTED] schrieb:
this, I have a couple of questions while I'm planning the supply -
First, which rail affected the noise component most?
I would like to add an extra question:
How about adding an extra filter after a cheap PC power supply?
73,
Rainer
On Fri, 2008-06-13 at 19:31 +0100, [EMAIL PROTECTED] wrote:
Hi Paul,
Interesting work posted here about phase noise and how the psu affects
this, I have a couple of questions while I'm planning the supply -
First, which rail affected the noise component most?
Interesting question.
On Fri, Jun 13, 2008 at 2:46 PM, Tim Cwik [EMAIL PROTECTED] wrote:
I have changed line 66 to:
gpsd_set_speed(session, session-gpsdata.baudrate, 'N', 1);
This results in:
[goodness snipped]
I hope this is progress, but I am not sure why gpsd closes the port and
who sends signal 2.
it's a
Mark Sims wrote:
Also forget the complication of trying to trim the cable length... the
effects of temperature, humidity, pressure, moisture, etc in commercial TV
cable being used at microwave frequencies will rather quickly render your
precise adjustments moot.
Dr. Rainer Meergans wrote:
[EMAIL PROTECTED] schrieb:
this, I have a couple of questions while I'm planning the supply -
First, which rail affected the noise component most?
I would like to add an extra question:
How about adding an extra filter after a cheap PC power supply?
To Bruce and Group Concerning Power Supply Flicker Noise on the
Thunderbolt GPS system.
wouldn't it be prefered to use the old linear supply rather than the compact
switcher to minimize this RF and Flicker noise ???
Bill KD4AF
On 6/13/08, Bruce Griffiths [EMAIL PROTECTED] wrote:
Dr. Rainer
Quoth Bill Smitherman at 2008-06-14 09:10...
To Bruce and Group Concerning Power Supply Flicker Noise on the
Thunderbolt GPS system.
wouldn't it be prefered to use the old linear supply rather than the compact
switcher to minimize this RF and Flicker noise ???
I was going to ask a similar
Matthew Smith wrote:
Quoth Bill Smitherman at 2008-06-14 09:10...
To Bruce and Group Concerning Power Supply Flicker Noise on the
Thunderbolt GPS system.
wouldn't it be prefered to use the old linear supply rather than the compact
switcher to minimize this RF and Flicker noise ???
Bill Smitherman wrote:
To Bruce and Group Concerning Power Supply Flicker Noise on the
Thunderbolt GPS system.
wouldn't it be prefered to use the old linear supply rather than the compact
switcher to minimize this RF and Flicker noise ???
Bill KD4AF
Yes, except that a dc-dc converter
A while back I did a project that used a 100 foot piece of (supposedly) fairly
good quality RG58. I checked it with my TDR and then installed it in an
outdoor application where it ran for a couple of weeks in good ole' Texas
weather. The outdoor connection was covered by a glass jar so water
Mark Sims wrote:
A while back I did a project that used a 100 foot piece of (supposedly)
fairly good quality RG58. I checked it with my TDR and then installed it in
an outdoor application where it ran for a couple of weeks in good ole' Texas
weather. The outdoor connection was covered by
Of course, any Time Nut worth the name would install a servo controlled
section of trombone line in his coax to maintain a constant electrical length
;-)
This demonstrates that achieving nanosecond propagation delay stability
is unlikely when using
Mark Sims wrote:
Of course, any Time Nut worth the name would install a servo controlled
section of trombone line in his coax to maintain a constant electrical length
;-)
This demonstrates that achieving nanosecond propagation delay stability
is
Chris Kuethe wrote:
On Fri, Jun 13, 2008 at 2:46 PM, Tim Cwik [EMAIL PROTECTED] wrote:
I have changed line 66 to:
gpsd_set_speed(session, session-gpsdata.baudrate, 'N', 1);
This results in:
[goodness snipped]
I hope this is progress, but I am not sure why gpsd closes the
I might try that too . . . except that the Thunderbolt has a
MiniCircuits ZFSC-2-1 splitter mounted on top, just above the DB9. The
splitter appears to be bolted from inside of the Thunderbolt, so the
Thunderbolt will have to be disassembled to remove the splitter.
Anyone taken a Thunderbolt
I might try that too . . . except that the Thunderbolt has a
MiniCircuits ZFSC-2-1 splitter mounted on top, just above the DB9. The
splitter appears to be bolted from inside of the Thunderbolt, so the
Thunderbolt will have to be disassembled to remove the splitter.
Yes, some of the
Sounds like an application just calling for hard line. I have some 75
foot lengths of 1/4 Superflex that I'll have to drag out and look at.
73, Dick, W1KSZ
-Original Message-
From: Mark Sims [EMAIL PROTECTED]
Sent: Jun 13, 2008 5:37 PM
To: time-nuts@febo.com
Subject: [time-nuts]
I've another antenna, but is a cheap one with
magnetic base, only used for a nixie clock :)
I have one of those as well, a Trimble 28367-40 from eBay, it is
feeding my Thunderbolt (thank you TVB!), and it works fine just
sitting on the window sill - inside!
I am curious, however...how
Jim Palfreyman wrote:
Hi all,
Well getting a second hand 5370B will be no big deal for those of you in the
US, but in Australia getting one of these units is very expensive due to
rare local availability and cost of postage from the US. I was recently
quoted US$350 - more than the unit
Try SETUP, POSITION, (enter values from survey), SAVE SEGMENT... I think
that's what got mine to remember the results of its (3 days to complete) self
survey.
---
I am curious, however...how does one get TboltMon to SAVE the
surveyed position? It had the proper value
I suspect that there is an initial rapid aging process (break-in period) that
occurs followed by longer term aging effects (much like a crystal oscillator).
The particular cable that I used was not new, but had only been used indoors
before. I suspect that each temperature cycle a cable goes
You can also just look yourself up on Google Earth and enter the coordinates
by hand.
-- john, KE5FX
-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Behalf Of Mark Sims
Sent: Friday, June 13, 2008 9:00 PM
To: time-nuts@febo.com
Subject: [time-nuts] Tboltmon
Thank you for the information, which I find rather disappointing.
For some reason, I had an expectation that a GPS would find its own
position and save it, perhaps with a manual click, rather than having
the operator write down the values and have to type them into some
data entry boxes on
Or you could also click Setup-Self-Survey-Save Position Flag-Save, Set
Survey, and Save Segment.
I agree that TboltMon's user interface is a bit offbeat in places, but I
don't think I'd hold Microsoft responsible for it. :-P
-- john, KE5FX
-Original Message-
From: [EMAIL PROTECTED]
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