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Old 23-11-2007, 19:52   #1
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Ham Radio Operators, Please Read

I'm looking for some experience in eliminating radiated RF hash from adjacent boats in the marina.

Specifically, I have eliminated or minimized to the extent practicable all conductive noise sources from my boat such that away from the dock, the noise floor on HF is nil. However, upon returning tot he marina, it returns regardless of whether we're plugged in. this leads me to believe it is radiated from adjacent sources (not a genius deduction, I know) but the description of my thought process might be of some help. Having effectively isolated the DC and Rf grounds and installed a large surface area counterpoise, I have gone as far as I can in terms of the installation on my own boat and eliminated all self-inflicted noise sources.

Since I have no clue which is the offending boat(s), I seem to be left with the option of buying or building some noise attenuation filter as a last resort and was wondering if anyone here has any experience in this area which is somewhat unique to typical HF radio home station issues.

Anyone else faced this problem successfully and if so, how?
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Old 23-11-2007, 21:39   #2
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It's a common problem when in a crowded anchorage as well.
I've got an electronic background as well as an Advance HAM ticket, but unfortunately I can't give you much hope.

Finding the offending party and using lots of tact is probably the best solution.
If it's voice they're using, simply turning down the mic gain might do it. If it's digital communications, all I can say is good luck, or move.

Hopefully someone else will have a better answer.

Steve B.
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Old 24-11-2007, 07:51   #3
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I recently was annoyed badly in lower Chesapeake Bay with same problem. I noticed it when an older gent was using his radio two slips down from me. Both of was were transients so, it was temporary for me. I would like to think, the offender isn't aware they are bothersome. Perhaps if you can identify a time pattern of usage, you can move around the marina and identify the individual. Perhaps a note left appraising them, their ssb/ham set may need a tune up would spur them to action? Delicately.
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Old 24-11-2007, 10:32   #4
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Illusion, If I read you correctly, you're not getting interference from other nearby radio operators, but instead are receiving RFI from the electronics and electrical devices in the area of your slip -- is this correct?

If so, there aren't likely to be any filters you can use on your boat, since the interference is relatively low-level, and on the frequencies where you are trying to operate. You have already verified that it isn't coming from your boat, and that it still is a problem even with your own shore-power disconnected, so if there is a next step, it will be to track down the interference source(s).

Can you temporarily park your boat in a different slip? This will let you see if the noise is from an adjacent boat, or if it is coming from farther off.

Is the noise worse on some frequencies? Is there some characteristic to it that might help you identify it (is it a continuous buzz, or is there some pattern to it?).

See if you can hear the noise on a portable AM radio. Tune it to the highest frequency, where there is no station broadcasting, and see if you can hear the same noise that you get on your boat radio. If you can hear the noise, you can use the radio as a direction-finder. Walk around and zero in on the source.

If you can isolate the source, then you get to use diplomacy. If there are many noise-sources, you probably are stuck.

Some examples of interference sources are:
* computers and electronic devices
* electric motors and relays (anything that makes a spark)
* neon signs
* dirty insulators on power lines
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Old 24-11-2007, 15:07   #5
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You may or may not be getting interference on the frequencies you are using. It could be coming in on an intermediate frequency, getting into your gear directly or through power lines (even if you aren't connected to shore power, your DC power lines can act as an antenna to convey energy into your equipment).

You could shotgun the problem by trying to shield your equipment better (make sure metal cases are grounded, use foil to shield plastic cases (including mics), put inductors on power feeds, make sure all connections are clean and secure) or -- if you can borrow a good spectrum analyzer you might be able to track down the high energy signals and then use a directional antenna with the SA to pin down the offenders.

I suspect you will find, given that your own installation is as good as it sounds you have made it, the best solution is to get away from others.

Good luck.
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Old 25-11-2007, 20:07   #6
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Cutting through the crap

Having spent sufficient time working with various RF problems, RF screen rooms and conducted/emitted ratings with calibrated antennas and spectrum analyzers here are a few comments:

1. The vicinity of your boat to other boats automatically reduces your ability to both transmit and receive with good signal-to-noise ratios at each "end".
2. Your received SSB (and/or HAM) noise floor will always be raised when near any/all computers or microprocessor based equipment. This includes all of your own electronics, i.e.; depth sounders, chart plotter, wind instruments, etc. Today I would not design a switch without having a microprocessor embedded in the design and those all add to the noise floor.
3. Even the best shore power or generator driven power supplies used to power your transceiver will raise the noise floor above what you can best measure using battery power alone.
4. Alternators charging your batteries will generate significant noise to the SSB/HAM noise floor for reception. If you want to get the best reception be at sea in a "good" location (Panama is not one of them, for example for shore based US transceivers) and shut everything down that is electronic and even use narrow band audio filters. CW rules in this extreme.
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Old 25-11-2007, 23:18   #7
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First, congratulations on having found/fixed/resolved your RF noise problems aboard your own boat. Not many of us have done this completely, since it can be a truly daunting task on a boat with complex systems aboard.

I've been chasing RFI aboard my own boat and in my marina for years. While I've made some progress, I don't hold out much hope for a full solution.

Marinas are VERY dirty places these days. I built a little RF sniffer device which I attach to a Yaesu FT-817. With this little wand, I can walk around my boat, and around the marina and sniff out RFI sources on different frequencies. What I've found is not very encouraging.

RFI is emitted by many, many devices and systems in a marina. Adjacent boats are a constant source, and one you can seldom do much about. So, too, are AC wiring and digital cables under the docks, wireless devices, anything with a computer, switching devices, battery chargers, inverters, engines, bilge pumps, voltmeters with digital displays, etc., etc.

What's even more insidious is that the RFI is not even across the frequency spectrum. I've got a particular problem on 40 meters, but it goes way down at 8 mHz and above. And, it comes and goes...not constant. And, it varies considerably by location. I can move along the docks or finger piers at my marina and find RFI levels increase or decrease significantly in just a few feet.

Bottom line is that every time I set out to investigate the sources at my marina I get really discouraged. There are so many, and they are not constant. Boats move around, devices go on and off, etc....it's all very maddening.

In my case, at least, I doubt seriously if any type of filtering would help. I can make contacts relatively easy by using my vertical dipoles and contacting a station I can hear above the noise level. But I can't hear most of the stations on some bands because of the high noise level, and thus far haven't been able to beat it in the marina.

Oh, yeah, I forgot....the Metro (train) tunnel runs directly beneath my dock. Wonder if that adds to the general din? :-)

Bill
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Old 04-12-2007, 17:20   #8
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Separate Battery for HF and VHF?

This seems as good a place as any for this post.

A ham buddy with extreme levels of experience and knowledge suggested that I should put all telecommunication use on a separate battery. Sooo... Since I have a little liveaboard cat with two engines/alternators, two solar panels, a wind generator, a 12 volt freezer, a dedicated inverter for a 220 volt inverter, etc., I've been thinking I might use only one of my 6 batteries for starting both engines, and use a separate battery (the bank that used to start the other engine) for my ham, vhf, and stereo equipment.

However, since I'd still need to shut off all energy creators, the inverters, and the 12 volt freezer off to optimize my ability to transmit and hear, what's the difference as to whether I have a dedicated telecommunication battery?
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Old 04-12-2007, 17:30   #9
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Unlerss you are very lucky, there may be no advantage depending on what type noise exists. Simply putm noise can either be conductive or radiated. The former will be reduced by having a dedicated source of power but this type noise occures only when something on your boat is running. Easy to fix with a separate electrical system.
The other type, radiated noise, is ubiquitious ambient noise unrelated to the power source.
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Old 04-12-2007, 17:38   #10
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Quote:
Originally Posted by Sonosailor View Post
This seems as good a place as any for this post.

A ham buddy with extreme levels of experience and knowledge suggested that I should put all telecommunication use on a separate battery. Sooo... Since I have a little liveaboard cat with two engines/alternators, two solar panels, a wind generator, a 12 volt freezer, a dedicated inverter for a 220 volt inverter, etc., I've been thinking I might use only one of my 6 batteries for starting both engines, and use a separate battery (the bank that used to start the other engine) for my ham, vhf, and stereo equipment.

However, since I'd still need to shut off all energy creators, the inverters, and the 12 volt freezer off to optimize my ability to transmit and hear, what's the difference as to whether I have a dedicated telecommunication battery?
I wonder why he thinks that? IMHO, it's not needed or even a good idea!

You don't need to go to all the bother of a dedicated comm battery and you shouldn't need to turn everything off either!

First, do you have a problem? Do you have excessive noise in your SSB receiver when listening? If so, try turning your other systems off one by one and diagnose which one(s) are causing the problem. Then either decide if you're going to filter the heck out of the guilty gadget or just leave it turned off.

Make sure that you've got a dedicated wire of sufficient size going to your breaker from the SSB and then to the battery. SSBs can draw a LOT of amps on transmit.

We've been using our SSB (Icom 710 RT) since 2001 on board without a dedicated battery - no problems - and we have one of the best signals in the fleet (but that's another story).

Regards,
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Old 04-12-2007, 18:54   #11
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When communications are difficult

Some HAM SSB transceivers have built-in ac/dc adapters to power the units using inverters, gen-sets or shore power. This convenience does not require, therefore, very short connections between a battery and the transceiver (still need short connections between the inverter and it battery). The downside is that all of these internal converters raise the recieve noise floor and slightly reduce the S/N ratio measureably.

Long has it been recognized that the best performance is realized by high battery voltage. This is why AGM batteries mounted electrically "close" to the transceiver offer the best chance of having internal voltage rails that give the best performance (AGM/GEL-cell batteries have higher terminal voltage under load than do flooded-cell batteries). Long has it been recognized that, in general, circuit breakers have a higher voltage drop than equivalent current-rated fuses and, therefore, if you begrudge and nit-pick every loss you will use fused and not circuit breakers. In fact, you will use one and only one fuse and no other breakers in the circuit between the battery and the transceiver. Get rid of those ICOM in-line power fuses and use only one fuse located close to the battery positive where it belongs. If you design the system properly you will not have nuisance blowing of that fuse. Overall this delivers the best S/N ratio along with the best transceiver efficiency.
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Old 04-12-2007, 18:58   #12
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You could start by pulling dock cords to see which boats are making the noise. Just kidding.
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Old 04-12-2007, 19:16   #13
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Rick -

One should have a Marine SSB (with HAM capabilities) on a cruising boat and not a HAM rig. The Marine SSBs I've seen are all powered by ships DC and don't have the AC power supplies you discussed.

Yes, Circuit Breakers do have a slightly greater voltage drop, but it's not enough to matter in any installation I've seen.

The radios I've looked at are all happy with a voltage over 11.75 VDC at the radio. They're even happier over 12 VDC.

David M -

The best way to make sure it's only your noise is to go anchor out and then do the testing.

Cheers,
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Old 04-12-2007, 19:24   #14
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HAM AND marine SSB radios

Actually there are good arguments for having BOTH a commercial SSB along with a HAM SSB rig. Many commercial rigs can be powered by a separate converter Like the IC PS-30 which will power both a HAM rig along with a commercial rig.

No rig is "happy" with any particular input terminal volgage. They are merely more or less efficient, if functional at all, and have more or less S/N ratios for particular operating parameters.

The difference in efficiency when using fuses versus circuit breakers will be observed using commercial rigs that have fixed PEP input power settings and strong modulation input levels and, therefore, you might not notice it when using HAM rigs set to minimum power levels that facilitate communication. Many installations have a battery, a fuse feeding a power panel, a main breaker, another branch breaker for the SSB and then a fuse in the SSB feed line. Add all of the internconnect resistances (terminal to terminal), wire resistance, breaker and fuse voltage drops and any other parasitic losses and you have a real loss in efficiency along with reliability.
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Old 04-12-2007, 19:26   #15
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Rick -

David M -

The best way to make sure it's only your noise is to go anchor out and then do the testing.

Cheers,
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Pulling dock cords was just an idea...for about two seconds.
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