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Old 10-16-2020, 12:10 PM   #11
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"Sometimes the solution to problems like this are multi-pronged, i.e. a "Belt, Suspenders, AND Duct Tape" kind of solution. I'll watch this thread for future developments."


I just installed new LED headlights, so I'll be interested in seeing where this thread leads, although I don't use the Am / FM radio. I do have an RFI issue though that may be related. My 2M / 440 ham rig will cause a hard reset in my stereo once in a while when I key up. Got any insight on this one?
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Old 10-16-2020, 01:08 PM   #12
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@A.T.: My "two cents" is probably much too wordy, so insert my heartfelt apologies here, but it would still read as follows:

The laws of physics are, of course, the same in both cases of possible/probable EMI, but there are some key differences in your ham radio case: 1) we can safely ASSUME the presence of a radiating RF source, i.e. your transmitting antenna, 2) there may be excessive unwanted coupling between the ham rig antenna and the stereo receiver's antenna, and 3) there may be a sudden voltage transient on the 12V supply caused by the transmitter of your ham rig turning on, which differs from the HID headlight case, in that the interference/problem with the HIDs is apparently continuous and steady-state, whereas your ham rig creating a hard reset of your stereo sounds like a transient condition/problem.

I'm always a fan of checking the basics first, just to try and avoid unwarranted assumptions, so let's pursue number 3) first - just for giggles. The justification for doing so is that there's an old rule of troubleshooting that goes something like: "When you hear hoofbeats, expect horses, not zebras." (unless you're in Africa, of course). So if the stereo reboots immediately when you "key up", and doesn't continuously remain in some kind of "reset" state while you're talking, then the first suspect in my mind would be a voltage transient on the 12V supply to the stereo. (Any chance your 2-meter / 440 MHz ham rig draws its power from a point that is both somewhat distant from the battery and also fairly close to where the stereo gets its power? Like the fuse block?)

The first test that I would perform is to grab a digital storage oscilloscope (if you have one), or maybe a good smart digital multimeter with "glitch capture" or Min/Max recording capability, and monitor the voltage to the stereo, measured at a point that's as physically close to the stereo itself as possible. Check the basic DC level first, with the stereo turned up as loud as you would normally be playing it (to simulate the Max. or at least "representative" power demand.) Then, look for glitches with the MIN/MAX or glitch-capture mode while you "key up" the ham rig a few times. Look for brief voltage transients that drop the voltage below about 10 Vdc or so when you press the transmit button. Some audio equipment manufacturers go cheap on power supply filtering, and also set their power-on-reset circuits a little on the "sensitive" side.

If you find these kinds of low-voltage transients, then a large-ish filter capacitor (and maybe a few smaller ones as well) on the 12V supply to the stereo, located as close to the stereo's power input terminals/wiring as possible, or maybe installing larger-gauge wires to supply power to your stereo, might be the first solutions to try.

If you have any further thoughts or questions about this, feel free to PM me!

Mike

P.S. If you're not using the "AM/FM radio", what kind of "stereo" is this? Are you playing CD's or something? 8-tracks? (Just kidding.) And if so, how loud do you have your stereo turned up? Is it drawing a lot of power through possibly under-sized 12V supply wires? Are you transmitting with more than just a few watts out of your ham rig to punch through the QRM? Sorry for all of the post-scriptum questions, but you've engaged my curiosity - at least a little bit.
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Old 10-16-2020, 03:15 PM   #13
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Quote:
Originally Posted by arctictraveller View Post
"Sometimes the solution to problems like this are multi-pronged, i.e. a "Belt, Suspenders, AND Duct Tape" kind of solution. I'll watch this thread for future developments."


I just installed new LED headlights, so I'll be interested in seeing where this thread leads, although I don't use the Am / FM radio. I do have an RFI issue though that may be related. My 2M / 440 ham rig will cause a hard reset in my stereo once in a while when I key up. Got any insight on this one?
Where is your ham radio power lead connected to? I assume you are using the factory wiring for the audio receiver in the dash correct?

My ham setup (also 2m/70cm Yaesu FTM-400XDR) has no interference issues or noise related to my audio system (very large setup). It is wired directly to a battery distribution panel that is independent from any factory wiring.

Scott
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Old 10-16-2020, 06:40 PM   #14
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Originally Posted by arctictraveller View Post
I just installed new LED headlights, so I'll be interested in seeing where this thread leads, although I don't use the Am / FM radio. I do have an RFI issue though that may be related. My 2M / 440 ham rig will cause a hard reset in my stereo once in a while when I key up. Got any insight on this one?

Since it's VHF/UHF, I'm assuming it's 50W output, so maybe 100W draw (probably less, since it's likely a class C amp rather than class A or AB). Unless you really chose poorly on your source for power and ground, I doubt that it's a power draw issue. Have you checked your antenna's VSWR? because symptoms like you describe are usually due to RF coming down the outside of the cable due to a mismatch. If so, tune your antenna and/or put ferrites on the cable to choke the RF off the shield. Also make sure that where you mounted the antenna has a good ground to the chassis - a lot of the metal elements on the van aren't well bonded to ground.
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Old 10-17-2020, 11:13 AM   #15
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My apology's to the original poster, it seems I have completely derailed his thread, sorry. I've gotten some good ideas though, but it's probably best if I start a different thread. Never the less, thanks for the replys, there are a couple things I'll check.
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Old 10-21-2020, 12:46 AM   #16
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There's a lot of trial and error in this stuff. I'd be tempted to try a small capacitor across the positive and ground wires of the headlight harness, close to the light. Maybe 0.1 uF or so -- a ceramic disc capacitor should be fine, and the exact value doesn't matter. The idea is the capacitor doesn't conduct DC, but forms a low-impedance path for RF. This might work well in combination with ferrite beads (which create higher impedance for RF.) The idea is to prevent the wiring harness from becoming an antenna that radiates the RF noise created by the lights.
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