Coaxial cabling.

You sure it's BNC?

There is a similar HT connector that won't fit BNC hardware.

BNC may be a misapplication.

RL

This one?

Do you really want 2.5 meters of coax cable stored in the engine compartment?

You could punch a round hole in the rubber plug, but it's easier and neater to cut and "X" in the rubber. If you change your mind later, an "X" is easier to reseal than a hole. Your 40mm plug is much larger than a 14mm BNC plug and therefore does not need an extension cable. Or, just remove the existing rubber plug and replace it with an aftermarket grommet:

Lemo connectors are expensive. SMA is easier and cheaper. However, for small diameter coaxial cable, such as RG-174/u, you will probably need to buy or borrow an SMA crimping too.

Dunno. Let's do the math. The HT-25 probe is allegedly a 10,000:1 voltage attenuator. Oddly, the specs say "up to 10,000:1" which suggests that it might be less than 10,000:1. You might need an additional safety factor. I suggest

Automobile ignitions are typically 30,000 to 50,000 volts. That would mean your oscilloscope input voltage might be 60 to 100 volts. That's acceptable for RG-174/U coaxial cable, which will work to 1500V RMS (about 2100V peak).

Ok, your cable is safe, but I'm not so sure about the oscilloscope input. The Owon spec sheet says maximum input voltage is 400VDC+AC, which I guess(tm) means peak-to-peak volts:

HT isn't here.

Thx, ... P.

These are the more popular RF connectors.

I can't tell. Too fuzzy and no contrast.

I have no way to see what you have here. Lemo is a connector manufacturer and not a specific type of connector.

This is a BNC HT/MHV connector:

If low capacitance, my guess(tm) is that it's 93 ohm RG-62/u coaxial cable.

The output of the Hantek HT-25 ignition pickup is not a high voltage signal, so any kind of shielded signal cable or connector should work.

Bayonet Neil-Concelman (BNC) hardware is used here for convenience only. Ratings 500Vpk max. Assemblies are prooftested at 1500V.

RL

The Hantek pick-up has a built-in 10,000:1 attenuator and is designed for direct connection to a standard 1Meg scope input - so it is internally padded for the 50ohm cable being supplied.Coax extensions will have little effect on your practical scope readings.

RL

Thanks, ... P.

With reading glasses, the small connectors in my photo are marked LEMO F 00 250 . Similar to the FFA 00 250.

Thx, ... P.

Ignition connection to firewall will take at least a meter. Surplus length is easily coiled and zip tied out of the way.

Good idea. Might do that. Thanks.

In this instance the grommet is oval with diameeter at one end bigger than the other. Unfortunately a round grommet won't work. Don't recall another opening in the firewall but will check again.

Thx, ... P.

No. There are many coaxial connectors.

I've posted a photo of four connectors.

Left to right in the photo.

(1) BNC to Lemo adapter with a Lemo patch cable connected. Connects to the Owon HDS2202S oscilloscope BNC connector.

(2) BNC to RCA with patch cable connected. Connects to the scope.

(3) BNC on the Hantek HT-25 automotive ignition pickup. Connects to the scope.

(4) ?? on a patch cable marked ITT WIRE & CABLE DIV. RG-59/u COAXIAL CABLE. The protrusion of the white insulator prevents connection to the scope.

(4) appears to be an instance. I don't see it in the Wikipedia list and don't have a name for it.

Now fairly certain I can connect the Owon well enough to see significant automotive ignition problems.

Thanks, ... P.

Aliexpress has several listings mentioning Q9. Eg.

Thx, ... P.

This should be easy. Measure the circumference of the oval hole. I suggest using a piece of copper wire. Grommets are specified by the equivalent diameter of the round hole that it will fit. Divide the measured oval hole circumference by 3.14 to obtain the diameter. Look for a grommet with the same diameter. If it's made from fairly flexible, the grommet should deform to the desired oval shape.

If the grommet size is too large for commodity grommets, try using a continuous grommet strip:

Also see "grommet edging"

"What is the Difference Between BNC Connector and Q9 Connector?"

I'd never heard of Q9 connectors, despite having been an intensive user of all sorts of coax and connectors for over 40 years. I gather Q9 is near enough to BNC to mate with it, but not enough to be reliable? If that is so, that's yet another connector perversion.

Grrr!

Jeroen Belleman

Don't panic. The connectors are almost identical. If the connector looks like something that should be used on test equipment (machined, brass, nickel/tin plated, or silver plated) it's probably BNC. If the connector is looks like something found on low end consumer electronics (die cast zinc and chrome plated), it's probably a Q9. Those are my general guidelines.

As I understand it, Q9 is common in China:

So far, I have not run into a product where the connector is specified as Q9 only. I also haven't run into any compatibility issues with potentially mixed connectors, such as my various TDR's (time domain reflectometer) that use both types depending on vendors. However, I have dealt with mechanical compatibility problems between 50 ohm and

I suppose the connector type might make a difference at the maximum frequency (4GHz) where a BNC connector might be found:

Also, I didn't have any luck finding specifications and dimensions for the Q9 connector. The Q9 connector also does not appear on the Wikipedia BNC page: