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SSB and RF problems with Autopilot


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SSB and RF problems with Autopilot.

This is a bit technical, and I have asked Advanced Trident and Navico in Norway for help, currently awaiting responses. Here is an outline to the problem;

 

I have an AP26 unit with an AC20, RF300 and rate compass. It works very well except when transmitting on the SSB. This has not been an issue normally, as I just have someone steer while we are transmitting. However, I am competing in the 2010 Fitzroy Yachts Solo Tasman race, and I need this sorted for that, as there is no one “else”!

 

There is an RF problem when transmitting that causes the rudder angle indicator to give false readings. The rudder is not moving, but the display says it is, and if active (Steering to compass, wind, or Nav) the AP will try to compensate for the “movement “ of the rudder.

 

I have done fairly extensive testing to isolate it as follows;

1. Connected transmitter directly to shielded dummy load. Problem gone!

2. Connect dummy load to ATU output. No problem

 

These two results indicate that the source of the RF is the antenna connection or the antenna The radio and Tuner provide no RF issues. So then;

 

1. Replaced Tuner to antenna cable with a shielded cable. No change, prob still there.

2. Substituted a whip antenna (normally use backstay). No Change, prob still there.

3. Tried RF bypass capacitors in the RF300 Cable, + to -, + to Shield, and – to Shield. No change, prob still there.

4. Tried relocating cables and moving the RF300 into the fwd cabin and other places. No change, prob still there.

5. Std RF suppression on all power cables to AC20, again no change

 

I have not been able to establish if the RF issue is coming from the rf300 or is induced into the AC20 directly. Is it possible to use a resistor or other as a dummy RF ? If so, what other steps can I take to remove this issue?

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Great work so far IT. You covered all the basics.

One question, what is the AC20? is that the control head unit?

 

1. Replaced Tuner to antenna cable with a shielded cable.

Is the antenna cable the backstay only? or is there any length of unshielded cable running inside the boat? The shielded cable needs to run all the way to the backstay and the shield must be connected at the ATU end only. Do not earth the shield at the backstay.

 

What is most likely happening is an RF signal is being induced into the Rudder Reference unit cable. This signal is a voltage that then adds/subtracts the voltage being sent to and recieved back from the Reference unit at the CPU.

I expect you may have already tried, cause you have covered most things already. But the first question is where is that cable run? Does it run anywhere near the antenna cable. Next thing to check is whether that cable is a coax or "shielded" cable. You may need to run a new shielded cable. The shield needs to be connected to the pilot CPU end to either the case if it is metal or to a common earthing point inside that unit. It does not have to be connected to the reference unit it's self and that may be a plastic housing anyway. Certainly do not connect it to anything metal at that end like the Rudder itself.

I won't go any further at this point till we clarify all those points first. Please continue to ask questions if anything is not clear or if you have covered all those things already.

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Is the antenna cable the backstay only? or is there any length of unshielded cable running inside the boat? The shielded cable needs to run all the way to the backstay and the shield must be connected at the ATU end only. Do not earth the shield at the backstay.

 

The Antenna cable (from the tuner to the backstay) is an unshielded GT0-15 Silicon insulated antenna cable. It does have about 750mm inside the boat. But today I tred a peice of coax suggested by the local radio engineer, with the shield attached to first the batt neg, then the ground plane. No Difference for either solution

 

What is most likely happening is an RF signal is being induced into the Rudder Reference unit cable. This signal is a voltage that then adds/subtracts the voltage being sent to and recieved back from the Reference unit at the CPU.

I expect you may have already tried, cause you have covered most things already. But the first question is where is that cable run? Does it run anywhere near the antenna cable. Next thing to check is whether that cable is a coax or "shielded" cable. You may need to run a new shielded cable. The shield needs to be connected to the pilot CPU end to either the case if it is metal or to a common earthing point inside that unit. It does not have to be connected to the reference unit it's self and that may be a plastic housing anyway. Certainly do not connect it to anything metal at that end like the Rudder itself.

I won't go any further at this point till we clarify all those points first. Please continue to ask questions if anything is not clear or if you have covered all those things already.

 

 

The rf300 (rudder feedback unit) is connecetd with a shielded twisted pair cable, and the shield is connected to the common shield ground at the AC20 (the computer head unit). This in turn is connected to the bat neg. I have completely removed the rf300, and tried cable runs in every conceivable location, even down the opposide side of the boat to the radio cables. No change. I even put the unit is the over (faraday cage?) no help there either..

 

Cheers

Matt

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Also the rf300 cable has ferrites at both ends, with 4 turns around each one. I had a radio engineer at the boat for most of the day today...

I'm begining to suspect that I won't be able to fix this..... :?

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Arrrr yep, many hrs of frustration and no one installation is ever the same.

 

Coax to the backstay is good and I would consider using that instead of the GTO-15. The coax MUST be the correct type for HF transmission and RF power. Or you will have it breakdown and short the output or load the output inccorectly. I imagine the Radio guy knows and supplied the right stuff. Your radio will be outputting at minimum 100W and more than likely 150W. That's a lot in RF power terms.

 

The coax to the backstay must be earthed at the ATU ONLY. There will be a terminal that connects to the ground plain. That is where you connect the shield. The shield must NOT be connected at the other end.

 

However, the backstay is probably outputting enough RF to be induced into the other cables and devices anyway. Using the Wip has proved that.

 

You need to ensure all Earths are connected at the correct termination points on all equipment. Do not ever shortcut directly to the battery negative. This is the issue with a DC system. The negative is not actually an Earth like we have in an Earthed Mains AC system. The negative is actually one side of the transmission AC signal.

Just to be reallyt annoying though, sometimes the shields can actually be the problem too and cutting a shield maybe the cure.

Ferrites are a good means of creating a filter. But you can only run the actual signal wires through the ferrites, not the shield. The next point on that is it may need a little maths used here and a more frequency specific ferrite filter being desinged. That means a certain size Ferrite and certain number of turns. A Ham radio guy could be of real help here. Some of those guys are very good at cooking up those kind of things. If you know of an older really experienced Ham guy, he could be worth his blood in Gold.

 

I am going to make another post with some bedtime reading for you to do.

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RF Interference

In case the drawings don't come out in this, here is the link to this following article.

http://id3431.securedata.net/siriuscyber/rfi.htm

 

© 1998-99 Jim Corenman, revised 10/14/99

 

Solving RF Interference Problems

 

Radio transmitters have a great fondness for causing interference. This is not surprising, since their primary job is to pump 100 watts or more of radio energy into the sky. Ideally all of this energy would be sent off towards the distant receiver, but this is not the case. Antennas, particularly small ones, radiate in all directions, and worse yet, any imbalance in the antenna system causes the coax cable, power wires, and every other interconnection to becme part of the antenna system and radiate also. In the days before digital communications this was a nuisance at worse, but when modems and computers get interconnected with transmitters and radios the potential for chaos is great. This is especially problematic for small installations such as boats and RV's where the antenna and ground system literally wrap around the radio and other components.

 

With respect to HF email, there are two primary symptoms that can be traced to wayward RF energy: distortion of the transmitted audio signal, and data errors between the computer and modem. The distortion problem is subtle because you will rarely hear it yourself. But if your transmitted signal gets back into the audio connection between the modem and transmitter, then it can be rectified and produce its own audio signal, which will be transmitted and produce more interference, etc.. It is very much like the "howl" that emits from a public-address system when the gain is turned up too high, noise feeding upon itself.

 

Data errors can occur in the modem's serial-port connection. These will usually be detected by the error checking associated with binary modes but it will not be at all obvious that RF is to blame. And if ASCII mode is used then the errors may simply be missed. Errors can happen either sending or receiving messages. If sending, then errors are likely at the beginning of the message transmission, as the computer is busy sending data to the controller's buffer memory at the same time that the controller is sending the beginning of the message over the radio. When receiving a message, the incoming data is usually being transferred to the computer at the same time that the controller is transmitting the "Ack" (Acknowledge) burst back to the sending station. In either case there are serial data transfers happening at the same time that the radio is transmitting digital data.

 

If an ASCII transmission is in progress then the usual symptom is that characters are lost from the message. Given the general lack of attention paid to spelling these days, such errors usually go unnoticed. If a binary transfer is in progress then a format or checksum error generally occurs because the binary protocol includes error checking. If an error is detected then an error message is sent and a disconnect occurs. Errors of this type are almost always related to RF interference related to ground system problems.

 

Airmail logs incoming serial-port errors in its Logfile.txt file, located in the c:\program files\airmail\ folder. Open this file and look for something resembling "comm: Error reported to input: 2", this indicates a framing error detected by airmail's serial-input driver. This may also correlate to a disconnect due to a binary format or checksum error. Note that errors in outgoing data would be detected by the controller and not by Airmail, and usually result in lost characters with no other indication of trouble. For the PTC-II controller, Airmail now uses CRC-Host mode which was developed for precisely this reason and which detects and corrects serial-port data errors. (There will be a "retry" entry in Airmail's log file).

 

Ground systems:

 

The usual marine antenna/ground system consists of an automatic tuner at the base of the backstay or stern-mounted vertical antenna, a grounding strap from the tuner to a ground system, and a coax cable to the transceiver which itself is usually grounded. Ideally all of the antenna current flows between the antenna wire and the seawater ground system through the tuner, and with a perfect ground system at the tuner then that is what would happen (see Fig. 1).

 

But grounds are never perfect, and even a ground connected to a large external metal keel has a ground strap of some length which can develop some resistance (impedance) at certain frequencies. If there were no other path then the impedance of the ground system wouldn't matter, but the radio itself is always grounded, either directly or via the DC power wiring, and the nice fat shield on the coax cable provides a good ground conductor. Note that the transmitted signal is balanced between the inner conductor and shield, this can be considered "inside" the coax caable and will not radiate. The stray ground path is on the shield alone, an unbalanced current, and will radiate. This is called a ground loop (see Fig. 2). Other loops are formed by the cables that connect the controller and computer, and their 12V power connections (which themselves are always grounded somewhere).

 

These ground loops have impedance just like any other wire, and DC wiring in particular makes a pretty poor ground conductor. RF antenna currents using these ground loops as alternative ground paths will radiate interference signals into other cables (just like an antenna) as well as by simple voltage drops due to the impedance of the ground loops themselves. These interference signals will raise havoc with everything.

 

It would seem attractive to simply beef up the ground system, i.e. reduce its impedance and make that path more attractive. This will certainly help and is a good first step, but it is equally important to make the unwanted paths less attractive.

 

The solution:

 

Changing frequencies will typically change the problem, making it better or worse depending on how the impedance of the various ground paths change with frequency. Reducing the output power will always reduce the interference, and is a definitive test to verify that the problem is RF-related (as long as there is enough power to maintain a good link). A permanent solution has three parts:

Make the primary ground system as good as possible;

Make the tuner-to-radio-to-ground path via the coax shield less attractive by using a ferrite "line isolator" add impedance to that loop;

and break up any additional ground loops between radio, controller and computer with clip-on ferrite chokes.

 

Task 1.

 

The first task is a careful review of the ground system connected to the tuner. The backstay or vertical antenna is only half of the antenna system, the other half being the ground system. Different frequencies will "see" the ground differently, so what works on one frequency band may not work well on another. Higher frequency signals (21-28 MHz) have a shorter wavelength and need a few square meters (tens of square feet) of metal surface located close to the tuner. Because the square-footage requirement is lower, a direct seawater connection is less important. Lower frequencies (7 to 10 MHz) have a longer wavelength and need more square footage of ground plane than can easily be provided, so a good seawater connection is required. This requires a few square feet of seawater contact but does not need to be as close as it would in order to be effective at high frequencies.

 

So the ideal ground system is a combination of a ground plane laid against the hull near the tuner, plus a connection to the engine, metal tanks, and any other large metal, and a connection to an external keel or other large underwater metal. These should all be interconnected with a network of 3-4" copper strap which will have a low impedance at all frequencies.

 

Consider electrolysis when connecting external metal parts (such as a through-hull or prop strut) to the ground system. You will never create a new problem by connecting underwater metal that are already connected to the green-wire DC bonding system, but connecting metal that was previously isolated can create a new electrolysis problem. If in doubt then provide a DC block. Stan Honey's method is simple and effective: cut a quarter-inch gap in the copper foil, and bridge that gap with a dozen ceramic disc capacitors (.01uF line-bypass caps would be a suitable choice). This blocks DC electrolysis currents while providing a low-impedance RF path for antenna currents.

 

Henry VE0ME, a Canadian ham of some considerable experience, favors an separate antenna ground with no connection to the rest of a vessel's ground system. In other words, run a ground strap from the tuner ground to a large underwater plate (such as the largest-sized Dynaplate), but do not connect this plate to the rest of the ship's ground system. Splitting the ground system this way would break up the major ground loop shown in fig. 2. The key to making this method work is providing a large enough ground plate for the isolated tuner ground, the smaller Dynaplates are not adequate. The disadvantages are those associated with grounding plates in general, drag unless the plate is set flush, and concerns about electrolysis.

 

For more information on grounding and electrolysis, see Stan Honey's excellent article in Practical Sailor, October 15, 1996 issue.

 

Task 2.

 

After we've done what we can with the ground, the second job is to make the alternative ground paths less attractive to the antenna currents. That is done by adding RF impedance to the coax, in the form of a Line Isolator (a large ferrite choke) or multiple clip-on ferrites. This adds impedance to unbalanced common-mode currents such as the ground currents using the shield as an RF path. The transmitter output to the tuner is a balanced signal, i.e. there are equal and opposite currents flowing in the shield and inner conductor). The net current from a balanced signal through the ferrite is zero, so there is no attenuation at all, i.e. zero impedance. But antenna currents using the shield as a ground path flow in one direction only and see the ferrite as an impedance (see Fig 3).

 

A typical line isolator is about 20 turns of RG-8X around a ferrite rod inside a plastic housing with a female coax connector on each end. Our favorite is the Radio Works model T-4 (ungrounded), about $30 from Radio Works (http://www.radioworks.com/ which also has a good discussion of grounding techniques), or also available for a few extra dollars from Farallon Electronics (gofarallon@aol.com) or HF Radio in Alameda (Don@hfradio.com). You will also need a male-male coax jumper to connect the line isolator to the tuner, as the line isolator comes with two female connectors. Clip-on ferrites will do the same job, but it would take a dozen or more to have the same effectiveness.

 

The best place to locate a line isolator is close to the tuner itself. In terms of ground currents it doesn't matter where it is located, but if the coax is long then it will still be able to radiate some signal if the line isolator is located at the radio end of the coax.

 

In addition to the line isolator on the tuner coax, one or more clip-on ferrites should also be added to the tuner control wires. These control signals are usually grounded to the tuner ground, and provide an alternative ground path if not blocked. An alternative to multiple ferrites is to use the large size and loop the wire through it a few times.

 

Adding a line isolator (and ferrites to the tuner control cable) should stop most of the ground currents from taking the detour through the "radio shack", but will not substitute for an adequate ground system. And of course never add any sort of ferrite choke to the ground connection itself. Many users have also reported that adding a line isolator also cleans up other problems such as autopilot interference, but that will depend on how the other equipment is configured.

 

Task 3.

 

Providing a good tuner ground and isolating the alternative coax path are the most important tasks, but while we are cleaning things up we should also break up the ground loops between the radio, controller and computer.

 

Isolating the ground loops is again done by adding common-mode impedance, in this case in the form of clip-on ferrites (see Fig 3 again). These are small split ferrite cylinders, about 3/4" in diameter, 1-1/4" long, with a 1/4" hole through the middle for a cable. Clip-on ferrites are sold by Radio Shack, but better ones are made by Fair-Rite, their part number for type-43 material in a 1/4" hole size is P/N 04-43-164-251 and available from Newark Electronics (http://www.newark.com/). Fair-Rite's type-31 material performs a little better at HF radio frequencies, their part number is 04-31-164-281 for the 1/4" hole size, and 04-31-164-181 for the 1/2" hole size. The type-31 parts are not sold by Newark but are available with a $50 minimum from Amidon and stocked by many dealers.

 

Use one ferrite to each end of the computer-to-controller cable, and one at each end of the controller-to-radio cable. And don't forget the tuner cable as noted above. The signals inside the cable will not be effected, only the ground currents trying to use the cable shield as an "sneak" path.

 

Important: The ferrite halves must meet perfectly in order to be effective. If in doubt, remove the ferrite halves from their plastic housing and secure with tape and/or tie-wraps.

 

And also make sure that the cables are properly shielded, with the shield connected to the connector shell (and equipment chassis) at both ends. This can be verified with an ohmmeter, and if the metal shells of the DIN or DB-style rectangular connector at each end are connected, then the shield is terminated correctly.

 

Metal boats:

 

Steel or aluminum boats don't have a problem with the ground system, but aluminum boats in particular usually have isolated 12V neutral wiring to protect against electrolysis and are subject to significant interference problems. In some cases the problem seems to be much worse than with a fiberglass or wood boat, probably because any stray RF energy is trapped inside a shielded box (the hull), analogous to the proverbial "fox in the henhouse".

 

The steps outlined above should be equally effective with metal boats. The line isolator in particular should eliminate the stray RF at the source and would be the logical first step. If additional help is needed, the 12V negative connections to the computer, controller and radio can be RF-grounded using capacitors to provide a RF ground with DC blocking. Also provide a similar capacitively-coupled RF ground for the radio chassis. Ceramic-disc capacitors are a good choice for this duty, and a dozen 0.01 line-voltage type capacitors wired in parallel will provide an inexpensive and low-impedance path for HF frequencies.

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Yep I expected the daigrams wouldn't show up, so make sure you do take a direct look. The little Diagrams are very important and helpful to understandign how to lay a system out.

I know the article is discussing interference more within a system, but much still relates to the rest of the equipment. It is all about controlling that stray RF signal and dumping it to earth as fast and efficiently as possible, so there is nothing spare to get to a sensitive device.

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On a delivery of a fairly new top end boat the first time we used the SSB the hi tech auto pilot was fried - hand steering the rest of the way across the Tasman.

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Squid, I will leave it up to you about Copywright. Perhaps leave the info up for a day or too and then maybe you need to delete that thread and just leave a link. I don't really know how all that works. But I did make sure I included the authors name and details.

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Hi Wheels,

 

Thanks for that. I have read most of that before (please don't let that put you off trying to help! - it's just so you know where I'm at..). I have the radio shack T5 grounded line isolator in the tuner-ATU coax, right by the ATU.

 

As part of my testing, it was interesting to see that there were NO rf issues with the dummy load connected to the ATU antenna connection. This install has allways caused the instrument panel lights to flicker when transmitting. They did not with the dummy load. This indicates that the RF issue is coming virtually 100% from the antenna system. This is why we tried the coax connection to the backstay.

 

The radio works very well. Maritime radio typically report 4x4 signals.

 

I must admit that I was surprised to find that this problem is eminating from the antenna - that is supposed to radiate RF!

I got a response from Navico this morning, asking for some more info, which I have sent...

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As part of my testing, it was interesting to see that there were NO rf issues with the dummy load connected to the ATU antenna connection. This install has allways caused the instrument panel lights to flicker when transmitting. They did not with the dummy load. This indicates that the RF issue is coming virtually 100% from the antenna system. This is why we tried the coax connection to the backstay.

I don't mind trying to pass on any info at all. You just never know when some small piece of info hits the target.

You are 100% onto the right cause. RF is a voltage. You only need to grab the backstay and you will find that out the hard way. DON'T try it though.

The "Voltage" simply gets transmited as a RadioWave. It then gets picked up in anything that will act as an antenna and fed down that antenna as a Voltage once again. Which of course is the cable running from the rf300 or any other wiring in the boat can all act as a great antenna. With HF SSB, the signal is radiated out from the antenna between the "Ground" and the antenna, being the backstay. The ground is also connected to the Negative side of all your DC system.

OK, so a little slightly side ways in thinking now then.

So what a shield does, is it acts just like a Farady cage and is supposed to absorb all the RF energy and "sink" or carry it away to ground, instead of that RF energy getting into the signal wiring and carried away to the sensitive electronics. You only ever connect a shield at one end so as you do not create a signal to be set up between the opposite ends of the shield and any return path. This is called a "Feedback loop" or "Earth Loop". You want to absorb RF and carry it away to a common point.

Now, I imagine you have done all of this, but make sure all electrical equipment has one Earthing point at the Negative Bus Bar. That Neg Bus Bar must run to one common Earth point for all the entire DC system which normally is situated at the engine Block at the Starter motor. Alternator Neg should also terminate here, along with Battery Neg of both House and Start banks. If you have bonded Anodes, they too should all come back to that point. All and every Ground/Negative wire should all come back to that one point. No other connection anywere else in the boat should be make. That includes the Sintered Bronze ground plain plate if you are using one. This one connection means no other electrical path in the earth/Neg system can exist.

So you need to check that no other equipment is connected in any such way that another path could be set up.

Next,

For an antenna to work efficiently, it has to be a Wave length or an equal fraction of a wave length. In otherwords, a 1/2 wave length or 1/4wave length. What the ATU does is it corrects the one length Backstay to meet the required wave length of the frequency being used. This "tunes" the Backstay and a tuned back stay will transmit the greatest signal, hence the transmission output indicator reading higher. The same applies to any antenna. As it is "tuned" by approaching the length of the wave that is being transmitted, it becomes more efficient at receiving and thus the signal becomes higher. So you can sometimes make the wire that has unintentiaonaly become an antenna, less of an antenna by changing it's length. Sometimes it is even possible to find a length that almost cancels a signal, but that is something that tends to happen in very high frequencies. This is called a Frequency trap in very ruff form. If your Radio fellow has a scope, he should be able to measure the frequency and if that is being seen on the rf300 cable and know which freq is causing the greatest problem, it could be that a Trap is built to go into that cable and actually take out that RF waveform. Now normally this is something that is done of sorts in the Autopilot design if it is of decent quality and those particular ones usually have a decent quality associated with them. Most circuits have some sort of "isolation" design to decouple unwanted signals from sensitive signal voltages. But in your instance, it is either not a good decoupling design, the unwanted signal is too powerful and breaking over, or the decoupling was never intended to keep out the kind of signal coming down the line.

 

Moving on, try this. What happens if you disconnect the rf300. Try both ends. First at the AP end. Then (which wont be so easy) at the rf300 end. And/Or, remove the rf300 unit from where it is fitted and take it to some other completely different part of the boat and see what happens. This may tell you if the signal is getting into the cable or the ref unit itself. There are several ways that these feedback units work. One is a very simple wire wound resistor and a wiper arm and it works as a linear potenteometer. This wire winding can easily act as an antenna and may need to be shielded in some way. Normally a good way of shielding is in a metal box, but the metal box needs to be grounded so as the signal is "sunk" to ground. And that can often be a problem on boats because you can't easily connect to ground and certainly not at both ends. So most times the manufacturer just uses a plastic case. So the next idea could be to see if a frequency trap actually fitted into the signal wires of that rf300 would work. Wrapping the wires through a Ferrite may not always work.

Oh boy, I hope something within all that works for you.

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Hi Wheels, all good stuff. Yep, I tried most of that, including putting the Rf300 in the oven!! (faraday cage - yes it was earthed!), the fwd cabin, all over. No luck.

 

BUT today I realised that the AP can be installed without a Rudd Feddback unit, and then used a "virtual feedback" system. I tried this this morning and the problem is gone!!! This indicates to me that the issue is definitely the RF300 and or it's cable.

 

I understand that the steering will be better with a feedback unit. I have asked Navico for advice, wether it is worth replaceing the RF300 (possibly faulty??) or what to do next, but at least it seems I've isolated the issue a bit more.

 

Cheers

Matt

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Well thats great to hear. Can the rf300 be set up so that it can be switched in and out? then when you use the SSB, you could switch to virtual so the boat is at least steering while you are not at the helm and then switched back on when you are not transmitting, like catching some shut eye.

Sorry, I remember you saying you put the rf300 in the oven. I should have gone back and read that to remind myself again.

Every now and then you get a hairy one like this. A right pain in the neck. Problem was, it always seemed to be that got the hairy ones. Really frustrating at the time, but it all adds up to experience that is like Gold in later years. If you ever come across some old fellow that just seems really smart, it is usually because he had a lifetime of experience.

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Man wheels you and I think alike. I've just come back from the boat, after fitting a switch just as you described! Prob do a sea trial tomorrow!!

Cheers

Matt

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Ok, I'm getting there with this. Navico have given me the following info;

Simrad RF300 rudder feedback units were modified in 2004 to pass new RFI requirements. The case and the product codes did not change, but if you have one where the letters between the Part no and Serial no are not FA, and you have an RFI issue, you need to replace it with a new one.

product code between the p/n and the s/n, i.e. XXXXXXXXFAxxxx.

This is not in any book or documentaion I can find, but this info came direct from the Navico Technical Team leader.

I have a new one on order..

Matt

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Bloody hell, this thread is one for the hall of fame. It makes my university lecture notes on atomic physics look like kindergarten.

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Wheels you are a legend.

Nahh, it's just that I am a jack of many trades and an expert of not a hell of a lot.

It would be interesting to know what they did to rectify the problem. I imagine a very simple Isolating circuit and Filter. Wich would be a risistor and capcitor or two.

IT, mate after you get that replaced, you are going to have one hell of a great system layout.

What frequency do you transmit on for the Race. I should listen in to the reports. Although my steam driven SSB doesn't have a lot of frequencies. It is not a radio I ever intended to use, it was only ever to suffice the Cat 1 requirements. But now there is the odd time i wish I could listen in to a few calls but I don't have the freqs.

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Bloody hell, this thread is one for the hall of fame. It makes my university lecture notes on atomic physics look like kindergarten.

 

Atomic physics, finally something in this thread I don't understand by at least know what it means :lol: :lol:

 

Note to self - don't argue with Wheels, I'll lose ;)

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