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Old 14-08-2016, 19:08   #1
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Hf Radio, Computer & Salt water = Madness

OK sorry for the weird title, but I don't know where to go with this.

We have been recharging the kitty in Honolulu for awhile, and are getting ready to shove off again next spring. My one day a week at WM has allowed many things to be fixed or upgraded. So here is a description of the variables and the results.

I replaced the rigging. After quite a bit of reading I reduced the distance between the backstay insulators. We had always had problems on the higher bands, and this sounded like part of the fix. I don't remember the measurement I used, but think it may have been 37' total length from the tuner.

We have changed laptops, currently on Lenove Thinkpad, replacing the old Toshiba.

The result:

When trying to get out on Sailmail we are good down below 8Mhz, where it will barely tune at all. Around 14Mhz the Com port on the computer disconnects . . .

What I've tried:

Ferrites EVERYWHERE, replaced the coax to the tuner, and finally put a USB extension to take the computer away from the nav station to test if stray RF there was causing the disconnect. The USB extension fixed the Com port disconnect on 14Mhz! Even when I move back to the nav station, but with it attached I get Com port disconnects on the lower freqs.

I don't see lights glowing, my hair isn't standing on end and I don't get zapped when running my hands all over the radio and coax while transmitting. That last only happened after holding my breath and offering a toast to Neptune. I figure there must be stray RF, but sure don't know what to do next.

The hardware is:
Icom 706 mkiig
Pactor PTC-IIusb
SGC 230
Edgeport USB to (Serial for GPS, and USB for Pactor)

So what do I throw at this mess next?

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Old 14-08-2016, 19:16   #2
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Re: Hf Radio, Computer & Salt water = Madness

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Originally Posted by romanystar View Post
...........


So what do I throw at this mess next?

I'd be checking how it works as a simple radio/tuner/ant setup and make sure that bit is working first. Maybe start by chucking in a dummy load and a SWR meter .

Just a thought....

I used to have laptop issues with Tx on Sailmail.... that was fixed by ferrites but I think you have already sorted that end.
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Old 14-08-2016, 19:27   #3
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Re: Hf Radio, Computer & Salt water = Madness

..check for a ground loop.. looks like you leaking RF trough wires.. also, could be antenna is just resonating.. cut or enlarge slightly.. add coaxial.. and I could try a manual antenna tuner like to type used to tune long wires antennas...
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Old 14-08-2016, 19:58   #4
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Re: Hf Radio, Computer & Salt water = Madness

Have heard the term ground loop many times over the years but haven't got a real clear idea of what it means or how to check for one.

The radio is grounded to the DC common, the tuner is grounded through a copper foil to a Dynaplate and the engine block
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Old 14-08-2016, 19:59   #5
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Re: Hf Radio, Computer & Salt water = Madness

The radio has built in SWR meter, and when it tunes up the SWR is always below 1.5, usually closer to 1.
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Old 14-08-2016, 20:33   #6
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Re: Hf Radio, Computer & Salt water = Madness

What kind of ferrites did you use, and how did you configure them? Using a ferrite optimized for VHF frequencies may not help at all on SSB HF frequencies. Using the appropriate ferrite, with multiple turns, and located adjacent to the equipment being affected can be extremely effective.

Here's a link to a presentation I did on at-sea communications. It includes some useful ferrite information: http://www.sailvalis.com/presentatio...ons%202012.pdf
See pages 11-14.
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Old 14-08-2016, 21:02   #7
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Re: Hf Radio, Computer & Salt water = Madness

You said that your antenna is 37 feet long. However, you were not clear if the length is from your antenna tuner to the insulator at the top of the mast. If it is, that would make it close to a half wave for 14 mHz. A half wave antenna has a very high impedance. It is possible that this could cause a high RF voltage to be present at the output of your tuner. These high voltages could be coupling to the vessel's wiring causing RFI. And, it would explain why 14 mHz seem to giving you the most problems.
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Old 14-08-2016, 21:36   #8
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Re: Hf Radio, Computer & Salt water = Madness

The ferrites are from Radio Shack. They are the snap on variety.

I'm pretty sure that 37' is the total length of the antenna counting lead from the tuner and the section of backstay. This sounds like a reasonable explanation of what I am seeing. It is one of the things that changed since it was working well a couple years ago. Unfortunately it is a pretty tough thing to experiment with. I'll have to order more wire and spend a half day messing around to see if this is the answer. Unfortunately my schedule puts that about a month away.

So what is an appropriate total antenna length? I use 8Mhz, 10Mhz, 14Mhz, 16Mhz and 18Mhz for communication on passage.
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Old 14-08-2016, 23:30   #9
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Re: Hf Radio, Computer & Salt water = Madness

Min antenna length is 23 feet, the longer the better. I would take a longish piece of wire connect one end to the tuner, the other to a halyard and experiment with different antenna lengths from 30 to 50 feet. Once you find the sweet spot for your target frequencies you can cut the backstay to the appropriate length.

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Old 15-08-2016, 00:02   #10
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Re: Hf Radio, Computer & Salt water = Madness

If the backstay below the lower insulator is grounded you can try to bypass the lower insulator with a jumper. It is a different type of backstay antenna that sometime works. Even though the antenna is grounded it wont hurt the antenna tuner.
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Old 15-08-2016, 00:45   #11
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Re: Hf Radio, Computer & Salt water = Madness

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Originally Posted by romanystar View Post
Have heard the term ground loop many times over the years but haven't got a real clear idea of what it means or how to check for one.

The radio is grounded to the DC common, the tuner is grounded through a copper foil to a Dynaplate and the engine block
Ground loop refers to current circulating in your "ground" wiring, when all the grounds are not equipotential, and a voltage offset exists where otherwise it should not.

DC: If you have two electronics boxes that have for example 5volt circuits in each that need to interface with one another, if they are not referenced correctly and equally to the same ground reference, then well 5 volts on one side might not be 5 volts on the other side.

And if DC and RF in the mix best for their ground references to be tied, and how directly they are or are not tied could present the opportunity for ground loops.

Might draw yourself a sketch of the ground connections, and how they eventually come together, and probe the various points looking for any voltage offsets.
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Old 15-08-2016, 15:24   #12
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Re: Hf Radio, Computer & Salt water = Madness

are the com port tolerances different from your old Toshiba to your new set up / some computer cables have ferrite's around them
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Old 15-08-2016, 16:20   #13
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Re: Hf Radio, Computer & Salt water = Madness

Disconnect your foil from the engine block. This is usually the cause of a ground loop.
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Old 16-08-2016, 23:52   #14
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Re: Hf Radio, Computer & Salt water = Madness

I think I have eliminated grounding as an issue. I borrowed a KISS grounding device from a neighbor who swears by it. Neat idea, tuned radials without any connection to the water. I'm going to probably buy one just to get rid of the sharp edges on the copper foil.

It took about two minutes to swap it in to replace the copper foil to Dynaplate to engine block ground that I have used for about 25 years. The Icom is grounded to the DC ground bus. The tuner is grounded to the KISS. Fired up the radio and the symptoms are exactly the same.

I am ordering some more SS wire and am going to increase the backstay antenna length and see what happens. Will report back in about a month when I can get it on the schedule.
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