NDX2 RP-SMA WiFi/BT un-used connectors; necessary to terminate?

Using my NDX2 exclusively via ethernet here and have no plans to use BT or WiFi. I have a light background in RF and, specifically, antenna systems. I’m used to supplying the system/transmitter/receiver an appropriate termination load on these types of un-used antenna connectors, when not in use.

Is this required or recommended by Naim when the antennas are not connected (still in their bag, lol)?

I have a few Amphenol RP-SMA 50ohm termination loads in my old field kit that I think may be appropriate for the task.

What does the brain trust say?

I’m half as concerned about dust/dander as I am about about correct termination…but there are all kinds of rubber connector boots that work fine for dust.

I’d suggest that you might be overthinking this. I’m not aware of anyone mentioning it previously.

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you could always screw in the antennae and leave them folded down if you’re that concerned. Also, afaik, the wifi is disabled when ethernet is connected. Overthinking? Yes!

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I may be. We obviously don’t have a bunch of NDX2’s with reported damage due to unterminated connectors, but it IS considered good RF hygiene to do so in professional environments. Hence my question.

I actually would like to avoid connecting the antenna for both aesthetic and RF reasons. I have a mesh satellite very nearby and would prefer that RF energy not get potentially mainlined to my network board in my NDX2.

Wife also hates the way they look.

Yeah I think I may be. Dust covers are cheap. I’m going to go that route most likely.

Thank you, both, for chiming in. :smiling_face::+1:

I come from an RF background so fully appreciate the ‘dummy load’ thinking but I think it’s really a non issue. On my NDX 2 I actually leave the antennae in and folded away as sometimes I tinker with Wifi and use bluetooth occasionally from my telly.

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We have never connected the antennae, on the basis that WiFi isn’t enabled when on Ethernet and our Bluetooth is disabled.

We expect the connections to be completely dormant.

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Good to know we are speaking the same language. Thank you! :+1:

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I wouldn’t worry. If you connect the ethernet lead, the WiFi unit is disabled. I suspect the Bluetooth is so ultra low level it’s totally inconsequential. I also suspect without an antenna load the RF load impedance will be way off optimal impedance for the RF amp, and likely the RF amp will shut off or severely attenuate so the resulting VSWR from the impedance mismatch (reflections) becomes irrelevant.

Your mobile phone at the other end of your room will likely have more impact.
Remember the NDX2 uses Zigbee for the remote which is super low power like Bluetooth.

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That was my original thought, that the radios would self-protect if a gross impedance mismatch was seen. Common in commercial radios but I’m not familiar with consumer-grade stuff nearly as much. Thanks Simon!

Dear cb01,

Being an ex-radio tech on aircraft. The antenna port on my GPS for pack communications on the bike is not used, and I have terminated that with a 50 ohm 2.4mm SMa dummy load. For peace of mind and dust prevention, I would terminate the connections as good RF practice.

Just my two bob.

Warm regards,

Mitch in Oz


Only if the RF amp is enabled and is designed to always see a specific load. Most modern very low power RF amps will attenuate if there is a significant VSWR… This has to be done in consumer products as the impedance seen can vary hugely even with an antenna attached because of the environment and placement of the antenna is very varied. Folding an antenna back against a metal case for example will vary its impedance potentially significantly.

Now sure if we had a RF power amp that was active, so we had tens of volts or hundreds of volts of RF then to protect the output gain devices of the amp we would apply a dummy load, rather than letting the signal reflect back potentially damaging the RF amplifier.

If you were wanting to terminate these as good practice, then you should equally terminate the SPDIF outputs on our streamers and possibly the automation output too when not using as these also use ‘RF’ voltages. I do think this is obsessive over thinking. If it was required and good practice it would be applied.

Remember it’s not the output that transmits RF energy, it’s the antenna or radiator the output connects to. Any impedance mis match will create reflections for AC signals if present.

The audio outputs are protected by relays, and these go open circuit when not being used I believe… akin to not having anything connected.

I am also qualified in RF techniques. (In HF).

So if wanted to terminate unused connections that use ‘RF voltages’ , to address some sort of OCD then the following loads would be:

SPDIF 75 ohms
Wifi 50 ohms
Automation 3K to 7k ohms (estimated based on RS232 specs)
Bluetooth 50 ohms

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It looks like I will have to purchase a 75 ohm for my SPDIF.

Thank you.

Mitch in Oz.

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I actually have all these in my field toolkit already. Some 75r Amphenol Hi-Perf 0-3GHz BNC terminators (.5w) and a tray-full of .5w 50r Amphenol RP-SMA terminators…still in wrappers. Mouser or DigiKey would have these as stocking items.

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