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Old 05-03-2012, 19:31   #1
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VHF / UHF HAM Radio Antenna ... and AIS?

Hi all,

I am gonna install a 50W HAM dual band radio with 2m and 70cm bands. This radio (Kenwood TM-D710) can also be modified for 25W marine VHF making it a nice all round radio, but we still keep the primary VHF too... which brings me to the antenna dilemma;

We are a ketch so have two great antenna positions. The main mast hold a very high quality marine VHF dipole antenna, used by the primary VHF. The mizzen hold a cheap stainless whip, used by AIS transponder.

I am thinking about putting a good dual band HAM 2m/70cm antenna in the mizzen, with a manual switch to choose between AIS and HAM VHF/UHF radio

I have only heard of cruisers using a marine VHF for 2m band, never the other way around.

1. Anybody ever tried this?
2. AIS output stage is a module with automatic SWR protection... but will the signal get out?
3. How about using the Kenwood at marine VHF frequencies... range of signal?

Much of this project has to do with APRS and Jedi will probably become a digipeater.

4. Has anyone used APRS aboard? In Central America? I'm trying to find other digipeaters in range, especially a couple with Internet gateways. I could add an amplifier if needed.

Another part will be buying a couple of Kenwood TH-D72 HT's which are also dual band and have GPS and APRS built in. They do beaconing and can even act as digipeaters themselves! Also, they can be opened for marine VHF.

5. Anybody used this handheld? How sensitive is it's GPS?

cheers,
Nick.
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Old 06-03-2012, 06:35   #2
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Re: VHF/UHF HAM radio antenna... and AIS?

Hi Nick,

Before we were struck by lightning, we had about the exact setup you are contemplating. We had a Kenwood dual band transceiver modified to also work marine frequencies going to a Diamond dual band antenna. The radio was the model that was superseded by the one you are considering. Our AIS was hooked to this antenna through a manual switch.

Everything worked very well.

The previous owner used the boat for APRS and it was configured as a digipeater.

He also had the previous model of Kenwood HT that you are looking at. These did not have the GPS, but they were opened for marine bands. I assume the HT's worked well, but he took those with him when he sold the boat.

Mark
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Old 06-03-2012, 06:45   #3
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Re: VHF/UHF HAM radio antenna... and AIS?

Nick,

No problem with the marine/ham setup on a single antenna, but I would definitely NOT use the same antenna for AIS. There's too much danger of cross-mod and making a mistake.

Much better to move the AIS antenna to a spreader or elsewhere. Do you REALLY need to receive AIS signals from 100 miles away?

:-)

Bill
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Old 06-03-2012, 07:10   #4
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Re: VHF/UHF HAM radio antenna... and AIS?

Quote:
Originally Posted by colemj View Post
Before we were struck by lightning, we had about the exact setup you are contemplating. We had a Kenwood dual band transceiver modified to also work marine frequencies going to a Diamond dual band antenna. The radio was the model that was superseded by the one you are considering. Our AIS was hooked to this antenna through a manual switch.

Everything worked very well.

The previous owner used the boat for APRS and it was configured as a digipeater.

He also had the previous model of Kenwood HT that you are looking at. These did not have the GPS, but they were opened for marine bands. I assume the HT's worked well, but he took those with him when he sold the boat.
Hey it's M&M How is the storm in Kuna Yala?!

Well, that is good news, amazing how I come up with a setup exactly like what you had... if it works well, you will have to upgrade all that burned-out gear too, so we can start tracking and digipeating
I saved up the money in PayPal from selling the old electronics like B&G, Garmin etc. and decided to put it into this gear.

I regained passwords for our FCC license entries so that we can renew them... it's amazing how fast 10 years go by and I was ashamed on how little I did with HAM radio over the years, just some HF CQ's and the rest cruiser nets etc. My license was still on that letter sized paper... I never cut it out and was surprised to find that credit-card sized one there too

I am now on Echotalk repeaters using my iPhone... amazing, it's better than Star Trek!

ciao!
Nick.
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Old 06-03-2012, 07:19   #5
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Re: VHF/UHF HAM radio antenna... and AIS?

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Originally Posted by btrayfors View Post
Nick,

No problem with the marine/ham setup on a single antenna, but I would definitely NOT use the same antenna for AIS. There's too much danger of cross-mod and making a mistake.

Much better to move the AIS antenna to a spreader or elsewhere. Do you REALLY need to receive AIS signals from 100 miles away?

:-)

Bill
Hi Bill, I knew you were gonna be here I have been thinking about putting an antenna on the spreader but I really hate to pull that cable. My AIS is class-A so I always have to program it before leaving with navigational state, persons on board, destination etc. and even if I forget to switch it on the antenna, then it's final VHF stage is a module with full SWR protection.

When I like the TM-D710 better than my Icom VHF, I consider to put a coax cross-switch to switch it to the primary marine VHF antenna when under sail. I just lose 70cm then but don't see me needing that while underway anyhow.

I'll see if I can dream up a setup with switches so that everything has either an antenna or dummy load attached.

ciao!
Nick.
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Old 06-03-2012, 07:35   #6
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Re: VHF/UHF HAM radio antenna... and AIS?

A friend was using an Icom 706 Mk2g for his VHF (as well as HF). Problem was, that unit pumps out ~40W at 162MHz, which is seriously illegal (& a bit silly). But nice having a single radio that will go from 1-500 MHz...
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Old 06-03-2012, 07:44   #7
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Re: VHF/UHF HAM radio antenna... and AIS?

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Originally Posted by Jon Hacking View Post
A friend was using an Icom 706 Mk2g for his VHF (as well as HF). Problem was, that unit pumps out ~40W at 162MHz, which is seriously illegal (& a bit silly). But nice having a single radio that will go from 1-500 MHz...
It's illegal because it's not approved (not even offered for approval) for marine VHF use, regardless of power output level. When you're in areas where they still use tamtams for communication, then there are barely rules let alone enforcement. During emergencies you are allowed to use any radio at any power output, so no problem there.

You can also reduce power output. The Kenwood goes down to 25W at the marine band because you're at the -3dB point of the filters I guess.

I wonder about receive performance compared to a marine VHF.

ciao!
Nick.
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Old 06-03-2012, 14:07   #8
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Re: VHF/UHF HAM radio antenna... and AIS?

G'day, mate. Based on the receive performance of my ICOM 706 on marine VHF, I highly suspect you will notice any difference with the Kenwood.

While responding to a Mayday situation with a sinking yacht a couple of years ago, having the capability to provide on sceen comms using 50 watts vastly made the task much easier with the Rescue Coordination Center and the helicopter crew in the adverse weather conditions that were present.

I use a series of switches to toggle in and out the various radios and antennas on board. It takes vigilance to make sure they are all set appropriately.

I assume you want the capability to transmit Jedi's GPS position to the handhelds when you're not aboard using the digipeater. If not, can you provide some addition insights on how you will use the system? Cheers.
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Old 06-03-2012, 15:19   #9
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Re: VHF/UHF HAM radio antenna... and AIS?

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Originally Posted by matauwhi View Post
G'day, mate. Based on the receive performance of my ICOM 706 on marine VHF, I highly suspect you will notice any difference with the Kenwood.

While responding to a Mayday situation with a sinking yacht a couple of years ago, having the capability to provide on sceen comms using 50 watts vastly made the task much easier with the Rescue Coordination Center and the helicopter crew in the adverse weather conditions that were present.

I use a series of switches to toggle in and out the various radios and antennas on board. It takes vigilance to make sure they are all set appropriately.

I assume you want the capability to transmit Jedi's GPS position to the handhelds when you're not aboard using the digipeater. If not, can you provide some addition insights on how you will use the system? Cheers.
Hi Matauwhi,

Yes, I've had the opportunity to use my Kenwood TS-480HX with 200W output and DSP filtering on the receiving end to copy & relay where marine radio's failed. It is often in conditions far from optimal where power and good filters make the difference. In optimal conditions we only need 10W to talk around the world.

The handhelds will be able to track the boat and each other and the boat can track the handhelds. They also support other messages, Kenwood has pretty much full APRS implementation.

I also need to find out a way to log the messages from a handheld in a GPX or KML file. I can download that from the handheld but would like to remotely log it too. We use that to geotag photo's, record expedition tracks etc. We also want to be able to find each other when we are dwelling through the jungle with handhelds, plus know which way the boat is etc.

Then there's the playing with things like cross band repeater mode, remote control of the HF rig from the handhelds etc.

ciao!
Nick.
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Old 06-03-2012, 15:56   #10
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Re: VHF/UHF HAM radio antenna... and AIS?

Thanks for that, Mate. Despite some views of others on CF that amateur radio is obselete, this is just another example where it is not. Along with the various HF (both amateur and marine) nets, there is active daily activity on the 2m/70cm bands down in this part of the world.

BTW, the better half and I had quite a discussion during the morning cuppa yesterday centered around the question, "If you could only have one, the ICOM 706 or the 406 EPIRB on board, which is?". We are still continuing the discussion.

All the best. Cheers.
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Old 06-03-2012, 16:43   #11
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Re: VHF/UHF HAM radio antenna... and AIS?

Hi Nick, I don't want to say what I have or have not done regarding freqs etc. so cant comment on your Q1. I wanted to say that I have built an antenna patch bay using BNC connectors. I have several radios and antennas that can be use in various configurations. I have no antenna switches. The 10 BNC panel females go to the various radios and antennas out the back of the PB. I have three short patch leads that I can connect any antenna to any radio. (the 706 has two) The best thing is that during a thunderstorm I remove the patch cables and the antennas go nowhere, we are a steel boat. I have 50Ohm terminators too, but have never used them. We had a lightning sidestrike in Club de Pesca Cartagena. Lost two laptops, microwave, genny regulator board, and alternator diodes. The radios were ok. The same t/storm killed a fisherman and injured another in Boca Grande that day. Good luck with the digipeater, keep is posted.

Oh, our handheld GPS did not work in the Jungle. The foreign legion guys laughed at us, they were using compasses, but then they went far further than we dared go.
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Old 14-03-2012, 22:05   #12
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Re: VHF / UHF HAM Radio Antenna ... and AIS?

Well, I just ordered the Kenwood TM-D710A, 2x the Kenwood TH-D72A, a Diamond mobile dual-band antenna with mount, car charger cord, cables, external speaker etc. The game is on

I also got approved for EchoLink so I can become either a digipeater with Internet Service or a Echolink repeater node for any HAM worldwide whenever I get a decent Internet link

Now I need to find a couple of close digipeaters and see if I can reach those

to be continued . . .

cheers,
Nick.
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Old 15-03-2012, 09:06   #13
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Re: VHF / UHF HAM Radio Antenna ... and AIS?

A Diamond mobile antenna? How are you going to mount that? I might be mistaken, but I thought that all of Diamond's mobile antennas were designed for the vehicle to provide the ground plane. In other words, you can't just mount one of those antennas on top of a mast and expect it to work.
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Old 15-03-2012, 09:16   #14
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Re: VHF / UHF HAM Radio Antenna ... and AIS?

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A Diamond mobile antenna? How are you going to mount that? I might be mistaken, but I thought that all of Diamond's mobile antennas were designed for the vehicle to provide the ground plane. In other words, you can't just mount one of those antennas on top of a mast and expect it to work.
Well, not all of them are... it is mentioned in the details. Most that can use the magnetic mount are okay I think.

But I have another ace up the sleeve... when I designed our hard top bimini 8 years ago, I included a little stainless plate in between the solar panels which will function as a base to put mobile mounts designed for trunks onto. It's also drilled for every type of mount I know of. So I decided that for now I will put the dual band antenna there. I ordered a mount that comes with 13.5' of that nifty thin coax (1/8" thick) with SMA connector which means I can easily route it into the boat. They add an adaptor to PL259 for the rest.

I'm hoping the solar panels provide a good ground plane I hope...

That Kenwood radio needs NMEA0183 just as I try to get rid of that...

ciao!
Nick.
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Old 15-03-2012, 17:34   #15
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Re: VHF / UHF HAM Radio Antenna ... and AIS?

The Diamond dual band antenna on our mast before the lightning strike had a loading coil and regular PL259 connector and did not need the mast for the ground. So does the spare we have on board (you should have mentioned all this earlier Nick - I could have saved you some shipping costs!).

Of course, mounting the antenna to the mast connects the ground to the mast - similar to most common metal whip VHF antennas with loading coils.

Mark

Edit: I just caught that you specified the Diamond mobile antenna, and I think I am talking about a different Diamond model.
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