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In sonar that would be called a tone burst.

On 7/21/22 9:17 AM, Roy J. Tellason, Sr. wrote:

On Wednesday 20 July 2022 03:58:49 pm Jim Lux wrote:

If you must, SO-239 / PL-259 connectors are *only* for HF use. ?Their
impedance is NOT controlled as are the other referenced RF connectors.

True, the UHF connector isn't constant impedance, however, if you have a
set of calibration standards in UHF, then that is managed in the
calibration.

Some time back I acquired a cable with connectors on each end that resemble PL-259s, but are *much* smaller. Anybody know what these are, and what sort of equipment is likely to use them?

There's a mini-UHF that I've seen on things like land mobile VHF radio, and on older cell phones (instead of a TNC). Unlike the PL-259, it's actually designed for constant impedance. It's really more of a Mini-TNC, but it has that serrated edge on the jack, and a TNC is a smooth edge.




Tessco

Jim, not just the UK. It's not the net Nazis. I could not access it
either. Something to do with no 'academic access" and, of course, not an
IEEE member. I'm not sure even an IEEE member would allow access.

Thanks for forwarding the paper, but I hope I can read it as its not the
sharpest "copy".

Dave - W?LEV

On Thu, Jul 21, 2022 at 5:12 PM Dragan Milivojevic <d.milivojevic@...>
wrote:

Had no idea that the UK censors the internet. Good reason to get a VPN.
Anyway: !AvpPJnaZGO4PiHD2Qt_oLBZfweoD?e=dxDhWi

On Thu, 21 Jul 2022 at 16:48, Ed G8FAX <ed@...> wrote:

On Wed, Jul 20, 2022 at 05:42 PM, Dragan Milivojevic wrote:

On Tue, 19 Jul 2022 at 07:48, Ed G8FAX <ed@...> wrote:

Jim Lux wrote: “google for "woodward balun balance quality 1983" “

Thanks, I no longer have academic access, so will need to buy or get

site

of the paper some other way. However, there might be

alternatives/better

solutions to pursue.

Thanks, but sc-hub.se is blocked in UK, so no access.

--
*Dave - W?LEV*
*Just Let Darwin Work*


--
Dave - W?LEV

Had no idea that the UK censors the internet. Good reason to get a VPN.
Anyway: !AvpPJnaZGO4PiHD2Qt_oLBZfweoD?e=dxDhWi

Ed, I just noticed that I misread the datasheet. The SWB2010-PCL goes from 5 kHz to 100 MHz at 3 dB down. The low end is remarkably low. The less flat SWB-2010-1-PCL goes from 40 kHz to 175 MHz.

Brian

On Thu, Jul 21, 2022 at 08:46 AM, Brian Beezley wrote:

Have you used it with nanoVNA tests?

I haven't, Ed, but N6LF has. What I like about this particular transformer is
that the passband is very flat. That reduces any calibration error that may
arise from interpolation between frequency samples. Check the datasheet for a
version with even wider frequency response that is not quite as flat.

Brian

Thanks Brian, information much appreciated

Ed, G8FAX

On Wednesday 20 July 2022 03:58:49 pm Jim Lux wrote:

If you must, SO-239 / PL-259 connectors are *only* for HF use. ?Their
impedance is NOT controlled as are the other referenced RF connectors.

True, the UHF connector isn't constant impedance, however, if you have a
set of calibration standards in UHF, then that is managed in the
calibration.

Some time back I acquired a cable with connectors on each end that resemble PL-259s, but are *much* smaller. Anybody know what these are, and what sort of equipment is likely to use them?


--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin

CAN Bus in a car has term resistor and each end.

On 7/21/22 6:12 AM, Magicbean wrote:

Hello - Totally new to VNA here...
I want to measure the characteristic impedance of 120 ohm shielded twisted pair wire. I know that you can measure it for 50 ohm coax using the NanoVNA but I wondered if there was any reason why it wouldn't work for non-50 ohm twisted-pair? The purpose of measurement is to make sure I fit the best termination resistors for long runs (100m ish) of cable for CAN bus cable.

It should work fine. That STP has a "reasonably well controlled" impedance, but i wouldn't be surprised by 5% changes. It might be most useful to do the TDR type display, rather than a S11. Then you can see the dips and peaks along the cable. (Fun experiment, tie a knot or kink it in the middle of the cable)

I do have a Siglent SSA3032X plus spectrum analyser for which there is a return loss bridge (RB3X25) but at around ?400. I'm not sure whether that would be useable for that kind of measurement, especially as the cable isn't 50 ohms.

No, that's not the right tool. The NanoVNA is what you want.

I assume the NanoVNA probably is suitable for measuring the 120 ohm pair and can probably offer more functionality even if some of the specs of the Siglent are rather better!? If so, what's the shortest length of twisted pair I could sensibly make measurements on? I have some 1m samples of cable which I would like to evaluate. The final cable runs will be in the order of 100m.

An interesting question. The "resolution" in TDR type displays is determined by the frequency span. So 1 GHz gives you 1 ns (20-30cm) resolution. The unambiguous range is set by the lowest frequency.

If you want to distinguish the "cable" from the "ends" (both at the VNA end and the termination end) you probably want the cable to be long enough that it's several resolution points. The NanoVNA can go up to 900 MHz, so a 3-4 m piece should be long enough.

Before you get into fixturing and all that, try it with a 2-3 m piece of 50 ohm coax, and see if you can distinguish the termination (i.e. do the cal with no cable, put the cable on, and then look at TDR with the short, open, and load at the far end)

BTW I know I can also fire a pulse down the cable and match with a variable resistor when the cable is easily accessible (and I might do that too) but I am interested to know if the NanoVNA would be useful for this and also, in some circumstances, I won't be able to get to the far end of some cables. Would it be necessary to normalise to something other than 50 ohms? Would I need any other components or equipment to do the test (apart form connectors to physically connect)?

NanoVNA does that nicely.

Whether you normalize or not depends on whether you need to have actual values, or if you're just doing a qualitative test. If you get a reflection from the end vs no reflection, you don't really care what the value is.

I have some other applications for the NanoVNA too, so I will probably get one (I was thinking NanoVNA H4 although there seems to be a bewlidering number of variants). I'd just like to know if it is suitable for this measurement as well. Or... if I could do everything with a Siglent RF bridge, maybe that would be a better focus as I already have the SA.
Thanks.

Have you used it with nanoVNA tests?

I haven't, Ed, but N6LF has. What I like about this particular transformer is that the passband is very flat. That reduces any calibration error that may arise from interpolation between frequency samples. Check the datasheet for a version with even wider frequency response that is not quite as flat.

Brian

On Thu, Jul 21, 2022 at 04:43 AM, Brian Beezley wrote:

Coilcraft SWB2010-PCL. 50 kHz to 100 MHz, 1:1 with secondary CT, 6-pin DIP.,
$4.54 each from Mouser. Note link to datasheet.




Brian

Looks useful.

Have you used it with nanoVNA tests?

Kind regards

Ed, G8FAX

On Wed, Jul 20, 2022 at 05:42 PM, Dragan Milivojevic wrote:

On Tue, 19 Jul 2022 at 07:48, Ed G8FAX <ed@...> wrote:

Jim Lux wrote: “google for "woodward balun balance quality 1983" “

Thanks, I no longer have academic access, so will need to buy or get site
of the paper some other way. However, there might be alternatives/better
solutions to pursue.

Thanks, but sc-hub.se is blocked in UK, so no access.

Hello - Totally new to VNA here...

I want to measure the characteristic impedance of 120 ohm shielded twisted pair wire. I know that you can measure it for 50 ohm coax using the NanoVNA but I wondered if there was any reason why it wouldn't work for non-50 ohm twisted-pair? The purpose of measurement is to make sure I fit the best termination resistors for long runs (100m ish) of cable for CAN bus cable.

I do have a Siglent SSA3032X plus spectrum analyser for which there is a return loss bridge (RB3X25) but at around ?400. I'm not sure whether that would be useable for that kind of measurement, especially as the cable isn't 50 ohms.

I assume the NanoVNA probably is suitable for measuring the 120 ohm pair and can probably offer more functionality even if some of the specs of the Siglent are rather better!? If so, what's the shortest length of twisted pair I could sensibly make measurements on? I have some 1m samples of cable which I would like to evaluate. The final cable runs will be in the order of 100m.

BTW I know I can also fire a pulse down the cable and match with a variable resistor when the cable is easily accessible (and I might do that too) but I am interested to know if the NanoVNA would be useful for this and also, in some circumstances, I won't be able to get to the far end of some cables. Would it be necessary to normalise to something other than 50 ohms? Would I need any other components or equipment to do the test (apart form connectors to physically connect)?

I have some other applications for the NanoVNA too, so I will probably get one (I was thinking NanoVNA H4 although there seems to be a bewlidering number of variants). I'd just like to know if it is suitable for this measurement as well. Or... if I could do everything with a Siglent RF bridge, maybe that would be a better focus as I already have the SA.

Thanks.

On 7/21/22 3:56 AM, DougVL wrote:

On Tue, Jul 19, 2022 at 09:00 AM, Jim Lux wrote:

Not actually pulses, it's a CW measurement

Sorry, my mistake.
How long does the CW signal last, at 101 measurement points?

Long enough for the synthesizers to stabilize, then capture ADC samples of the 5kHz output from the mixer for the receivers. A few milliseconds.

I thought that length would be called a pulse.
(In my Air Force AC&W radar technician days, a 6 millisecond transmission was called a pulse.)

Sure, it's pulsed, but the reason I describe it as CW is that the measurement is not made with looking at the reflection of a transmitted pulse as in a radar.

It's a pulsed CW measurement, and the measurement is made at the same time as the source is on.

The entire sweep is a few hundred milliseconds.

Coilcraft SWB2010-PCL. 50 kHz to 100 MHz, 1:1 with secondary CT, 6-pin DIP., $4.54 each from Mouser. Note link to datasheet.



Brian

On Tue, Jul 19, 2022 at 09:00 AM, Jim Lux wrote:

Not actually pulses, it's a CW measurement

Sorry, my mistake.
How long does the CW signal last, at 101 measurement points?
I thought that length would be called a pulse.
(In my Air Force AC&W radar technician days, a 6 millisecond transmission was called a pulse.)
--
Doug, K8RFT

THANKS!!!

Rather than cutting the cable, you should calibrate with the cable attached
to the nanovna, attaching the calibration standards at the other end of the
cable, using connector adapters if necessary. This way ensures that all
aspects of the cable (length, loss, etc.) are compensated for by the
calibration, perfectly removing all those circles from the smith chart.
Stan