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Old 07-07-2007, 15:51   #1
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Radio interferance

On the newly installed Yaseau l am gettig radio interfearance from the newly installed refrigeration unit...now it is a more efficient reefer and does not cycle as frequently as the older one but l never had the rfi noise before...any ideas...ferrite beads??
Dave
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Old 07-07-2007, 17:54   #2
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Check out this thread, it may help.

SSCA Discussion Board :: View topic - 12 v Danfoss compressors - RF noise - radio interference
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Old 09-07-2007, 08:49   #3
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Thanks for that excellent link!
Though it is a known (defect?)with the reefer compresser l can't imagine them not correcting it, the old unit made NO NOISE at all.
Dave
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Old 09-07-2007, 18:26   #4
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If I understand the information in the thread Danfoss leaves it up to the folks who build the refigeration unit, and they are dropping the ball (well, they are both dropping the ball). You might try a .22 uf capacitor (epoxy or ceramic) across the DC power leads. Make sure it has a high enough voltage rating (at least 30 volts or better, 50 volts) and is non-polarized.
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Old 07-01-2008, 08:59   #5
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Same here, a new danfoss bd50 is causing the interference to the SSB radio where the old one didn't cause it.
DeepFrz, your solution assumes that the interference is carries through the DC wiring of the danfoss compressor. Does that mean that the interference gets picked up the the SSB radio via its DC power wires? I was also wondering if the noise the danfoss compressor produces is picked up by SSB antenna via air? I only get it at certain frequencies. Putting the ferrites across the dc cables did not help. I guess that must be because they are there to attenuate ground loops in RF cabling and not DC cables.
Thanks for the suggestion about the cap. We'll try that next.
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Old 07-01-2008, 09:07   #6
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I've gotten interference on a FM transmitter before from a 60Hz battery charger: yes, the interference comes through the 12v lines. One way it can happen is if you don't have good batteries; that was our problem. Batteries tend to absorb a certain amount of line noise. Once we replaced our batteries (which we tested and saw that they couldn't hold a charge), the problem went away.

The 60Hz hum (which is quite low frequency) started showing up in broadcasts, and no one could figure out what it was. Once we determined it to be 60Hz, we knew it was coming from the AC somewhere, and from there it was easy.

Essentially the radio (receiver or txm) is using the 12v to bump the speaker, and oscilates it for the transmission. If there's already a bit of oscilation to the current, that can sneak through. Filters vary by radio; some are more and less effective, depending upon the inbound frequency.
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Old 07-01-2008, 09:39   #7
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Dave,

Ite interference is very likely reaching your radio via the 12v supply. Placing a capacitor in paralell at the compressor AND at the radio may help. Also placing an inductor in series can help. I haven't installed one in years but we used to buy kits with the cap & inductor to be used in mobile installation of HF Ham gear to reduce various noise issues. One in particular I remember was somewhat similar to yours. The 12 motor that ran the windshield wipers caused terrible interference on the gentlemans HF rig.
The above solution resolved the issue.

If you would like to try it, your best source may be a well stocked Ham Radio store such as Ham Radio Outlet or Amateur Radio Supply.
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Old 07-01-2008, 13:12   #8
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Disconnect your antenna lead, if the interference stops its RF interference not power supply
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Old 07-01-2008, 17:49   #9
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If the batteries are somewhat remote from the distribution buss they are less able to absorb the ripple. The radios should have their own mini buss and cable from the batts.

Mike
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