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Old 24-11-2015, 08:00   #1
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SSB in steel boat

Here's another steel boat SSB question. Situation: Icom 725, 23' whip, tuner just under antenna inside steel hull. Grounds by copper plates to hull. Recieves well enough for me to listen to Bahamas net from Floria panhandle. Does not tune on any frequency, can get only 10% transmit power around 14 MHz, other bands it shuts off when I press the PPT. The radio itself has been plugged into a ham setup and works fine. Idea: Is it possible that the antenna wire leaving the tuner and going through a small hole in the steel deck to reach the whip is leaking RF to ground (the boat)? Other possible problems? Thanks. --Tim
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Old 24-11-2015, 09:57   #2
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Re: SSB in steel boat

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Originally Posted by tkeithlu View Post
Here's another steel boat SSB question. Situation: Icom 725, 23' whip, tuner just under antenna inside steel hull. Grounds by copper plates to hull. Recieves well enough for me to listen to Bahamas net from Floria panhandle. Does not tune on any frequency, can get only 10% transmit power around 14 MHz, other bands it shuts off when I press the PPT. The radio itself has been plugged into a ham setup and works fine. Idea: Is it possible that the antenna wire leaving the tuner and going through a small hole in the steel deck to reach the whip is leaking RF to ground (the boat)? Other possible problems? Thanks. --Tim
Very possible. You could try continuity testing between the wire terminals and the hull, for starters. Also possible that the small tuner control cables (x4) between the black box and tuner (if it is an Icom set) have worked loose, or are mildly corroded, or otherwise not properly connected. This would cause a tuning failure and is fairly common. I have on more than one set ditched the proprietary connector and rewired using crimped terminals (very small ones!).
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Old 24-11-2015, 12:08   #3
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Re: SSB in steel boat

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Here's another steel boat SSB question. Situation: Icom 725, 23' whip, tuner just under antenna inside steel hull. Grounds by copper plates to hull. . --Tim
As a fellow Steel boat owner with SSB I do not like the sound of grounding with copper plates, it sounds like a recipe for massive and rapid corrosion.

My ground is a short length of alternator cable bolted from the ATU to one of the steel frames and I am told it works very well.

There is an issue with the ICOM 802 that even when the headset is switched off the set still leaks DC current through the ground cable to the hull (another way to loose steel). I am not sure if your model has the same issue but if it does there are simple solutions to this problem
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Old 24-11-2015, 12:31   #4
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Re: SSB in steel boat

No mention of what tuner you are using.

Through the deck I would be using something like this.. Porcelain Feedthrough Standoff Insulator - High-Voltage Johnson Model 51 - VETCO.NET
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Old 24-11-2015, 14:11   #5
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Re: SSB in steel boat

I'm using and LDG IT-100 automatic tuner with two feet of high voltage wire to the Shakespeare 23' whip. The "at rest" resistance between the antenna and the boat is about 5.5 Kohms. One experienced ham says I need a manual tuner between the automatic tuner and the antenna, but the automatic is supposed to do just this job. I mistakenly (off my licensed bands) got a radio check from someone 2000 miles away in the 14 MHz range, but the radio will not transmit in any other frequency range. Further thoughts?
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Old 24-11-2015, 14:17   #6
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Re: SSB in steel boat

Further: I'm getting a porcelain through-hull insulator, thanks. The copper straps are in very dry locations, and this installation is new, so there has not been time for corrosion problems. I will check my stray current/anodes meter - thanks for that warning.
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Old 24-11-2015, 14:33   #7
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Re: SSB in steel boat

I'm using an LDG IT-100 with an Icom 718 ashore with assorted wires in the sky... works good. I do have a Diamond SWR meter in the line though.... so I can see that it is tuning OK.

Only thing I can think is an issue with your whip.... try running a simple long wire to the mast head and see what happens.

Two other points...compatable radio? from the manual..
'Compatible Transceivers
The IT-100 is designed to be used with any Icom 100 watt transceiver that supports the AH-3 or AH-4 Icom antenna tuners. Currently, this includes:
• IC-706
• IC-718 (select AH-4) • IC-746
• IC-7000'

and - I know you already know this .... just running through the list - the LDG isn't fully automatic as far as I know.. you have to 'press to tune'.
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Old 24-11-2015, 14:37   #8
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Re: SSB in steel boat

Another thought....what have you attached the copper strap to? The ground stud on the tuner or the shield/outer on the co-ax?
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Old 24-11-2015, 17:11   #9
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Re: SSB in steel boat

Lots of good thinking going on here to my benefit, which I appreciate. The Icom 725 specifies the AH-3, so I'm assuming it is compatible, but I have not asked LDG. I will. The copper straps are connected to the grounding studs on the radio and the tuner, and reach about six inches to the nearest steel, with two 1/4" stainless steel bolts holding that end. Any concern about the high voltage antenna lead going through a small hole in the steel to reach the whip?
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Old 24-11-2015, 17:23   #10
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Re: SSB in steel boat

tkeithlu,
1) Understand that the IT-100 is not really designed for end-fed, random-length antennas!! And, as such, it might not actually work well for your application....(although you should be able to attain a match at some frequencies, and you should be able to sustain a contact with someone...assuming that you are actually getting the tuner to function!!)

Here's a copy of the manual, if you don't have one...
http://www.ldgelectronics.com/assets...-100Manual.pdf


2) Secondly, be aware that the IC-725 is notorious for having RFI issues!! (distorted transmit audio, RF power fold-back, and in the worst cases the transmitter shuts down completely)
The 725 is very susceptible to RFI, and while getting the GTO-15 wire away from the steel hull, might improve things....having a "line isolator" in your coax line (at the tuner end), and having a more proper tuner (such as an AH-2, AH-4, AT-130/AT-140, etc.), would be the ultimate solution!!

{also, even though the 725 checked out okay at a local ham's shack....this does not mean all is well!! it could still have significant RFI issues on-board, and check out fine on-shore, on resonant antennas, etc...}



3) As for your specific query....
First off, I'm assuming that you also have a tuner control cable attached between the IC-725 and the IT-100??
And, you are pushing the "tune" button/function??
And, that the IT-100 is indicating that it is working??

Have a look here in red....
Quote:
Originally Posted by tkeithlu View Post
I'm using and LDG IT-100 automatic tuner with two feet of high voltage wire to the Shakespeare 23' whip.
This should give you a natural resonance near 9.4mhz to 10mhz....so, even if the IT-100 is not functioning, you should be able to get the 725 to output full power at 10mhz, assuming there wasn't RFI effecting it (which is probable)


The "at rest" resistance between the antenna and the boat is about 5.5 Kohms.
Remember this is measured at DC, not RF....but, this 5.5kohms is good to know!
While this should be in the meg-ohm range, 5.5kohms should actually be okay...

One experienced ham says I need a manual tuner between the automatic tuner and the antenna, but the automatic is supposed to do just this job.
This is NOT true!
Although you could make anything work to some extent, trying is a waste of time/money/effort....not to mention wasting a lot of your power in the tuners!!!



I mistakenly (off my licensed bands) got a radio check from someone 2000 miles away in the 14 MHz range, but the radio will not transmit in any other frequency range.
Is it that it will not transmit, or just that you cannot make contact??
There is a big difference between these two things!
Further thoughts?
Lots, of 'em....
But, you've gotten some good advice here already....so, just a few...

Make sure you have a direct connection from the IT-100 ground lug to your hull / hull frame / etc....and NO other ground connection (except of course the negative DC power connection).....
You can use any short, heavy wire....no need to copper strapping with a steel hull!!!

Please share more details / clarifications....
I hope this helps....

Fair winds...

John
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Old 24-11-2015, 17:58   #11
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Re: SSB in steel boat

Try grounding the chassis of the radio to the hull as well. The coax outer is not enough to carry that to the tuner.

I like a T or L configuration where the radio chassis is grounded to the tuner, and both to the hull. Copper foil is correct, you might want to tin it to get a long life.

Feedwire must not go through a small hole in the steel, or a metal grommet. Plastic or glass is ok but the wire should have a 1/2" clearance around it.

Make sure the tuner is grounded by its grounding terminal NOT the mounting brackets.

Feedline connection to whip must be clean and coated, no right angles, and not running tied to lifelines or guard rails, at least not parallel , the feedline can cross at 90deg.

good luck.
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Old 24-11-2015, 18:58   #12
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Re: SSB in steel boat

Moving right along.... the manual states '• For dipoles, verticals, Vees, beams or any coax-fed antenna.'

Mine can be -and often is- connected to a vertical. However it is connected via coax... nothing is attached to that ground stud on back of tuner.
I have a vertical in the paddock with a swag of copper wire radials at its base which comprise the ground. Coax from tuner to vert where it is split.

Maybe you could attach co-ax to the Ant socket and then connect centre to vertical and shield to your hull?

That is essentially how the 130/140 type tuners are hooked up... is just done in the box is all.

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Old 25-11-2015, 12:48   #13
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Re: SSB in steel boat

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I'm using and LDG IT-100 automatic tuner with two feet of high voltage wire to the Shakespeare 23' whip.[...]
There's your problem! As El Pinguino points out, the LDT-100 tuner is designed to feed "any coax-fed antenna". The specified tuning range is 4-800 Ohms, and your Shakespeare will have a much higher impedance than that at most frequencies.

Your 23' whip, with a 2' feedline will be quarter-wave resonant at about 9.3 MHz -- at this and some other frequencies it will present an impedance that your tuner can handlle, but you really need a different tuner for a random-length vertical.

As the tuner manual mentions, you can try putting an external BALUN at the tuner output, which will transform the high impedance of the whip to a lower value that the tuner might be able to handle.

[note: there are many types of balun, and in this case you need one that acts as a step-down transformer. BALUN means "balanced to unbalanced", but in this case you are actually connecting "unbalanced to unbalanced".]

This is getting pretty technical, so you should get some experienced help, or replace the LDG tuner with something designed for your type of antenna.
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Old 25-11-2015, 13:32   #14
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Re: SSB in steel boat

The 725 simply shuts down (frequency screen goes to dashes) upon pushing the PTT at frequencies away from 14 MHz.

I think my next step is to borrow a good manual tuner and a 50 ohm dummy load from my nearby (but unfortunately not able to climb on my boat) very experienced ham, and determine that the radio is transmitting and can be tuned. Sounds like the IT-100 is just not up to the job.

What a lot of very generous help! I greatly appreciate it. Do have a wonderful break, and I'll revisit the thread with news about the middle of the week. By then I should also have passed the general test.

Best wishes, --Tim.
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Old 25-11-2015, 17:38   #15
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Re: SSB in steel boat

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The 725 simply shuts down (frequency screen goes to dashes) upon pushing the PTT at frequencies away from 14 MHz.
That's common and is a feature to prevent burning the amplifier stage of the radio.

Quote:
By then I should also have passed the general test.
Good luck with the test! Let us know your call sign so we can welcome you to the ham club
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