Cables and Attenuators

[Ranger14]

I am looking to get some bnc patch cables for use on my scope,funtion gen,and counter .. But does it matter if you buy chinese cables or try to purchase quality
Also I was looking to make some attenuators and how hard would these be to make and can they be use to make measurement ?? I was interested in 2x,5x,10, attenuators..
Are the bnc connectors male and female out of china any good to use in taking measurement and cal

[TimFox]

The connections on quality cable assemblies are more reliable than on cheap ones -- almost a law of nature.
If you are not using high frequencies, you don't need to worry (much) about mismatch, etc., but intermittent connections are horrible when testing things.
When making your own attenuators, etc., try to keep the assembly short -- much, much shorter than the shortest wavelength you intend to use.  For audio, that means that a normal aluminum project box with BNC connectors should work without trouble.

[German_EE]

1) Quality will last longer, you only have to buy a good tool once.

2) Quality cables will leak less. This may not be important with a 10dB attenuator but when you are aiming for 60dB attenuation you will find that the amount of leakage from your sockets and cables is a measurable amount.

3) Quality cables will have a constant impedance from end to end including the connector, this is important for some RF measurements as a poor quality cable could be a source of error.

Most of my RF measurements are done with cable of reasonable quality but for some low-level tests such as MDS (Minimum Discernible Signal) I have two Minicircuits cables. These are DC to 18 GHz (although I never work that high), triple shielded, have less than 1dB loss from end to end and were sixty Euro each. I suspect that they will never fail.

[karoru]

I am looking to get some bnc patch cables for use on my scope,funtion gen,and counter .. But does it matter if you buy chinese cables or try to purchase quality
Also I was looking to make some attenuators and how hard would these be to make and can they be use to make measurement ?? I was interested in 2x,5x,10, attenuators..
Are the bnc connectors male and female out of china any good to use in taking measurement and cal

Buy some Chinese cheapies anyway, they don't cost much and you never know when you need that additional piece of coax for connecting some random non-critical test setup. And ask around some IT LAN people, they'll probably have boxes and drawers full of 50 Ohm ethernet coax, terminators & BNC T adapters that just lie around collecting dust and waiting for nuclear winter.

[Ranger14]

Thanks for the great info

I forgot to ask when building your own cables for scope function gens do you use RG-174 or RG-58 and why ??


Thanks

[onesixright]

I would use RG58. The main difference is that the attenuation is less for RG58, especially on higher frequencies.