Failed BNC opened

Hmmm, and to think that I started with RG-213 and N type connectors… well, I do use 2m and 70cm. I thought you HF types used wet string anyway - no need to carry the water to wet the string on most GM summits. :wink:

My preferred cable is now 5D-FB with its special size BNC connectors (solder type). Being low loss semi-rigid I find it much easier to roll up in sub-zero temperatures. If there is any cursing to be done on a summit it is usually on account of the RG-58 HF dipole feeder. I appreciate many prefer crimped connectors, but I have had no issues with the soldered BNCs on either feeder. Mind you I do keep a check on them after every round of activations…the 6P principle and all that.

Agree entirely with this. The cable can get in the way when trying to make adjustments to the controls, particularly with numb fingers in cold conditions…

73, Gerald G4OIG

Hi Adrian

I’ve used crimped BNC’s for a good few years now on my SOTA kit (and the shack based stuff) and not had any failures, even on repeatedly-used patch leads. I have occasionally found when assembled the central pin has come up a bit short - presumably due to “operator error” on my part - which perhaps would give the pin more wiggle room and thus increase the chances of fatigue of the inner conductor at the interface between it and the crimp on the pin, but I’ve weeded these out before they’ve gone into service.

I use a heavy duty rubber boot rather than heat shrink, and put a small cable tie at the cable entry end to hold in place. Also a stripping tool set to the correct dims for preparing the cable, so no risk of nicking. The combination fortunately seems to give me excellent reliability (he said just knowing the next activation will be the one when the BNC falls off…)

73 de Paul G4MD

Thanks everyone for your thoughts, interesting and helpful.

Closer scrutiny of the broken wire shows that it broke right up against the crimp, and not right next to the end of the insulation where “nicking” would be most likely. There is maybe 0.5mm difference, as the crimp grips the wire just inside the “tube” of the centre pin, and not right at the open end.

I guess that the BNC was optimised as a constant impedance connector, and any robust cable grip would risk compressing the cable, causing a blip. So, it may not be ideal for SOTA type field work, although obviously it works well for many of you here.

I like the idea of a BNC right angle adaptor, and will be acquiring one at the next opportunity.
I don’t really want to use the rear connector, as I often operate with ft817 standing on end. I have fitted a cover over the SO239 to protect it.

Anyway, I’ve just fitted a new connector to the antenna coax, taking great care to avoid damaging the wire. This time, I have made the centre pin crimp closer to the tiny inspection hole, and therefore away from the open end. I hope this will mean that the pinch point of the crimp, where fracture seems most likely, will be protected a little from strain.

I’ll also rethink what to carry with me as backup, though in this case it didn’t cause me too much of a problem.

Best 73, and thanks again for all comments,


1 Like

Hi Adrian,
I wonder if there are right-angle connectors (plugs) rather than adding an adapter to a straight plug. I know there are for PL-259s so hopefully they exist also for BNC, that way it’s one less component to go wrong - get left behind, etc.


[quote=“DD5LP, post:24, topic:12375”]hopefully they exist also for BNC[/quote]Yes, they exist, but you may have to go somewhere like Farnell or RS to find them.

I suggest the crimp is fine and I agree with others that the failure has resulted from the plug wagging about whilst the cable is moved. The resulting articulation will be applied to the point on the inner between the pin and the insulation. This is the common mode of failure for ALL BNC plugs. I have also experience of socket damage caused by the pin wagging within the socket. The direct solution is to use TNC’s (threaded N connector) for this type of application. These are direct peplacements for BNC’s but they are more difficult to source. They are the solution for wagging cables. Being screwed together a mechanical solution is achieved, the pin is unable to articulate the plug lasts for ever.

David G0EVV

The jury must still be out on that one surely?

1 Like

Found this one on eBay but I suspect it might be 75 ohm rather than 50 ohm.


Don’t be a cheapskate, buy your connectors from manufacturers like Greenpar, Andrew or Radiall.

At surplus sales/ham radio rallies etc. you can often fine very high quality path leads for a fraction of the cost of the components. I picked up a 20cm lead with a right angle BNC male and BNC straight female with RG-223 cable. Double screened cable, strain relief grommets etc. for £0.50 (Eu0.67, $0.73) The right angle connector kept the cable clear of the 817 multi function control.

So does a PL-259! :grinning:


[quote=“DD5LP, post:28, topic:12375”]it might be 75 ohm rather than 50 ohm.[/quote]…or possibly somewhere half-way(-ish) between so they can (try to) sell the same item as either… :wink: :wink:

Ed has a point - I salvaged several of the 75 ohm free TNC plugs (unused - and a whole roll of 75 ohm coax) when they cleared out a disused lab at work once, but haven’t found any use for them. They seem to fit a BNC socket…


75 Ohm is incredibly useful for Z matching - best case example an el-cheapo power divider. AKA a Wilkinson Splitter.

Credit : G3WOS

Worth keeping !


1 Like

Essential for feeding the pair of 17 elements I use on 2m from a summit… :wink:

1 Like

Is it true that using the rear so239 socket on the 817 uses more power than the front BNC? I understood that the rear socket involved a relay.


Yes, the FT-817 will use 20mA more power for the rear so239 socket because of the relay.

My understanding is that the pin is a different diameter - hence if you use a 75 ohm plug on a 50 ohm socket, 50ohm plugs may not make a good contact afterwards. 75 ohm BNC plugs are useful for phasing harnesses for VHF/UHF beams.

73 Ed.

50 and 75-Ohm BNC connectors are (meant to be) mechanically compatible.

OK, I must be mixing this up with a different connector then.

Ed, I have also heard that the 75ohm BNC pins are physically larger than the 50ohm BNC pins and should not be used with 50ohm BNC sockets. Not completely convinced, but would be nice to know for sure. In any event, there are plugs for any type of use, so right angle BNC in 50ohm will be available with a little bit of searching around.