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Communications

HAM radio

A woman in North Central Florida has demanded that a HAM radio operator in her neighborhood stop using his equipment because it is interfering with her insulin pump.

This is bullshit. According to the FCC database, the HAM operator in question has a callsign of WB9UYK. He lives at 8546 SW 79th Ave, and has since June of 2019. The woman who is complaining lives at 8566 SW 79th. Ave, according to voter records. Using Google maps, the two houses are 74 feet apart, at their closest.

If I were the HAM operator, I would demand an engineer’s assessment showing that MY equipment was the cause of the interference. There is a Reddit thread on this one. Greybeard: if you see this, what do you think?

EDIT: There is also a thread on QRZ.

One reply on “HAM radio”

I first heard about this last night when I got an email from my ARRL Section Manager about it. They didn’t say much other than be careful when talking to the press and have the RF Safety worksheet completed for your station so you can say, “according to the standards, it should be safe and here are my numbers to back that up. ”

As usual, none of these sites, Reddit, QRZ, or Channel 9 present the facts we can use to determine how realistic her claim is. The sources go back and forth between saying the wireless insulin pump uses 900 MHz and saying he can’t use his HF station. HF has nothing in common with 900 MHz except for being radio. We’re talking at least the 31st harmonic of an HF frequency.

The insulin pump is probably the problem. Those devices are required to be resistant to RF interference and if they suffer interference, it’s the “receiver”, the device being interfered with, that needs to be fixed. That email from the ARRL said, “If you’re active, it pays to be an ARRL member! We can get involved early, and help collapse situations before they get to this point. For example, RFI to medical devices are an issue for the FDA. “The medical device manufacturer is obligated to report it to the FDA as specified at 21 CFR Part 803.” That would have involved the manufacturer, who are likely eager to resolve this issue.”

Use the 74 feet as the worst case distance. There’s a table from the ARRL for distances that exempt a station from even having to calculate those numbers. I have it here:
https://thesilicongraybeard.blogspot.com/2021/04/licensed-hams-new-rule-on-may-3rd.html
The table distances are in meters: 74 feet is 22.6m, so round it up to 23m. According to that table, the only place in the entire HF spectrum he’d have to even do the calculation is if he’s running over 1000 Watts on the top of the HF spectrum, 29.7 MHz. For every other band, he could be running 1000 Watts and being 23m away is exempt from needing to calculate the exposure.

I checked for an amplifier in the Ch 9 video and saw one, an Ameritron AL-811H. I looked it up and it’s an 800W amplifier, incapable of achieving the power limits they require more calculations for.

I think a reasonable first step would be for her to demonstrate the times when her pump screws up match his times transmitting.

The Ch.9 video goes by fast, but I didn’t see an antenna. Communities that don’t allow outdoor antennas always end up making interference problems worse. Antennas produce lower fields near the ground when they’re higher up.

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