Safely getting the electrical length of a connected antenna feedline
Gate drivers are pretty zippy when you leave out the capacitive load of a
power fet's gate. They are also available in 8 pin dip.
On Monday, 8 August 2016, Bob Albert via time-nuts time-nuts@febo.com
wrote:
Your comments on layout made me think again of how to implement these
projects. How do you use a 14 pin SMD IC? I could try to connect it with
flying leads but I'd like something better. Is there some kind of socket
for these devices? Or a generic board to receive such things?
Bob
On Monday, August 8, 2016 8:02 PM, David <davidwhess@gmail.com
javascript:;> wrote:
I actually tested various 74120 dual 4-input NAND drivers which
produce the sync output on my B&K function generator to find ones
which would provide the fastest and cleanest pulse. AS (advanced
schottky) and FAST (fast advanced schottky TTL) were the best for me.
Modern inexpensive discrete logic however can do a much better these
days.
One interesting thing I learned is that the dual 4-input NAND pinout
overlaps the quad 2-input NAND pinout so in a properly designed layout
where only 2 gates are used, either part can be used.
On Mon, 08 Aug 2016 16:31:44 -0400, you wrote:
If you have a function generator with a sync output, you can use that
pulse
into a T connector with your scope to do a TDR measurement of the cable.
If
you have a scrap of the new cable, you can use that to calibrate the
setup.
Regards,
Tom
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Thanks for the tip! I found a few at around a buck apiece. Now to do due diligence to see if they will fit my parts.
Bob
On Monday, August 8, 2016 9:06 PM, Richard W. Solomon <w1ksz@earthlink.net> wrote:
There are a few adapters over on that "auction" site.
Do a search on 14 pin smd to 14 pin dip.
73, Dick, W1KSZ
-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces@febo.com] On Behalf Of Bob Albert via time-nuts
Sent: Monday, August 08, 2016 8:37 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Safely getting the electrical length of a connected antenna feedline
Your comments on layout made me think again of how to implement these projects. How do you use a 14 pin SMD IC? I could try to connect it with flying leads but I'd like something better. Is there some kind of socket for these devices? Or a generic board to receive such things?
Bob
On Monday, August 8, 2016 8:02 PM, David davidwhess@gmail.com wrote:
I actually tested various 74120 dual 4-input NAND drivers which produce the sync output on my B&K function generator to find ones which would provide the fastest and cleanest pulse. AS (advanced
schottky) and FAST (fast advanced schottky TTL) were the best for me.
Modern inexpensive discrete logic however can do a much better these days.
One interesting thing I learned is that the dual 4-input NAND pinout overlaps the quad 2-input NAND pinout so in a properly designed layout where only 2 gates are used, either part can be used.
On Mon, 08 Aug 2016 16:31:44 -0400, you wrote:
If you have a function generator with a sync output, you can use that
pulse into a T connector with your scope to do a TDR measurement of the
cable. If you have a scrap of the new cable, you can use that to calibrate the setup.
Regards,
Tom
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.
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and follow the instructions there.
Richard mentioned the SMD to leaded adapters which work well.
Another way which is more suitable for Manhattan or dead bug type
construction is to glue or solder down just tiny printed circuit board
which has the SMD footprint and then solder directly to the leads or
extensions to the pads. This does not increase the lead length any
more than necessary and places the ground plane in close proximity for
best RF performance. If you are desperate, you can cut an SMD
footprint out of an existing unused donor board.
On Tue, 9 Aug 2016 03:37:07 +0000 (UTC), you wrote:
Your comments on layout made me think again of how to implement these projects. How do you use a 14 pin SMD IC? I could try to connect it with flying leads but I'd like something better. Is there some kind of socket for these devices? Or a generic board to receive such things?
Bob
On Monday, August 8, 2016 8:02 PM, David davidwhess@gmail.com wrote:
I actually tested various 74120 dual 4-input NAND drivers which
produce the sync output on my B&K function generator to find ones
which would provide the fastest and cleanest pulse. AS (advanced
schottky) and FAST (fast advanced schottky TTL) were the best for me.
Modern inexpensive discrete logic however can do a much better these
days.
One interesting thing I learned is that the dual 4-input NAND pinout
overlaps the quad 2-input NAND pinout so in a properly designed layout
where only 2 gates are used, either part can be used.
I doubt it's worth mentioning that a random SMD footprint cut from a larger
board and some of the currently available eBay SMD adapter boards may have
plated through holes which could short if used to prototype on copper clad
board so it's worth paying a little attention to insulating the
'underside' of the boards.
On 9 Aug 2016 08:00, "David" davidwhess@gmail.com wrote:
Richard mentioned the SMD to leaded adapters which work well.
Another way which is more suitable for Manhattan or dead bug type
construction is to glue or solder down just tiny printed circuit board
which has the SMD footprint and then solder directly to the leads or
extensions to the pads. This does not increase the lead length any
more than necessary and places the ground plane in close proximity for
best RF performance. If you are desperate, you can cut an SMD
footprint out of an existing unused donor board.
On Tue, 9 Aug 2016 03:37:07 +0000 (UTC), you wrote:
Your comments on layout made me think again of how to implement these
projects. How do you use a 14 pin SMD IC? I could try to connect it with
flying leads but I'd like something better. Is there some kind of socket
for these devices? Or a generic board to receive such things?
Bob
On Monday, August 8, 2016 8:02 PM, David davidwhess@gmail.com wrote:
I actually tested various 74120 dual 4-input NAND drivers which
produce the sync output on my B&K function generator to find ones
which would provide the fastest and cleanest pulse. AS (advanced
schottky) and FAST (fast advanced schottky TTL) were the best for me.
Modern inexpensive discrete logic however can do a much better these
days.
One interesting thing I learned is that the dual 4-input NAND pinout
overlaps the quad 2-input NAND pinout so in a properly designed layout
where only 2 gates are used, either part can be used.
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.
On 8 Aug 2016 21:23, "Bob Camp" kb8tq@n1k.org wrote:
Hi
An even more significant question:
Is it worth doing?
Your antenna and module could easily have delays
in the 40 ns range. It has no impact on a “frequency” GPSDO. It is one of
a number of static offsets in a time transfer system.
Even the NIST level outfits seem to have issues coming up with a purely
mathematical answer to “what is the offset”.
I thought i might be possible to do this with a VNA, and a test antenna
located a known distance apart. So I asked in the Keysight forum on 8th Feb
2015
https://community.keysight.com/thread/23082
There's a replay by Dr_Joel, who is a VNA guru. Dr. Joel Dunsmore,
suggesting the use of the group delay function. In one sentence he wrote
"What is the level of delay accuracy you are looking to achieve. With this
method, 1 nsec is reasonable, but if you need 100 psec or 10 psec, then we
will have to be much more careful."
The thread never got a complete solution, but it might help if other look
at that, and perhaps start another thread on a similar topic, as that one
is very old. However, if you don't have a VNA, I would not bother asking,
as you are not going to get a response (no pun intended), to a non-VNA
question on a VNA forum.
But IF it was possible to determine the delay through the antenna/filter
within a ns, it would make measurements of coax length useful, whereas as
Bob said, it is pointless unless you know the characteristics of the active
antenna.
I don't know if there would be a way of generating a pulse and feeding that
into two antenna
-
Active one.
-
Passive one at the same distance, and same length of cable.
The pulse should arrive at the same time if the two antennas had equal
delay. But the signal from the active one will arrive later due to the
delay. That might be possible to see on a scope.
I think assuming that the delay in the active antenna can't be measured is
maybe an assumption that is untrue. You could perhaps do better if you
built your own antenna, and characterized the SAW filter separately.
Dave
If you have the active antenna, it is pretty easy to
make a little quadrapole circularly polarized antenna out
of a couple of pieces of 141 semi-riged coax, and to transmit
signal into the active GPS antenna, and measure the signal
coming out of the active GPS antenna.
If you don't have the actual antenna being used, you could
get close by using another of the same type and manufacture.
I tested all of my GPS antennas that way for gain, as a way
to be sure that they were functioning properly, but there is
no reason that you couldn't use a VNA to test them for phase
delay, group delay, whatever you desire.
You could even modulate your sweep generator with a pulse,
detect the pulse with a diode, and measure the delay with
your oscilloscope.
-Chuck Harris
Dr. David Kirkby (Kirkby Microwave Ltd) wrote:
On 8 Aug 2016 21:23, "Bob Camp" kb8tq@n1k.org wrote:
Hi
An even more significant question:
Is it worth doing?
Your antenna and module could easily have delays
in the 40 ns range. It has no impact on a “frequency” GPSDO. It is one of
a number of static offsets in a time transfer system.
Even the NIST level outfits seem to have issues coming up with a purely
mathematical answer to “what is the offset”.
I thought i might be possible to do this with a VNA, and a test antenna
located a known distance apart. So I asked in the Keysight forum on 8th Feb
2015
https://community.keysight.com/thread/23082
There's a replay by Dr_Joel, who is a VNA guru. Dr. Joel Dunsmore,
suggesting the use of the group delay function. In one sentence he wrote
"What is the level of delay accuracy you are looking to achieve. With this
method, 1 nsec is reasonable, but if you need 100 psec or 10 psec, then we
will have to be much more careful."
The thread never got a complete solution, but it might help if other look
at that, and perhaps start another thread on a similar topic, as that one
is very old. However, if you don't have a VNA, I would not bother asking,
as you are not going to get a response (no pun intended), to a non-VNA
question on a VNA forum.
But IF it was possible to determine the delay through the antenna/filter
within a ns, it would make measurements of coax length useful, whereas as
Bob said, it is pointless unless you know the characteristics of the active
antenna.
I don't know if there would be a way of generating a pulse and feeding that
into two antenna
-
Active one.
-
Passive one at the same distance, and same length of cable.
The pulse should arrive at the same time if the two antennas had equal
delay. But the signal from the active one will arrive later due to the
delay. That might be possible to see on a scope.
I think assuming that the delay in the active antenna can't be measured is
maybe an assumption that is untrue. You could perhaps do better if you
built your own antenna, and characterized the SAW filter separately.
Dave
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and follow the instructions there.
From: Dr. David Kirkby (Kirkby Microwave Ltd)
I thought i might be possible to do this with a VNA, and a test antenna
located a known distance apart. So I asked in the Keysight forum on 8th Feb
2015
[]
Dave
Folks,
Yes, I've used the DG8SAQ Vector Network Analyser to measure cable lengths
and impedance very easily. The procedure is documented on page 458 et.seq.
of this help file:
http://sdr-kits.net/DG8SAQ/VNWA/VNWA_HELP.pdf
The VNWA proven one of the most useful pieces of kit I've bought, and
support is superb.
http://sdr-kits.net/VNWA3_Description.html
Cheers,
David
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-taylor@blueyonder.co.uk
Twitter: @gm8arv
Yes, a board with the required footprint would be the way to go. Where does one find that?
On Tuesday, August 9, 2016 12:00 AM, David <davidwhess@gmail.com> wrote:
Richard mentioned the SMD to leaded adapters which work well.
Another way which is more suitable for Manhattan or dead bug type
construction is to glue or solder down just tiny printed circuit board
which has the SMD footprint and then solder directly to the leads or
extensions to the pads. This does not increase the lead length any
more than necessary and places the ground plane in close proximity for
best RF performance. If you are desperate, you can cut an SMD
footprint out of an existing unused donor board.
On Tue, 9 Aug 2016 03:37:07 +0000 (UTC), you wrote:
Your comments on layout made me think again of how to implement these projects. How do you use a 14 pin SMD IC? I could try to connect it with flying leads but I'd like something better. Is there some kind of socket for these devices? Or a generic board to receive such things?
Bob
On Monday, August 8, 2016 8:02 PM, David davidwhess@gmail.com wrote:
I actually tested various 74120 dual 4-input NAND drivers which
produce the sync output on my B&K function generator to find ones
which would provide the fastest and cleanest pulse. AS (advanced
schottky) and FAST (fast advanced schottky TTL) were the best for me.
Modern inexpensive discrete logic however can do a much better these
days.
One interesting thing I learned is that the dual 4-input NAND pinout
overlaps the quad 2-input NAND pinout so in a properly designed layout
where only 2 gates are used, either part can be used.
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.
On Tue, Aug 9, 2016 at 9:10 AM, Bob Albert via time-nuts
time-nuts@febo.com wrote:
Yes, a board with the required footprint would be the way to go. Where does one find that?
You can have small PCBs made for $3 each.
There are places here in the US that will do PCBs for $3/square inch
with a one square inch minimum. basicpcb.com sone of these.
It is not hard to design a basic "carrier board" that has just one
chip's footprint and maybe a decoupling capacitor and a 0.1" header
connector. Many times the chip's data sheet will have an example PCB
layout you can borrow that will fit in a one square inch board.
--
Chris Albertson
Redondo Beach, California
Hi:
I've had good luck using any of the the ExpressPCB services that include solder mask with surface mount parts where the
pitch is 0.05" (half normal DIP) and hand soldering (requires stereo microscope).
http://www.prc68.com/I/BTSG.shtml (battery top signal generator)
http://www.prc68.com/I/Images/ICS525v1o.jpg
http://www.prc68.com/I/SMT.shtml http://www.prc68.com/I/SMT.shtml
--
Have Fun,
Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
The lesser of evils is still evil.