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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.


Thanks,

Allan.
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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.
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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?

Allan,
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 better....as 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 disappointed.....fyi, "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 boats....so, 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...

Quote:
Originally Posted by ka4wja View Post
Allan,
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).











https://www.eham.net/reviews/view-product?id=3094
https://www.eham.net/reviews/view-product?id=7368

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...
https://www.eham.net/reviews/view-product?id=3424
https://www.eham.net/reviews/view-product?id=5236

https://www.dxengineering.com/search/product-line/diamond-antenna-sx20c-power-meters?autoview=SKU&keyword=diamond%20meter&sortby =BestKeywordMatch&sortorder=Ascending

https://www.dxengineering.com/search/product-line/diamond-antenna-sx40c-power-meters?autoview=SKU&keyword=diamond%20meter&sortby =BestKeywordMatch&sortorder=Ascending



Or, you may decide on a full-sized power/swr meters, such as Daiwa CN-901 series....
https://www.dxengineering.com/search/brand/daiwa-products/department/meters-and-test-equipment/part-type/swr-wattmeters/product-line/daiwa-cn-901-professional-series-bench-meters?autoview=SKU&sortby=Default&sortorder=Ascen 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....
But, before you choose/decide, please read this thread here:
https://www.cruisersforum.com/forums/f13/recommended-swr-meter-for-ssb-panel-meter-158526-2.html




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, etc....you'll see these meters in operation...

Maritime HF Communications
https://www.youtube.com/playlist?list=PLnN6ygtZ3h2nPNdApNsZDo_Jk3NB_Bt1y


HF-DSC Comms
https://www.youtube.com/playlist?list=PLnN6ygtZ3h2n3z5nlv-ga2zYuPozhUXZX


Icom M-802 Instruction Videos
https://www.youtube.com/playlist?list=PLnN6ygtZ3h2npivDjoFrC-8QKVyMb4tVr


Offshore Weather
https://www.youtube.com/playlist?list=PLnN6ygtZ3h2mPZAx2vWzdjTJjHlChruyY



And, just for fun:
Offshore Sailing
https://www.youtube.com/playlist?list=PLnN6ygtZ3h2nbwAGh5DKgTCj15iyl6qoY



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.)
https://www.cruisersforum.com/forums/f13/marine-ssb-stuff-how-to-better-use-properly-install-ssb-and-troubleshoot-rfi-etc-133496.html

HF-SSB Radio, Proper Installation Tips/Techniques, etc.
https://www.cruisersforum.com/forums/f13/hf-ssb-radio-proper-installation-tips-techniques-etc-198305.html



I do hope this helps?

Fair winds.

John




Fair winds.

John
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