VHF radio affected by the on board fridge

[hd002e]

Hi there,

I have a Uniden UM380 radio that is wired through a blue sea systems breaker panel to the house battery (very typical install). I also have a 12V fridge, (simliar to the dometic) wired through a completely different circuitry directly to the battery. Whenever the compressor turns on, I can hear a lot of static on the radio even when the radio is OFF. How can I isolate the radio such that it does not get affected?

Than you!

[donradcliffe]

What happens if you turn the VHF circuit breaker off ?

[continuouswave]

Originally Posted by hd002e

...I can hear a lot of static on the radio even when the radio is OFF.

If the radio is OFF as in OFF meaning there is no power applied to the radio, it will be extraordinarily unlikely that the speaker in the radio could produce an aural output from being electrically excited by the amplifier in the radio.

The only possible cause for a speaker to produce aural output without an electrical signal being applied to the speaker voice coil might be from the speaker being in a very strong magnetic field as might result from being very close to a powerful source of a magnetic field. Perhaps there is a powerful motor in the refrigerator that generates a magnetic field and affects the speaker. If the speaker is remote from the radio, the cable connecting the speaker to the radio might be picking up a stray electrical field and inducing a signal into the speaker.

Re "static" and radio reception: static is generally considered to be an atmospheric radio noise signal resulting from thunderstorms and lightning, which produces an amplitude modulated signal. VHF Marine Band radios are FM receivers and are generally immune to amplitude modulated signals.

FM receivers generally state their immunity to demodulation of an amplitude modulated signal in their specifications.

The noise you hear from an FM receiver when the squelch is open and there is no signal is just the thermal electrical noise in the receiver's own circuitry. It is not atmospheric noise from a thunderstorm.

[continuouswave]

Also re "static": at VHF frequencies the propagation of atmospheric noise from thunderstorms is limited to the local region, depending on the height of the thunderstorms and lightning, while on HF atmosphere noise signals can propagate from a 1,000-miles away. Thus on VHF frequencies if there is no thunderstorm activity in your region, there generally won't be any atmospheric noise or static being produced. This is one of the principal advantages of VHF FM communication over HF AM communication.

[a64pilot]

I am going to guess that you may have a powered amplified speaker and it’s not off even when the radio is.
I can’t imagine an unpowered speaker making a noise from electrical interference

[donradcliffe]

While I agree with most of what was said, the Domitec units use BD35 or BD50 compressors, which have a brushless motor driven by an inverter. These inverters are notorious for putting a whine on the DC buss. The Uniden transceiver may not be OFF when the switch is off, which is why I asked the OP to turn off the VHF breaker and listen again.

[markcouz]

Google "ferrite bead".

Install on both ends of fridge supply and both ends of VHF supply.

[Reefmagnet]

Uniden radios (well, that model at least) will make noises even when turned off by using the volume/off control. You need to actually switch the power supply to them off to stop them making noises.