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Jasen Betts
Guest

Wed Feb 06, 2019 10:31 pm   



On 2019-02-06, Jeff Liebermann <jeffl_at_cruzio.com> wrote:
Quote:
On Tue, 05 Feb 2019 20:58:52 -0800, John Larkin
jjlarkin_at_highlandtechnology.com> wrote:


I wonder what's special about 6 GHz. Most tees spec 6 GHz.

Dunno. My guess is that 6GHz is where the BNC connector craps out.
SMA will go much higher in frequency, but most of Bias-Tee devices I
played with many years ago used BNC.
http://www.interfacebus.com/RF_Connector_Frequency_Range.html
Tradition must be maintained even if nobody can remember why.

Mine seems to use a small inductor or, likely, a ferrite bead.
https://www.dropbox.com/s/hz4wj3fltsetqqj/Amazon_Tee.jpg?dl=0

Probably a solenoid wound inductor (or straight through wire) wrapped
in a ferrite bead. That would allow placement on the PCB without an
air gap and reduce any tendency for the inductor to turn into an
antenna.

Same Bias-Tee for only $3.21 from Hong Kong. Just add a can and you
saved about $25:
https://www.ebay.com/itm/Bias-Tee-10-6000-MHz-6GHz-For-HAM-radio-RTL-SDR-LNA-Low-Noise-Amplifier-/192724549249
(Sorry, but I'm pathologically cheap).


Well, that explains the solder on edge-mount SMA pads in John's photo!

--
When I tried casting out nines I made a hash of it.


Guest

Wed Feb 06, 2019 10:45 pm   



>"Use relays. "

Actually I am thinking of resistoring it so that it simply works both ways. That is easier said than done.

It would be just that the remote control range was extended there. Now the RF can't go both ways but now that I think of it they do switch between channel three and four. So conceivably both signals could exist in one coax.

I think that might make a bitch out of impedance but this is only channel three and four.

Thing is DC would not be going to the power tap, the amplified and buffed IR pulses would. And since there is hardly any current, relays are not the way to go.

Gerhard Hoffmann
Guest

Thu Feb 07, 2019 12:45 am   



Am 06.02.19 um 16:35 schrieb John Larkin:
Quote:
On Wed, 6 Feb 2019 06:51:17 +0100, Gerhard Hoffmann
ghf_at_hoffmann-hochfrequenz.de> wrote:

I have just opened a Mini circuits ZFBT-4R2G-FT.
https://ww2.minicircuits.com/pdfs/ZFBT-4R2G-FT+.pdf

The first impression was OMG! everything was wrapped in some
teflon tape / goo and I was thinking: Whatever is inside, I can
do that better. So I cut it open, which was more work than expected.

There are 2 toroids close to the stripline and 3 larger two-hole cores.
2 of them have a lot of windings, trifilar or worse and all in series.
There are also some resistors and a lot of red glue to fix everything.
So, there seems more to it than meets the eye, but only one 1210 cap.

Tonight, I'll take some photos.

Please!

So here they are:


<
https://www.flickr.com/photos/137684711_at_N07/32069053397/in/album-72157706443876665/
>

First the Mini circuits bias tee open, risetime on TDR and frequency
response on VNA.

Then a single Piconics coil on a 50 Ohms stripline, without shielding,
damping or whatever, simply open. There may be radiation losses.

The microstrip is on a multilayer made from some ceramic-filled prepreg.
Also step and frequency response.

There are some comments below the pics.

cheers,
Gerhard

Gerhard Hoffmann
Guest

Thu Feb 07, 2019 12:45 am   



Am 05.02.19 um 09:48 schrieb Tom Gardner:
Quote:
On 05/02/19 04:38, Gerhard Hoffmann wrote:
That's a hi temperature field in Iceland. They skimp on warning signs.
But when there is one, you better respect it. If you walk there,
you might break into a hole with hot sulfuric slime around your knees.

They are getting "better", e.g. there are now safety rails
at Gullfoss waterfall.
https://i1.wp.com/www.followmeaway.com/wp-content/uploads/2018/01/gullfoss-waterfall-iceland-closed-viewpoint.jpg


When I last went they took the attitude that if you couldn't
work out that spray+rocks+chasm means you might fall and die,
then that would merely improve the species.


I do like this one, esp. the line about the hospital.

<
https://www.flickr.com/photos/137684711_at_N07/40044445253/in/album-72157688304045365/
Quote:



cheers,
Gerhard

John Larkin
Guest

Thu Feb 07, 2019 6:45 am   



On Wed, 06 Feb 2019 07:34:08 -0800, John Larkin
<jjlarkin_at_highlandtechnology.com> wrote:

Quote:
On Tue, 05 Feb 2019 21:45:10 -0800, Jeff Liebermann <jeffl_at_cruzio.com
wrote:

On Tue, 05 Feb 2019 20:58:52 -0800, John Larkin
jjlarkin_at_highlandtechnology.com> wrote:


I wonder what's special about 6 GHz. Most tees spec 6 GHz.

Dunno. My guess is that 6GHz is where the BNC connector craps out.
SMA will go much higher in frequency, but most of Bias-Tee devices I
played with many years ago used BNC.
http://www.interfacebus.com/RF_Connector_Frequency_Range.html
Tradition must be maintained even if nobody can remember why.

Mine seems to use a small inductor or, likely, a ferrite bead.
https://www.dropbox.com/s/hz4wj3fltsetqqj/Amazon_Tee.jpg?dl=0

Probably a solenoid wound inductor (or straight through wire) wrapped
in a ferrite bead. That would allow placement on the PCB without an
air gap and reduce any tendency for the inductor to turn into an
antenna.

Same Bias-Tee for only $3.21 from Hong Kong. Just add a can and you
saved about $25:
https://www.ebay.com/itm/Bias-Tee-10-6000-MHz-6GHz-For-HAM-radio-RTL-SDR-LNA-Low-Noise-Amplifier-/192724549249
(Sorry, but I'm pathologically cheap).

I had an engineer waiting to test a part, so I got two at $25 each,
overnight, in a can with SMAs. Engineers are pathologically expensive.


It has about a 60 ps rise time, which corresponds to about 6 GHz.

0.35 / rise_time(nsec) = bandwidth(GHz)
0.35 / 0.060nsec = 5.83GHz.
Yep, close enough.

I just figured that 6x6 = 36.


I thought you were also looking at reflections along the 50 ohm
transmission line with the TDR. Methinks you'll find impedance bumps
at the SMA to PCB transition distance.

When I get to work (later... this is Slacker Wednesday) I'll post the
TDR pics.



https://www.dropbox.com/s/hz4wj3fltsetqqj/Amazon_Tee.jpg?dl=0

https://www.dropbox.com/s/obvfz8knmq9xj94/Amazon_Tee_TDR1.JPG?dl=0

https://www.dropbox.com/s/fd7r5qlipqvoqvm/Amazon_Tee_TDR2.JPG?dl=0

https://www.dropbox.com/s/oraseq9sml5yy97/Amazon_Tee_TDR3.JPG?dl=0

Looks like the microstrip traces are about 500 ps long and 43 ohms,
which actually isn't bad for a production FR4 board.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

Clifford Heath
Guest

Thu Feb 07, 2019 7:45 am   



On 7/2/19 3:54 pm, John Larkin wrote:
Quote:
On Wed, 06 Feb 2019 07:34:08 -0800, John Larkin
jjlarkin_at_highlandtechnology.com> wrote:

On Tue, 05 Feb 2019 21:45:10 -0800, Jeff Liebermann <jeffl_at_cruzio.com
wrote:

On Tue, 05 Feb 2019 20:58:52 -0800, John Larkin
jjlarkin_at_highlandtechnology.com> wrote:


I wonder what's special about 6 GHz. Most tees spec 6 GHz.

Dunno. My guess is that 6GHz is where the BNC connector craps out.
SMA will go much higher in frequency, but most of Bias-Tee devices I
played with many years ago used BNC.
http://www.interfacebus.com/RF_Connector_Frequency_Range.html
Tradition must be maintained even if nobody can remember why.

Mine seems to use a small inductor or, likely, a ferrite bead.
https://www.dropbox.com/s/hz4wj3fltsetqqj/Amazon_Tee.jpg?dl=0

Probably a solenoid wound inductor (or straight through wire) wrapped
in a ferrite bead. That would allow placement on the PCB without an
air gap and reduce any tendency for the inductor to turn into an
antenna.

Same Bias-Tee for only $3.21 from Hong Kong. Just add a can and you
saved about $25:
https://www.ebay.com/itm/Bias-Tee-10-6000-MHz-6GHz-For-HAM-radio-RTL-SDR-LNA-Low-Noise-Amplifier-/192724549249
(Sorry, but I'm pathologically cheap).

I had an engineer waiting to test a part, so I got two at $25 each,
overnight, in a can with SMAs. Engineers are pathologically expensive.


It has about a 60 ps rise time, which corresponds to about 6 GHz.

0.35 / rise_time(nsec) = bandwidth(GHz)
0.35 / 0.060nsec = 5.83GHz.
Yep, close enough.

I just figured that 6x6 = 36.


I thought you were also looking at reflections along the 50 ohm
transmission line with the TDR. Methinks you'll find impedance bumps
at the SMA to PCB transition distance.

When I get to work (later... this is Slacker Wednesday) I'll post the
TDR pics.



https://www.dropbox.com/s/hz4wj3fltsetqqj/Amazon_Tee.jpg?dl=0

https://www.dropbox.com/s/obvfz8knmq9xj94/Amazon_Tee_TDR1.JPG?dl=0

https://www.dropbox.com/s/fd7r5qlipqvoqvm/Amazon_Tee_TDR2.JPG?dl=0

https://www.dropbox.com/s/oraseq9sml5yy97/Amazon_Tee_TDR3.JPG?dl=0

Looks like the microstrip traces are about 500 ps long and 43 ohms,
which actually isn't bad for a production FR4 board.



For those of us not familiar with reading TDR plots, can you point to
some of the main landmarks (by grid reference)?

Clifford Heath.

John Larkin
Guest

Thu Feb 07, 2019 7:45 am   



On Thu, 7 Feb 2019 16:48:51 +1100, Clifford Heath <no.spam_at_please.net>
wrote:

Quote:
On 7/2/19 3:54 pm, John Larkin wrote:
On Wed, 06 Feb 2019 07:34:08 -0800, John Larkin
jjlarkin_at_highlandtechnology.com> wrote:

On Tue, 05 Feb 2019 21:45:10 -0800, Jeff Liebermann <jeffl_at_cruzio.com
wrote:

On Tue, 05 Feb 2019 20:58:52 -0800, John Larkin
jjlarkin_at_highlandtechnology.com> wrote:


I wonder what's special about 6 GHz. Most tees spec 6 GHz.

Dunno. My guess is that 6GHz is where the BNC connector craps out.
SMA will go much higher in frequency, but most of Bias-Tee devices I
played with many years ago used BNC.
http://www.interfacebus.com/RF_Connector_Frequency_Range.html
Tradition must be maintained even if nobody can remember why.

Mine seems to use a small inductor or, likely, a ferrite bead.
https://www.dropbox.com/s/hz4wj3fltsetqqj/Amazon_Tee.jpg?dl=0

Probably a solenoid wound inductor (or straight through wire) wrapped
in a ferrite bead. That would allow placement on the PCB without an
air gap and reduce any tendency for the inductor to turn into an
antenna.

Same Bias-Tee for only $3.21 from Hong Kong. Just add a can and you
saved about $25:
https://www.ebay.com/itm/Bias-Tee-10-6000-MHz-6GHz-For-HAM-radio-RTL-SDR-LNA-Low-Noise-Amplifier-/192724549249
(Sorry, but I'm pathologically cheap).

I had an engineer waiting to test a part, so I got two at $25 each,
overnight, in a can with SMAs. Engineers are pathologically expensive.


It has about a 60 ps rise time, which corresponds to about 6 GHz.

0.35 / rise_time(nsec) = bandwidth(GHz)
0.35 / 0.060nsec = 5.83GHz.
Yep, close enough.

I just figured that 6x6 = 36.


I thought you were also looking at reflections along the 50 ohm
transmission line with the TDR. Methinks you'll find impedance bumps
at the SMA to PCB transition distance.

When I get to work (later... this is Slacker Wednesday) I'll post the
TDR pics.



https://www.dropbox.com/s/hz4wj3fltsetqqj/Amazon_Tee.jpg?dl=0

https://www.dropbox.com/s/obvfz8knmq9xj94/Amazon_Tee_TDR1.JPG?dl=0

https://www.dropbox.com/s/fd7r5qlipqvoqvm/Amazon_Tee_TDR2.JPG?dl=0

https://www.dropbox.com/s/oraseq9sml5yy97/Amazon_Tee_TDR3.JPG?dl=0

Looks like the microstrip traces are about 500 ps long and 43 ohms,
which actually isn't bad for a production FR4 board.



For those of us not familiar with reading TDR plots, can you point to
some of the main landmarks (by grid reference)?

Clifford Heath.


The equivalent circuit is a 50 ohm step generator (sampled by the
lower oscilloscope channel), a piece of hardline, the bias tee,
another hardline, and the other 50 ohm scope input.

The lower trace is the TDR, approximately a graph of impedance vs
distance. There's the initial step, then a 50 ohm hardline coax, then
the bias tee (the wiggly part), another hardline, and then the 50 ohm
termination of the other sampling scope channel. The inductor in the
bias tee gradually shorts everything out; the time constant is L/R
where R=25 ohms (50 ohms in both directions from the inductor.)

The upper trace is TDT, time domain transmission, namely the other
sampling scope channel at the end of the second line. That is the step
response of a fast pulse that goes through the tee.

The indicated TDT step rise time is 60 ps, which corresponds to about
6 GHz bandwidth. For gaussian steps, Tr*BW = 0.35.

The TDR3 shot has two cursor dots, one midway along the first
hardline, and one inside the tee. Impedances are shown below.

The scope TDR speed is about 30 ps, so that observed 60 ps step
response is actually a bit faster, more like 52 ps maybe, so the tee
is a bit better than 6 GHz.



--

John Larkin Highland Technology, Inc

lunatic fringe electronics

Tom Gardner
Guest

Thu Feb 07, 2019 8:45 am   



On 06/02/19 23:42, Gerhard Hoffmann wrote:
Quote:
Am 05.02.19 um 09:48 schrieb Tom Gardner:
On 05/02/19 04:38, Gerhard Hoffmann wrote:
That's a hi temperature field in Iceland. They skimp on warning signs.
But when there is one, you better respect it. If you walk there,
you might break into a hole with hot sulfuric slime around your knees.

They are getting "better", e.g. there are now safety rails
at Gullfoss waterfall.
https://i1.wp.com/www.followmeaway.com/wp-content/uploads/2018/01/gullfoss-waterfall-iceland-closed-viewpoint.jpg


When I last went they took the attitude that if you couldn't
work out that spray+rocks+chasm means you might fall and die,
then that would merely improve the species.

I do like this one, esp. the line about the hospital.


https://www.flickr.com/photos/137684711_at_N07/40044445253/in/album-72157688304045365/
 


That looks like Strokkur. I don't remember seeing any safety
signs or barriers there.

There was a justifiable safety warning at Námaskarð.
Justifiable because it warned of a strange situation
that wasn't blindingly obvious to someone with a brain
that they had turned on when they woke up.

It said something like "you can tread on the red and
brown soil but if you tread on the yellow or white soil
it can give way without warning, and you can slip into
boiling mud".

Nice picture of yours at Gullfoss
https://www.flickr.com/photos/137684711_at_N07/37245860655/in/album-72157688304045365/

You can see a ledge about 10ft/3m below the people.
I'm pretty sure I can find photos I took when I walked
along that. I'm also pretty sure it has eroded since
I was there!

Robert Baer
Guest

Tue Feb 12, 2019 1:45 am   



Clifford Heath wrote:
Quote:
On 5/2/19 9:28 am, John Larkin wrote:

https://www.amazon.com/gp/product/B07D1GMXMD/ref=ppx_yo_dt_b_asin_title_o02__o00_s00?ie=UTF8&psc=1


We needed some bias tees so I tried Amazon. Prime, extra $4 for
overnight delivery.

Amazon is amazing.

We TDRd them, and they really are pretty good 6 GHz tees.

Gotta open one up and see what's inside.

Have you played with conical-wound broadband inductors? There are some
amazing examples. E.g. <https://www.coilcraft.com/conicals/index.cfm

Clifford Heath
Looks like a perfect antenna..


Robert Baer
Guest

Tue Feb 12, 2019 1:45 am   



John Larkin wrote:
Quote:

https://www.amazon.com/gp/product/B07D1GMXMD/ref=ppx_yo_dt_b_asin_title_o02__o00_s00?ie=UTF8&psc=1

We needed some bias tees so I tried Amazon. Prime, extra $4 for
overnight delivery.

Amazon is amazing.

We TDRd them, and they really are pretty good 6 GHz tees.

Gotta open one up and see what's inside.


Yeah. Amazon-ing. Ordered some Cleaning Duster and it arrived by way
of the local Office Depot.

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