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Discussion Starter #1
I've recently purchased a new Icom 802 SSB and tuner, and currently have a Simrad 4g radar gimballed mounted on my backstay(I also have a hydraulic pump for the backstay). I want to install isolators on the backstay. Where is the best location for the isolators on the backstay? Can the lower isolator be placed below the gimballed unit? I've seen similar setups with the lower isolator placed above the gimballed unit, but wasn't sure if this is necessary.
I'm a little worried about how the SSB, when in use, will affect the radar operation. Any comments would be appreciated. Thanks!
 

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Mermaid Hunter
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What kind of boat? With a backstay adjuster you nee to feed the backstay above the adjuster. Can you post a picture of the bottom of the radar support?

This is a mechanical issue. There is no reason to be concerned about interference between the radar and SSB.
 

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If you make your radar unit part of the SSB antenna, the transmitting energy will pass through the TWT and other circuitry. Don’t know if it will completely fry the electronics, but I wouldn’t want to try it. The transmitting energy will also travel down the radar’s wiring and into the boat’s wiring system. This will definitely degrade your transmitting range. Plus, you wouldn’t want the antenna to be anywhere near where it can shock you while you steer the boat. Of course the best thing is to abandon the idea of having an SSB on board and selling me the ICOM. Feel free to PM anytime, day or night.;)
 

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Discussion Starter #5
I've seen other units mounted in this fashion, as I mentioned imoq. Are they not able to transmit with the radar at the same time that they are on the SSB?
As far as selling...HA!
 

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Mermaid Hunter
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I've recently purchased a new Icom 802 SSB and tuner, and currently have a Simrad 4g radar gimballed mounted on my backstay(I also have a hydraulic pump for the backstay). I want to install isolators on the backstay. Where is the best location for the isolators on the backstay? Can the lower isolator be placed below the gimballed unit? I've seen similar setups with the lower isolator placed above the gimballed unit, but wasn't sure if this is necessary.
I'm a little worried about how the SSB, when in use, will affect the radar operation. Any comments would be appreciated. Thanks!
Below are three images. One of the pump, the gimballed unit, and the top of mast.
I have a 38' little harbor.
Thanks
I have a 38' little harbor.
I haven't touched a Simrad 4G radar. My only concern would be the data rate from the scanner to the display unit. If it is, for example, a 10 Mbps Ethernet there is the potential for some interference although damage is unlikely.

You could put an insulator above the radar and a few feet below the masthead. Note that the entire antenna length is measured from the GTO-15 connection on your tuner to the upper insulator. There are some lengths that are hard to tune. I have built a spreadsheet that calculates those.

An alternative is an "alternate backstay" that avoids mechanical issues with the adjuster and the radar.
 

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SV Auspicious, can you send me a copy of that spreadsheet via a PM?
 

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How do you ground the SSB?
 

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Discussion Starter #10
SV auspicious, can you post that spreadsheet?
Thanks
Do you see a problem mounting the lower insulator below the gimbal unit. I spoke with Gordon West, and he recommended it lower rather than higher for maintenance reasons. Didn't seem he was to worried about the shock factor?
 

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Mermaid Hunter
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SV auspicious, can you post that spreadsheet?
Not really. It is an interactive tool. You plug in the notional antenna length and it tells you if any of the marine or ham bands will be hard for the antenna tuner to match to.

Try http://AuspiciousWorks.com/AntennaLength.xlsx

Do you see a problem mounting the lower insulator below the gimbal unit. I spoke with Gordon West, and he recommended it lower rather than higher for maintenance reasons. Didn't seem he was to worried about the shock factor?
Fair enough for maintenance, although if you do it right you should only need to touch it once every couple of years. My concern is the space and other things going on between the adjuster and the gimbal pipe. The picture you posted isn't very clear.
 

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Even with an insulator above the radar, the GtO feed line running up to the insulator is part of the antenna anyway. Have you considered a wire antenna on a separate halyard? I put my tuner up on the arch portside, with the antenna wire up to a topping lift. It does run sort of parallel to the backstay, but nothing was cut or needed to be insulated. My backstay splits some 12-15' above the deck, so feeding/insulating it would have been messy in its own way.


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I have my insulator above my backstay mounted radar unit. "Service" for the GTO-15 attachment to the backstay is required almost never. Why take any risks with your radar for no advantage?
 
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