counterpoise layout

[Wahoo Sails]

We have an SSB aboard but the existing counterpoise is a small Dynaplate which I understand is not very effecient. Have just bought 25' of copper foil which I plan to attach to the Dynaplate. My question is; which is better? To spread the copper foil over as large an area as possible (visualize a 25' run) or to create a "loop" running the foil forward, across then back again reattaching it to the starting point? We will soon be adding a dodger/bimini with over 100' of SS tubing in it ... sounds to me like attaching this to the counterpoise is a good idea also .... ?

Bob & Lynn

[Rick]

An SSB "ground" connection to a Dynaplate does not constitute a counterpoise. This is perhaps "good news" in that a good Dynaplate connection MAY facilitate a much better connection to the sea which can constitute a "ground" plane almost ideal which a counterpiose does not.

I cannot overemphasize that no yacht without a 20 meter (or more) radius (40 meter diameter) available for a counterpoise geometry just cannot make one which will work on the 8MHz band or higher, it certainly will not work on the lower frequencies well. What most cruisers who discuss using copper foils in their installations do not realize is that they are NOT attempting to create a counterpoise they are attempting to create a capacitor to the sea which will adequately couple the rf through the hull with minimal loss. A counterpoise for a quarter wavelength radiator is a quarter wavelength raduis of many wires spaced angularly sufficiently small so as to effect a simulated disc of conductor which "reflects" to the radiator a mirror image of the radiator into the "ground" or no-ground or sea.

Because your vessel on the ocean is already floating on a conductor much larger than any disc you merely must either connect directly to it (via a Dynaplate) or capacitively couple to it via various hodpodges of mesh or radiators or foils. If done fairly directly the Dynaplate (or even a relatively small bronze through-hull) one may dispense with the apparent complexity of determining whether or not the hull separation distance significantly negates any foil application and area inside a hull realizing that the capacitance exponentially decreases as the hull separation from the sea increases.

What often confuses this whole installation issue is the physics fact that even a very lousy installation may allow a generation of a few milli-Watts of effective power from a 200 Watt peak-envelope power input that a highly directional and sensitive receive antenna can create an O.K. signal from. This does not constitute a single point evaluation of the whole transmit installation to guarantee good communications under more adverse conditions.

How many times have I inspected lousy installations where the captains have proudly claimed that my reservations were obviously unfounded because at the marina they got very good communication responses? Only later when they were around Panama (or the like) did they complain that their installation "had degraded".

Nonetheless, there are several ideas to keep in mind with what will ALWAYS be a compromise installation on a yacht less than about 150 ft on deck with a 60 ft beam made of steel or aluminum.

Do not use a lower insulator (an upper one may be fine yet may also not be necessary depending upon geometry). Drive the backstay (or other stay) directly below decks. By using a lower insulator you are forced to marry a so-called HV feed line too close to the lower end of the metallic stay which magnetically "robs" the preponderance of a generating field to the atmosphere. The lower end exhibits a voltage minimum anyway when tuned properly and, therefore, is not such a fear for rf burns if contacted by human personnell. The UPPER end is where the high voltage is exhibited by the radiator.

Place an automatic tuner immediately and geometrically in line with the radiator below decks if possible. Run an rf "ground" line from the tuner to the Dynaplate using a cable run that guarantees negligible inductance at the lowest frequency of operation. This can be done by using "Young's guideline" for HF SSB bands. This "guideline" recommends using a number of parallel intimately married and separately insulated conductors equal to the number of feet between the tuner and the Dynaplate (or bronze through-hull fitting) divided by two. So for a five foot run use a 2.5 (obvoulsly round up to three) conductor # 14 AWG cable. A convient way to do this is to use a 14-3 ac marine grade conductor easily available at marine stores. Longer runs may require a 14-3 and a 14-2 or whatever. Marry them intimately together with tie wraps every 10 inches or so.

Keep in mind that a ground wire at the transceiver has NO effect or benefit to the rf transmission/reception of the installation. It has ONLY to do with safety.

There are many other installation "tricks" which may be employed yet the thrust of this submission is to debunk what many SSB installers have done to inadvertently degrade your ability to generate the most effective radiated power from your already compromised ability to make the best use of your SSB output power.

[Rick]

Using parallel conductors to create a low inductance path to the sea is generally less expensive and a lower inductance (better quality) than using copper foil. In addition the multiple parallel conductors using marine grade wire give you crossion resistance and MUCH more flexibility in the installation that copper foil just does not allow without treatment and creation of large geometric "holes" or spaces.

[Wahoo Sails]

Rick,
This is my first encounter with an SSB transciever, and it apparently needs to be rerigged. If I had the time, I am certain there are many good books that would educate me in how to do this properly ... unfortunately, time is of the essence, so I have resorted to asking those that know ... or appear to know, and this may have been a BIG mistake. I have never seen an issue where opinions vary so widely, the information I have recieved has been not only confusing, but often times downright contradictory. Juding from your response, this must be your field of expertise ... therefore I'm going to say "You Da Man" .. and ask you to help enlighten me
Let's start with what I'm working with. An Icom IC-M700 transciever, an AT120 tuner, a Dynaplate & a "long wire" antenna (more about that later). One lead ftom the tuner is loosely wrapped around the through bolt of the Dynaplate ... a black wire from the tuner (I'm presuming this is a battery ground) is not hooked up at all ... uh ... ya think it might need to be re-rigged?
What I'm hoping to achieve is an adequetly functional rig ... not "perfection" ... with what I have. The "common wisdom" (which may be all wrong) is that the Dynaplate isn't adequete, I have been advised to install as much copper foil as possible, bond it to every metal thing in sight ... and call that my counterpoise. If I read your reply correctly, you're saying that, that isn't correct, and in fact is the wrong way to go. One brief tutorial I read even recommended including the engine block in the counterpoise .. which since it is battery ground, would tie the "sea water ground" with the battery ground ... an idea I found dubious at best. Clearly, the lead going to the Dynaplate needs to be attached properly ... and ALL of the rest of the wiring needs to be inspected and hooked up properly as well.
As for the "long wire" antenna .. this is run up the backstay ... but insulated from it. One friend (who in a previous life was a Motorola technician) say's this will be perfectly adequete ... most others are simply aghast at the very idea of it! Then again ... most others weren't even aware that a "long wire" antenna existed!
It sounds like I should simply re-rig what is already existing .. and see how it works. Any thoughts or suggestions from you on how to make this work optimally with what I have would be much appreciated!

Bob & Lynn

[Weyalan]

This stuff fascinates me. My recently acquired vessel has an old Wagner / AWA HF/SSB radio and antenna tuner, which is probably perfectly functional, but might as well be a particle accelerometer or Magnetic Resonance Image Scanner for all the good it does me, because I don't know the first thiing about it!

There is an Marine HF radio course starting soon that I am going to sign up for - it ends up with the HF operator's certificate, and it is qite expensive, so I'm hoping that its going to be quite thorough.

In the longer term, I plan to upgrade my HF radio & tuner to the new synthesised auto-tuning technology, but in the meantime, assuming my current "antique" is ok, it will be nice to know how to work it.

I wouldn't mind buying a "definitive" guide to marine HF...any recommendations?

[Rick]

You already have a long wire installed...its called the back stay. Drive the chainplate connected to the backstay with your AT120 from the insulated stud on the AT120 as directly upward as possible. You may choose to jumper around your chainplate toggles with a flexible piece of rigging wire just to make you feel better about the connection...that is optional. Do not marry another long wire with your backstay due to the huge losses you will encounter as mentioned before.

Run a multiple set of conductors from the rf ground stud located on the bottom of the AT 120 as mentioned before directly to your Dynaplate. Forget making any other connections to that rf "ground" wire this is the only one that counts.

A battery ground connection to the AT120 is only made via the control cable which passes to the M700. I've worked with that specific combination for years and it can be a good set up. If you do not have documentation for that AT120 control cable let me know...I used to fix a lot of ICOM radios and tuners.

The AT120 will "tune" to anything, ground or no ground, so just because it acheives a tune does not mean that you are getting an effective radiated output power.

The physics related to this installation is not difficult or black magic. The multiple conductors will allow you to "build" an rf ground wire that has lower inductance than any copper foil, not that copper foil is bad, just that with this method you can merely add more wires in paralled and achieve as low an inductance as you desire for HF bands without haveing to fool with the foil.

By driving your whole rig (backstay, mast, forstay, etc.) you have somethin which is not purely a long wire yet relatively small vessels never truly achieve a quarter wave antenna installation due to the proximity of all other metals around the boat. By driving your rig you may be surprised at how good an SWR you might have on 4, 8, 12, and 16 MHz. 16 might be a little "touchy". On the other hand, some bands might proove to be difficult to get a good effective radiated output power due to your specific geometry.

Technically with a long wire you would not even use an AT120 but I have found that the 120 may do a good job at facilitating at least a 50 Ohm match for the transceiver to "see" which allows the transmitter to put out power (again, that doesn't mean that much power gets out to the atmosphere).

[Longhair]

Rick,

I have a split backstay, How do propose to conect it to a At120....

Thanks,

matt

[EngNate]

Rick's 100% on the counterpoise/ground distinction and the exercise in futility in trying to make a counterpoise on a small boat. Capacitive coupling, to be effective, requires a tremendous amount of surface area. That skimpy looking plate (assuming it is a Dynaplate or equal) is what works and works well. Nay on the multi-conductored RF ground, use the foil between the transciever/tuner and plate, at least 2" wide. Where foil is hard to run, I use heavy tinned braid - 3/4" round or 1" flat, 4AWG equivalent. The RF Ground is important for performance, as is the fully-isolated radiating element - insulators at both ends - just use the single wire up from the split stays. I posted the following on another forum recently:

RF Grounding and Stray Current

The question asked: Should the RF Ground of an HF (SSB) radio be connected to the bonding system, (thus the DC Negative and AC Safety Ground circuits)?

This will come to a specific answer, but you’ll have to slog through the fundamentals.

To effectively radiate an HF signal, it must be applied between the earth and the sky, so the RF ground is critical for good performance. If a grounding plate, e.g., Dynaplate, is installed, it will provide an effective RF ground by itself. There are two reasons then for connecting it to the bonding system. One is the ABYC (and prudent practice) requirement that all underwater metal parts be connected to the AC Safety Ground for the protection of a person in the water in the event of a fault. With a bare copper strap running from the radio to the plate, and various other wires running concealed with it, it’s plausible that a fault could occur that would put 110VAC to the plate. The surrounding water would be very hazardous to anyone in it. The second reason is for the protection of the plate from corrosion. They are made of porous bronze and fairly, but not highly, corrosion resistant. The pores provide the contact area with the water important for RF performance, and internal corrosion actually tends to improve performance. Usually the first noted sign of a problem is the thru-bolts breaking off.

Now, if we skirt around the safety aspect, we could effectively protect the plate with it’s own zinc, mounted on (a) stud(s) somewhere and connected with a wire. Connecting it to the bonding system is much more convenient, but produces a stray-current condition. This is because we have added a shared return path for the negative side of the supply to the radio, and likely other equipment along the way. Current flowing along any path produces voltage differences along the conductor due to resistance. Bonding system circuits typically have lots of resistance. The portion of the bonding circuit between the radio and battery can then have significant voltage differences along the way, with associated problems of electrolytic corrosion.

There are two ways to solve this problem all around. One is hard to get, the other takes a bit of work to implement. The easy, effective way is to place an appropriate capacitor in series with the ground strap. Capacitors pass AC and block DC. But what is needed is an uncommon critter, called a Transmitting Capacitor in the industry. High voltages are generated at the output of a HF radio. The capacitor must have a voltage rating of at least 1500 volts, preferably 2000, even though the voltage measurable across it will, under normal conditions, be zero. The capacitance value needed is 1.5 microfarads, minimum, preferably at least 2.2. These are hermetically sealed metal cans with ceramic posts and screw connections. I think they can be gotten from industrial electronics vendors like Allied Electronics and/or Newark Electronics. They are costly. I pick them up when I can at electronics surplus dealers. With the capacitor installed, the grounding plate is connected to the bonding system like any other underwater metal part, with no adverse consequences. The benefit of additional ground coupling from the rest of the connected parts is gained. On metal hull boats, this is the only solution to avoid DC ground-faults to the hull.

On non-metal hulls, there is another solution, and it involves laying out the interconnection points of the bonding, DC, and RF ground systems in such a way that there is not a shared path for DC power. Current will only flow in a continuous loop from its source and back, not down a dead-end. A proper arrangement of wiring will make the Ground Plate and/or bonding system a dead-end to the DC, while a path to the RF.

[Rick]

Yet if you know the physics regarding the inductance of conductors you will realize that it does not take many parallel conductors to "beat" the inductance values of any flattened conductor. In fact, if one merely were to cut blank parallel traces on a flat conductor one would approach, yet not reach, the lower inductance of a multiple parallel round bundle of conductors as I outlined. So, why are you still proprosing an implied advantage of a flat conductor? It is not justified except in the case of replacing a SINGLE conductor with a flat one?

Stray current is a separate issue regarding any bonding system which CAN be at least intellictually separated from this discussion.

[Rick]

A "grounding" capacitor for the HF band (by definition, 2-30 MHz) need only be 0.1 microfarads (more than ten times that which you recommended). It is also a MYTH that a 200 Watt peak-envelope-power transceiver needs to have capacitors having 1500V ratings. In theory, no one reading this thread has a "legal" transceiver for non-ham bands and power ratings requiring such a high voltage rating. There is more to capacitor voltage ratings than a theoretical mistune of an output antenna/tuner. Power plays a part as well. (I used to work on 100kW ssb transmitters etc.)

The point is that no one out "there" needs to be concerned about extremely high voltages even on open antennas "not" connected to their SSB transceivers. Why? Because virtually ALL SSB transceivers (ham as well as commercial) automatically decrease the output power as the antenna reflected SWR increases. This AUTOMATICALLY decreases the peak voltage anywhere in the system.

As a practical point, I have never experienced a 1kV rated capacitor approach destruction in such installations. Don't scare people unnecessarily. In fact, if one truly has a quarter wave antenna drive, the voltage "seen" by the tuner and transceiver is very minimal. Keep in mind, that the maximum voltage observed in such installations occur only at the END (top) of the antenna, not at the transceiver.

In addition, if one installs a transceiver (of any frequency) properly, there is no issue with a vessel bonding system because if there is ANY connection to the bonding system it is made at one and only one point in the bonding system. That is why I pointed out that NO battery connection should be made to the antenna or tuner except for the low-current control cable to the tuner. Yes, there are concerns there regarding a "bonding" system yet most of these concerns are due to unnecessary battery connections made to the rf system which are totally unnecessasry from an rf point of view.

[Rick]

An HF SSB rf "ground" capacitor needs only to have a 50 Volt rating!!!!!

[EngNate]

Inductance is not an issue, 'skin effect' is. In a conductor carrying RF current, electrons vacate the center of the mass and crowd the surface, resulting in an increase in effective resistance to the RF. You want surface area, it doesn't matter what shape it's in, but a flat strap has the most, a braid next... Don't take my word for it, query your choice of SSB manufacturers' tech support.

RF impedance to ground needs to be kept low, a very small percentage of the system impedance (50 ohms). The capacitive reactance is the impedance of the capacitor: Xc = 1 / 2 Pi F C. A 0.1 mfd cap at 1.8 mhz = about 2 ohms. Get over 1 mfd and it's really negligible. As for voltage rating, what I install must be [free of potential liability issues] no matter what happens, so I will bend as low as 500, but that's it. I did mention that normally the voltage across it will be zero.

If you're installing a SSB and Grounding plate, stray current is a 'current' issue. There is a B- connection to your transciever and tuner's chassis, the neg power cable. Now install an RF ground and you can have a loop that includes underwater parts.

NEA
USCG Lic. 500T D.D.E.
FCC Gen Class Broadcast

To really be certain you must know either everything or nothing at all.

[Rick]

No small vessel can generate a worthy effective radiated output power below 4MHz and at that freq. a 0.1uF cap has less than 0.4 Ohms impedance. Worthy long distance communications for small vessels "starts" on the 7MHz HAM band or the 8MHz commercial band. Otherwise VHF is used. (Try to get good comms on 2MHz over 100 miles on a small vessel, besides no one cruising would normally use that band.

You are misinformed that inductance does not matter. How could you say that when you state: "RF impedance to ground needs to be kept low"? If there is significant inductance then the impedance will not be low. If a radiator is an appropriate quarter wavelength for a particular frequency then the "ground" must be a low inductance to prevent changing the antenna characteristics.

You are also misinformed that multiple parallel inductors cannot exhibit sufficiently low skin effect as compared to a flat conductor. Skin effect currents are not limited to the bundle circumference they are limited by each individual wire and, yes, are influenced by adjacent currents as well just as are skin effect currents in flat conductors. Take note that not as many high-frequency switch mode transformers are made with flat conductors as compared to multiple conductors. In fact, Litz wire is just for that purpose. Such transformers generally do not use flat conductors for the same reasons that I state: difficulty in "dressing" the leads, the cost, and the availability. In short, both work.

We are not in disagreement regarding a battery negative ground-loop via any rf installation.

[EngNate]

Inductance is not an issue, because the value is insignificant. Get out H.H. Sam's Handbook of Electronic Tables and Formulas or similar reference, and calculate the expected inductance of say, 40 ft, of single straight conductor at 22 mhz...

As I said in other words, reduction of skin effect resistance is directly related to increase in surface area, no matter how you obtain it. A 2" strap has 4 in. sq. surface area per inch of run. You'd need nine 10awg wires to equal. That's higher cost and labor, for what? If the copper foil is too difficult to work with, wouldn't you rather pull a single braid than a bunch of bundled wires? I would, because it means a better value to my customer.

Quite true, though, that splitting a large conductor reduces inductance - you have inductors in parallel. However, bundling them together works against your objective because of mutual inductance. Again, the value of inductance we're dealing with here is low to begin with, so there is little to be gained in reducing it.

I can't see bringing in transformer design for comparison, there's a whole range of additional considerations, many physical rather than electrical. No transformer is wound with a flat ribbon. Some use square or rectangular wire, but I think that's to increase ampacity (more conductor area in the same winding space) and winding density (layers closer together). It brings the drawback you mentioned and also problems related to thermal expansion and magnetostriction.

If you're going to use a 50 - 200V capacitor, why quibble about a dollar's worth of capacitance? More is better in this application. The cap's I use are in hermetically sealed cans and have #10 stud connections on ceramic posts. They're durable stand-alone components. Your suggestion would be a small, rather delicate, package with very small gauge leads made of solder-plated copper-clad steel.

I've run into this a lot, the idea that anything at all accomplished with stone knives and bear skins has a special merit of its own. Yes, I love bailing wire, too, for hay. I just hate it when the rope-bound bales fall apart when you try to throw them on the wagon...

[Rick]

Sorry, man, you're wrong about the physics. Mutual inductance AIDS to lower the overall inductance by bundling. The mutual factor is not merely a multiplier it is geometric in the decrease of inductance as the number of conductors increase. In addition, it is the impedance of the tuner ground wire which IS significant in HF installations with 6 ft or more of "ground wire". The distributed impedance works against the distributed impedance of the radiator. So, an apparent inductance having a lumped value which mathmatically appars to be insignificant is not (and I have measured the same using impedance and noise bridges in actual installations).

I have also verified that skin effect is not significant with bundled ground wires by using an rf ammeter at the drive point of the radiator for 200W PEP HF transceivers, so you cannot argue with success (which I claim is backed by the physics).

Now in the case of a nasty 10 ft run of a ground strap one strap will not allow good effective radiated output power on 12 MHz and above and the bundled wires DO! What, in effect, the bundle enables is the creation of a phantom ground "appearing" directly below the tuner that a single braid or strap will not do.

I'm not against using the straps or braid I just know that the bundled wires work better, are easier to run and do not corrode as easy.

You are also wrong about transformers not being wound with flat ribbons and copper foil. They are being used by both Xantrex (some, not all) and Cummins high-frequency swithc-mode inverters as well as many other industrial designs...and have been for decades.

In light of the advantages of the bundled wires I view the use of braid and copper foil in small vessel ground systems to be "stone-age" by comparison from a technical point of view just like quoting Sams do-it-yourself source material as being a bit away from using physics textbooks and other technical literature used by scientists and engineers.