EAS interference also heard in MagicJack

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Shane
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EAS interference also heard in MagicJack

Post by Shane » Sun Aug 28, 2016 9:56 pm

This might be better posted to an EAS forum but I thought I might get a different perspective here.

When we receive certain EAS alerts there is sometimes a squealy sound in the not-too-far-back-ground. This has been cussed and discussed on our state EAS forum and I don't believe we've found the cause.

The sound is something like the beat tone you'd get from an unstable oscillator.

Now, here's the thing. On another thread we are comparing VoIP solutions and I brought up MagicJack, which I have used for several years now.

But...I moved a few years ago to a neighborhood I once swore (maybe swore is too strong a word) I would never want to be in because of all the RF floating around. I am less than a mile in one direction from a 5kw AM whose field strength I once measured not very far from here at 2 VOLTS; and about the same distance from another AM that is 1kw Day. Plus most of the TV and FM stations in the market are only a little more than a mile away on towers which I can clearly see more than half of from my back yard!

Guess what. My Magic Jack line now has the exact same squealy noise in it.

So it makes me wonder if the origination of that same sound in the EAS alerts is being caused by RF getting into one of the relay stations' ENDECs or the unbalanced feed thereto.

And I guess I need to shield the MagicJack dongle and discourage RF in the line to the phone that distributes the service (a cordless phone base which could itself be affected by the RF).

Concerning EAS, anyone else inside or outside of Nebraska recognize this in their relaying of messages?
Mike Shane, CBRE
---Omaha---

kcbooboo
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Re: EAS interference also heard in MagicJack

Post by kcbooboo » Mon Aug 29, 2016 5:32 am

I've got a 5kw station about 1.2 miles from me and the field intensity is 160-180mV/m depending on ground conditions and where in the house I measure it. When I do the EPM spectrums in the fall, I'm at a point 1km from the station and I get about 600mV/m there. This is non-D daytime. If you're getting 2V/m, you must be in a major lobe or the station is at the bottom end of the band.

Even at 1.2 miles I still can pick up the AM station with my oscilloscopes.

Bob M.

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KPJL FM
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Re: EAS interference also heard in MagicJack

Post by KPJL FM » Mon Aug 29, 2016 9:05 am

For the MJ, run the Ethernet and POTS line thru torroids. It's probably the POTs wire from the MJ that's getting the unwanted signal. This won't, however, stop those unwanted telemarketers or middle-of-the-night remote control calls. :roll:
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Shane
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Re: EAS interference also heard in MagicJack

Post by Shane » Mon Aug 29, 2016 8:56 pm

Can't choke Madame Burk that way, eh?

On the 5kw station: yes it's low on the dial - 590 - but it's non-D day and night. Has a horizontal wire antenna on phone poles they can use for a backup with about 2kw. I think the 2V point was a few blocks closer than I am. The 1kw is on 660 with 54 grandiose watts of night power!

Either way, on one radio here that isn't particularly selective - one can tell because all the highs are present - if I turn the radio much off the axis to 660, 590 will blast thru. Much more noticeable and touchy at night, of course, but can still get a full quieting signal on the 660 @ 54 watts if radio is tuned and oriented correctly. Meaning pointing a side directly at 590 to null it.

Thanks for the suggestions, KPJL. I'll try those first. Then we can try the same thing on the offending EAS box once we figure out whose it is. :roll:
Mike Shane, CBRE
---Omaha---

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