High Power DMR + Seiko Watch Concern

General Discussion
#1

In all my years, this is a new one - but perhaps worth sharing.

Sitting in the office, attempting to get a number of DMR radios to work through the local repeater and be able to talk to each other, one is a 10W output radio, which I’d not really actually considered. I programmed it and with it in my left hand pressed the PTT button.

About 15 mins later I noticed my Seiko, old and expensive watch had stopped. I had to open it up, remove the nearly new battery and reinsert it. It restarted and seems OK - but although old, it’s been brilliant but the DMR 10W RF output in the stopped it dead.

I’ve never given it a thought before, but maybe 10W of digital RF is capable of doing more than messing up watches. RF close to your head at the usual 3-5W never really worried me, even when UK Government implemented a mandatory RF awareness check with their licences - but maybe 10W really is a bit much. If it fries a wristwatch in a sealed metal, waterproof case …

#2

Did you try to repeat what happened? I wouldn’t want you to destroy a good watch, however, being able to repeat the exercise while focusing on the watch would help to confirm it was the radio.

The reason I ask is my wife had given me a nice diver type watch for an anniversary and when I wore it at work it would gain time. Over a period of a week I documented the time using two different clocks when I arrived and left and the time gain. Never figured out what was causing the anomaly but it only happened at that location. I could repeat the exercise but couldn’t explain it.

#3

I decided not to repeat the experience - I like the watch too much, but ten Watts with a rubber duck just a few inches from the watch suggests it was the culprit. It will have to remain a mystery. I’ve got a cheap digital watch somewhere - so maybe I can try that.

#4

Understood. I worked with an old guy back in the 80’s that used to ask me the time every time I saw him. One night I asked him why he didn’t wear a watch. He told me to give him my watch which was a Sieko automatic Divers watch from the 70’s. He laid it across his wrist and it stopped. He handed it back to me and it started running again. I would not have believed it if it weren’t my watch and I hadn’t been standing there. Does anybody really know what time it is?

#5

I wear an Apple Watch Ultra. I would hate to think what 10 watts would do to a computerized electronic watch. The fact that you’re dealing with a digital signal as opposed to analog may have something to do with the type of interference.
At any rate, 10 watts, that close to the brain, is something I would be very concerned about.

I have an old Midland signal strength/VSWR meter in my office with it’s little antenna. When I key the mike on a Midland MXT400 or 500 it almost blows up that little meter unless I turn the potentiometer way down on it. The radios are using 6db antennas about 10 to 15’ feet away.
As a young Broadcast Engineer, many decades ago, I remember going out into the field where our 5000 watt AM broadcast tower was located, walking around with an 8’ fluorescent tube lighting up in my hand from the RF radiation. People in the little town just couldn’t believe it😂

As we all know, RF radiation is definitely something to take seriously. It can kill.
Tom WRQE346

#6

My office is multipurpose - a big open space. At one end I have a small 3 camera video studio, audio equipment inhabits another area and the other end has the office where I do editing, audio and radio programming. Rarely at the same time. However, this time I was doing a big video project that meant lots of waiting, so in the ‘waits’, I had 4 DMR radios which I was programming.The 10W radio was really audio unfriendly - the motorboat sound burst out of the monitor speakers and though I can’t be certain, I think it also got into the computer network too, because the video render failed at the same time. The computer monitors flickered and flashed too. The square waves and the constant pulsing make DMR very difficult used near anything sensitive. I suppose the known impact of RF on cells is the same (or perhaps even less as it’s not on continually?) I never smile when we have just installed a PA system with 12,000Watts of amplifier power, and somebody leaves their phone on the mixer, with the volume up! That can be painful. Sticking a 10W DMR near the sensitive kit would be horrible.