Forum - Recent Threads

RE: RF Connectors Assortment

shabaz — Sun, 30 Aug 2026 15:17:50 GMT

It's some off-the-shelf watering system they installed, just happens to not provide good alerts when the water is low. There is an enclosure and solar panel, so an option is to open up the box and stick it there if there's space (I have not thought the installation through! will leave that to them to figure out : ) The design is a bit ad hoc.. maybe a PCB antenna would have been better all round.

RF Connectors Assortment

shabaz — Fri, 10 Dec 2021 19:47:24 GMT

I spent a good 20 minutes the other day, trying to make an antenna fit a Wireless LAN (WLAN) card. It just wouldn't snap on, and finally, I realized the antenna had a U.FL plug, whereas the WLAN card had a MHF 4 socket : )

I'd never heard of MHF 4 before, but it seems to be very popular in the laptop computer world. Anyway, while I was at it trying to visually compare the connectors, I took this photo - perhaps useful for identifying connectors in the future : )

The photo is missing connectors, especially some common ones like N connector, and the PL-259 (popular in ham radio equipment).

BNC of course is very popular, as is SMA. I really like SMB, it's like a hassle-free version of SMA, but unfortunately, it is not as popular on equipment.

(Click photo to enlarge):

EDIT:

Decided to re-take the photo and add N and TNC. Also added a PL-259.

RE: RF Connectors Assortment

beacon_dave — Sat, 29 Aug 2026 21:35:45 GMT

[quote userid="123345" url="~/technologies/test-and-measurement/f/forum/50334/rf-connectors-assortment/237961"]Incidentally, I was also wondering how to make it more permanent, because I won't be around when this board is installed in an enclosure, it is for a friend to fit in their garden watering "system". They would not know how to re-snap that connector in, if it worked loose. [/quote]

Is this some sort of 'extreme watering/gardening' thing we should know about ? 🙂

Perhaps a couple of holes through the PCB and a thin cable tie or loop of tinned copper wire through them and around the back of the connector ?

Could do similar with the cable instead of the Polydoh/UV glue..

RE: RF Connectors Assortment

shabaz — Sat, 29 Aug 2026 19:56:00 GMT

Not a bad idea, since that won't drip inside the connector : )

RE: RF Connectors Assortment

obones — Sat, 29 Aug 2026 19:00:43 GMT

I'm more of a glue gun kind of guy, but I guess there are reasons not to use that in such a situation .

RE: RF Connectors Assortment

beacon_dave — Sat, 29 Aug 2026 18:18:55 GMT

[quote userid="17018" url="~/technologies/test-and-measurement/f/forum/50334/rf-connectors-assortment/237919"](and with your tongue in the right angle)[/quote]

That's slightly ambiguous - do you have a photo ? 😛

RE: RF Connectors Assortment

shabaz — Sat, 29 Aug 2026 15:36:40 GMT

I gave that a shot!! You're absolutely right, the trick is to hold and look at the coax, and make sure it is parallel to the board. For the snapping-in, I still didn't trust myself, so I ended up finding a short length (about 50mm) of acrylic rod, and pushed with that (it was easy to see that the rod was vertical) although I guess there is a risk it could slide off while pushing. Might place a few-$ order for a 3D-printed tool with any next PCB order.

Incidentally, I was also wondering how to make it more permanent, because I won't be around when this board is installed in an enclosure, it is for a friend to fit in their garden watering "system". They would not know how to re-snap that connector in, if it worked loose.

The experiment for now (I'm not very happy with it) was to add some strain relief to the coax. I used a small blob of black polydoh, and pressed in the coax to form a cradle to support the wire. Polydoh isn't adhesive, the cradle would slide around, so then I placed a few drops of UV glue on top, and cured that.

I might go back and put some other glue onto the connector itself, but I'm unsure since it might seep inside it. Maybe it's already fine. I also still need to add a coating to the board, since it will be outdoors.

RE: RF Connectors Assortment

Jan Cumps — Sat, 22 Aug 2026 15:22:44 GMT

> I find it very difficult to keep the u.FL connector aligned while pushing until it snaps in.

I have a trick. The first time I tried one, it embedded itself under the skin of my thumb 😞.

But if you align it over the connector by holding the coax cable between thumb and index finger, just in the right position (and with your tongue in the right angle), you can press it down and it snaps in.

RE: RF Connectors Assortment

shabaz — Sat, 22 Aug 2026 12:31:06 GMT

Nice assortment! I prefer SMA antennas and recently got some u.FL to SMA cables.. but I need to improve using those, I find it very difficult to keep the u.FL connector aligned while pushing until it snaps in. I have tried using round bar, since then I can keep that vertical, I just about manage. Might try to make a tool one day, or buy something (don't want to spend a lot since I don't plug so many in!).

RE: RF Connectors Assortment

Jan Cumps — Sat, 22 Aug 2026 07:16:17 GMT

I got some SMA components recently. To check which ones I can use best for measurements. A few T-adapters, BNC to SMA adapters, a bit of 50 Ohm cable, 50 Ohm terminators.

RE: A quick way to map physical RS232 connectors to Windows COM ports

misaz — Tue, 11 Aug 2026 14:13:05 GMT

Interesting idea, but it is quite a expensive toy considering that at the end it is pretty simple loop. Also note that It could be also dangerous since it likely transmit data to 3rd party "generic" devices to "test them". Finally, Windows also has new API since Windows 10 which no longer use COMx devices which are inheritance from DOS era. Especially in case of newer Windows-on-ARM boards, your tool will not identify onboard ports simply because new drivers (SerCx2 based) no longer creates these legacy devices and new API (or huge amount of Win32 work) is required for accessing them.

A quick way to map physical RS232 connectors to Windows COM ports

ehsanshenavar — Tue, 11 Aug 2026 13:16:37 GMT

Disclosure: I developed the PORTYX application mentioned below.

When working with a multi-port USB-to-RS232 adapter, Windows shows several COM numbers but does not make it obvious which physical DB9 connector corresponds to each one. On an 8-port StarTech ICUSB2328I, checking ports one by one in Device Manager was cumbersome.

The method I use is:

1. Attach a DB9 RS232 loopback tester to one physical connector.
2. Run a loopback scan across the available COM ports.
3. Record the COM port that successfully echoes the transmitted data.
4. Move the tester to the next connector and repeat.

I added this workflow to PORTYX RS232 Loopback Assistant so the scan and identification are automatic.

Microsoft Store:
apps.microsoft.com/.../9nfdlhgtpsnx

The method is not specific to that StarTech model and should work with other multi-port USB-to-RS232 adapters. A suitable hardware plug can be found by searching for RS232 DB9 loopback tester.

I would be interested in results from other adapter chipsets or port counts.

first impressions: multicomp PRO handheld oscilloscope

Jan Cumps — Sun, 15 Jan 2023 19:07:23 GMT

With the shopping cart I won in a project14 month, I ordered a handheld oscilloscope. In this post: my first impressions.
I 'll focus on using the instrument the very first time as a handheld test instrument. I will not review software, specs, competition.

If you have an Owon HDS200 series instrument, you can follow along. It's the same.

3 instruments in one

I have an [embed:ad4490ac-0ce8-4f2d-a04c-9285646d5689:232405f2-0c88-4e91-8243-0ca39e34d8c1:text=MP720783&style=link&farnell=3703267&newark=25AK2942&cpc=&avnetemea=&avnetema=&avnetasia=&comoverride=&cmpoverride=&AreaInteracted=rte-content&bom=]. A 70 MHz 2 channel oscilloscope, a DMM and function generator in a package that has the size and weight of a DMM. The 3 instruments can operate at the same time, but only one has the screen and buttons active at a time. You can use the function generator to serve an input test signal for your design, then use the oscilloscope and DMM to probe your design.

Overall look-and-feel is good. The buttons feel good and the display readability / clarity is good. Connections (except USB) are easy to get at. And there's a stable stand (if you dare to open it beyond the scary click position). I prefer to use the stand, because the reading angle is mediocre.

Overall first impressions are good, for all 3 modes. Using the instrument as a basic scope, generator or DMM is easy and intuitive. You can learn this in minutes, if you have previous experience.
Beyond that point, the interface gets more complex. The options are logical, not annoying and comparable to what other advanced instruments do. But at this point, the instrument is not as intuitive as a well designed bench instrument.

Being handheld, the instrument has an options that some bench instrument don't offer: (safe) isolation. The DMM is fully isolated, as expected. But also the oscilloscope and function generator aren't ground referenced. This can be an asset.
Be aware though, that the generator output and oscilloscope channel 1 + 2 grounds are common. And that both are also common with the USB connector shield. The instrument gives you safe options (CAT II) to do isolated probing. But you have to bring your brains to the party.

In the box:

an x1/x10 probe (with the usual accessories) and 2 BNC-to-crocodile probes.
rechargeable batteries
USB cable for charging and interfacing, wall wart
DMM probes
a pouch
manuals, software

Oscilloscope

This is the only relevant section you should care about. You'd get this instrument for its oscilloscope functions.

Two channel, 70 MHz in my case - there is a 40 MHz version too. The usual channel options are available:

probe x1 -> x10000
AC / DC coupled, GND
bandwidth 20 MHz / full
time base from 10 ns to 500 s
10 mV to 10 V / div
Sample and Peak Detect mode
X/Y

Measure

7 measures (6 visible at a time across 2 channels), and a hardware counter
cursors (CH1 or CH2 vertical, or time)

Trigger

auto, normal, manual triggering and force
rising / falling edge
AC / DC coupled

Varia

sample depth (4K / 8K)
store wave form or screen print
auto

Overall look, feel and use is easy. You get a common signal on the display as fast as you would with a bench instrument. Scaling and moving X and Y are a bit more involved.
It gets harder (compared to a bench instrument) when you want to zoom in to a part of a captured wave, or trigger on more advanced scenarios (there's no hold/delay or external trigger). The functions I use in my day-to-day probing are available.

Signals are clear on the display. The annotations on the screen are easy to read. Refresh rate OK.

Function Generator

This module is not available on all models. It has the usual signals: sinus, square, ramp. Up to 25 MHz for sinus, in the low MHz for the other waves. There's also a set of popular signals, called arbitrary. They are predefined, so that name is a bit odd.

There's one BNC output. You can set frequency, amplitude (+- 10 mV to 2.5 Vp/p), offset and impedance. The +- 2.5 V includes any DC offset applied. For some waveforms, there's a symmetry setting. It sets the duty cycle for pulse waves and skews the ramps for triangle wave. The rise / fall time of the pulse wave can be set too. The ground is shared with the oscilloscope and the USB connector.

Experience: It works. Definitely useable when you need a permanent test signal. The user interface of this module has seen less love than the scope. I don't see me using this on a regular base, except if I need one of the base waves quickly.

Arbitrary means that something is not predefined. This instrument says that it has arbitrary waveforms, but the ones served in that section are a known set of predefined waveforms. Your opinion may differ, but I would not call a fixed set of predefined waveforms arbitrary.

I did not find an option in this instrument, under the arbitrary waveform menu, to define arbitrary waveforms.

DMM

This option is available on all instruments of the series. A fully isolated DMM. The ground is not shared with scope, generator or USB. Specs are good, not spectacular. The 20000 count is the spec that stands out.

t's not difficult to use, but the user interface is different from how a DMM normally behaves.
There are also quirks e.g.:

how auto / manual behaves in different modes,
that it displays intermediate / way-off measurement values while it stabilises, without showing it's still stabilising (other meters show ---- or the likes)

The diode mode is good. I like the speed and latch of the continuity buzzer: just the right speed and stability to scratch over an IC and have beeps when there's contact.

Experience: works and will do the job. I do not like working with it though, because the interface is too different from what DMMs do. I believe this could be solved by having a UI engineer have a go at it.

Summary / verdict

This is a good product. The oscilloscope is a winner. An instrument that can have a main spot on the desk and in the toolbox. The two other options are useful, but I would never buy a separate handheld waveform generator or DMM that operates like these two options.

The unit sits good on the table, and using it with the probes is easy. A little bit too wide/rectangular for my hands to hold for a long time, but doable. The screen is clear inside and outside. A bit glary though, and scratch-prone.

end advice: Get it for the oscilloscope functionality. Take advantage of the two other options, but don't let them influence your purchase.

link to all posts

RE: first impressions: multicomp PRO handheld oscilloscope

Jan Cumps — Fri, 31 Jul 2026 11:03:41 GMT

One advantage of this model is that you can use the function generator and oscilloscope at the same time.

set up the function generator and switch on the output
switch to the oscilloscope and use it

You can switch between the two user interfaces with the Mode button

In this action photo: the device generates an input signal for a differential amplifier. The oscilloscope is used to monitor in- and output.

the function generator is set to sinus, 1 kHz, 100 mVpp
scope channel 1 measures that input
scope channel 2 measures the output.

It 'll often be easier to have a separate bench size generator and oscilloscope. In particular when you regularly want to change the signal.

But this option has advantages too. Tiny footprint, can be used in the field. And isolated from other grounds when desired.

RE: MULTICOMP PRO MP750065 Function Generator - 1st impressions

Jan Cumps — Wed, 01 Jul 2026 13:41:53 GMT

microknight if you share your settings, I'll see if I can replicate it.

MULTICOMP PRO MP750065 Function Generator - 1st impressions

Jan Cumps — Mon, 28 Feb 2022 12:24:04 GMT

Since yesterday, I have a [embed:ad4490ac-0ce8-4f2d-a04c-9285646d5689:5398a281-4fab-4270-b8eb-55b46af15ece:text=MP750065&style=link&farnell=3130266&newark=&comoverride=&AreaInteracted=rte-content&cpc=&avnetemea=&avnetema=&avnetasia=&bom=] function generator and counter.

Specs:

DC to 5 MHz
1 µHz resolution
5 Vpp in 50Ω (10 Vpp in high impedance)
sine, pulse and flank (triangle)
variable duty cycle for pulse. For the other two waveforms this function changes the symmetry
Sweep linear and Log, start, end and speed are configurable
AM and FM modulation, with external input
Sync output, can be used to trigger an oscilloscope while sweeping
arbitrary waveforms, 20 preloaded. 20 custom waves can be stored
power output that can drive 4W, with a 200 kHz upper limit.
counter up to 100 MHz
USB, remote software

Unexpected specs:

it's SCPI programmable. This is not mentioned on the e14 shops, but a great feature
the OEM is UNI-T. This device is the twin of the UTG900C-II

First Use

The basic functionality is easy to use: switching the traditional wave forms, frequency, amplitude. Even duty cycle.
I got started with the instrument in minutes. It shows a default waveform when switching the device and output on. A 1 kHz, 100 mVpp (in 50Ω) sine wave.
Because the popular parameters can be set with function keys, altering that form just works as you'd expect it to.

A few other functions, such as the output impedance switch from high to 50Ω were less intuitive, but I found how to do that without reading the manual too.
Once you go to the more advanced functions, like sweep setup, you'll need the manual the first few times. It's not difficult, but they require that you know the steps.

I haven't used the arbitrary functionality or the counter yet.

Teardown

(I did a more detailed teardown in a later post)

I took a look inside. Mainly two sections: power supply at the back, Instrument and user interface up front. The middle of the box is empty.
To remove front and back, you pull the baby bumpers on both sides. There's a screw under each of them. The connection point of the bumpers is near the end. Releasing and re-fixing them is easy and requires little force.

You can then carefully pull both ends of the instrument from the housing. If you disconnect a few cables, you can remove them fully. I haven't done that.

Here are a few photos of the PSU at the back:

… and some of the instrument side. Spot the ARM and FPGA.

The next one is unsharp. I added it because it gives a good impression of the front panel's backside.

Finally, a peek inside the box:

One of the things I learned while peeking inside, is that the PCB had a type number mechanism typically used by UNI-T.
Knowing that MULTICOMP PRO uses OEMs, I went to look online to find the matching model. It's the UTG9000C-II.
It has the identical looks, specs and user documentation. But also a programmer's guide that's not available on AVNET's shops.
There I found that this device should be SCPI controllable. I'll test this out with LabVIEW at a later time.

edit after investigation: it is LabVIEW programmable - but not your typical NI-VISA and SCPI approach. It automates well though.

[View:https://youtu.be/19Hv33z5KmQ:640:360]

Thank you for reading.

Programming Pt1: SDK Demo

Programming Pt2: LabVIEW tryout (a)

Programming Pt3: LabVIEW tryout (b)

Programming Pt4: LabVIEW Driver Lib Init block

Programming Pt5: LabVIEW Driver Lib Read, Write and Close blocks

Programming Pt6: LabVIEW Driver Lib: High Level Functional blocks

Repair and teardown

RE: MULTICOMP PRO MP750065 Function Generator - 1st impressions

shabaz — Tue, 30 Jun 2026 12:22:04 GMT

Hi, could that be due to delay from your circuitry? Or are you observing the input of the circuit (i.e. function gen output) directly too?

RE: MULTICOMP PRO MP750065 Function Generator - 1st impressions

microknight — Tue, 30 Jun 2026 12:10:36 GMT

I watched your reviews a few years ago, just before I got mine. I've used the sweep function fairly often, but today I've been trying to use the sync output. I'm just capturing the output of an audio circuit sweeping from 300 to 6K, so not very taxing. However, I'm finding that the sync occurs about 2.5mS early and you get the last few cycle of the previous sweep after the trigger. Is there some setting I'm missing. Obviously I can adjust my scope trigger delay, but it doesn't seem right to have to do this.

RE: Observing 96MHz clock signal and its divisions leads to "strange" results

Robert Peter Oakes — Sun, 16 Nov 2025 19:43:34 GMT

one thing I did not see being mentioned is about the scope (And probes). Bandwidth of 100Mhz will be 3db down already but the reference for this is a sine wave, not a square wave.

A square wave is made up of an infinite series of odd-numbered harmonics, including the fundamental frequency. For an ideal square wave, these harmonics are all in phase, with the amplitude of each successive harmonic decreasing by an amount inversely proportional to its harmonic number

so if the square wave is 96Mhz then you will also have signals of 288Mhz, 480Mhz and that's just 3rd and 5h harmonic there are a lot more to get a good square wave but as the scope is max 100Mhz with 3db down on a sine wave then these harmonics needed to shape the wave form are long gone into oblivion, hence you seeing more and more like a sign wave (Triangle ish in your case). even at the much lower frequencies you will see a distorted square wave due to harmonics being filtered . even a 30Mhz signal will have 3rd and 5th harmonics at or beyond the scopes bandwidth 30Mhz primary, 90Mhz 3rd harmonic and 150Mhz 5th harmonic. I hope this help you understand more of what your seeing.

Observing 96MHz clock signal and its divisions leads to "strange" results

obones — Thu, 13 Nov 2025 10:52:32 GMT

Hello all,

I'm toying (pun intended) with ideas in the context of a future challenge and while I'm not settled on what the thing should do, I'm decided on using the MAX32666FTHR2 board that I was gifted with a couple of years back.

The "Light Up Your Life Challenge" gave me a push to finally use the 8*8 WS2812B matrix that I once bought because it looked nice and was not expensive, and so I'm trying to hook it up to the board.

As I can't seem to get the proper output signal to send to the LEDs, I decided to observe what's coming out of the MAX32666 pins.

My first experiment was to use a continuous timer, whose clock is half the system clock (96MHz) and which toggles the output pin every time the counter reaches the comparison value. Here is what I get with two relatively high values:

The signal should be a nice square wave, it does not look that clean, but I know there's always some rise and fall time coming into play.

But things get worse when the comparison value for the timer is even lower, like here with 3:

After further fiddling with the various peripherals on the MCU, I was able to output the 96MHz clock signal, and this is what I get:

I had to stop the oscilloscope because it was not able to see a proper trigger level, let alone compute the frequency from such small signal.

Now, if I read the graph properly, there's about 10ns between two peaks, which is consistent with a 96MHz frequency for the signal.

However, what I'm really wondering about is the fact that the faster the signal, the more distorted I observe it, to the point where it won't even reach full voltage swing between 0V and 3.3V.

Out the top of my head, I can see three reasons for these results:

Reaching the limits of the MAX32666 pin switching capabilities
Reaching the limits of what the oscilloscope can see
Reaching the limits of my own stupidity

For point 1, I tried looking for rise and fall time on output pins in the electrical characteristics for the MAX32666 but could not find anything related to this in the (somewhat confusing) datasheet.

For point 2, the DSO is said to be "100MHz" so as 96 is lower than 100, it should be fine. But maybe Shannon law should be taken into account and 100/2 being lower than 96, the results are expected.

For point 3, well, it could come on top of the two other points, and so I won't rule it out just yet.

I know there is a "Oscilloscope 101" webinar in the works which might actually answer those questions just fine. If that's the case, I'd gladly wait for it.

Thanks for your attention.

RE: Observing 96MHz clock signal and its divisions leads to "strange" results

jc2048 — Sun, 16 Nov 2025 11:28:45 GMT

I quite often improvise 'springy clips', like this

That way, you can solder them, rather than hold the probe with one hand whilst working the controls with the other, though in this case it's quite precarious the way that I just have the tip touching the blob of solder (don't do that in the middle of a valuable board that you don't want to damage). The component between the blobs of solder is the SMD load resistor that I'm trying to probe as cleanly as possible. Sometimes, if I can be bothered, I'll do a little spiral for the probe tip to sit in which can also be soldered in place.

My improvised ground clip was a lead offcut from a component (some old, cheap, but actually very good LEDs) and is plated steel rather than copper - copper is too soft and won't hold it's shape gripping the ground sleeve of the probe.

If you want to see what I was doing with it, it's in the blog below; re-reading that, it's a right mess - I haven't explained what I was doing at all well. And I was wrong about the risetime. That was done with an old 200MHz Tek 2-series scope and the x10 passive probe that came with the scope, so the risetime you see in the waveforms is actually that of the scope and not the pin drivers on the Arduino Uno, nor the output of the transformer, which are both probably beating the scope, but it does show the clean results, without ringing, you can get in a low impedance circuit where the probe isn't loading it too much, and it does show how good the performance of a transmission-line pulse transformer can be, so not entirely wasted as a blog.

https://community.element14.com/members-area/b/blog/posts/experimenting-with-a-transmission-line-transformer

RE: Observing 96MHz clock signal and its divisions leads to "strange" results

obones — Sat, 15 Nov 2025 15:40:13 GMT

Ah!
So that's what this spring is about!
I thought it was a spare for the spring inside the hook...

RE: Observing 96MHz clock signal and its divisions leads to "strange" results

dang74 — Sat, 15 Nov 2025 11:56:39 GMT

Agreed... and the shape change to me is more profound than the 3dB drop. You first notice it in the edges... rather than a nice clean edge they become sine like. And although mathematically they have nothing to do with triangles, to me, in terms of appearance, they do look like imperfect triangular waves... and ultimately when you get really close to the limit, they become miniscule sinewaves. If the signal being probed was a pure sine wave I suppose the amplitude would be 70.7% at the bandwidth limit... but since, as you pointed out, that a square wave is composed of even higher frequency components, the amplitude will be much less than 70.7%.

RE: Observing 96MHz clock signal and its divisions leads to "strange" results

Jan Cumps — Sat, 15 Nov 2025 09:11:05 GMT

The oscilloscope has a 100 Mhz bandwidth. If you probe a 100 MHz square wave signal with it, you 'll notice a few things - even with perfect probing techniques

The signal root wave (a 96 MHz sinus) level will be 3 dB down
The rest of the square wave is made up of frequencies above the scope's upper bandwidth level. You will not get those.

So in general: if you use the x10 mode, you'll get an attenuated sinus-ish result at best.

RE: Observing 96MHz clock signal and its divisions leads to "strange" results

Gough Lui — Fri, 14 Nov 2025 22:31:17 GMT

Yeah. That's a bad idea. Probe loading is hefty at 1x. You should be using 10:1 for anything above around 8MHz in my experience.

- Gough