Which RF Connectors to "Standardize" for Home Lab?  - Page 1
Forum section: electronics / rf-microwave

author: NT0Z
author_rank: Regular Contributor
timestamp: January 27, 2023, 01:15:41 am
content: Hi, gang,I'm building out my home RF lab. I have a variety of older and newer devices/equipment, and I'm wondering if there's a "best" way to standardize on a particular connector type, as I have to build a bunch of coaxial lab jumpers.Considerations...1. My equipment has a mix of Type-N, BNC, and SMA connectors, while my radios have mostly SO-238s.2. Mostly used at MF/HF, with potential to use at 50-450 MHz.3. Ease of construction: Unless I win the lotto or someone can point me to a treasure trove, I want to make these jumpers, probably with RG-58X or LMR-195/240. I have a crimping tool with all necessary dies. I have crimped many Type-F compression connectors, a bunch of PL-259s, but no BNC, Type-N or SMAs.Which BNC and N-type connectors are easiest to install by non-pro users such as myself? I plan to get a cable prep tool, set it up perfectly for the chosen cable/connector combo, and use it as my own internal "standard" to encourage success over time.I have a bunch of coaxial adapters -- and plan to get more -- but I'd prefer to use as few as possible.As always, thanks,Kirk, NT0Z

author: james_s
author_rank: Super Contributor
timestamp: January 27, 2023, 01:36:12 am
content: I use BNC and SMA, but it depends on what you're doing. There's a reason there are so many different types, there is no one size fits all connector.

author: Bud
author_rank: Super Contributor
timestamp: January 27, 2023, 01:46:10 am
content: I wanted to standardize on N but ended up with SMA cables and N/BNC/PL adapters, for convenience reasons. Too many combinations of jumpers if to use dedicated specific connector types cables. Test and measurement equioment is typically BNC and N, but they are bulky and inconvenient when probing around PCBs. Using SMA provides convenience, takes less space and you need less cables. The coax is thinner. And if I would do it again I would have gone with SMB, just push/pull to connect/disconnect.

author: Psi
author_rank: Super Contributor
timestamp: January 27, 2023, 01:48:34 am
content: Just don't use RP-SMA. Don't let them win.

author: xrunner
author_rank: Super Contributor
timestamp: January 27, 2023, 02:02:08 am
content: Quote from: james_s on January 27, 2023, 01:36:12 amLike James_s, BNC and SMA here ... plus some adapters to go from N to BNC and SMA, for some other RF generators and spectrum analyzers.

author: NT0Z
author_rank: Regular Contributor
timestamp: January 27, 2023, 02:15:29 am
content: Interesting about SMA. My historical concern with SMA has been connector lifespan. Has that been overcome?Thanks,--Kirk, NT0Z

author: paul@yahrprobert.com
author_rank: Regular Contributor
timestamp: January 27, 2023, 03:48:17 am
content: Oh, man, what a subject. I've been tinkering with RF for about 55 years and if I had tried to "standardize" back in the beginning it would have been all banana plugs and UHF connectors. But nowadays most of my work is with N, SMA, and BNC. I would say you won't ever regret accumulating a bunch of BNC cables. And I find myself always wanting more SMA to N and SMA to BNC adapters. I also find myself throwing out cheap chinese SMA adapters, which sometimes destroy good SMA connectors in the mating process. Also watch out for cheap N to SMA adapters - I've come across some that crap out above 2 or 3 GHz.I think its fair to say that as time goes on you'll be going to higher frequencies so keep that in mind if stocking up on things.I think a good philosophy is to buy stuff based on your current projects. Don't try to think to far in the future. I think connectors and cables are tools more than merely supplies, and for tools you'll never regret buying quality.You mentioned the UHF connectors such as SO239 and PL259. In my view those are inferior and whenever I buy something like an antenna tuner or transceiver I try to replace the panel mount socket with a type N, and that way I don't have to have any cables with UHF connectors on them.Finally, as far as SMA wear, you can minimize that with care when assembling. Never let the center conductor spin in the socket while tightening. That is, hold the body of both sides while tightening the nut. And keep them aligned while tightening so that the center pin doesn't mash the socket. And if the center pin is off center or the center socket is mashed, throw it out.The threads on the SMA connector can generate fine metal shavings, especially if plated. Keep a can of dusting spray around and blow it out often.Good luck!

author: radiolistener
author_rank: Super Contributor
timestamp: January 27, 2023, 04:09:15 am
content: I'm using SMA, also have two BNC pigtails, but often using SMA pigtail with SMA-BNC adapters. When I need other type I'm using adapters.SMA is more reliable, but BNC is more comfortable to connect. On equipment with SO238 I'm using SO238-BNC adapters, and I never disconnect these adapters

author: vk6zgo
author_rank: Super Contributor
timestamp: January 27, 2023, 04:11:03 am
content: Quote from: Bud on January 27, 2023, 01:46:10 amFunny thing is, I had a lot of SMBs salvaged from cannibalised equipment.I had no use for them for years, & now they would be good for some odd stuff they all seem to have disappeared.Most of my stuff is too big for SMAs, so I will stick with BNC & N, with just a few SMAs for the nanoVNA, etc.SO239/ PL259? There will always be room for them, as I am not going on a witch hunt to chase up a fraction of a dB of mismatch loss at most of the frequencies I use.I've been trying to hunt up the weird connectors Icom & some other radio makers use for internal connections, but they are "unobtanium" in VK, & I've only seen one supplier (in the UK), at "break the bank" prices, which is why it would be nice to find the SMBs & replace the whole dodgy run of cable.

author: tchiwam
author_rank: Regular Contributor
timestamp: January 27, 2023, 04:17:57 am
content: Under 3GHz, BNCGet BNC to what ever adapters, they are common.BNC to what ever cable are easy to do and one of the end will fit neatly anywhere.>3GHz SMA / NI have SMC/SMB/SMB/3.5mm/7mm/7/16/N/BNC/WGxxx and way too many other connectors... I play in the HF/MF/VHF/UHF/ L and S band

author: AFTORF
author_rank: Contributor
timestamp: January 27, 2023, 07:04:05 am
content: And don't forget to use adapters in front panel of your measurement devices. If your jumpers center pins are not well mounted, you'll destroy only adapters not expensive connectors complicated to replace !

author: NT0Z
author_rank: Regular Contributor
timestamp: January 27, 2023, 12:26:10 pm
content: Yes, I have "sacrificial connector protectors" on all the devices.BTW, are SMB connectors the super-tiny press-on jobbers used on laptop wifi chips? If so, I hate them.Even when I had two good hands they were problematic. I have a nanoVNA "test board" with tons of those pesky wifi-style connectors. Ugh!Question: Can mere mortals attach SMA connectors to raw cables, or must they practically be purchased pre-made?--Kirk, NT0Z

author: berke
author_rank: Frequent Contributor
timestamp: January 27, 2023, 01:28:18 pm
content: Quote from: NT0Z on January 27, 2023, 12:26:10 pmSure, for example I used solderable plugs (Linx Technologies, CONSMA007) and jacks (CONSMA011), and panel mount connectors (Molex 0732510930) with coax. I must have made around 10 so far, and may have botched one or two. You usually still need a crimp tool for fastening the connector to the cable. They also exist in crimp versions.Not any harder than BNCs IMHO, as usual you have to watch out for these things:- Get the right cable- Trim and cut at the right lengths (the mechanical drawings usually give this information)OTOH you can buy SMA patch cables for quite cheap on Amazon. Depends how you value your time.

author: nctnico
author_rank: Super Contributor
timestamp: January 27, 2023, 05:09:30 pm
content: Quote from: NT0Z on January 27, 2023, 12:26:10 pmNo SMB is a bit smaller compared to SMA. I like SMB because it is quicker to plug in / plug out. For experimenting I typically use SMB. However, there are also plug-in SMA adapters so you don't have to tighten the nut on the SMA which is very convenient.

author: fourfathom
author_rank: Super Contributor
timestamp: January 27, 2023, 05:18:48 pm
content: Quote from: AFTORF on January 27, 2023, 07:04:05 amI recently got some sacrificial SMA connectors (male-to-female stubby) to use on my SMA-style test gear. Is there some threadlocker I can use that will keep the connecter semi-permanently mated?I could use Loctite Blue (the weaker stuff), but I don't want to insulate the connection.

author: james_s
author_rank: Super Contributor
timestamp: January 27, 2023, 07:48:11 pm
content: Quote from: NT0Z on January 27, 2023, 12:26:10 pmYes, it's not hard at all. I bought the dies for my crimp tool a few years ago, I think the tool with the dies cost less than $50 at the time.

author: jonpaul
author_rank: Super Contributor
timestamp: January 27, 2023, 08:05:57 pm
content: Since 1940s the BNC (Berkely Neucleonics Corp) is a standard for most instruments,BayonetMany varieties eg 50, 75 Ohm, HV, wideband to many Ghz.Robust, easy to terminate with proper connector and crimp tools.We found SMA, SMB fine for use inside ight designs but delicate and hard to terminate.Finally APC-7 is on many HP NVA, Z an with very wide band and defined measurement plan.Jon

author: AFTORF
author_rank: Contributor
timestamp: January 27, 2023, 10:11:30 pm
content: Quote from: fourfathom on January 27, 2023, 05:18:48 pmI borrowed nail polish from my wife to soft-block RF connectors, screw, nuts and bolts. It's reversible and free of charge !

author: DH7DN
author_rank: Regular Contributor
timestamp: January 30, 2023, 01:21:03 pm
content: I stopped "standardizing" a while ago, because there are so many different instruments which have their own connectors... So everything RF is about having the right adapter (at least 2..4 of them)My lab's measurement capabilities go roughly up to 3 GHz so having BNC, SMA and N-type connectors is fine.I have also stumbled upon few cursed connector types such as K (2.92 mm), SMB, SMC, Microdot, PL, MMCX and probably a dozen of other types (and I'm not even talking about microwave regime)Amateurs will be happy with BNC and PL-type connectors, RF lovers will try to avoid BNC and use the "good stuff"

author: M0HZH
author_rank: Regular Contributor
timestamp: January 30, 2023, 04:19:51 pm
content: In this order:BNC for most test equipmentSMA for prototyping, testing jigs or inter-board connectionsN for high-power RFQuality BNC<>BNC and SMA<>SMA leads and a box of adaptors can cover most needs.

author: radiolistener
author_rank: Super Contributor
timestamp: January 30, 2023, 11:45:19 pm
content: Also there is a sense to use N connector or SO238 if you're needs to transfer more than 100 Watt RF power.As I remember SMA connector has a limit about 200 Watt, in practice it is usable up to 100-150 Watt.So, if you're needs to work with 1-2 kW, SMA connector cannot handle it and you're needs N or SO238...N connector works better than SO238 for VHF/UHF.

author: tchiwam
author_rank: Regular Contributor
timestamp: January 31, 2023, 01:59:45 am
content: I use U.FL for test points on my PCB designs, beats trying to stick a scope probe somewhere...

author: coppercone2
author_rank: Super Contributor
timestamp: January 31, 2023, 09:43:17 am
content: if you really want to homogenize things, replace everything with GR connectors

author: David Hess
author_rank: Super Contributor
timestamp: January 31, 2023, 02:19:47 pm
content: With some exceptions, I think your connector requirements will be dictated by what your test instruments use. Most of my cables are BNC, but I have SMA for higher frequency stuff and SMB for auxiliary connections to older test equipment which help prevent connecting a high power output to a low power input which could be damaged. N connectors are common for microwave stuff but I do not currently have anything like that.However if you are doing sensitive receiver testing, threaded connectors and double shielded cable will be necessary to achieve low enough leakage. I really liked the old TNC connectors for this, but N connectors have pretty much replaced them.Quote from: NT0Z on January 27, 2023, 12:26:10 pmNo, SMB is about the same length as SMA but with a long and narrow profile.QuoteI use the crimp versions of SMA and SMB all the time with RG-174/RG-316 (0.1 inch) and RG-178 (0.07 inch) cable. Get a ratcheting all metal crimper.

author: M0HZH
author_rank: Regular Contributor
timestamp: January 31, 2023, 04:45:30 pm
content: Quote from: radiolistener on January 30, 2023, 11:45:19 pmSMA is rated 600W @ 1Ghz by Amphenol I think, also confirmed by these people:https://www.centricrf.com/power-handling-connectors/I use them in my designs at 600W up to 70MHz, Hilberling uses them in 1kW @ 50MHz applications in expensive commercial products, other manufacturers use them as well so I tend to think the ratings are correct. Thermal camera shows no significant heating in the connector.

author: NT0Z
author_rank: Regular Contributor
timestamp: January 31, 2023, 10:02:06 pm
content: David and the gang,The RG-178 comment is unexpected, as I acquired a 500-foot spool of RG-178 about 20 years ago, ostensibly to create interconnects between homebrew PC boards, etc.I have a metal ratcheting crimper, and I can get the appropriate die if I don't already have it. But I'm wondering about which crimp connectors to get, as RG-174 and RG-178 differ in diameter?Also, RG-178 has lots of attenuation, even at 50 MHz. Is that a factor when making measurements, connecting instruments, etc?Thank you,--Kirk, NT0Z

author: David Hess
author_rank: Super Contributor
timestamp: February 01, 2023, 01:52:07 am
content: Quote from: NT0Z on January 31, 2023, 10:02:06 pmObviously the specific connector has to be made for RG-178, but I have not had any trouble finding them. I have the Paladin Tools CrimpAll and a set of dies for the common coaxial cable crimps down to RG-178.QuoteI have only used it for short lengths and mostly for carrying pulses rather than RF.