Cables, Connectors (N/SMA/BNC) & Adapters with Measured Results for Comparisons

[KungFuJosh]

They have some nice cables that are also ~$30. We don't have any (yet?), but will probably order some next time we order from them (or Mouser).

I may try one at some point for comparison, but I just blew a bunch of money on the M&P stuff, which I'm happy with anyway.

Having them custom make me that Stealthflex 7 cable was about $34 after conversion, so not bad at all really. That price included the fee for the attached report I was also curious about.

Thanks,
Josh

You should do a test of the cable to compare with OEM Data sheet. Nice they provide the measurement and for a custom quality cable with N and BNC type connectors at that price!! The M&P cables/connectors look like a very good value and quality product.

Since these newer DSOs are venturing into the upper UHF region, maybe start a thread on cables, connectors (N/SMA/BNC) & Adapters with measured results for comparisons.  Most DSOs utilize BNC inputs, so info should emphasize at least 1 BNC connector/adapter/cable type.

This might prove useful for folks and save some $ as we've all been down the cheap cable/connector route, ourselves more times than we care to admit

We need to set some standard testing parameters that people can do with scopes. I don't have a VNA yet to test cables.

Maybe we should set some test parameters for different devices.

Thanks,
Josh

[KungFuJosh]

...a high quality inline attenuator of at least 6 dB (more is better) directly at the generator output.

How's this?: https://www.pasternack.com/12db-fixed-n-male-n-female-2-watts-attenuator-pe7047-12-p.aspx

This one looks very good. It will allow you to explot the full bandwidth of your generator.

I assume this is not good enough: https://www.amazon.com/dp/B0DKFDD3KT/

It doesn't look that bad, but with a rated bandwidth of 3 GHz, it might not perform optimally at frequencies above 1 GHz. On the other hand, cables have a frequency dependant attenuation also, hence this concern might not apply.

With regard to the cable, the Hyperflex 5 is about the best with ~5 mm diameter we can get up to 2 GHz. You would have a hard time finding a better one, regardless the price.

Above 2 GHz, there might be better options, although vastly more expensive.

M&P's datasheet seems to be pretty good. It even suggest using thicker cables for specific situations.

In my case, at least for the moment, I won't be going above 1 or 2GHz, so I hope I can get away with the 6GHz max attenuator Mike suggested, the UNAT-10A+ (datasheet attached). It was only ~$30 on Mouser. A few dollars cheaper on DigiKey.

Thanks,
Josh

[Kosmic]

If you don't have the money for a real VNA, just use a nanovna or litevna. Pretty sure you would get better result than trying to macgyver something with a scope and siggen. At least it's going to be simpler.

[mawyatt]

^^^ Agree

@ Josh

Get one of those inexpensive VNAs, this can serve as a "Reference" for the cable DUT. Then the DSO results will have a good comparison to work with, if the cable, like your M&P, comes with a measured data sheet all the better!!

Anyway, thanks for creating this thread, think it will be very useful of many folks!!

Best

[KungFuJosh]

Fine, fine. I'll buy a VNA. I'm planning to anyway, I'm just waiting for a good deal. I probably won't buy a TinyVNA. I have a TinySA Ultra, and it still makes me want a real SA or VNA.

We still need parameters for test setups. I don't know how to setup a cable test on a VNA, considering I've never used a VNA.

Thanks,
Josh

[Martin72]

At the time, I was advised to buy an inexpensive Nano VNA first before embarking on the adventure of a “real” VNA.
I am still grateful for this advice today, because I recently sold my Nano VNA—it was all too fiddly for me, and then there was always the calibration before every use.
(Well, I could now convert my new SSA3021Xplus into a 3.2 GHz VNA, but I still need to think about that very carefully).

[KungFuJosh]

My experience with the TinySA Ultra was similar. All it did was convince me I need a full size / more powerful SA. I think I'll skip that step this time.

[egonotto]

At the time, I was advised to buy an inexpensive Nano VNA first before embarking on the adventure of a “real” VNA.
I am still grateful for this advice today, because I recently sold my Nano VNA—it was all too fiddly for me, and then there was always the calibration before every use.
(Well, I could now convert my new SSA3021Xplus into a 3.2 GHz VNA, but I still need to think about that very carefully).

Hello,

Calibration is also necessary for expensive VNAs. However, there are certain automatic devices available.
There are good PC programs for the NanoVNA, which make it convenient to use.

But VNAs are great.

The PicoVNA manual is good, as it can also be applied to other VNAs.

Best regards
egonotto

[KungFuJosh]

Which version of the NanoVNA is good? I might get one to screw with until I find a decent deal on a "real" VNA.

[Grandchuck]

LiteVNA

https://video.search.yahoo.com/search/video?fr=mcafee&p=lite+vna+joe+smith&type=E210US105G91906#id=2&vid=21b38ba6f56bd4d68b3de47b72ec2abf&action=click

[Martin72]

The one I had is supposed to be good.

I asked myself the same question last year, Josh:
https://www.eevblog.com/forum/testgear/nano-vna-like-sand-on-the-sea-who-is-the-good-one/msg5567911/#msg5567911

[Kosmic]

Which version of the NanoVNA is good? I might get one to screw with until I find a decent deal on a "real" VNA.

NanoVNA is good at low freq, LiteVNA at higher freq. I bought from Zeenko store in the past and they are reliable (https://zeenko.ja.aliexpress.com/store/1101394653).

The screen size and battery might not matter if you are planning to use it connected to a computer.

[Kosmic]

I am still grateful for this advice today, because I recently sold my Nano VNA—it was all too fiddly for me, and then there was always the calibration before every use.

You can save calibration on the device or PC if using a external software.

I normally use it via a computer and have bunch of calibration saved for different setups.

[KungFuJosh]

Would I be better off with the LibreVNA if I'm going to use it on a computer anyway?

[Martin72]

You know you can save calibration right ?

Too late...
But thanks anyway.

[Kosmic]

Would I be better off with the LibreVNA if I'm going to use it on a computer anyway?

I personally have no experience with the LIbreVNA, but the electronic calibration kit for it is interesting https://www.aliexpress.com/item/1005008002497171.html

[KungFuJosh]

Would I be better off with the LibreVNA if I'm going to use it on a computer anyway?

I personally have no experience with the LIbreVNA, but the electronic calibration kit for it is interesting https://www.aliexpress.com/item/1005008002497171.html

Apparently it can be used to calibrate other VNAs too. A user on this site used it on a Siglent VNA.

[Kosmic]

Would I be better off with the LibreVNA if I'm going to use it on a computer anyway?

I personally have no experience with the LIbreVNA, but the electronic calibration kit for it is interesting https://www.aliexpress.com/item/1005008002497171.html

Also look like the LibreVNA is a full 2 ports device (can measure all S parameters) and the other cheap VNA are not (only S11, S21).

[KungFuJosh]

There's also the NanoVNA SV4401A. That looks interesting too. 7" screen with 2 N ports.

[KungFuJosh]

NanoVNA is good at low freq, LiteVNA at higher freq.

Why? What makes one better than the other?

LiteVNA-64 max is 6GHz, and NanoVNA-F V3 is also maxed at 6GHz. Is there something else that makes one better than the other in your opinion?

I'm leaning towards the NanoVNA-F V2 that Martin had, since 3GHz is probably good enough for me, and the price is better.

More importantly- can these devices be used for the purpose of this thread- to accurate test cables?

Thanks,
Josh

[joeqsmith]

NanoVNA is good at low freq, LiteVNA at higher freq.

Why? What makes one better than the other?

LiteVNA-64 max is 6GHz, and NanoVNA-F V3 is also maxed at 6GHz. Is there something else that makes one better than the other in your opinion?

I'm leaning towards the NanoVNA-F V2 that Martin had, since 3GHz is probably good enough for me, and the price is better.

More importantly- can these devices be used for the purpose of this thread- to accurate test cables?

Thanks,
Josh

Maybe 9G with harmonics.

We need to set some standard testing parameters that people can do with scopes. I don't have a VNA yet to test cables.

You mention testing them with a scope so I am assuming you are referring to typical patch cables for low frequency use around the home lab.  I would just eye ball the connectors for damage, clean them and check if flexing them causes any problems.   

Obviously all cables are not the same.  Higher grade cables like you may use with a VNA could costs thousands of USD each!  They can be easily damaged.   

Someone was recently shitting on various brands for making cables that did not meet spec.   I made an attempt to measure a few and provide further details.
https://www.eevblog.com/forum/testgear/dont-buy-sma-cable-assemblies-from-centricrf/

The very last post I made was using the LiteVNA to measure insertion loss of a Mini-Circuits cable.  That particular cable is spec'ed out to 18GHz which is outside what could be measured with the LiteVNA.
https://www.eevblog.com/forum/testgear/dont-buy-sma-cable-assemblies-from-centricrf/msg5923980/#msg5923980

[joeqsmith]

... since 3GHz is probably good enough for me ...

The following link shows using a T-check with the LiteVNA.  This is just a simple method to verify your setup after calibration.  After attempts to remove as many variables as possible, I was able to squeeze decent performance to 3GHz with it.   

https://www.eevblog.com/forum/rf-microwave/nanovna-custom-software/msg5685217/#msg5685217

Showing the dynamic range of the three hardware revisions of the LiteVNA to 9GHz. Consider you would normally want about 10dB margin.  Still, for very rough measurements, it could be useful.
https://www.eevblog.com/forum/rf-microwave/nanovna-custom-software/2450/

[Kosmic]

NanoVNA is good at low freq, LiteVNA at higher freq.

Why? What makes one better than the other?

I remember reading/listing joeqsmith experiments with the litevna and he was mentioning the original nanovna was performing better at lower freq. Maybe joe could elaborate more.

[KungFuJosh]

I'll have the NanoVNA-F V2 tomorrow. Now I just need to learn how to use a VNA. 🤷

[joeqsmith]

From a black box view point, the original NanoVNA had lower noise and could be used for narrow band measurements (crystal filters) which the LiteVNA, V2+ can't.   The cost was less than half.   

We bought two H4s which are similar to the original NanoVNA with a 4" display.  These never performed as well as the original NanoVNAs we bought.   I ended up damaging my H4 and while trying to repair it stumbled onto that the mixers they used in the original NanoVNA induced less noise. I ended up adding a few caps and changing the mixers on the H4 and it out performed the original NanoVNA.  I ended up making the same mods to my friend's H4 and the performance was on-par with mine.  Maybe the early H4's were better.   I posted about it here:

https://www.eevblog.com/forum/rf-microwave/nanovna-custom-software/msg5695997/#msg5695997

The H4 and NanoVNA are only good for about 300MHz.  They support harmonics but the dynamic range is poor.   So, < 300MHz, narrow band, PDN sort of measurements,  NanoVNA.   Greater than 300, LiteVNA.  They are low cost, so if you play with RF, get them both and you're set.   

Just don't be fooled into thinking they are going to compete with a name brand VNA.  They are slower, missing key features and use a square wave.  People will post how the square wave doesn't matter.  I agree in most applications that is true.  Certainly for passive devices.   However, if you are playing with active circuits that may not be the case, even when working with very low frequencies.   Here I demonstrate a 1MHz amplifier that I purposely designed to show how the square wave can be problematic.