Sangoma S70x phones and Walkie Talkie Interference

I’ve got a client we deployed a couple dozen S705’s. The client is a warehouse with most of the phones in their office portion, and a few in the warehouse. They heavily use walkie talkies to communicate.

I’ve observed their radios frequently interfere with the Sangoma Phones and cause all kinds of strange behavior. It frequently causes false button presses, like placing calls on hold, or enabling DND among other unwanted behavior.

I’m 100% certain the radios are the cause. Phones are powered by POE. Obviously asking the client not to use their radios isn’t going to fly. Tomorrow I’m going to put some Digium phones out there to see if the behavior persists. It did not happen with their old Merlin system FWIW.

I thought about adding ferrite cores around the patch cables, but am unclear if the patch cable itself is acting as the antenna here or if the phone itself is just accepting the interference (as FCC mandates they do) because the radios are frequently only a few feet away from the phones.

Anyone run into this, or have ideas on how to address it short of replacing the phones with a different brand?

These phones are Wifi capable, I initially thought that you are using them on Wifi, and this is why it’s happening.
I am shocked that this is happening without actually using Wifi…

I think the only way to go, is to contact support, and have them look into it.

We have several S500/5s in a facility that uses walkie talkies as well, and no issues.

What type/brand of walkie talkies?

Uhm, turn off the wifi on the phones?

If the radios are on then they can pick up things. RF is RF.

Apples to oranges. The S500/5’s don’t have wifi radios.

The ARRL website has this to say about interference: The FCC rules require the equipment manufacturer or importer to design and test his products to ensure that they do not exceed the absolute maximum limits. In addition, the FCC requires that Part 15 devices be operated in such a way that they not cause harmful interference .

If the radios do not exceed the allowable interference levels, the receiving device “should absorb” as much as possible.

Also, LMRs (Land Mobile Radios) in a commercial environment MUST be licensed. You can’t use consumer/hobby class LMRs in any commercial environment.

I’d check the following:

  1. Make sure the LMRs being used are licensed for commercial use.
  2. Check to make sure that your equipment is properly grounded. This includes any radio base stations or repeaters, as well as network devices.
  3. If you can’t knock it down that way, the first party that needs to react is the radio manufacturer. If they are within limits, check with your other equipment providers to make sure they have done the minimum for harmful interference rejection.

I apologize if I was not clear. There is no Wi-fi involved. The phones are Poe anyway. The radios are handheld types and they appear to be of commercial quality, though I’m unclear of the wattage output or if they’ve been “overclocked”. Either way they’re not going to replace their radios that’s just the fact of it. They probably have 20-30k in radios and as they like to remind me “we didn’t have these problems with our old system”.

I’m bringing some digiun phones today to see if they’re going to be any different.

Ok, I took a couple Digium D70’s out there and confirmed the problem does not happen (it’s really easy to reproduce, just key up on the radio and the Sangoma phone will wig out). It only happens on the Sangoma phones, and it happens on all of them, so I don’t believe it’s a “bad egg” here.

Short of a way to fix this, I need to replace all the phones with a different brand to avoid the interference it appears. I’ll open a support ticket, but I doubt there is anything that can be done here.

Recommendations on phones to supplant with? Was thinking Yealink, however the Sangoma phones seem awfully similar… so I’m concerned they’d have the same problem. Obviously I’d have to order one phone to test with first.

The walkie’s are standard Motorola Handhelds, Model CLS1110 and are not “overclocked” or otherwise have any modifications.

The way to reproduce the issue is simple, get your radio within a foot or two of the phone and key up. The phone will wig out. The closer to the phone the easier it is to reproduce. Unfortunately it happens in a normal “sitting at your desk” situation too (just not as frequently) so I can’t ask them to do anything different here behavior-wise. It happens in normal everyday use scenario, I’ve observed it.


Does every radio handset cause this issue?

Yes. Every radio they have causes the issue. I’ve also tried changing frequencies, which made no difference either.

I opened a case with Sangoma support, they replied that this is a known issue (for 2 years now apparently per their response), but their phones comply with FCC requirements, so they have no plans to address it. They offered me no recourse either. I asked why the datasheets and sales slicks do not mention this anywhere, and my question was ignored. I get from a marketing standpoint you wouldn’t want to publish negatives, but this is kind of important as it could eliminate the phones from consideration in many use cases.

Kind of a shoddy response; the old phones as well as other modern phones I’ve tested with do not have this problem.


First, I feel for you. Your situation sucks and it feels like you’re all alone. We’ve all been there. It’s time for you to step up, though, and realize that making this our problem isn’t going to solve it for you. You’ve found a solution, it may be time to try it.

This might sound harsh. That’s not my intention, but truth quickly often sounds mean. I apologize for that. Next, a couple things:

  1. This is a user forum. If you have a problem with Sangoma, tell them. While it’s interesting and fun to whine in public, this isn’t the place for it. We’ve heard your concern and it’s now available for anyone that has this same problem. It will be as intractable for them as it was for you.

  2. The FCCs position on this is CRYSTAL CLEAR and has not fundamentally changed in over 50 years. The INTERFERING COMPONENT is responsible for solving this problem. Yes, other companies may not have this problem, but that’s the same as saying “My friend’s car got hit by a truck so they need to pay for the hail damages to my boat.”

Sangoma has said they are compliant and has the FCC certification to prove it. The FCC has consistently said that this type of problem is an issue with the transmitter. Have you climbed up on Motorola’s back about this? Their radios are causing interference - it’s their responsibility to provide a solution.

The answer is not to your liking? Whining at us isn’t going to fix it. We’re users. We don’t work for Sangoma. We, as a group, don’t have this problem and have recommended all of the solutions we have. If the phones don’t work, send them back or switch to a different phone. If that isn’t to your liking, fix the transmission bleed. You’re the engineer here - engineer for a minute.

Having said that - I’ve been the base frequency manager for several Joint Task Forces in several places, and it’s not a new problem. There are ways to fix this issue that are outside of everyone’s control but yours. I had a similar problem with Motorola 2-meter radios and a Merlin phone system in one location, so I know what you’re up against. We ended up replacing a truck-load of 50-pair with shielded 50 and grounding a lot of lines and phones to knock down the interference. Motorola was just as unsympathetic as Sangoma is here, and the Merlin folks just laughed at us - their suggestion was “put the chargers outside the offices and don’t let them bring their radios in”. We never did eliminate the problem, but between training the grunts to not key their radios with them next to their phones (no small feat, let me tell you - you ever tried to train someone in the Army? It literally requires cartoons…) and the cable upgrades we did, we got it to the point where we only had to remind a few of them a couple times a week not to do that…

Remember, we’re here to support you, but we’re out of ideas. There’s nothing else we can do.

What? I already stated clearly that I am aware of the FCC requirements. I get how it works. I was just asking if others had this problem and a possible solution short of replacing the phones or radios (which I stated this was not an option)…hence me mentioning ferrite core, etc. Maybe someone else will benefit from my experience.

I already did “step up” (thanks for that) and am replacing the phones with Digium ones which are not affected. I only responded again because someone asked me a question about the radios.

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Well FWIW, the Motorola Handhelds, Model CLS1110 operates legally on UHF (421–470 MHz) PLMR (Private Land Mobile Radio) band.

It can only be expected that they will emit rf emissions, but this should obviously not be construed as interference.

If a phone is built with some of its circuitry resonant in that frequency with a negative effect but without adequate shielding surely that speaks of poor design.

In the good old days of NexTel, you could seem almost clairvoyent if you caught the preamble pattern and picked up the phone before it started talking.

In the good old days of NexTel, you could seem almost clairvoyent if you caught the preamble pattern and picked up the phone before it started talking.

Hahaha I remember those days! That old “zzzt zzzt” you’d hear over the stereo before a call came in, brings back memories.

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I was curious simply because it’s unlikely all the radios are going to emit the same spurious harmonics. i’m following this thread with interest.

Again, this is not spurious harmonics, it is likely not even harmonics because Motorola probably know better how to be FCC compliant after developing the prototypical walkie-talkie of WWII way more so than whoever makes these hardwares .

Given a likely lack of radiated sub or just harmonics (a big FCC no-no), the carrier frequencies are legitimate channels in a legitimate licensable part of the rf spectrum , thus all the devices use precisely the same set of frequencies.

The OP already stated that he has tried ‘changing channels’ so, the “parasitic” receiver built into this particular phone apparently has a low q but definite susceptibility in the PLMR reserved spectrum and likely a lot wider.


Anectodally, as a boy, we made ‘crystal sets’ out of an oa71 germanium diode, a few turns of wire on a toilet roll , a variable capacitor and 150 foot of wire and a cheap earpiece, with that we could listen to radio moscow 1800 miles away (batteries neither included nor needed)

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Cats whisker sets, been there :wink:

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Nah, finding the g-spot on a whatever lump of rock wasn’t worth the sixpence spent at radiospares which became rs components :wink:

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(It would be interesting to see if rotating the phone itself through its three polar axes has any effect. 1/4 wave swr is right around 6 inches at that frequency, also i would try wrapping the phone in a sheet of cooking foil from Mrs. Faraday’s Kitchen Store)

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That’s actually an excellent idea. Of course, just replacing the phone with one that doesn’t have the problem would be a solution, but the little engineer in my head would love to see if grounding aluminum foil would work.

Jokes aside, the orientation of the radio’s antenna did indeed influence the “strength” of the effect. Putting my tinker hat on, and if I had unlimited time and energy, I wonder if a small sheet of foil or other metal, cut into the template of the phone’s front facia plastic and mounted behind said plastic (a sort of “gasket” if you will, grounded or otherwise) would be enough to tamper the effect.