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Old 22-12-2010, 07:50   #31
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No, there's no provision for a single-wire antenna. Remember, this is a HAM RADIO (see post #16).. . .Bill WA6CCA
Most of the modern HF radios used on cruising boats these days - ICOM or SGC, etc. are "dual" capable of both HAM and Marine HF/SSB. Adapting a land HAM rig for use on a boat will probably require some advanced knowledge like you have. I was under the impression that you could use a "tuner" (common name, but not its real name) even with the old HAM rigs if you are using a backstay or 23' whip antenna.
- - I get my parts from Radio Works or RF Parts or Fallalon Elect in Calif or where-ever. My HAM use is strictly for Cruising use with nets and Winlink/Airmail. Since the weather nets and such are all on Marine HF/SSB - is the OP's radio set up to access those channels? If not what is the usefulness of such a HAM radio for Cruising People/Cruising Boats?
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Old 22-12-2010, 09:06   #32
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Most of the modern HF radios used on cruising boats these days - ICOM or SGC, etc. are "dual" capable of both HAM and Marine HF/SSB. Adapting a land HAM rig for use on a boat will probably require some advanced knowledge like you have. I was under the impression that you could use a "tuner" (common name, but not its real name) even with the old HAM rigs if you are using a backstay or 23' whip antenna.
- - I get my parts from Radio Works or RF Parts or Fallalon Elect in Calif or where-ever. My HAM use is strictly for Cruising use with nets and Winlink/Airmail. Since the weather nets and such are all on Marine HF/SSB - is the OP's radio set up to access those channels? If not what is the usefulness of such a HAM radio for Cruising People/Cruising Boats?
All radios -- ham or marine -- used on boats will require:

1. some sort of antenna and antenna coupler (tuner); and

2. some sort of RF ground (counterpoise).

Most all HF radios these days come with a SO-239 UHF female connector on the rear for use in attaching the antenna. Marine radios will use this to connect to an automatic coupler via a random length of 50-ohm coax (RG-8X or RG-213, RG-214, etc.). Typical automatic couplers include the Icom series (AT-120/130/140), the SG-230, and others.

Similarly, ham radios will use the SO-239 to attach coax leading either to a tuner of some sort or, if the radio has an internal antenna tuner -- and many ham radios do -- the coax can lead directly to an antenna or, as recommended above, to an UN-UN and then to an end-fed antenna. Some hams without radios having internal tuners will use a manual tuner in lieu of an automatic tuner in order to save $$$. This works OK, but takes a bit of knowledge and experience.

Virtually all ham radios built in the past 20 years or so have wide-band receive capability. No problem, therefore, copying traffic on the marine nets. BTW, many ham nets also provide WX information regularly, including the 14300 kHz Maritime Mobile Service Net (every hour on the 1/2 hour), the WaterWay Net on 7268 kHz, and others.

It is not legal, of course, to use a ham rig to transmit on any band other than those specifically set aside for amateur use, i.e., not on marine bands, aircraft bands, land-mobile bands, military bands, etc. However, you can listen anywhere on the HF and VHF bands and, in an extreme life-threatening emergency, you can also transmit.

Those intending to use the marine bands for 2-way traffic would be well advised to fit a genuine marine SSB radio. Not only does this meet the legal requirement, but marine rigs have several advantages over most all of their ham cousins including low-voltage tolerance, excellent audio, ease of use, etc. If you count the total cost of ownership, including acquisition and installation costs, a marine radio will not cost much more than a ham radio.

Bill
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Old 22-12-2010, 09:27   #33
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I'm very new a this and I only intend to install the radio as a receiver,maybe later as a transceiver. i want to thank everyone for their help.
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Old 22-12-2010, 11:21   #34
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If you only want to use the radio as a receiver, it will work just fine to run your coax to your backstay chainplate or the bottom of your backstay and attach the center conductor of the coax there. The shield of the coax can be pulled back and would ideally be attached to a "ground" point or some sort of counterpoise - which could even be your stainless steel lifeline that runs around the boat. You certainly don't need an un-un for receive only purposes.

If you wanted, you could even run the GTO-15 to your Kenwood and with a banana plug on the end, plug it into the center of the SO-239 antenna jack on the back of your radio. You would still want some sort of ground connection for best reception.

On boats, the farther you can get your receiving antenna from potential RF noise sources, the better, so running the coax to your backstay, or a whip mounted on the stern, is probably going to be the best solution. Running the coax to your stern would make it ready to accept an un-un or wide range autotuner if you ever decide to gear up for transmitting too.
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Old 22-01-2011, 07:22   #35
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I am installing an Icom 718 HAM set and intend to remove the diode which restricts it from transmitting on Marine Bands. I had previously bought a used Kenwood set which turned out to be garbage. I bought a manual tuner for the Kenwood since it didn't support an automatic tuner.

So my question is, if I install the radio and atuner at the navstation, I would need to run 15 feet or more of GTO-15 below decks and then up the backstay. I am thinking that this will put lots of radio wave power bouncing around inside the boat creating rf interference on all the electronics.

My question is can/should I buy an unun from balun designs, and run rg-213 from the tuner to the unun in the stern by the backstay, tell the tuner it is a coax ant. and attach the kiss-ssb counterpoise and the GTO-15 to the unun? Seems to me that less rf would be in the boat with this setup.

Am I missing something, or is this the correct strategy?

Thanks
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Old 22-01-2011, 07:30   #36
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.....

My question is can/should I buy an unun from balun designs, and run rg-213 from the tuner to the unun in the stern by the backstay, tell the tuner it is a coax ant. and attach the kiss-ssb counterpoise and the GTO-15 to the unun? Seems to me that less rf would be in the boat with this setup.

Am I missing something, or is this the correct strategy?

Thanks
No, you've got it right. That should work just fine.

Small improvement: you could use RG-214 (double-shielded coax) or LMR-400 in lieu of RG-213 for greater RFI suppression.

Depending on results, you might also want to install some healthy size ferrites and/or a RadioWorks isolator on the coax.

Bill
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Old 22-01-2011, 09:59   #37
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Something else that MIGHT work for you, though rarely recommended, is to put the tuner at the nav station, and from the tuner run low loss coax to the base of the backstay. At that point attach the shield braid to your ground/counterpoise system, and the center conductor to your backstay - via GTO-15 if you need to run it above a lower backstay insulator.

There would be very high SWR and voltage nodes along the coax, even if your tuner is matching it to your transmitter. This high SWR will result in additional power loss in the coax, but when you do the calculations with a fairly short run (say 20 feet) and good coax, the losses are not extremely high, maybe on the order of 10 to 30 watts at worst (but often less depending on the band) if you are transmitting 100 watts. This would make hardly any practical difference to the receiving station.

I've done this when my AT-140 was not functional, and it worked, but it certainly is not the ideal.

I wouldn't do this with poor quality coax, or with high transmitter powers, but you could experiement with it and see how it goes for you. You might be surprised.
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Old 22-01-2011, 10:09   #38
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Thanks

Does this look like the correct unun?
4:1 Unun for Monopoles, Wire Verticals & Long Wires - 5kw - #4134
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Old 24-01-2011, 08:30   #39
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That would be the right balun. It will help at those frequencies where the SWR is high because antenna impedance is high, but for those frequencies where impedance is low, this will make it even lower and potentially worsen the match. It all depends on the characteristics of your particular antenna installation and the bands you will be wanting to operate on.

Your best bet would be to borrow or buy an antenna analyzer (the MFJ-259b is one) and use that to determine what will work best for you.
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Old 24-01-2011, 11:48   #40
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You know I am new to this but my antenna will be the backstay which is 5/16" SS 1x19 wire. I will primarily be transmitting on the marine band frequencies in the 4000, 6000, 8000 frequency ranges although I may need other frequencies later. What Iam trying to do is avoid a long run of GTO-15 cable that will inject lots of rf interference inside the boat.

What other moere optimal strategy might be worth considering?
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Old 24-01-2011, 12:16   #41
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Your easiest/most versatile all around strategy is to run coax to an automatic tuner installed at the base of the backstay, and from there run GTO-15 to your backstay antenna. Downside is you will need another $400 to $500 of hardware. Plenty of information on doing this on this site and others.
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Old 24-01-2011, 12:37   #42
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.... I will primarily be transmitting on the marine band frequencies in the 4000, 6000, 8000 frequency ranges although I may need other frequencies later. ......
Be advised that the Icom 718 is NOT type accepted to operate on the marine bands, i.e., it is illegal to do so except in an extreme emergency.

Lots of people do it nonetheless, but it's not a great idea and could someday land you in a bunch of trouble.

Bill
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Old 02-05-2011, 12:12   #43
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Re: Attaching GTO15 Cable to Antenna Tuner

Hi, I have q question about all of this, I have an Antenna that connects to the back stay through a plastic shielding and the GTO 15 cable connects to that and then my tuner. when transmitting is that connection "live" can I get a shock from it? or if it touches anything such as fabric or the backstay, can anyone, such as pets get hurt?
How important are the standoffs cause my backstay goes through both my enclosure and bimini.

regards

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Old 02-05-2011, 12:50   #44
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Re: Attaching GTO15 Cable to Antenna Tuner

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Originally Posted by fawcettm View Post
Hi, I have q question about all of this, I have an Antenna that connects to the back stay through a plastic shielding and the GTO 15 cable connects to that and then my tuner. when transmitting is that connection "live" can I get a shock from it? or if it touches anything such as fabric or the backstay, can anyone, such as pets get hurt?
How important are the standoffs cause my backstay goes through both my enclosure and bimini.

regards

Mark
Mark,

The insulation on GTO-15 wire is rated at 15,000 volts. It is highly unlikely that you'd get a shock from this wire. You, your crew, and your pets should be OK.

Standoffs are a good idea, but not absolutely necessary.

Bill
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Old 02-05-2011, 12:58   #45
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Re: Attaching GTO15 Cable to Antenna Tuner

Thanks Bill, so then the standoffs are so that there is better transmission and reception? Forgive me, I am just installing the equipment, I am trying to learn all of this as I go.
the threads are good though, I can learn alot here.....

regards

Mark
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