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Old 02-03-2008, 09:55   #1
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Making a ground for the SSB. Will this work?

Aloha,
I need to ground my SSB. I was wondering if the extra three quarter inch ridge copper pipe ( I have sevral hundred feet) could be used. I was thinking of soldering it into a mat to fit the the ceiling of the egine conpartment, Or soldering it into a tight bundle and sticking it in the corner of the hanging locker? If this would work about how much would be enough? Thanks, David B.
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Old 02-03-2008, 10:17   #2
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David,

Need a bit more info to answer your question correctly. It would be helpful to know:

1. What antenna you're using (standard "backstay" antenna?);
2. What radio and, especially, what tuner you're using and where it is mounted; and
3. Your intended use: (marine only, ham only, both; all bands?)

In general, one can say that..

- IF you mount the tuner at the base of the antenna; and

- IF you run a short copper strap or other heavy ground strap from the tuner ground lug to the nearest bronze thru-hull (which, preferably, should NOT be otherwise connected to the DC ground system);

- THEN almost anything else you add to this setup will work.

The more copper the better.

If practical, it might be useful to lay out what you plan on the cockpit floor or sidedecks, hook it to the tuner ground lug via as short a connection as you can, and see how it works.

Don't know if it's practical, but if you can run that copper under the side decks or cabin top as well, it would certainly be helpful.

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Old 02-03-2008, 11:15   #3
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What you want is AREA not mass, preferably either close to or in contact with seawater.

Steve B.
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Old 02-03-2008, 11:58   #4
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What is the real question?

Are you asking about how to ground the chassis of the radio for safety purposes or how to make a radio-frequency ground for your tuner/antenna?
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Old 02-03-2008, 12:22   #5
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More info. Thanks Bill, Steve and Rick

Aloha some more,
Bill the make is ICOM 700, the antenna tuner is ICOM 120 and the boat has an insulated backstay.
Rick I think it would be for marine use only and It would be for the radio frequecy ground.
Thanks again.David B.
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Old 02-03-2008, 12:51   #6
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We're talking here about a ccounter-poise for a vertical antenna. If the antenna used is a plain Whip, then the conter poise should be equal in length, and in the opposite direction. It is the ground half orf simple dipole. Since this is not very pratical on most boats making contact with the water is. The closer the bottom of the upper 1/2 of the antenna the better. Since this is not a calculated ground plane or is not adjustable, the best approach is to use an antenna analyizer to see how the match is. The effect of the ground is very important. Make such adjustments that are possible, like the distance from the antenna mount to the water, the length of the antenna, or the height of the antenna. Use a decent size piece of wire when grounding and connect the ground plane connection to the radio. This is normally done thru the outer brade of the co-ax cable connecting the radio to the antenna? I'm simply connecting the ground thru my ground plates on my 36' sailboat, and have adjustem the antenna length for the best match on each band. I am running a Ham radio on 3 bands with seperate antennas. The range from small loaded antennas is terrific and I can reach the mid-west and California with ease. By the way, SSB is a mode of transmission, not a frequency.
Paul (AF4UQ Amerature Extra)
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Old 02-03-2008, 14:24   #7
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There are a number of diverse viewpoints regarding counterpoise efficacy, all of which are typically limited to the individual's limited experience.

You might be better served to review the pdf file attached in this link from Icom Corporation which provides an authoritative source.

Icom America - Knowledge Base Article 57DG216861
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Old 02-03-2008, 16:18   #8
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David,

With your M700, the AT120, and your intended use (marine bands only), my original comments apply.

Paul was perhaps thinking about a tuned antenna system, not a random length but fixed, end-fed antenna (which is what your insulated backstay is). You don't have the luxury of adjusting it's length or position, or running multiple antennas.

While the "authoritative source" cited (which appears to have been written by Farrallon Electronics for Icom) spews the usual stuff (like the almost magical "100 square feet of copper"), it's not necessarily either the best or the only way to go.

You don't need 100 sq ft. A "counterpoise" needn't be "at or below the waterline"; in fact, they work better above the waterline. You don't have to tie in your keel, or use external groundplates (which are expensive and...after a few months...just about worthless).

Run a simple heavy strap to a nearby bronze thruhull. Then, run copper straps, or tubes, or wire (any size, insulated) under the decks, inside the hull, wherever you can. The more the merrier, but even a few will work.

An easy way to connect multiple "radials" to the tuner is to use a heavy bus bar with, e.g., 1/4" studs. Mount this near the tuner and connect one of the studs to the tuner with heavy copper or ground strap. Then, connect the other parts of your "counterpoise" system....wires, tubes, copper, etc. to the other studs.

Another thing which works well on many boats, including my own, are aluminum toerails and the pushpit/pulpit/lifeline complex.

Don't be afraid to experiment or be intimidated by "experts". A lot of pure bunk has been repeated over and over in texts and lectures and practice for a lotta years.

Let us know how things work out.

Bill
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Old 02-03-2008, 16:41   #9
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Bill
while I agree with you that some shortcuts will likely result in insignificant differences and sometimes it's easier to limit both the extent and placement of a counterpoise if only for practical reasons, I wouldn't dismiss Icom or Farrallon's expertise or imply someone shouldn't emulate it to the extent practicable.
I think we both have enough years in working with antennas to know there is no definitive best but working off a good game-plan using their document as a point of departure is always good advice for the novice in devising a boat-specifc plan
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Old 02-03-2008, 19:04   #10
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This is an interesting tread, especially since I am reinstalling my radio ground system at the present time after replacing a fuel and water tank.

I have read in various instruction manuals, books, etc. (all of which come from creditable sources) that (1) RF grounds should be kept seperate from DC grounds (to reduce interference to instruments etc.), (2) DC grounds and AC grounds (dockside and gen-set) should be kept seperate or (3) all grounds (engine, tanks, keel, generator,thruhulls, etc.) should be tied together into one common ground.

In the past I have had all three tied together and never had any interference with instruments however I have had a rather serious ground loop probelm.

Does anyone have any thughts or experience with this.

WBG6061 - KE5QLO
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Old 02-03-2008, 19:11   #11
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Thanks every one for the input.
I down loaded the info. from ICOM
Bill, It will be a few months before I give it a try and I will let you know how it comes out. I guess the worst is I won't have much range, I'll play with it.
Oh another question, When people say one hunderd Sq. feet of copper for the ground, do they mean copper foil, or 16ga. copper plate or what?
Many Thanks. David B.
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Old 02-03-2008, 19:49   #12
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With respect to the ground loop, it can occur regardless of whether or not you tie all the grounds together. The conventional wisdom is to have only one common point at which the grounds are connected but that is true for reasons other than the groud loop effect - primarily to preclue differing ground potentials throughout the boat.
It is problemmatic to point to any one cause of the ground loop but I can give you a hint how to easily identify the specific problem area. Get a small wattage neon bulb and run that along the various points of the ground wires (when transmitting an audio signal)- where it glows brightly will be the point where stray RF is found thereby identifying the offending location of the loop.

Regarding the area of the counterpoise, it's irrelevent what the thickness of the copper is, foil or anything else, as the RF travels on the surface. For example, a dynaplate can have an apparent surface area much larger than the physical dimension of the plate would indicate. Whether it is an effective counterpoise is debatable though. Although some so-called experts would argue the need to have 100 sq ft surface area, suffice it to say that the more, the better depending on the efficacy of it's capacitance coupling to ground. What you are really doing is making that coupling as good as possible and the common way to measure that, without actually measuring the coupling which is usually beyond the ability of some boaters, is to increase surface area. The sq ft figure is therefore a surrogate measure of how much capacitance to have.

If this is too confusing, let us know as I know there are a few folks here probably better able to explain this.
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Old 02-03-2008, 19:57   #13
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Random length antennas are just that, and are not tuned to your transmitted frequency or your transmitters output impedance. Both of these have everything to do with range or "getting out" The use of so called "antenna tuners" can help in the efficency of getting your signal from the transmitter to the antenna. They are not tuning the antenna as the name implies, they are matching the output of the transmitter to the antenna so that maximun power can be transfered between the two. That solves one problem. The other is getting out of the antenna to the ether, and that can only be done by tuning the antenna to the transmitted frequency. This is not a black art, but well know antenna design principals. You can cut and center feed a back stay to the proper frequency where as you can not do it with end feeding it!

Paul
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Old 02-03-2008, 20:35   #14
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Paul,

I'm with you about half-way, but I'm not sure what you are trying to say about "the other half" of the job.

It's true that the term "tuner" as typically used in marine applications is somewhat misleading. A better term is, "coupling", because what you're doing is coupling the signal emitted by your transmitter and carried along the coax feedline to the tuner/coupler to the antenna system.

The purpose of a tuner or coupler used this way is to present a 50-ohm load to the transmitter which is what it was designed to work with, resulting in a low VSWR and a maximum transfer of power from the transmitter to the antenna system.

I say, "system", because it is absolutely necessary for effective radiation to occur that the common mode current flowing into the near end of the antenna be exactly matched by the common mode current flowing into the ground plane (or "RF ground" or "counterpoise" if you prefer). This is true no matter the length of the antenna, the materials it is constructed from, or most anything else. For current to flow into the antenna and be radiated, it has also to be matched--exactly-- by the current flowing into the ground plane.

While there are "tuned" end-fed antennas which are resonant at the transmitting frequency (e.g., a 1/4-wave end-fed vertical), that's not what we're talking about here. These can be very effective if set up correctly, don't require a tuner, etc., but they're good for one band only.

What we're talking about here is the ubiquitous insulated backstay antenna which is end-fed at the bottom, using high-insulated wire from an automatic tuner/coupler located nearby. This antenna is expected to work on all desired bands -- ham and marine -- from 2mHz or so to 30mHz. Without physically changing anything. Without operator intervention.

As noted above, it will only work if there's a satisfactory ground plane/counterpoise/RF ground present. There are numerous approaches to rigging an effective ground plane, many of which have been discussed at length on this and other boards. See, e.g., my postings on the SSCA board re: "RF Grounds in the Marine Environment", as well as many others. SSCA Discussion Board :: View topic - RF GROUNDS IN THE MARINE ENVIRONMENT

The insulated backstay antenna with a good coupler and a good RF ground can acquit itself quite well on many bands. It's not a great antenna system on any band, but it's utility comes from its robust nature and its extreme flexibility to transmit on any desired frequency band without fiddling.

Hope we haven't wandered too far astray, here.

Bill
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Old 03-03-2008, 23:18   #15
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Quote:
Originally Posted by btrayfors View Post
.....The insulated backstay antenna with a good coupler and a good RF ground can acquit itself quite well on many bands. It's not a great antenna system on any band, but it's utility comes from its robust nature and its extreme flexibility to transmit on any desired frequency band without fiddling...
For what it is worth, I couldn't agree more and I have messed with quite a few antennas over the years.
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