An exercise in balance
Aquabelle is roughly from the year 2000 and thus the radio equipment that was on the boat when I bought her in 2021 was slightly out of date and worn out. The antenna I figured out after extensive googling, looking through old receipts for the previous owner, and on labels on equipment, was probably a Delta 1000s system. In the masthead the antenna was fastened with what looks like a hose clamp to a bracket, the the coax runs through a pipe inside the mast, routing through the interior of the boat, through a FM/VHF splitter, through a GMS amplifying box and then to the radio. In other words, a lot of connections, which all potentially increases the losses of the radio signal. The VHF itself was also in pretty rough shape. It was an old Navico RT 6500 and probably really good when it was made, but time has moved on. A new radio will provide more functionality, where the emergency DSC might be the most desirable. Digital Selective Calling enables for example emergency broadcasting along with GPS position at the press of a button, which could come in handy.
The majority of the time a VHF is used in coastal waters it is used from the cockpit so I wanted to be able to have a talking but more importantly listening possibilities from there. But I also want to be able to have the same from below. This is not easy to accomplish on Aquabelle since the companionway is a solid meter long and then the classic placement of the Radio at the navigation table would add another meter. I also wanted to install an AIS unit, a transponder for boats that would let me see other boats (most importantly big ones) and they me, on the electronic chart plotters. It enables collision warnings among other things which allows small course corrections at longer ranges to avoid collisions.
For a long time I had been looking a the B&G v60-b which is a combined VHF and AIS unit. To it I would then buy an external wireless handset to have in the companionway. The VHF antenna would be places in the mast and the AIS antenna would go on a stick on the aft of the boat. So far so good. Just to be sure I asked around on internet forums and it became apparent that a lot of people were not entirely sold on this combination. Low sound volume and software issues were among the common complaints. Since my solution relied on the handset being quite loud it was back to the selection of units again.
So requirements:
- Keeping costs down to a reasonable level.
- Keeping amount of boatwork down to a minimum, there are more projects to be done.
- Possibility of using the VHF both from the cockpit and from inside the boat.
- If possible, being able to reasonably easy interface the units with the existing plotter so that the full functionality of AIS and DSC can be used.
- A simpler VHF at the nav-station with the plan to upgrade when budget allows.
- A more expensive VHF at the nav-station with plans to add an extra handset in the companionway when budget allows.
- A blackbox VHF with the handset strategically placed in the companionway so that it can also be used below.
For the AIS the choice was slightly simpler with the choices being:
- An AIS with built in antenna splitter so that the antenna can be shared between the AIS and the VHF.
- An AIS without splitter, and then having an AIS antenna on the aft of the boat on a stick.
Another thing was the communication issue between the units which I initially thought was going to be a pain and/or expensive to set up since there was no existing network in Aquabelle. The communication standards in consumer level stuff on boats can generally be said to be NMEA-0183 and NMEA-2000.
NMEA-0183 is a one-to-many type protocol where one sender can send information to many receivers. NMEA-2000 is a bus-protocol where all the units are talking and listening on the same piece of cable. NMEA-0183 is a bit more challenging to set up but generally should be more stable once figured out once (at least in micro size networks) while the NMEA-2000 is generally more plug and play, but some people experience strange errors installing new equipment from time to time. NMEA-0183 allows for simple soldering of whatever cable you have at home to the data connectors (even though thought should be put into what cable one would use) while the NMEA-2000 network due to being a bus requires special connectors, terminators and cable, thus more cost.
The actual choices I considered is shown in the following tables.
| VHF Unit | NMEA | Price at the time | Extras needed | Total price (SEK) | Comment |
|---|---|---|---|---|---|
| B&G v60-b | 2000 | 12500 | wireless handset H60 | 17500 | Including AIS |
| Ray63 | 2000 | 5000 | Raymic | 8000 | Felt like flimsy buttons in the store |
| Ray90 Blackbox | 2000 | 11700 | 11700 | ||
| ICOM - M400BBE Blackbox | 0183 | 5000 | NMEA converter | 7300 | Sale |
| ICOM - 423GE | 0183 | 5000 | NMEA converter, handset | 9900 | Sale |
| Standard Horizon GX1850 | 2000 | 4000 | handset | 6400 | might be possible to find cheaper |
| Garmin VHF 115/i | 2000 | 5150 | handset | 8650 |
| AIS unit | NMEA | Splitter | Price | Extras needed | Total Price | Comment |
|---|---|---|---|---|---|---|
| Raymarine AIS700 | 2000 | Yes | 9000 | 9000 | B+, Blackbox, on sale | |
| ICOM MA500TR | 0183 | No | 9000 | Antenna and cable | 10700 | with its own screen, will enable DSC calls from AIS |
| Garmin AIS 800 | 2000 | Yes | 10000 | 10000 | ||
| Em-trak B921 | 2000 | No | 6200 | Antenna and cable | 7900 | |
| Em-trak B923 | 2000 | Yes | 10500 | 10500 | ||
| Amec camino 108 | 2000 | No | 6121 | Antenna and cable | 7821 | Needed to order from overseas. |
I sketched out and combined different things from the list to compared to my requirements. Quite quickly the Garmin stuff was discarded because of price since there is no real benefit to the units unless everything on the boat is Garmin, but Aquabelle is equipped with an old Raymarine multi function display. The Icom – 423G was also discarded because for that it seemed like I was going to have to buy a handset as well, and only very limited extra usability compared to the ICOM blackbox unit. I stumbled on some review on the Standard horizon stuff that was lees than promising, for example a less than waterproof handset, so this was out, I don’t want to have to replace stuff, there are a lot of projects going on already. The Raymarine Blackbox was also out quite quickly because of cost. This left the ICOM – 440BBE blackbox, Ray63, and the original B&G v60-b.
Now I started to read very carefully the manuals and driving around to the boat stores in the city to talk with people. Things that stood out was that it was really tricky to figure out what data was being sent on which communication protocols for the different units, and that ICOM radios (being hunting walkie talkies or whatever) generally had a good and clear sound. I managed to get to look at a Ray73 radio which in appearance and hardware looks to be very similar to the Ray63. The turning knob was, for me, notably of center and felt flimsy. I was certain it would break. The reviews on the Raymarine handset waterproofness was not promising either. During all the consulting of family and friends I had an epifany – the radio is for talking and listening with. Therefore the sensitivity of the receiver and clearness of voice should be prioritised. This along with me dislike for having a battery in the B&G handset strongly indicated to me that the ICOM – 440BBE might be the unit, but I was worried about having to still build an NMEA-2000 backbone and buy extra equipment to have the ICOM VHF properly send information to the plotter.
I had initially planned to start building an NMEA-2000 backbone but then I discovered that my old Raymarine A-67 MFD should support listening to two different NMEA-0183 channels at the same time, which would be just enough for an AIS and a VHF. This piece of information put my earlier cost calculations into new light. Now the ICOM – 440BBE would cost me just 5000 SEK on the Christmas sale!
Let’s have a look at the potential AISes. It seemed like the major choice here was with or without splitter. Generally without would be 1000 SEK cheaper but many hours more in labour late in spring since holes needed to be drilled in the boat and covered up somehow. The prospect of adding more (even though miniscule) weight aft and having another thing in the way while handling lines was also unappealing, so with splitter was decided on, if not the VHF choice fell on the B&G v60-b.
Even with the most expensive option AIS it seemed like it would still be cheaper to go with ICOM – 440BBE and and AIS rather than the B&G v60-b option, so the B&G was discarded. Since the Raymarine AIS700 was on Christmas sale and also supports B+ protocol which is slightly higher prioritized than the B in traffic, and that it sends with 5W power instead of 2W, the choice eventually fell on buying a Raymarin AIS700 unit.
The total cost so far was 14000 SEK, way below the initial budget and a better solution to that.
Measurement headaches
With the VHF and AIS units decided on and ordered I started looking at the existing cable and antenna. Two things are very important when trying to send radio-waves, that as much power as possible is sent out from the antenna and that as little as possible power is reflected back into the radio. The reflection is really important to keep under control when a slitter is used in an AIS since the AIS sending power is way less (5W in this case) than the VHF which can send out 25W. The AIS components are not built to the same level of sturdiness as the VHF because of this and For the Raymarine AIS700 it is explicitly instructed that the so called VSWR is to be below 2:1 for all used frequencies. The major problem is that antennas has to be tuned to a frequency that they will optimally send out without reflecting back power. Generally the further away the sent frequency is from the optimal the higher the VSWR is (not entirely true, but you will have to google antenna frequency VSWR plots).
Now, AIS sends its information on around 162 MHz while the ordinary VHF channels are around 156-157 MHz. This means that if an antenna is optimised for VHF use it might not work for AIS. I suspected that my 20 year old pre-AIS antenna did not take this into consideration so I was prepared to buy a new one. Furthermore, regarding the existing coaxial cable in the mast. Over time coaxial cables that are exposed to moisture oxidise internally which will make a lot of the signal power sent get lost on the way to the antenna due to the increased resistance and poorer shielding. I was definitely prepared to buy a new one, but before buying new stuff of course I had to measure exactly how bad and if the antenna and cable might be fine!
One way to do a simple test on a coaxial cable to be able to determine not if it is good but if it is bad, is to test the resistance. On a non-connected cable the shield and the center should have no electrical connected, and both of them should have approximately 0 resistance end to end. I went to the mast-shed with my multi-meter prepared. Measuring the resistance between the shielding and the center I got infinite resistance, so far so good. Now I tried to short one end center to shield while measuring the resistance between them at the other, but it was very hard trying to do that with the ends of the cable being a mast length apart. Eventually I got some measurments of 8 Mohm, which is a lot. Just to be sure I swung by a boat store and measured one of their readymade ones, 1,7 ohm, i.e. my cable has more than a million times the resistance. A new cable it is!
For the decision of a new cable I used this online tool a lot together with reading in the Boatowner’s Electrical and Mechanical Manual. The book recommends a maximum total loss of 3 db (halfing the signal power) from the VHF to the antenna with a book loss of 0.5 db for each connection. For my needed 21 meters it therefore needs to be a quite good cable. In general the thicker a coax cable the lower the losses, so RG 213 used to be the go to choice for leisure sailing boats of moderate size. In recent years however newer cables with better shielding have come out on the market which enables lower loss and smaller diameters. For 21 meters with an extra connection at the mast base for easier unstepping of the mast in the autumn, RG58 was right out of the choices with 3.347 db loss for just the cable length. The boat stores had sale at the time of buying for ready made lengths of RG8x, a popular cable for VHF. For just the length of cable I needed that would mean a loss of 2.93 db, maybe acceptable in a pinch. I punched in the numbers for the lmr240 cable that was used as an example in the book since this cable is also quite flexible allowing for tighter routing in the boat without damage compared to RG213 (and also half the weight). The loss now was 2.123 db. This cable also has a tinned shield and therefore should hold up a little bit to wetness and corrosion.
The problem was the cost at nearly 43 SEK per meter where I could buy it, then contacts and tools on top of that. This seemed to expensive. Then through my googling I stumbled upon an lmr240 copy that is made in Italy and sold buy a radio guy in Sweden that also sells connections and the fitting of them. At 15 SEK per meter the cable cost would only be 300 SEK with the total cost 1000 SEK. This seemed really good compared to the RG8x which would be slightly more expensive. He mailed back with a suggestion of another cable: Ultraflex 7 Sahara. This had even better performance and 30% more total cost but worse bending radius, so in the end I decided to go the cheap route and order the copy of lmr240.
With the cable in hand and complete radio equipment I started to measure the VSWR of the old antenna with the build in measure things in the AIS. To my immidiate disapointment the VSWR was 10.8:1. People adviced me to buy a new antenna. Do you remember the thing about the separation of AIS and VHF channels affecting the antenna design? Well, it turns out producers of antennas don’t like to specify exactly how well their antennas perform at different frequencies. I found that Vesper Marine did produce an antenna that was optimised at 159 Mhz, right in the sweetspot to be able to have good performance for both VHf and AIS, but Vesper got bought by Garmin around new years and have no intention of continuing the sale of this.
The googling for specs commenced once again. A lot of manufacturers say there antenna will work 156-162Mhz with a nominal VSWR of X at 156 Mhz but with little to no other information. Glomex sales rep claims 1.3:1 VSWR at 156 and 162 Mhz but no respons regarding the curve or bandwidth of their antennas has been obtained so far. In the end I have bought a simple steel-whip antenna from Ramnav here in Gothenburg. It is a Scan VHF 23. The thing that convinced me was not the VS
WR claims which are not the best but adequate at below 1.6:1 at 156 Mhz, but that they post the typical VSWR curve of the antenna, and there it is clear that the optimum is somewhere in the neighbourhood of 159 Mhz. Testing this antenna at home later the AIS measured 1.5-1.7:1 VSWR while I with analogue measurement equipment measured 1.2:1 for the VHF.
I seems like I now have radio equipment consisting of:
- ICOM – 440BBE balckbox VHF
- Raymarine AIS700
- LTA240 coaxial cable
- Scan 23 VHF antenna
Left to do is installing everything and interfacing it with the plotter.