Adding a non-marine antenna tuner to the boat

Feb 17, 2006
5,102
Lancer 27PS MCB Camp Pendleton KF6BL
I am still in the process of finishing my SSB installation. Just lost motivation recently but it seems to be coming back.

With the demise of the Kenwood TS-50, I purchased an Icom IC-707. It is an older radio but like the TS-50, it has very little in the way of bells and whistles. Simplistic sums up this radio. It has been opened to allow all band Tx. Not that I will ever use it, but...

As part of the on-going project, I will be installing a 35' Alternate Backstay Antenna. It will be connected to an MFJ-939 automatic antenna tuner. The MFJ is not marine grade by any stretch of the imagination. So one must improvise, adapt, and overcome.

I purchased a watertight box off of eBay to use as the housing for the tuner. The tuner is attached with #4 sheet metal screws to the bottom of the box. The screws are driven into the rubber feet. This seems to hold well but it might come loose under harsh sea conditions.

The three entry points are for control (left), radio (center), and antenna (right). Ground is on the right side of the box. The glands are sized for .25" cables. The antenna cable will be GTO-15.

I have a sea dog cable gland coming for the GTO-15 to exit the deck.

So there we go. Got that portion of the project done. Maybe it was enough to get my motivation back up. We will see.

DSCF4479_1.jpg

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Rick D

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Jun 14, 2008
7,004
Hunter Legend 40.5 Shoreline Marina Long Beach CA
Brian, can you point me to that waterproof box? I couldn't find it on e-bay although I did find some that will work? I like yours better.
 

Rick D

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Jun 14, 2008
7,004
Hunter Legend 40.5 Shoreline Marina Long Beach CA
OK, got a different box for the IT-100 tuner which is smaller. I decided to sell both the ICOM M700 and the AT-120 tuner as a set (on e-bay). We'll see... Thanks for the idea.
 

Rick D

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Jun 14, 2008
7,004
Hunter Legend 40.5 Shoreline Marina Long Beach CA
Hey, all: I am mimicking what Brian did. So, the antenna connector is for coax; the antenna is GTO-15. At least I think; insulated wire. So, how do I connect that to a coax lead?
 
Mar 13, 2011
175
Islander Freeport 41 Longmont
Sounds like you know what you are doing.

I already have the radio (Icom 802) and the auto-tuner installed. For some reason the antennae is missing. My boat an Islander 41 Freeport Ketch, has a separate tang mounted on the Mizzen for a "backstay" antennae, I have the lead out of the auto-tuner up through the deck and I assume there is a point to mount this at teh top of the Main mast. My two questions.
1. What do you use for an insulator at the top and lower end of the antennae wire?
2. What type of wire are you using for your antennae

I already have a trip up the main mast planned and would love to be able to get this working at the same time.
Great to read/see your progress. Keep the story going.

Thanks,

Victor
S/V Desiderada
 
Feb 17, 2006
5,102
Lancer 27PS MCB Camp Pendleton KF6BL
@Rick D , the GTO-15 looks and feels exactly like RG8X. So you can solder a PL-259 to the GTO-15 and connect it to the antenna tuner. There is no shield on the GTO-15 so no worries there. The ground lug from the tuner will connect to a screw you install on the box like I did. It will be connected to whatever you use; KISS, seawater, engine block...

@vhoisington , I use wire-rope. The same material used for lifelines. Any insulator will work. You can make your own with PVC pipe or order "egg insulators" from ebay or Amazon. The lead from the tuner you see will connect to the bottom of the wire you run to the top of your mast. The top most insulator should be about 2' (5cm) from the top of the mast. Length of wire can be any but recommend >23' (7m).
 
Oct 25, 2011
572
Island Packet IP31 Lake St. Louis, Montreal
Perhaps a dumb question, but does the tuner produce any heat?

Matt
 

Rick D

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Jun 14, 2008
7,004
Hunter Legend 40.5 Shoreline Marina Long Beach CA
Exactly what I needed to know. Thanks Brian!
 
Feb 17, 2006
5,102
Lancer 27PS MCB Camp Pendleton KF6BL
@py26129, yes it does, but only when the turner is NOT tuned correctly to the frequency being used for the length of antenna. It is important, IMHO, that the length of the wire being used as the antenna can be matched, or tuned. If the length is correct and the tuner is happy, no heat per se.

This is a very good read: Using Auto Tuners
 
Feb 17, 2006
5,102
Lancer 27PS MCB Camp Pendleton KF6BL
@vhoisington, I need to clarify about the insulator. The one that I mentioned should only be used on an alternate backstay antenna. This antenna is NOT a load bearing backstay, or stay of any type. It is totally independent. You might check your backstay(s) to see if they have insulators at the bottom and the top. If so, that was your antenna. Otherwise, if you do not have anything, AND, if you have a spare halyard, you can add an alternate backstay antenna.

So remember, these insulators are for non-loadbearing stays.
 
Mar 13, 2011
175
Islander Freeport 41 Longmont
Yes, mine would be a non load bearing stay. I believe I have a mounting point at the mast and need to tension this such that it remains above the actual back stay but it should be fine otherwise. I was most interested in the material used for the antennae wire and any specific insulators you used.

Thanks,

V
 
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Feb 17, 2006
5,102
Lancer 27PS MCB Camp Pendleton KF6BL
Here is a link to an interesting blog about a guy adding an alternate backstay antenna. The "Bill" he mentions in the blog is Bill Trayfors, WA6CCA. My website (shameless plug here) has a link to a page on how to build vertical dipoles.
You will note that the author did not use insulators for his antenna.

Anyway, I digressed. Alternate Backstay Antenna (You will note that the author did not use insulators for his antenna.)
 
Feb 17, 2006
5,102
Lancer 27PS MCB Camp Pendleton KF6BL
One more observation I would like to point out from the blog above. In one of the photos you can see the "lead" wire (red?) connected to the antenna wire. Notice that the antenna wire is about 4' to 5' above the deck. Assume the antenna wire is 35' long going to the top of the mast. Assume that the run from the antenna connection above deck to the tuner is 7'. Since the "lead" is connected from the antenna to the tuner, it is considered part of the antenna. So the total length of the "antenna" now is 42'. That would be 7' of "lead" plus 35' of antenna.

Also, I must warn you that this portion of the antenna, the lower portion, is the most dangerous part. It carries the high voltage of the antenna and if one comes in contact while the radio is transmitting, one can get a nasty RF burn. The whole antenna is rather dangerous but more so the lower part.

So if you want a specific length of "antenna" you must include antenna wire AND antenna lead back to the tuner.

Just a FYI for anyone following and interested in adding a SSB antenna to their vessel.