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SSB vs GPS

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Oct 25, 2005
735
Catalina 30 Banderas Bay, Mexico
I'm planning the install of an SSB radio. I'm planning to use the backstay as the antenna. Do I need to worry about the relative height of the GPS receiver and Radar? The GPS is mounted on a hoop over the Radome about 9 feet of the deck. Should I put the lower insulator above the GPS for any reason? I want to keep the antenna as long as possible and the connection cable as short as possible. This means the bottom of the SSB antenna will be lower than the GPS and Radome. I don't mind if using the SSB causes some interference as long as it does no damage. Thanks in advance, Randy
 

Ross

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Jun 15, 2004
14,693
Islander/Wayfairer 30 sail number 25 Perryville,Md.
The length of the coax won't be a problem

if you use a large enough wire gauge. I would check with Garmin, or Trimble, or Magellan about over loading the GPS antenna with your HF transmissions. In the Air Force our antenna farms were a half mile apart with the Voice of America station in between and we could receive Voice of America on the telephone lines. We were able to tune it out on the VHF and UHF receivers. We had to ground the perimeter fence to avoid electrical shock. Voice of America transmitted 50,000 watts.
 
Jun 12, 2004
1,181
Allied Mistress 39 Ketch Kemah,Tx.
Insulated Backstay?

The SSB should not hurt your GPS or Radar, but will definately affect it only when transmitting, but again....no permanent damage. I assume you are referring to an insulated backstay with an antenna tuner? Tony B
 
Sep 25, 2008
6,037
Alden 50 Sarasota, Florida
one more comment

I just bought a new chartplotter which I have been playing with in my home office in which my ham radio SSB kilowatt transmitter is also located. The two antennas could not be closer and there is no interaction. As long as the SWR on the transmission line to your SSB antenna is low (i.e., no high voltage) the SSB won't interefere.
 
Oct 25, 2005
735
Catalina 30 Banderas Bay, Mexico
Thanks!

Yes, the backstay will be insulated. I'm getting an Icom 802 with the matching tuner, and a SCS Practor III USB modem. To minimize the number of joints in the backstay, I'm putting the top insulator in-line and the lower insulator has an eye to attach to the top of the split backstay legs. The two challenges I see are making sure that the HF system does no damage to the other electronics and getting the Coax past the backstay adjuster. After reading the answers here, I don't think I have to worry about the damage, I'll keep a close watch on any interference when transmitting. I'll use the best Coax I can find and run it up one backstay leg using stand-offs. All I have to engineer is enough of a gap so the adjuster car can still move up and down on the legs. All the information I've read tells me that the Coax from the tuner to the antenna element should be as short as practically possible. I'm planning to mount the tuner at the aft end of the quarter berth or inside the lazerette. I'm planning to use the keel as counterpoise by tapping a connector into a keel bolt and running the copper tape to the radio array for the RF ground system. I'm planning to protect the ground tape with a layer of glass epoxied over it to bond it to the hull. Am I missing anything so far? (I confess that I'm a virgin at HF radio installs). Thanks again, as usual the forum comes through!
 
Sep 25, 2008
6,037
Alden 50 Sarasota, Florida
Moody

You don't need high quality or for that matter, any coax for this antenna although it won't hurt. Coax is intended to feed balanced antennas such as a dipole. Any high voltage insulated cable will do including coax which is obvioulsy well insulated. The antenna effectively begins at the output point from the tuner, hence the reason to keep the feed line short since this is typically the point of highest voltage in any antenna making it the common source for radiated RF interference with the other stuff onboard. Not sure what you refer to here: "I'm planning to use the keel as counterpoise by tapping a connector into a keel bolt and running the copper tape to the radio array for the RF ground system." To say it another way, the copper counterpoise foil connection should run from the keel bolt to the antenna tuner ground post.
 
Feb 17, 2006
5,024
Lancer 27PS MCB Camp Pendleton KF6BL
I'm sure you aware that...

GPS works in the L-band frequency range around 1575 MHz. Unless you have some serious side splatter from your radio that as a multiple results in a carrier at 1575 MHz, there shouldn't be an issue. However, most GPS receivers use a 10 MHz reference frequency to stabilize any receiver drift. If you work in the 10 MHz amateur band, you could very well interfere with the GPS. Could I say, not so much as will interfere. I'm not sure if you mentioned this, but make sure your tuner is at the backstay, not the SSB. Run double shielded coax from the SSB to the tuner. This will keep unwanted RF out of the cabin. Just my thoughts.
 
J

Jeff Jellick / 2006 Hunter 45 CC Sooooo Lucky

No Backstay

We purchased a new Hunter 45 Center Cockpit last year and are also planning on installing a SSB radio. However on the new Hunters there is no backstay. From the limited research that I have done, I have two options, one, using a long whip anatenna, or since I am going to have a custom arch built to fit on the aft, I was thinking of installing a backstay from the mast head to the top of the new arch, which would not interfear with the main sail, and use this as the antenna. I saw this setup on the Hunter 46 Wanderlust II, at the Hunter rendezvous in Catalina last year. Does any one out there have any experience with using the long whip antenna with the Icom 802 SSB Radio, or with installing a seperate backstay for this purpose? Thanks, any information would be appreciated. Jeff J
 
Feb 17, 2006
5,024
Lancer 27PS MCB Camp Pendleton KF6BL
Jeff...

You can use a tunable long wire from the stern of the boat, up to the top of the mast and then down to the bow following the head stay. This would be just like using a back stay except you'd get twice the length. Now, I am not talking from experience here, so I have no credibility in this regard. But I was thinking of using a dipole in the same configuration except running the center up the mast using an installed halyard at the mast top. Will this work? I don't know. For what you want to do, a vertical whip seems to work in just about any location as long as there is a good counterpoise. Just my thoughts.
 
Jun 4, 2004
174
Oday 272LE Newport
Basic answer ... at 150W you "shouldn't" have

a problem. You don't use coax to feed the backstay ... GTO-15 unshielded high voltage insulated wire instead ... tuner as close as possible to where the feed exits the cabin. Don't run anything along the forestay. Check the link. Although stand offs are recommended ... probably can just use a Sked 40 1/2in. pvc pipe as a conduit. Grounding direct into the keel is a toss up ... you probably have everything grounded for lightning anyway so depending on the grounding wires you may just want to ground to the engine ... and see if that is all you need. It really isn't gounding to the water that is the key, but to a large square ft area of metal that seems to be the thing ... it's an RF ground. Not a lightning ground that the radio needs. When we kick up the wattage to 1000W ... then things get to be a real problem ... I've run 500W out of a Taurus Sedan with no real problems ... other than some hair falling out. And hey ... that car was on four rubber tires insulated from the ground. Worked most of the US from Hawaii from that car with a 7 ft. antenna on 40M. Vic "Seven" WW 4 OK
 
D

Dick McKee

Moody....I have the exact same set up on our 470

an ICOM 802 with a 140 tunner and a Pactor III. I alos use a "little Dnaplate" as Al put it with no problem. It is simple, clean and without copper all over the boat.It works great with no feed back and no damage to the radar or GPS. Dick McKee SV ONE9TEEN KE7KRM
 
Oct 25, 2005
735
Catalina 30 Banderas Bay, Mexico
More information ...

Great stuff folk! I found an article about ground systems that was written by Stan Honey. http://www.sailmail.com/grounds.htm For those that don't know Stan: Stan is the founder of the Sailmail SSB e-mail network (the reason that I'm adding an SSB radio to the boat). He held the single-handed Trans-Pac record for many years with his Cal 40 "Illusion". He wrote the software that allowed his Alpha Autopilot to sail the boat to target polars and to surf waves. He has been the navigator on many winning Trans-Pac boats (including Pyewacket) and was the navigator on ABN AMRO One. For you sports fans, the digital ten yard line in football, the "k-zone used in baseball, and the glowing puck in hockey television coverage were invented by Stan's company, "Sportsvision"
 
Jun 6, 2006
6,992
currently boatless wishing Harrington Harbor North, MD
Try ARRL.org

ARRL has lots of information from successful hams living on boats. Not that all the folks out there are not successful by we have not published many books. Ham brings up a lot of other options if you get away from the Marine radio = High frequency. There are several "multi-band" radios that can give you a mobile base station (read GMRS like) for handytalkies your kids can take with them in the dingy. You can access the "local" (200-500 mi) ham nets in the 10 meter band ...... The list of things multi-band offers is limited only by your imagination. They can also be set up for using PROCTOR and email... You are going to love the community Moody
 
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