How to make cables to connect between test equipment? - Page 1
Forum section: electronics / projects

author: Merlysys
author_rank: Regular Contributor
timestamp: April 07, 2014, 02:30:46 pm
content: I want to make one to connect signal generator to the frequency counter. Whats the name of such cable? Its for below 1Mhz work. Will using RG-? cable with BNC connectors at each end do?I would rather make than buy so I can cut them to length and make when necessary. What sites you know have examples on making them?

author: c4757p
author_rank: Super Contributor
timestamp: April 07, 2014, 02:36:42 pm
content: Yup. RG-58 with BNC at each end is common. I actually prefer RG-316 around the lab for its size and its "Hi! I'm an obvious piece of bright coax, not some random bit of black wire" appearance, but it's lossier and kind of expensive.Making them is pretty easy and obvious, but depends on the type of connector you have.

author: w2aew
author_rank: Super Contributor
timestamp: April 07, 2014, 02:37:10 pm
content: Quote from: Merlysys on April 07, 2014, 02:30:46 pmYes, a 50ohm cable such as RG-58 type, with BNC connectors will work fine. Doing good quality BNC attachment requires special tools (high quality BNC connectors and proper stripping and crimping tools). Unless you're going to be making dozens of cables, it'll be cheaper to buy quality BNC cables of various lengths.

author: ajb
author_rank: Super Contributor
timestamp: April 07, 2014, 06:15:47 pm
content: I was actually going to post a similar question. I see Pasternack, for instance, offers made-to-order 50? cables in RG58, RG223, RG142, RG178, RG316, RG188, RG174, PE-195, and PE-B100, but I'm not familiar with all of those options to be able to tell if any might be better or worse for test leads versus any others.

author: Halfdead
author_rank: Contributor
timestamp: April 07, 2014, 06:20:36 pm
content: Quote from: w2aew on April 07, 2014, 02:37:10 pmMight you recommend such a quality brand?

author: 128er
author_rank: Regular Contributor
timestamp: April 07, 2014, 06:23:17 pm
content: Quote from: w2aew on April 07, 2014, 02:37:10 pmAnd always remember this sentence from W2AEW. A few days ago, i buyed some cheap BNC connectors in a store here. Some of them have a very loose Shield/GND Connection at the BNC-Male. And then you wonder why your project does not properly work.

author: nanofrog
author_rank: Super Contributor
timestamp: April 07, 2014, 07:57:26 pm
content: Quote from: Halfdead on April 07, 2014, 06:20:36 pmPomona would be one such brand to take a look at (should be easy enough to find, but understand good BNC products aren't exactly cheap, so adds up fairly quickly).

author: georges80
author_rank: Frequent Contributor
timestamp: April 07, 2014, 08:40:56 pm
content: Quote from: Merlysys on April 07, 2014, 02:30:46 pmRG174 is what I use for test leads that are only a 1' to 4' in length the loss even up in the 1GHz range is mostly a non issue. You can get it with solid center wire or flexible. Times Microwave sells 'fancier' RG174 equivalent.For your 1MHz work, coax loss is not even the tiniest of concern and you aren't pushing any appreciable power through the coax.Lots of places sell RG174 and you can find decent crimp BNC - just purchase the right die for your crimper. The assembly technique will depend mostly on the BNC connectors you source. I like to put a inch or so of heatshrink (the type with the adhesive liner) over the crimped end - helps to protect the wire from bend radius issues as it exits the crimped sleeve.I recently made about half a dozen leads and it's nice to make them the right length to go between various pieces of test equipment BNC connectors (function generator, scope, current probe, diff probe, spectrum analyser etc).cheers,george.

author: mark03
author_rank: Frequent Contributor
timestamp: April 08, 2014, 02:16:46 pm
content: Does anyone make their own cables with soldered BNCs? I've seen way too many cables go bad (usually causing hours of wasted time, because it's the last thing one thinks to check). I'm sure it's because of poor quality rather than crimp vs solder, but if making my own I'd worry that I hadn't crimped correctly.

author: georges80
author_rank: Frequent Contributor
timestamp: April 08, 2014, 02:48:29 pm
content: Quote from: mark03 on April 08, 2014, 02:16:46 pmTip pin is soldered,shield/braid is crimped. The whole point of crimping is to use the CORRECT die for the (quality) BNC and coax you are using. A CORRECT crimp will be very secure and even 'professional' cables are made that way.cheers,george.

author: nctnico
author_rank: Super Contributor
timestamp: April 08, 2014, 03:50:22 pm
content: Quote from: mark03 on April 08, 2014, 02:16:46 pmMaking your own BNC cables is not easy. I got a couple of these from Ebay:http://www.ebay.com/itm/271114510329http://www.ebay.com/itm/281032666015They work OK.

author: Holograph
author_rank: Regular Contributor
timestamp: April 08, 2014, 03:54:20 pm
content: Quote from: ajb on April 07, 2014, 06:15:47 pmGet the thinnest cable that is within your frequency/loss/EMI specifications and with an acceptable price, availability (both of the wire and of the tools needed to use it), etc. For 1MHz, just about any coax should be good. I'd normally recommend the brands Belden or Canare, but for 1MHz, even that is probably not that important. I'm not sure offhand which brand BNC connectors might be the best. I use Neutrik brand connectors fairly often.http://www.rfcafe.com/references/electrical/coax-chart.htm

author: georges80
author_rank: Frequent Contributor
timestamp: April 08, 2014, 04:32:58 pm
content: Quote from: nctnico on April 08, 2014, 03:50:22 pmSeems very easy to me. Takes me maybe 10 minutes to do both ends with RG174, strip, solder center, crimp and heatshrink.A nice ratchet crimper, the right die and some attention to detail and you end up with a professional job and a cable the length you need.I would rather (and do) make my own test cables with known coax and reasonable quality connectors than rely on some unknown ebay product. Making your own coax leads seems a pretty basic skill if you're into electronics and have purchased test equipment.cheers,george.

author: 128er
author_rank: Regular Contributor
timestamp: April 08, 2014, 05:59:31 pm
content: Fully agree to georges80...And its not rocket scienceThe attention to detail is important. Look for a proper shield connection, all around your cable (no pigtails). If you dont want to spend your money for "expensive" Crimptools, than use one of these in my attachment for example.I would say, make your own cables. If it fails, try again. Until it works. increase your skills!

author: Dave Turner
author_rank: Frequent Contributor
timestamp: April 08, 2014, 09:46:45 pm
content: Back in the days when 10 Base T was prevalent I installed and troubleshot many segments. All using good quality crimped connections. The only real problems that I encountered were due to user/environmental mishandling, which was quite normal, and very rarely worn crimpers. The latter was a '££$%' to realise and required an improvement in testing procedures.

author: cellularmitosis
author_rank: Unknown
timestamp: April 08, 2014, 10:24:13 pm
content: I ran into a noise problem on my DSO while trying to put together a little DIY faraday cage:https://www.eevblog.com/forum/beginners/90-mhz-noise-on-scope/15/(oops, I never did post my updated measurements with that cable).It turns out the problem was (partly) the RG-58 cable I used (they were the Jameco Valuepro cables).I went on ebay and ordered an RG-6 cable, made with Canare L-5CFB cable. This appears to have improved my noise situation by quite a bit, so I can give this cable a thumbs-up.http://en.wikipedia.org/wiki/RG-6http://www.canare.com/ProductItemDisplay.aspx?productItemID=80The ebay seller was "cablebuyer" and the listing title was "Canare L-5CFB RG6 HDTV SDI/HD, Digital Video BNC Male to BNC Male Cable, 1.5 Ft."Here's his current listing for that cable (it has gone up in price):http://www.ebay.com/itm/Canare-L-5CFB-RG6-HDTV-SDI-HD-Digital-Video-BNC-Male-BNC-Male-Cable-1-5-Ft-/151265388203?pt=US_Video_Cables_Adapters&hash=item23381ea6ab

author: cellularmitosis
author_rank: Unknown
timestamp: April 08, 2014, 10:29:23 pm
content: Hmm, looking closer at the manufacturer's page, I probably should have gone with the L-7CFB cable, which has a 96% braid over 100% foil, which should be slightly better than 93% braid over 100% foil.It turns out the same ebay seller offers this cable as well:http://www.ebay.com/itm/1-5-ft-Canare-L-7CFB-HDTV-SDI-HD-Digital-Video-BNC-Male-to-BNC-Male-Cable-/121143717606?pt=US_Video_Cables_Adapters&hash=item1c34ba6ee6

author: calexanian
author_rank: Super Contributor
timestamp: April 09, 2014, 05:23:19 am
content: As far as general inter connection for various gear. Power supplies and such, I have re discovered Pomona stuff. I have become a genuine believer again in Banana plug/mini grabber cable sets for meters and power supplies. I snag them whenever I can at ham fests and add to my box. So convenient and they really help keep things in check on the bench. As time goes on I like BNC less and less. For RF I only do 50 and 300 to 450 ohm stuff (RG8, 58, lmr 400, twin lead, and ladder like ham stuff) so I try to keep to UHF connectors. Obviously out of the HP gear, scopes, my sweep function generator, etc, I need BNC. I just find it apart from scope probes to be a fairly weak connector that frays easily.Long Live the Pomona MiniGrabber!!! Worth the sky high cost. Do not accept the cheap impostors!