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Old 05-10-2020, 08:17   #1
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Minimum distance between SSB backstay antenna and a parallel cable?

Is there a recommended minimum distance between a SSB backstay antenna and another metal rigging cable running parallel? Viewing the attached photo, the backstay is circled in red, and it runs parallel, at about a 12" distance, to another metal cable.


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Old 05-10-2020, 08:37   #2
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Re: Minimum distance between SSB backstay antenna and a parallel cable?

Some books say 1/2 wavelength. If we look at VHF, we know that we are told to keep the VHF separate from the AIS antenna by about 3 ft.

On a boat, real estate is precious and in cases there really isn't any good separation. I think you mentioned 12". That should be OK. When we run the GTO15 out the transom we like to keep it separate from the aft railing by around 3" or so. Even when we run the GTO15 up a backstay to the feed point we also keep some separation.
Brian D
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Old 05-10-2020, 08:46   #3
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Re: Minimum distance between SSB backstay antenna and a parallel cable?

There is no "right answer" to your question!
Whatever anyone else tells you, this is a fact....there is no right answer here...

Okay, now that I got that out of the way, how about I try to give you something useful?

1) In general, the father away the any metallic conductors running parallel to an antenna will couple-to the antenna...

And, this coupling can be a bad thing....but can also be inconsequential...
(you see one reason why there is no "right answer" here?)

{Heck, there are expensive, store-bought marine SSB antennas (GAM Split-Lead) that actually couple-to your backstay (and entire rig), in order to perform....and in some circumstances they do work well, but most users are, "shunt'fed". "slant-fed", and "coupled" HF verticals have been tried since the 1920's, and even today with 21st Century computer modeling, these are generally not good wide-band/multi-band antennas, and as such they are generally a "crap-shoot"....}

2) Remember, that it's a sailboat.....and the rigging is the necessity, not the antenna...

Getting you antenna out in the clear is usually an impossible task on our, we just deal with weird antenna patterns, and occasional transmit RFI, etc...

But, as I wrote above:
In general, the farther away - the better...

3) Before you go out and start trying to figure out this, piece-by-piece....please take some time and read the stickies above and watch the videos, etc....(that I just linked to in your other thread...)
You will find that in order to save yourself money ($$$$) and time (!!!!), you should approach this as a "system", not bits and pieces...

Originally Posted by ka4wja View Post
Yes, they are power/swr meters...
The long answer is:
These specific meters are Daiwa CN-410M and CN-460M, for my HF and VHF radios (respectively).

Although, those particular meters are no longer manufactured, you can occasionally find them for sale used, on ebay, etc...

Or, you can look at similar small-sized / mobile-type meters, made by Diamond....the Diamond SX-20c and the Diamond SX-40c... =BestKeywordMatch&sortorder=Ascending =BestKeywordMatch&sortorder=Ascending

Or, you may decide on a full-sized power/swr meters, such as Daiwa CN-901 series.... ding
But, I prefer the "mobile" meters, as they have a bit easier resolution for use with 100-150 watt radios, as well as being smaller and easier to find good mounting location on-board...

But, before you choose/decide, please read this thread here:

And, have a look at these video playlists, where in addition to learning a lot about HF communications / marine HF comms, DSC comms, offshore weather,'ll see these meters in operation...

Maritime HF Communications

HF-DSC Comms

Icom M-802 Instruction Videos

Offshore Weather

And, just for fun:
Offshore Sailing

And, last but not least....have a look at the stickies at the top of the Marine Electronics page here....where, you'll find not only the answer to your specific question here, but a wealth of HF / Radio communications info / reference material, and answers to many "Marine SSB" questions...

Marine SSB Stuff (how-to better use / properly-install SSB, & troubleshoot RFI, etc.)

HF-SSB Radio, Proper Installation Tips/Techniques, etc.

I do hope this helps?

Fair winds.


Fair winds.

John, KA4WJA
s/v Annie Laurie, WDB6927
MMSI# 366933110
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antenna, ssb

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