I just finished installing an SSB on my boat. When I turn on my freezer
I get noise on the radio that sounds like morse code. The freezer has a
Danfoss BD50 compressor with a digital thermostat. Has anyone else had
this problem. I think I remember Gordon West writing about this problem
in one of the sailing mags. but can't remember which one or when.
krj

"krj" wrote in message
...
I just finished installing an SSB on my boat. When I turn on my freezer I
get noise on the radio that sounds like morse code. The freezer has a
Danfoss BD50 compressor with a digital thermostat. Has anyone else had this
problem. I think I remember Gordon West writing about this problem in one
of the sailing mags. but can't remember which one or when.
krj

krj wrote:
I just finished installing an SSB on my boat. When I turn on my freezer
I get noise on the radio that sounds like morse code. The freezer has a
Danfoss BD50 compressor with a digital thermostat. Has anyone else had
this problem. I think I remember Gordon West writing about this problem
in one of the sailing mags. but can't remember which one or when.

Sail magazine, June 2005.

Gordon West recommended:

1. Wrap compressor and controller in copper foil and ground the foil to
the compressor's metal mounting legs;
2. Install ferrite chokes on the control wires coming out of the
controller, as close as possible to the plastic controller box; and
3. Wrap controller box with copper screen from a hardware store.

Cheers

wrote:
krj wrote:
I just finished installing an SSB on my boat. When I turn on my freezer
I get noise on the radio that sounds like morse code. The freezer has a
Danfoss BD50 compressor with a digital thermostat. Has anyone else had
this problem. I think I remember Gordon West writing about this problem
in one of the sailing mags. but can't remember which one or when.

Sail magazine, June 2005.

Oops! It was the July issue, 2005, not June.

Cheers

Bil

wrote:
krj wrote:
I just finished installing an SSB on my boat. When I turn on my freezer
I get noise on the radio that sounds like morse code. The freezer has a
Danfoss BD50 compressor with a digital thermostat. Has anyone else had
this problem. I think I remember Gordon West writing about this problem
in one of the sailing mags. but can't remember which one or when.

Sail magazine, June 2005.

Gordon West recommended:

1. Wrap compressor and controller in copper foil and ground the foil to
the compressor's metal mounting legs;
2. Install ferrite chokes on the control wires coming out of the
controller, as close as possible to the plastic controller box; and
3. Wrap controller box with copper screen from a hardware store.

Cheers

Thanks for the info. I guess I'll go get some copper screen and try it.
krj

krj wrote:
I just finished installing an SSB on my boat. When I turn on my freezer
I get noise on the radio that sounds like morse code. The freezer has a
Danfoss BD50 compressor with a digital thermostat. Has anyone else had
this problem. I think I remember Gordon West writing about this problem
in one of the sailing mags. but can't remember which one or when.
krj

I'm not familiar with the Gordon West article, but the following may help.

Digital thermostats often use microcontrollers capable of generating RF
interference. That is more likely the problem than the compressor itself.

The interference can be transmitted to the SSB either by radiation, in
which case the SSB is picking it up via its antenna, or by conduction
through the 12 VDC wiring.

To test the former possibility, radiation, simply remove the coax
connector from the SSB and carefully short the center conductor on the
SSB to the grounded outer conductor. Use as short a wire as possible and
try not to touch it. There is no risk whatever to the SSB or to you. The
idea is that your body not serve as an "antenna". Next, listen for
freezer noise on the SSB. If it is gone or even reduced significantly,
then a good portion of the noise is being radiated. Short of providing
RF shielding of the freezer electronics (which may be quite a task) your
best option may be to contact the manufacturer. These units are often
constructed with explicit RFI reduction circuits/components, which could
be defective in your unit.

If the noise is not being radiated, then it is being conducted via the
12 volt wiring. Bypass capacitors at the 12 volt connections to the
freezer (right at the unit itself) may cure the problem. Chokes and RF
filters could also be added to the SSB 12 volt line, although they would
have to be able to handle the current drawn by the SSB during transmit:
20- 30 amps.

There is a lot of useful info on the web, but it is important to know
how the interference is reaching the SSB. Meanwhile, maybe someone will
remember the Gordon West article.

Good luck.

Chuck

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This has been discussed on Rparts forum a couple of times. The power unit
of the BD series of compressors is a variable frequency inverter and is
notorious for creating RF noise. Danfoss makes an aluminum shielded model
but they are hard to find and don't help with conducted noise. The digital
thermostat is not normally a source.

Some things that will help are ferrite chokes on all wires going to the
power unit to reduce conducted noise. You may have to experiment with the
size to cut the frequencies that you need. Also lining the compressor
locker with metal screening tied to ground reduces radiated noise.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"krj" wrote in message
...
I just finished installing an SSB on my boat. When I turn on my freezer I
get noise on the radio that sounds like morse code. The freezer has a
Danfoss BD50 compressor with a digital thermostat. Has anyone else had this
problem. I think I remember Gordon West writing about this problem in one
of the sailing mags. but can't remember which one or when.
krj

Glenn Ashmore wrote:
This has been discussed on Rparts forum a couple of times. The power unit
of the BD series of compressors is a variable frequency inverter and is
notorious for creating RF noise. Danfoss makes an aluminum shielded model
but they are hard to find and don't help with conducted noise. The digital
thermostat is not normally a source.

Some things that will help are ferrite chokes on all wires going to the
power unit to reduce conducted noise. You may have to experiment with the
size to cut the frequencies that you need. Also lining the compressor
locker with metal screening tied to ground reduces radiated noise.

Glenn,
You are right. It is not the digital thermostat. I disconnected the
thermostat leads from the compressor module and put a jumper between the
terminals to turn on the compressor. The noise is still there. It is
being radiated. I have clamp on ferrites on all the wires to the
thermostat, power leads, etc. Any idea where to purchase the shielded
module. The local marine refrigeration shop didn't seem to know anything
about it.
krj

There are 4 different electronic modules for the BD series.:
You probably have the standard 101N0210 single speed with the plastic box.
The Danfoss part number for the single speed shielded module is 101N0220.
The 101N0300 is the AEO variable speed with plastic box and the 101N500 is
AEO with shield.

The AEO future saves a bunch of amp hours by adjusting compressor speed to
the load but the single speed models can be hooked to the Frigoboat SSC and
get the same optimization with a slightly better algorithm. They both work
on the principle that the system is most efficient when it runs for long
cycles at the lowest speed but the SSC has an override to run at full speed
for chill down.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"krj" wrote in message
...
Glenn Ashmore wrote:
This has been discussed on Rparts forum a couple of times. The power
unit of the BD series of compressors is a variable frequency inverter and
is notorious for creating RF noise. Danfoss makes an aluminum shielded
model but they are hard to find and don't help with conducted noise. The
digital thermostat is not normally a source.

Some things that will help are ferrite chokes on all wires going to the
power unit to reduce conducted noise. You may have to experiment with
the size to cut the frequencies that you need. Also lining the
compressor locker with metal screening tied to ground reduces radiated
noise.

Glenn,
You are right. It is not the digital thermostat. I disconnected the
thermostat leads from the compressor module and put a jumper between the
terminals to turn on the compressor. The noise is still there. It is being
radiated. I have clamp on ferrites on all the wires to the thermostat,
power leads, etc. Any idea where to purchase the shielded module. The
local marine refrigeration shop didn't seem to know anything about it.
krj

Glenn Ashmore wrote:
There are 4 different electronic modules for the BD series.:
You probably have the standard 101N0210 single speed with the plastic box.
The Danfoss part number for the single speed shielded module is 101N0220.
The 101N0300 is the AEO variable speed with plastic box and the 101N500 is
AEO with shield.

The AEO future saves a bunch of amp hours by adjusting compressor speed to
the load but the single speed models can be hooked to the Frigoboat SSC and
get the same optimization with a slightly better algorithm. They both work
on the principle that the system is most efficient when it runs for long
cycles at the lowest speed but the SSC has an override to run at full speed
for chill down.

Glenn,
Yes, I checked the module and it is the 101N0210. I guess the next task
is to find someone in Ft. Lauderdale who can get the 101N220 module.
Hope it isn't a BOATbuc to get a shielded moudle. You sure changing the
module will solve the problem?
krj