Advice sought on good-value HF measurement cable (N connector to SMA) - Page 1
Forum section: electronics / testgear

author: RBBVNL9
author_rank: Frequent Contributor
timestamp: April 12, 2021, 11:25:48 am
content: Dear all,I am looking for pair of measurement cables to be used with a 3GHz spectrum analyzer (for analyzer input and TG output), with an N connector on one side and an SMA male connector on the other.I ordered a pair of such cables from a supplier recently, but they were much too stiff for measurement leads use (even though they were advertised as such).So, what cables are a good choice? They should be appropriate for use up to 3GHz, have decent characteristics (but not necessarily high end), mechanically satisfactory, flexible, and of reasonably good price/performance. Preferably something that is available from a European distributor. Any thoughts?

author: tautech
author_rank: Super Contributor
timestamp: April 12, 2021, 01:23:57 pm
content: List on these is USD49https://www.siglenteu.com/accessory/n-sma-6l/However the ones I have are a heavier and stiffer cable ~6mm dia like these:https://www.siglenteu.com/accessory/n-bnc-2l/These cloth covered non-crush 18 GHz on the other hand are next level quality made by Rosenberger.https://www.siglenteu.com/accessory/n-sma-18l/239 USDOh and BTW, both have SN#'s and come with characterization sheets.

author: geggi1
author_rank: Frequent Contributor
timestamp: April 12, 2021, 03:39:19 pm
content: The first thing you have to consider is what frequency range and signal level you are going to work at most of the time. If you are working with levels at about 0dBm and most of the time less than 500Mhz regular RG-58 homemede cables is usually good enough. There are also pre-made foam dielectric cables ment for mobile-phone and WIFI that comes with FEM connectors. Then you just get an adapter from FME to whatever connector you plan to use.Remember to also get some adapters like SMA/SMA or N/N when you are normalizing before measurements.

author: tkamiya
author_rank: Super Contributor
timestamp: April 12, 2021, 03:58:50 pm
content: I often use Times Microwave LMR 195 or 200. They are both double shielded quality cables.It is very important to get a cable with good connectors. A LOT of import type connectors are rather poor. They couple loosely both mechanically and electrically.One advice I'd give is you might want to consider getting SMA to SMA cable. At spectrum analyzer end, you can use QUALITY N to sma adapter. I often buy mine from Mini-circuit or Amphenol. Again, be wary of cheap ones.

author: graybeard
author_rank: Frequent Contributor
timestamp: April 12, 2021, 04:11:39 pm
content: I have purchasedSMA cables from Minicircuitsfor that frequency range and have been very happy with them. I am using some at work in a 1.5 GHz test fixture now. You can order the cables with N on one end and SMA on the other. I am using one like that to connect a N connector directional coupler to a SMA fixture.

author: RBBVNL9
author_rank: Frequent Contributor
timestamp: April 13, 2021, 06:51:31 am
content: Thanks for the various replies.The Siglent cables look quite nice but are a bit shorter than I was looking for.The ones from Minicircuits look interesting too - I have some attenuators from them and a DC block and I like these. Need to find out though about Minicircuits shipping costs, shipping time, and import (custom) fees, as it seems these cables are not held in stock by European suppliers.As for using SMA-SMA (or FME-FME) cables plus adapters; this is similar to my current scenario. Although I could (should) update the current SMA-SMA cables I use, I thought I rather not introduce unnecessary adapters and go to cables with N-connectors on the instrument side right away. But of course, you lose some flexibility.If others have good tips; let me know!

author: tautech
author_rank: Super Contributor
timestamp: April 13, 2021, 07:30:26 am
content: The cheaper Siglent cables @ 700mm are sufficient IMO as when used on these lightweight analyzers that are more easily moved about than some heavyweight legacy boat anchor.Like others I too believe a sacrificial adapter is a good idea to minimize the mating cycles on analyzer fittings.YMMV

author: RBBVNL9
author_rank: Frequent Contributor
timestamp: April 13, 2021, 08:52:27 am
content: QuoteGenerally, I'd agree, but my spectrum analyzer is not sitting directly on a desk but is standing on a bench at approx. 30cm above desk level. For that reason, I was hoping to find 100cm cables...QuoteThat makes sense. But I'd need to find better N-to-SMA adapters than I currently use (where the SMA part turns freely and cannot be held in position and can cause the cable to 'stuck' on the adapter).

author: tautech
author_rank: Super Contributor
timestamp: April 13, 2021, 08:59:54 am
content: Quote from: RBBVNL9 on April 13, 2021, 08:52:27 amI've not been long in the RF game however particularly with VNA's N type fittings they need to be tight, not snug but tight !When they are you don't have issues with N-anything turning when you fit cables and it's something to be avoided at all costs as turning fittings or cables will damage the fitting it's attached to and dramatically reduce the mating cycles.This really shows up when calibrating a VNA if N type fittings or adapters are not good and tight.

author: RBBVNL9
author_rank: Frequent Contributor
timestamp: April 13, 2021, 09:27:59 am
content: QuoteI may not have explained myself well when I talked about 'turning' parts.With the N-to-SMA adapters I have, when the connector is not connected to anything, the 'inner part' (SMA threat on one side, inside part of N connector on the other) can freely turn. When in use - connected to SA and to an SMA cable - nothing turns. However, when I take the adapter away from the SAA, sometimes the SMA cable is stuck to this inner part and I find it difficult to take it off because I cannot hold this rotating inner part of the adapter in any way. Not sure if all N-to-SMA adapters are like that but mine are...

author: tautech
author_rank: Super Contributor
timestamp: April 13, 2021, 09:32:19 am
content: No holding flats like this one ?https://www.aliexpress.com/item/1005001644379887.html?spm=a2g0o.productlist.0.0.7a052c0fP7NASG&algo_pvid=03d8335b-ba17-48ec-bfcb-620f6854eaa5&algo_expid=03d8335b-ba17-48ec-bfcb-620f6854eaa5-5&btsid=0bb0600116183062151081286ee654&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_

author: RBBVNL9
author_rank: Frequent Contributor
timestamp: April 13, 2021, 10:11:38 am
content: QuoteUnfortunately not. The ones I have are Rosenberger 53S132-K00L5(link)which I purchased from Mouser.These do not have holding flats... Wish they did.

author: Ice-Tea
author_rank: Super Contributor
timestamp: April 13, 2021, 10:17:26 am
content: The only RF I was ever *really* happy with have been Mini-Cuircuits.Mouser carries them...https://www.mouser.be/Mini-Circuits/Wire-Cable/Cable-Assemblies/RF-Cable-Assemblies/_/N-bkrix?P=1y7wkxeZ1yzsqvgZ1yzsqux&Keyword=rf+cable&FS=True

author: RBBVNL9
author_rank: Frequent Contributor
timestamp: April 13, 2021, 06:36:48 pm
content: QuoteYes, thinking more and more about leads from Mini-circuits. But strangely, all cable lengths up to, say, 60cm can be easily found at Mouser and others, but all lengths of, say, 1m or more cannot. I'd need to import them into Europe, which usually is slow and expensive (import taxes).Should someone know of a European supplier that stocks them, please tell me.

author: tautech
author_rank: Super Contributor
timestamp: April 13, 2021, 06:41:48 pm
content: Hunt for Rosenberger stuff:https://www.rosenberger.com/products/cable-assemblies/rf-and-microwave-test-cables/

author: Ice-Tea
author_rank: Super Contributor
timestamp: April 13, 2021, 06:59:05 pm
content: Quote from: RBBVNL9 on April 13, 2021, 06:36:48 pmMouser (and DigiKey for that matter) handle import duties on their end, you prepay it and there's no additional fees to be payed. Shipping is normally 3-4 days or so but lately it has been more due to CoVID, storms and whatnot.

author: RBBVNL9
author_rank: Frequent Contributor
timestamp: April 13, 2021, 07:52:34 pm
content: QuoteMmm. Rosenberger is the make of the inconvenient N-SMA adapter I have, the one that lacks holding flats (see above). Not keen on buying from them, really.QuoteYes, this is true. But they do not sell the Minicircuit cables of longer than ~60cm... The only way to get them seems to be ordering from Minicircuit directly, and they will not handle import duties like Mouser does.

author: RBBVNL9
author_rank: Frequent Contributor
timestamp: April 14, 2021, 01:57:09 pm
content: I now further investigated Minicircuit's quite extensive offer on test cables (including the ULC, CBL, and APC series), as well as their even wider offer on interconnect cables.I also found out this company can ship orders not only out of the US but also right out of the UK, which makes things a bit easier if you live in Europe, and ended up ordering the ULC-1M-SMNM+, which is a well-specced, 1 meter N (male) to SMA (male), very flexible cable meant for applications such as test and measurement, R&D labs, and field RF testing. It is also reasonably priced for what it is, I believe.Looking forwards to testing that cable when it gets here, and if I feel happy with it, I might get more cables from them.Thanks for the various input provided!

author: pe1oxp
author_rank: Regular Contributor
timestamp: April 14, 2021, 05:10:14 pm
content: Quote from: Ice-Tea on April 13, 2021, 06:59:05 pmMouser ships Fedex and has no pickup points in the Netherlands when not at home.For Digikey shipped with UPS, you only have to pay the VAT to UPS (including VAT over the free shipping)Both normally 1..2 days before receiving the goods.PS last time I ordered from Mini-Circuits they shipped from Germany, so also no problems with UK customs.

author: RBBVNL9
author_rank: Frequent Contributor
timestamp: April 15, 2021, 11:55:39 am
content: QuoteInteresting! When I ordered from them earlier this week, the only options shown were (international) shipping from the US or international shipping from the UK. But perhaps they actually ship from Germany... We will see.For someone living in the EU, the issue with shipping from the UK (which after all left the EU) or the US is that you have to pay (1) VAT (typically 21%, threshold 22 Euro), (2) import duties (0% to 17%, threshold 150 Euro) from and (3) customs clearance fees (these vary). Both my kids occasionally order from webshops outside the EU and I indeed get to see these bills...My recent order with Mini-Circuits was deliberately below 150 Euro, to prevent import duties. If they ship from Germany I can also place bigger orders...

author: pe1oxp
author_rank: Regular Contributor
timestamp: April 15, 2021, 05:11:15 pm
content: Quote from: RBBVNL9 on April 15, 2021, 11:55:39 amI also had only the option international shipping from the UK in december or january. It last some time before the goods were shipped and I was surprised it was shipped from Germany. So at that moment less worries about extra costs for VAT and duties.So just ask before ordering....

author: RBBVNL9
author_rank: Frequent Contributor
timestamp: April 22, 2021, 03:40:15 pm
content: I now received the MiniCircuits ULC-1M-SMNM+ cable. My first impression is that it is a very nice test cable indeed, just what I was looking for. Good specifications, a detaileddata sheet, and reasonably priced. Thanks totkamiya,graybeard,Ice-Teaandpe1oxpfor suggesting this! While I already had other products from them (a handful of attenuators, and a DC block), I initially did not think of them when looking for a test cable.QuoteMy shipment came indeed from Germany too. Today I talked to the support desk at MiniCircuits, and learned that post-Brexit, they decided to set up a German branch (with a German VAT ID) as of January 2021 and thus can ship items to EU customers without them facing import duties.(Note: to order, you still use the regular international website[url=http://www.minicircuits.com]www.minicircuits.com, but during the ordering process, at the question “Chose Ship from Location” you should select “United Kingdom”. Their UK office then processes the order, but if you are yourself located in the EU, they will actually ship from their German hub. I suggest you contact them directly to be sure they ship it that way, via sales@uk.minicircuits.com.)

author: pe1oxp
author_rank: Regular Contributor
timestamp: April 22, 2021, 05:25:00 pm
content: Quote from: RBBVNL9 on April 22, 2021, 03:40:15 pmGood to hear!Fast shipment, my last order needed about a month before delivery even all goods were in stock. Maybe due the Christmas holiday and the problems with Brexit.