replacement RG174 50  ohm coax - any difference ? - Page 1
Forum section: electronics / repair

author: vjekobalas
author_rank: Regular Contributor
timestamp: February 01, 2022, 06:47:07 pm
content: Maybe someone with good RF knowledge could clarify whether the replacementcables I found would be compatible as I couldn't find the original cable in short lengths.The problem is that there is variation in conductor material (copper/copper clad steel)and resistance of shield. If the replacements are questionable, I will just put the originalones back and keep searching for that type for a later replacement.I would like to replace two 3m 50 ohm RG174 coax cables soldered to ultrasound transducersin a beauty parlor ultrasound machine head and BNC connected to the machine(15W collimated beam, 1MHz/20-60KHz modulated frequency) as I am replacingother cables in the bundle.The cables undergo certain heating as well as movementat the ultrasound head end and have hardened there.Original RG174 cable is the Prospecta I043. According to the spec, the inner conductor iscopper stranded wire (a strong magnet confirms this).The other cables are all copper clad steel except, I am not certain about the cable from mauritzthe sales person said copper (the spec says full copper and then "Staku" -maybe a native Germanspeaker can confirm,

author: 2N3055
author_rank: Super Contributor
timestamp: February 01, 2022, 08:42:32 pm
content: StaKu is short for Stahl-Kupfer (Stahlkern mit Kupfermantel).Meaning steel core with copper surface. Those cables can have good performance but I guess full copper cable made from strands will be softer and withstand bending better. And I would think you need that.These would be exactly what you need , take 2 and snip off SMA connector.https://hr.mouser.com/ProductDetail/Amphenol-Cables-on-Demand/CO-174SMAZBNC-010?qs=BA62vJVifGqS1zIRp2dfQA%3D%3DUnfortunately not in stock...But if you get good cable and connectors these could be crimped no problem. Frequencies are very low.

author: vjekobalas
author_rank: Regular Contributor
timestamp: February 02, 2022, 08:08:10 am
content: I found this one in stock:https://hr.mouser.com/ProductDetail/Amphenol-RF/095-850-249M300?qs=W%2FMpXkg%252bdQ4okyQCxuk6DQ==&utm_source=eciaauthorized&utm_medium=aggregator&utm_campaign=095-850-249M300&utm_term=095-850-249M300&utm_content=Amphenolbut no info on cable.I wouldn't have anything against crimping but I don't have any crimping tools andas far as I understand anything good is costly and I don't see myself makingany use of the tool afterwards. Other than that, I didn't find a similar cable(all are copper clad steel) and the original needs to be purchased in 100m length.I also need to wrap this up with the cables this week as the machine is needed

author: vjekobalas
author_rank: Regular Contributor
timestamp: February 02, 2022, 08:57:13 am
content: I found this one with 2 BNC connectors / cable description is the same:https://www.digikey.si/en/products/detail/amphenol-cables-on-demand/CO-174BNCX200-025/13877687?s=N4IgTCBcDaIMIHkC0BGA7AFgEIDk4A0wAGIpIsAVhAF0BfIAThe only question is - is there any possibility that a difference in coax requiressome sort of adjustment in the machine (I have no service manual, no voltage/signal levelsto compare to - or am I overthinking this -it's not an ultrasound imaging devicethe machine just sends out the signal/ couldn't be that much differencein effect from the cables right ?

author: 2N3055
author_rank: Super Contributor
timestamp: February 02, 2022, 09:26:36 am
content: Quote from: vjekobalas on February 02, 2022, 08:57:13 amNo need to adjust anything, cable specs (electrically) will be just fine. Problem is mechanically, if that is a moving probe (and it is) then cable has to be soft and pliable so it doesn't break inside from movements.If you're in a hurry, any cable will do, it's just it might not last long...

author: vjekobalas
author_rank: Regular Contributor
timestamp: February 02, 2022, 09:35:21 am
content: Your input is much appreciated ! I will then purchase the cable I found.The cables are in a flexible steel wire (spring shape) supported conduitand from the present group of cables, the multicore 4x2x0,25 signallingcable is the only one that has been damaged - the coax and one 2x0,34cable are OK but hardened near the ultrasound head (I am assuming from heat and movement)so I hope all will be well - now to order the cable and to try to put it togetheragain