VHF transmit interference

[olegreg]

My VFH radios transmit a AC hum which makes it hard to hear me. I have 2 sets with their own antennas. Even my handheld. Tracked it down the house charger/inverter. It is a Xantrex modified sine and I have been told this is my issue. I have Link 2000 R and a Pathmaker with 2 alternators on one engine. It all works very well. I would rather not replace it with a pure sine unit.
Anybody have any success with attenuation of the hum? I want to do it at the source.

 

[meridian]

I would check to see if the Xantrex is grounded properly.

 

[psneeld]

The radios too.

Often they sre not an issue, but cant hurt as it is recommended Often not done at install.

There are filters available, took one off my boat that was there for the old LORAN unit.

Guess the alternator interfered with it.

 

[olegreg]

Grounds good,
Thanks

 

[diver dave]

HIghly unlikely 3 radios are transmitting hum on the signal, especially the HH. Please describe the test condition.
I do believe the non-sine invertor is a noisy device, electronically speaking, however.

"Non-sine" or "Modified sine" means there are many frequencies being generated beyond 60Hz, which is not an advantage to any comm device.

 

[olegreg]

Dave,
The hum was first reported to me from a dock master when we requesting berth assignment. Other guys just said I was hard to hear. He described is as an AC hum. So, later I started tracking it down by shutting down systems and devices. When it got to the inverter/charger, it went away on the main radio and it's remote. The dock master stood on the dock and reported what he heard. We repeated this with the main, remote and back up set. I had my HH listening too. Just for kicks I transmitted on HH and he heard the hum also, but a lot fainter.
Happened to discuss this with a marine systems guy, and he mentioned that the Xantrex modified sine unit with its squared waves and harmoncs is well known for this. Xantrex now offers a pure sine unit that will be a drop in. I can keep the Link 2000 and network including the Pathmaker.
Expensive solution. For now through the rest of our cruise in BC inside passage, I will shut down the charger before I transmit.
BR,
Greg

 

[High Wire]

Long shot but check your battery electrolyte levels. Twice I've found this to solve the problem when there was no problem then was with no other system changes.

 

[olegreg]

Just added water several days ago.
Thanks

 

[olegreg]

BTW,
The chopped up wave fried my new Keuric, had a fan smoke on another boat. Inductive loads do not like square wave.

 

[koliver]

Is yours the Xantrex MS2000?
I use that unit. I have never had any radio interference. I use only one radio, a Standard Horizon mounted at the lower helm, with a Remote Mike (RAM) mounted up top. More likely it is your radios fighting each other.

 

[diver dave]

Dave,
When it got to the inverter/charger, it went away on the main radio and it's remote. The dock master stood on the dock and reported what he heard. We repeated this with the main, remote and back up set. I had my HH listening too. Just for kicks I transmitted on HH and he heard the hum also, but a lot fainter.
Happened to discuss this with a marine systems guy, and he mentioned that the Xantrex modified sine unit with its squared waves and harmoncs is well known for this. Xantrex now offers a pure sine unit that will be a drop in. I can keep the Link 2000 and network including the Pathmaker.
Expensive solution. For now through the rest of our cruise in BC inside passage, I will shut down the charger before I transmit.
BR,
Greg

Wow; this is one evil charger. If you were closer, I'd like to investigate this one. I do EMC stuff at work and have a pretty extensive radio background.
As a general rule, if you can listen to your transmit audio on another radio, and the mic is quiet, you should not hear anything. (transmit hum and noise spec).

Is the Xantrex in invertor mode or charger mode?

 

[olegreg]

Keith,
MS2000 is a true wave, mine is the Freedom modified wave.
I use only one radio, Raymarine Ray/70 with a remote Ray Mic . The Standard Horizon is a backup unit sharing it's antenna with the AIS transponder through an A/B switch.

 

[olegreg]

Dave,
Charger mode.

 

[diver dave]

CHarger hum. It might be possible for you to measure this offensive signal on your DC bus with a DMM in AC mode. THis is why a previous posted mentioned adding water to his house battery. If the plates were not covered, and then you added water, it would lower the impedance of the battery and tend to reduce this noise voltage.
Even better to use what I have, a self powered digital oscilloscope.

 

[rwidman]

If the interference is when the unit is operating as a charger (connected to shore power), we can forget about all the "modified sine wave stuff".

Battery chargers are notorious for creating RF interference but it's rare to transmit on a VHF radio when plugged into shore power and charging the batteries.

RF Interference can be transmitted two ways, through the air like a small radio station or through the AC or DC power system. If it's being transmitted through the air, it might interfere with receiving devices like your VHF reception or AN/FM reception but your VHF won't retransmit it.

So - if everything you have posted is accurate, the interference is being carried on your DC power circuit and is entering the VHF through the power leads and is being retransmitted by the VHF.

So - You need to filter the DC leads as close to the charger as possible. You need to keep everything but DC voltage off the leads. A capacitor across the leads is a pretty basic filter and will short the interference from one lead to the other. This may solve your problem or you may need a more sophisticated filter with one or more capacitors and an inductor.

I suggest going to a place that installs high end car stereos and talking to them about filters. Keep in mind that this filter must pass 40 amps or more of DC current so a small, cheap filter may burn out.

BTW: One of the best ways for someone who doesn't want to buy expensive equipment to trace RF interference is to buy an "old time" hand held transistor radio. Tune it between stations and move it around until the static increases dramatically. That's where the RF is coming from.

 

[psneeld]

Might try one of these...they come in different amp capacities...what I took off between my alternator and batteries years ago.

Newmar 150-A Alternator Line Noise Filter 150 Amp

Attenuates conducted line noise generated by alternators, ignition systems and motors. This interference takes the form of popping or static on radios or audio gear and can render a vehicle or radio or other electronic equipment useless.

powerwerx.com

 

[diver dave]

If the interference is when the unit is operating as a charger (connected to shore power), we can forget about all the "modified sine wave stuff".

Battery chargers are notorious for creating RF interference but it's rare to transmit on a VHF radio when plugged into shore power and charging the batteries.

RF Interference can be transmitted two ways, through the air like a small radio station or through the AC or DC power system. If it's being transmitted through the air, it might interfere with receiving devices like your VHF reception or AN/FM reception but your VHF won't retransmit it.

So - if everything you have posted is accurate, the interference is being carried on your DC power circuit and is entering the VHF through the power leads and is being retransmitted by the VHF.

So - You need to filter the DC leads as close to the charger as possible. You need to keep everything but DC voltage off the leads. A capacitor across the leads is a pretty basic filter and will short the interference from one lead to the other. This may solve your problem or you may need a more sophisticated filter with one or more capacitors and an inductor.

I suggest going to a place that installs high end car stereos and talking to them about filters. Keep in mind that this filter must pass 40 amps or more of DC current so a small, cheap filter may burn out.

BTW: One of the best ways for someone who doesn't want to buy expensive equipment to trace RF interference is to buy an "old time" hand held transistor radio. Tune it between stations and move it around until the static increases dramatically. That's where the RF is coming from.

agreed. And, I have a 1963 Zenith pocket AM radio for jobs like this.

 

[olegreg]

Dave,
Yeah,
.009 vac on the DC with charger off.
.115 with it on.
Wes,
This is definitely a 60/120 hz hum being transmitted .
I am am going to add a LC filter when I get back from our cruise. Kinda hard to find 40 amp chokes up here on the BC islands.
But in the end, I will change out the inverter /charger as there is no way to get around the fact that it is taking out appliances with inductive loads

 

[diver dave]

Wow, small world. I've been working on a device causing BC Hydro problems in substations. LIke, 90 seconds ago!

 

[olegreg]

Curious,
I used to work in that world before I retired.
Can you elaborate?

 

[diver dave]

I design electronic monitoring equipment for power gen and substations. Hydro, nuke, on the gen side. Some travel.
Taking data and setting alarms for large circuit breakers, transformers, and bushings. Control room annunciator/alarming systems esp nuke sites.
Before that, hand held radio engineer. Public safety and military. VHF, UHF, 800 MHz.
Rolled out a huge project for USMC for battlefield radios in '07. Interesting travel.

 

[VA7YQQ]

If you are in the Campbell River area there are a couple of good radio shops in town. Large fishing fleet with radios have to be serviced.

 

[olegreg]

Been out of coverage...
Not to change the thread but I used to spend a fair amount of time in the Hydro Generation dams on the Columbia and Snake when I reped ABB motors and controls.

 

[olegreg]

Been there, done that
Tried to find parts for a low pass LC filter