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Apr 11, 2003

This is a pretty bizarre RF interference problem but it's kind of driving me nuts:

I drive a taxi and we use a UHF repeater setup with handhelds for our communications. Specifically, we're using the pride of the Chinese HT market: The Baofeng UV-5R. They're great radios, really - hard to beat for functionality and cost. One thing about these radios that isn't so great is the fact that the squelch is useless. There's a few ham nerd sites that have conclusively proven it through rigorous testing that's way over my head. In the same vein, the radios DO have working CTCSS and DCS. Our repeater is setup for CTCSS, using the 127.3 tone. Man, it was a good day when I figured that poo poo out because on carrier squelch, there's so much random poo poo that interferes with our frequency.

So about that frequency - the FCC license and equipment came into the company before I did, so I really don't have too much control over them. Granted, I could reprogram the repeater radios to whatever freqs I want, but it would also require sending the duplexer out to be tuned, so, no. Our handhelds Rx on 452.250 and Tx on 457.250. Before the repeater was setup, I just had everything programmed for simplex on the 457.250 freq - not a single thing interfered. 425.250 is like some sort of UHF shitstorm magic number that everything broadcasting an RF signal seems to gently caress with. Plasma TVs, wireless internet antennas, random automatic beacon things on boats, and, the real problem: iPod classic LCD screens

When a song title scrolls on the screen or you operate the click wheel, the radio goes loving nuts. It breaks squelch a bunch of times in rapid succession creating a bunch of irritating pops and flashing LEDs. As far as I can tell, the iPod drawing the color black on the screen seems to be the culprit. When the screen turns off, the interference stops immediately. Using CTCSS keeps the radio speaker from breaking squelch for the most part but it's still annoying as all hell.

I've tried this with several different iPods (all 5.5 or 6 gen) and radios, all with the same results. Plugging an aux cable from the ipod into the car seems to make it worse, with the cable acting as an antenna. In my vain attempts to stop this from happening, I've tried to make a little RF blocking sleeve with beer coozies, speed tape and gorilla tape and the aux cable has a ferrite bead on it. These don't seem to do much as even stowed away inside the center console the RF signal coming off the ipod is still powerful enough to open the squelch on the radio. What would be the best solution to block stray RF coming off of the ipod? Wrap it up in copper mesh? Ground loop isolator for the aux cable? Smash everything electronic and become a neo-luddite?


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