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Hey guys, I'm helping a buddy remount a bunch of stuff on the arch of his fishing boat. Is there any problem that you all are aware of with running the GPS feed cable down the tube (2") with a few 12v leads for navigation lights, spotlights, etc.? Thanks. Jeff
If the boat has radar you have to keep the antenna out of the beam of the radar.
No radar, thanks for the input Tinkerer.
Well, I've been searching and reading. The consensus is; Maybe
This one seems to be the most informative. But, some of the others on the net almost all have two conclusions. A bad ground wire anywhere in the boat is usually the biggest culprit to a faulty GPS. ANd, they can be intermittent if the ground issue is with something that is not continuously on, such as a bilge pump or VHF radio, etc.
http://www.fishingandboats.com/gps-product.html
Here is part one:
GPS-product RFI Problem Solving Starts Here
TROUBLESHOOTING RFI on your GPS-product
If you want to understand troubleshooting the problem of RFI on your electronics, marine-radios and GPS-product then you have to understand the causes.
The average boat has several RFI noise sources often found on your gps-unit, gps-receiver, gps-navigation-system and radios-marine.
These noises are often classified as Radio Frequency Interference (RFI) or Electromagnetic Interference (EMI). They are am insidious enemy of communications and electronics systems.
It corrupts the GPS position fixes, makes a mess of your communications and generally causes electronics performance degradation. Solve noise and interference on your GPS-product, GPS-unit and save on radio-repair costs.
WHAT IS RFI?
Essentially RFI is interference and noise that is superimposed as a disturbance or a voltage transient either on the equipment such as the radios or even the whole boat electrical power supply, or on the data and signal lines that carry your GPS or navigation data between each other. This noise is then processed along with all of the good data, which then corrupts or degrades the processed information. Solve noise and interference on your GPS-product, GPS-unit and save on radio-repair costs.
THE VOLTAGE TRANSIENT
The voltage transient is probably the most damaging and has it’s source in many locations. Probably the best known effect is the corruption of your GPS and LORAN position data where the equipment power is taken off an engine starting battery.
What happens is that when a significant load is applied to the battery, such as starting the engine, a momentary voltage drop is created and what is often called a brown out condition occurs. This is then followed by a sharp voltage increase. This under-voltage disturbance can exceed 100 volts in some cases, which is very damaging to the equipment power supplies, and causes wiping of the memories or corruption of the data.
The same problem also applies to dual battery systems where the house bank supplies power to items such as the electric toilets and other large current equipment such as a windlass. The starting battery voltage can experience a 3 to 4 volt dip on a motor starting.
Transients are also caused by the variation or interruption of current in the equipment power conductor. Solve noise and interference on your GPS-product, GPS-unit, gps-unit, gps-receiver, gps-navigation-system, weather-radio and save on radio-repair costs.
WHAT IS INDUCED INTERFERENCE
The second common RFI noise source is called induced interference. Electrical fields are radiated from all cables and equipment. This can be induced into other closely located cables or equipment such as radios or GPS or depth sounder. The most common cause of this is where cables running parallel or within the same cable bundle, and this is also called mutual coupling.
Always make sure they are installed so that are laid so that power supply cables and data cables are kept separate and make any cable crossovers at 90º. Always install power cables to any sensitive equipment completely separate to the main power cables so as to reduce inductive and capacitive coupling to the data and signal conductors. Solve noise and interference on your GPS-product, GPS-unit and save on radio-repair costs.
Part 2 of this 3 Part Series on RFI and Interference problem solving on your GPS and radios. Click on this link to find out more about. Part 2 RFI and all
Part Two:
WHERE DOES INTERFERENCE ON YOUR GPS-UNIT COME FROM
RFI noise occurs in a range of frequencies. In fact equipment may only be prone to problems within a specific frequency range. In many cases you will have multiple noise sources that overlay each other.
This will result in a gradual degradation of the electronics components and when the cumulative effects reach a critical point the devices will subsequently fail. Solve noise and interference on your GPS-product, GPS-unit, gps-receiver, gps-navigation-system, weather-radio and save on radio-repair costs.
WHAT IS ARCING NOISE?
These are repetitive spikes that are caused by electric motor commutators and the sparking of brushes. For example the brushes on an alternator, particularly if dirty can cause this sparking and radio noise. This is common in charging systems where loose connections may exist. The most common cause is usually loose or poor engine return paths for alternators, when the negative path arcs across points of poor electrical contact. It pays to regularly check and tighten your negative terminals.
Another cause is that of noise on ignition systems from distributors and spark plugs being impressed onto a DC system, and frequently this is through radiation any adjacent cables. When troubleshooting the first step is always to determine what is operating at the time. Solve noise and interference on your GPS-product, GPS-unit and save on radio-repair costs.
WHAT IS UNDUCED COUPLING INTERFERENCE?
Electrical wires that are installed in parallel with other wires can suffer from what is termed inductive coupling interference. The symptom is buzzes and humming sounds on the radios-marine. This happens due to a transformer effect with a single turn primary and secondary coil, with the magnetic effects creating the induction.
Low ground impedances and unbalanced circuits are the greatest source of problems with serial data, multi-cable control and co-axial cables being the most susceptible to noise. Again the best measure is to keep all signal cables installed separately so you don’t have parallel runs with the main power wiring.
The first step in troubleshooting RFI is to determine what equipment is operating at the time as this will directly affect the cables involved and will aid in fault localization. Solve noise and interference on your GPS-product, GPS-unit and save on radio-repair costs.
WHAT IS RIPPLE NOISE?
Ripple is an affect created in rectifier bridges (such as the diode or SCR bridge). These are found in charging alternators, battery chargers, fluorescent lights and AC inverters. It usually presents as a high-pitched whine sound on radios-marine. Most good quality equipment will have suppressed electronics. Ripple will cause severe communications audio quality degradation on radios. As before always determine which lights are operating, whether charger is on, and whether the engine is running. It is often a sign that an alternator diode has blown. Solve noise and interference on your GPS-product, GPS-unit and save on radio-repair costs.
WHAT ARE STATIC CHARGES?
Static charges have several sources. External charge interference appears usually due to static build-ups in sailboat rigging. The static charge will attain a certain voltage level, before it discharges to ground which causes the interference on radios. Another very common source is when dry offshore winds occur, and this causes a high net static charge to build up on GRP deck surfaces. This problem is more prevalent on larger GRP vessels such as catamarans with relatively large deck surface areas.
A lightning protection system does serve this purpose well and can ground out these static charges. The engine and propeller shaft can also accumulate charges when rotating, and interference is caused when the accumulated charges ground out. These charges arise due to static build-ups, both induced and due to the interaction of moving parts within the engine. The static charge will discharge to ground when it gets high enough and will also cause RFI interference. Solve noise and interference on your GPS-product, GPS-unit and save on radio-repair costs.
WHAT IS SURGE? (Electromagnetic Pulse)
This interference is caused by local lightning activity. The pulses are generally induced into electrical wiring supplying your gps-unit, gps-receiver, gps-navigation-system, weather-radio and radios-marine or other aerials.
WHAT IS A SPIKE?
A common cause is the turn-on spike which results from the initial charging of power supply input filters on power supplies. Turn-off spikes happen when reactive loads are switched, and the magnetic fields collapse on inductive loads. These are usually on transformers, relay or contactor coils, solenoid coils, pump motors etc. A common suppression method is the use of MOV suppressors which are connected across the coils. Solve noise and interference on your GPS-product, GPS-unit and save on radio-repair costs.
ABOUT SOLAR ACTIVITY
This source is from activity and changes within the ionosphere and solar or sun spot activity. The main result is signal losses or major data corruption. A good basic check is to verify that there is no current major activity. Solve noise and interference on your GPS-product, GPS-unit and save on radio-repair costs.
Part 3 of this 3 Part Series on RFI and Interference problem solving on your GPS and radios. Click on this link to find out more about. Part 3 RFI and Interference and all you need to know.
And Part Three:
HOW TO START TROUBLESHOOTING RFI PROBLEMS
Before you thing radio-repair first look at the source of all this RFI and you can start troubleshooting the source of the RFI on your gps-unit, gps-receiver, gps-navigation-system and weather-radio. This is actually a relatively simple method of locating the troublesome noise source. It is really a matter of logic and the use of systematic sequence of switching off of each item of equipment to locate the noise source.
When the noise stops the cause is generally located. While it is a simple process of elimination, it isn’t always so easy. Most cases will involve the identification of two or more noise sources that are overlaid to create a cumulative noise effect. A proportion of RFI noise will be intermittent, and this includes static discharges and lightning pulses, which will not be easy to identify. Solve noise and interference on your GPS-product, GPS-unit and save on radio-repair costs.
WHAT RF DETECTION TOOLS ARE REQUIRED?
The best is a cheap and small battery powered AM radio. This is a great little tool for tracking down and sniffing out those radiated sources on the boat causing troubles on your gps-unit, gps-receiver, gps-navigation-system and weather-radio. When the radio is passed close to the cables or equipment the radio will detect the noise.
Some noise is simply related to time of day. Remember that interference from solar activity and ionosphere factors on radios is one source that must always be factored in. These sources will also affect your GPS, SSB, HAM and radios-marine and satellite communications all simultaneously, leading to a conclusion of a greater problem. As this usually occurs around dusk you may already have the answer. Wait until later and try your radios again. Solve noise and interference on your GPS-product, GPS-unit and save on radio-repair costs.
The first step in troubleshooting problems on your on your gps-unit, gps-receiver, gps-navigation-system and weather-radio is the disconnection of the antenna. If the noise continues then the noise is probably caused by the electrical system.
If the RFI tends to increase when the GPS or radios-marine aerials are reconnected, the cause may then be atmospheric or from some other emission source that is being picked up through the antenna feed cables. It is important to remind you that RFI may be coming from more than one source or path, so investigate all possibilities. Solve noise and interference on your GPS-product, GPS-unit and save on radio-repair costs.
Why is there a ticking sound on the radio
If the noise on your on your gps-unit, gps-receiver, gps-navigation-system, ssb-radio or vhf-radio presents as a ticking noise that seems to vary with the speed of the engine, then you are probably picking up ignition noise or it is from the alternator. In practice this would usually affect the power wire to the equipment.
The most common sources for this noise are usually the distributor, ignition coil, spark plug wires and the spark plugs. If the ignition noise is identified, relocate the power wire as far as practicable away from any of these sources. If things don’t improve then a check will have to carried out on all of these components. It is prudent to verify that the spark plug wires and the spark plugs are RFI shielded. Solve noise and interference on your GPS-product, GPS-unit and save on radio-repair costs.
Which noise suppression method is best?
There are several methods available that can be utilized to reduce or eliminate RFI interference on your gps-unit, gps-receiver, gps-navigation-system and weather-radio. The first is the use of shielded cables along with proper grounding.
In many cases suppressors such as a filter or capacitor connected close to the noise causing equipment is common. This effectively short circuits noise in the protected frequency range. Suppression filters can be in several types and suppressor capacitors are often required on alternators. Solve noise and interference on your GPS-product, GPS-unit, on your gps-unit, gps-receiver, gps-navigation-system, weather-radio and save on radio-repair costs.
ABOUT GROUNDING AND RFI
If you want optimum electronics performance then grounding must be carried our properly. It is a fact that the majority of RFI problems that include the noises, hums, buzzes, interference or cross talk on your on your gps-unit, gps-receiver, gps-navigation-system and radios-marine are often caused by bad grounding practices.
When a difference in voltage is created between the 2 different ground points, this will cause current flow and therefore problems. These currents that flow through the different grounds are called ground loops. Solve noise and interference on your GPS-product, GPS-unit and save on radio-repair costs.
The ground in any GPS and radios-marine electronics system is the reference voltage point for all signals and is nominally equal to 0 Volts. To prevent ground loops from arising, all of the signal grounds should be connected to one single common ground point. Cable shields are generally designed to protect against interference from unknown or unspecified sources. Solve noise and interference on your GPS-product, GPS-unit and save on radio-repair costs.
The effectiveness of cable shields is measured in terms of transfer impedance. This is a measure of effectiveness in capturing the interference field and preventing it from reaching the conductor pairs inside, in other words its protection efficiency.
Signal and data cables also have shields that are made from foil/polymer laminate tapes or they have layers of copper braiding. These may also have a drain wire installed to facilitate the termination of the screen to ground. In general the majority of equipment manufacturers will nominate the termination of shields to ground. Solve noise and interference on your GPS-product, GPS-unit and save on radio-repair costs.
A simple rule, never ground the cable screen at both ends, only ground at one end. Typically this is usually nominated as the equipment end. It is actually very common to find that cable shields are not connected at all. Always check and connect them, as it may be a source of your elusive RFI. Solve noise and interference on your GPS-product, GPS-unit and save on radio-repair costs.
Thanks Paul, I really appreciate that. There is a TON of info there.
Jeff
I really hate it when someone asks a question that makes really good common sense, and I have zero clue what the answer is......:mad:
I'm still not positive the complete answer has been found. But, I have some calls in to someone who should know. Not sure where in the world he is right now, but we'll see one of these days......
muchas gracias mi amigo
Garmin says no. But, they also say run it and test with all the other items being on/off to check for interference before permanent mount.
Still looking........
http://www8.garmin.com/manuals/GPS17...ationGuide.pdf
I see the most important info on this project listed in the Garmin brochure, to wit - keep the GPS receiver dome 3' away from the VHF antenna. Thanks Paul.