Velocity factor of co-ax

If you have a high enough frequency and can resolve it, you ought to be able to 'see' this clearly enough? I know for a fact it's do-able.

There are lots of very cheap VNAs around now.

Do any come with the software to transform TDRs?

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

It's an arbitrary decision as to where the thing actually starts.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

Am 23.01.26 um 19:50 schrieb Cursitor Doom:

There is no standard for RG58. There was one defined in WWII but it has been withdrawn some eons ago. Nowadays you can write RG58 on just about everything. The first thing to get worse was the amount of copper in the shield. See-thru now.

Gerhard

RG58 STD 04M

Seem to be normal RG58.

Definitely short of copper but, presumably. this is compensated by the use of foil which completely covers the dielectric.

Mine does.

Yeah. The underlying claim is that any cable sold as RG-58 is 50-ohm and can be terminated with a RG-58 connector. So the best way to tell what a mystery cable is to cut a sample apart and measure the various diameters with a digital caliper.

Joe

Some of 'em have an internal taper which really bluntens the effect. I believe the idea is to minimize reflections during dimensional shifts.

I once designed and build this for my 27 MHz CB transmitter:

So much hype, ever bigger stuff, not even a moon landing! I worked for Tek. When Bushman invaded Iraq under false pretences (weapons of mass destruction) I left. So elated they were about all the new orders! Sick country, Apes as leader, doomed?

Designed and build my own scope in the sixties, Vidicon camera too. And shortwave 250 W transmitter 1967! Then I was the pirate :-) Now I have a license and we have our own satellite QO100 Thinking about dropping the license, it costs more every year here.

ape invades my country.

He will declare that the the Antillies have to be part of the USA first, because that's where the oil seems to be coming from.

If he does decide to invade 'Holland', he will probably finish up in Lincolnshire.

If you've seen the state of Boston lately, that would probably be a good thing.

North and South Holland are just two of the seven united provinces of the Netherlands. The other five are Utrecht, Zeeland, Gelderland, Friesland and Groningen.

Trump may not know that. East Anglia is closer to the Netherlands than Lincolnshire, and was drained by Dutch engineers.

The US air force knows lots about both of them. They are less knowledgeable about the Netherlands, and bombed Nijmegen (in Gelderland) in 1944 because they thought that is was Dusseldorf.

I suppose that there's got to be a first time for everything, but Donald Trump getting anything right is remarkably unlikely. His judgement is even more lamentably defective than Cursitor Doom's.

This is Ham radio's "year of the club" (at least in the USA). Casper's hosting the 2026 Ham Convention for the Rocky Mountain Division (Colorado, New Mexico, Utah, & Wyoming). The website's not ready for prime time yet: wyohamcon.org During our meeting last Wednesday, the SWR VNA Ham mentioned earlier, showed off an amateur mesh network. He uploaded Linux firmware into MicroTik omnidirectional and parabolic antennas. The omnidirectional is slated for the county's Casper Mountain shack. We're in the process of moving radio infrastructure from the old dilapidated shack into a new sea can sitting nearby. The parabolic antennas, in turn, are housed at each ham's home. The most intriguing aspect about this network is its utilization of network cable. There's no coax. Instead, network cable dangles down from the omnidirectional anchored up in the tower. Our sister club in Cheyenne hosted the 2022 Convention. On Friday they held an all day long satellite class. The President said it was one of the more popular events. Long story short, the QO-100 may prove popular for our own Convention. Thank you for sharing.

I think sine waves are boring - they just go around in circles - but we may be doing some RF switch modules and I guess people will expect some sort of S-parameter things. Or at least a spec of some Sxx at some max frequency, which will be 3 GHz in our case.

I guess we can buy a cheap Amazon VNA and measure a couple of points. We could check its calibration with a couple of hanks of hardline or something.

Sounds like an intern project.

Can anyone suggest a suitable small inexpensive VNA? We might use it

The generic Amazons are about $150 for 3 GHz and twice that for 6.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

The best one I know of is the NanoVNA NanoVNA | Very tiny handheld Vector Network Analyzer

Arie

Didn’t you folks get a NanoVNA a year or so back?

You want the genuine one, not the fleabay or jungle ones.

Phil Hobbs

I can't recall. Maybe one of my guys did.

We should probably go to 6 GHz, especially since these things are so cheap.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics