ssb ground

[davemaskell]

i know its imperative to run the copper strap from the ground plate to the tuner, i'm mounting the tuner close to the ground plate. the receiver is located in the nav station pretty far away. would it be alright to ground the back of the receiver with a wire to the bonding system of the boat that's in the dc distribution panel right next to my receiver.

[Rick]

Placing a wire between the transceiver chassis and the bonding system is for your electrical safety ONLY. Such a wire will do nothing for your ability to radiate and effective signal from your tuner on transmit.

You need to visualize just what constitutes your antenna. Your antenna "drive point" consists of the two wires exiting your tuner in terms of the "high voltage" output wire and the so-called "ground" wire. The tuner desires to "see" an antenna consisting of a radiator connected to the "high voltage" connection approaching a quarter of a wave length at the desired frequency of operation and to "see" effectively nothing (zero) in terms of radiation resistance at the "ground" connection.

If you do not have a good radio-frequeny ground and/or a near quarter-wavelength radiator then you WILL NOT generate much effective radiated output power into the atmosphere. IT MAY BE TRUE that your tuner achieves a "tune" indicating that an impedance match has been acquired enabling your transmitter to output real power into the tuner HOWEVER, there may be NO effective output power from the tuner with bad approximations to the proper wire lengths.

Most tuners today WILL literally "tune" to anything, including an open circuit. All that does is enable the transmitter to be fooled into outputing real power into the tuner's internal resistive losses. this goes up in heat, not ratiated output power.

Work at minimising the inductance of any connections between your tuner 'ground" terminal and the sea. Let me know if you need an improvement over the usual copper foil.

Regards,
Ric

[captjohn360]

well how do you ground the transceiver? or is it necessary at all?...jt

[davemaskell]

this is where i get confused. i looked up the icom ssb manual and it says there must be a good rf ground from the transceiver and the tuner to a ground plate or suitable ground. they show a picture of the ground strap connecting to the ground lug on the transceiver. i thought that was only for a ground wire for protection.

[Alan Wheeler]

First to answer John.
We are assuming the case of seperate tuner to reciever. The earth on the Transciever is not and should not be called earth. It is infact the Negative power supply. This (depending on design) is seperate to the Transmission Earth. The transmision Earth is found on the Tuner along with the RF terminal. The RF transmision earth is connected to the earth plate and earth plate only.
Here is a good rule for any electrical device. If the manufacturer supplies a Negative termina/wire on the device, then connect that to negative supply. Any other connection, even if it is somehow connected to negative via say the case or what ever, should only ever be connected to what the manufacturer has intended it to be connected to.
OK, to bring Dave into this now. SSB is an AM radio transmission. The VHF radio uses FM transmision. The two are very different in the way the RF is radiated from the Antenna. The AM system has two parts to how it is radiated. One being the Ground plane, which is effectively the surrounding water. But this water must be coupled to your transmitter, hence the grounding plate. Commonly a copper plate is used and you will sometimes come across a sintered material, that because of its porouse makeup, results in a far greater contact surface with the water, thus a better ground plane.
Dave, I suggest you spend a few hours of reading and studying this subject. You need a good basic understanding to enable you to do a proper install. Don't fret, you don't need to know complex electronics, just some basics.

[Rick]

I repeat, any "ground" connection made to a transceiver has NOTHING to do with the transmission line (coax or twinlead or whatever), the antenna tuner (if any required), or the antenna.

An RF "ground" only affects the antenna as far as emitting effective radiated output power into the atmosphere and, therefore, if it is required for proper propogation CAN only be located AT the drive point of the antenna. The transceiver has NOTHING to do with this (or any connections made to the transceiver.

RF grounds are ONLY required for vertically polarized quarter or five-eighths wavelength antennas. Other antenna designs requiring RF grounds (like a rhombic) are not important to this discussion because you just don't have a boat big enough to carry one for HAM or commercial SSB frequencies.

An antenna is NOT affected by AM, FM, PM, AM SSB or any type of MODULATION imposed upon the RF carrier. In other words, an antenna type is unaffected by the modulation unless the modulation bandwidth is so wide as to exceed the bandwidth of the antenna. AM SSB is quite narrow as compared to FM (which actually is almost infinitely wide yet the multiples fall off fairly rapidly.

In the last decade or so it has been shown that a scintered RF ground plate does not offer a significant improvement over an ordinary rough copper plate of the same dimensions in sea water for either lightning protection or for antenna grounds. The scintered plate sounds good on paper yet fails to deliver the claim. They ARE good plates, they just don't deliver on the claim of being significantly BETTER than non-scintered plates in this regard.

Rick

[Strygaldwir]

Ric;

You said "Let me know if you need an improvement over the usual copper foil." I'd love to know what that is. I have foil, and before I go through the process of laying about, I'd love to know what is the most optimal configuration for the RF ground.

Thanks,

Keith

[Rick]

For HF SSB frequencies and below, you can apply "Young's method" to determine the number of married conductors to use in order to get better (lower) inductance characteristics over that of copper foil. Divide the number of feet required for the "run" by two and that is the number of married conductors to use.

For example, if you need to make a run of 10 feet between contacts which you desire to have a low inductance to HF then you need 5 married conductors. In order to have good tolerance to vibration, mechanical abuse, and salt water, use marine grade (tinned) stranded #14 AWG wire. You can make up the married bundle with any combination of wires whichever is convenient to obtain. Be sure to marry them as closely as possible using tie wraps or any other method of securing them close together.

By doing this you take advantage of the mutual inductance that adjacent insulated conductors exhibit in addition to the lowered inductance obtained merely by having conductors in parallel. It is the geometry of a flat conductor that gives lower inductance over the same cross-sectional area as a round one. Flat copper foil would be improved if there were longitudinal grooves cut into it to give this mutual inductance effect. Naturally, copper foil looses much of that low inductance advantage everytime that you kink it in order to pass it through tigh areas or to make it go around corners in tight places. Married conductors do not have that disadvantage.

Strip the ends of the conductors at each end and join them together with an appropriate terminal for your application. Do not solder. Keep in mind that no aircraft or aerospace application allows soldering of flexible conductors due to the degradation of resistance to stress failure. USCG inspected vessels are not allowed to use soldering. in EVERY case where you might be tempted to solder it is because you do not have the correct tools for the specific terminals (there is no universal "approved" crimper for all brands of terminals, they are in fact brand specific). Soldering has nothing to do with proper sealing (if that is what you desire) or strain relief, or low resistance termination in comparison with proper crimping equipment.

Naturally you can use more conductors than the minimum specified by "Young's rule" in order to further lower inductance. If you still feel the desire to use copper foil (I like to use the term strap because foil connotes a too-thin cross section as to compared to a more-difficult-to-handle and more expensive strap) make sure that it is at least 20 mills thick and 1/25 inches wide (or more).

[Strygaldwir]

Rick;

Forgot to thank you for the insight. I used the married connector approach to tie in my tank to my counterpoise This was a pretty thick bundle. I had 26 feet to go. Used up most of a roll of 14 AWG. (good thing I bought a 500 foot roll! That was 26 x 13 right???


Thanks

Keith

[Rick]

What a bundle!

[svcattales]

Rick, request your help again on SSB install on my 37' Privilege cat. You helped me previously in the thread about using my arch as an RF ground. Currently, I've assembled all the parts and have the tuner, antenna (24' whip) and transceiver installed. Here are two issues where I need some guidance:

Location of RF seawater ground plate: I have flexibility where I mount the plate (will be hauling out soon). Can I assume that I should locate the RF plate as close to the tuner as possible? Let's say I mount the plate only four feet from the tuner, then according to your formula I would only need one length of 14 AWG duplex wire. Intuitively, that doesn't sound like a heavy enough connection, but I don't have a good grasp of the physics. What would you recommend as the optimum distance from the RF plate to the tuner and number of wires in the bundle? Are more wires in the bundle desirable even though the distance is short?

Routing of coax feed line and control wire from tranceiver to tuner: Almost all of the wiring on the boat is led through PVC conduit. There is a direct path to run the control wire and RG-8U coax through conduits that also contain DC battery cable connections from house bank to main DC distribution panel. Will this create a major RFI problem? (I have a large line isolator from Radio Works to minimize RFI, but it obviously won't get rid of all of it.)

Thanks for sharing you wealth of expertise on this subject and cutting through the "voodoo" of the SSB groundplane controversy.

[Rick]

The closer the ground plate to the tuner the better. Yes, the more wires that you add between the tuner and the ground plate the better off you are. 4 feet divided by two yields two wires, not one. Use two or more married wires.

Because coax loss using good quality coax at HF is not great you do not need to be overly concerned about cable length for either the coax or the control cables. RF contamination to these cables generally would occur only when you have an antenna ground or radiator that is way off base for the frequencies used. Your element should be good for the ham and marine HF bands to use like 20 meters.

If you desire to make sure that any cables in the vicinity of the tuner not transmit RF to some other part of the vessel make several turns of the coax, cable bundle or whatever you have, around a torroidal magnetic core designed for HF and you will thereby be making an inductor out of your cables which tends to not pass HF currents. Of course the number of turns placed on the core can be calculated for a given core material yet any is better than none.

For HAM installations when the operator is knowledgeable in using the transceiver to obtain a reasonable indication of SWR using built-in SWR meters I recommend using a coax length of 1/2 wavelength multiples at the band of measurement interest. For example, if you install about 62 feet of an appropriate coax between the transceiver and the tuner then you will have 1/2 wave multiples for both the 40 meter and 20 meter bands. Two important concepts are working here. First, the length of the coax is reduced below the theoretical physical calculated length proportional to the loss of the line. Second, the length of any 1/2 wave transmission line "transforms" directly what appears at one end to the other. Other lengths of line will transform a SWR into a value having meaning which can be calculated from Smith charts, not what you want to do in a hurry.

If you do not have a 1/2 wavelength multiple then you must make all SWR measurements at the tuner end of the coax to be valid. One way to get the exact measurment correct for a 1/2 wavelength of a particular coax is to use an inexpensive noise bridge to cut-to-length a 1/2 wave piece.

[Rick]

When I mentioned line loss I should have technically said that the velocity of the frequency traveling down the coax will be decreased over the velocity traveling in a vacuum and, it turns out, that for transmission lines, in general, the lossier the line the slower the wave travels down it. Regardless, a noise bridge will reveal the correct "cut" for the length of the line due to its speed and loss characteristics.

[svcattales]

Rick,

Thanks again for the help. We will be using HAM bands between 40 and 20 meters and marine SSB freqs in the 8-12 MHZ range, so I think the tuner and whip antenna should be able match up OK without much RFI. We will also be using WINLINK via a PTCIIe TNC which can produce lots of interference, but I found on my last boat that transmitting at low power reduces problems and still provides good connections.

Thanks for the tip on coax length since I'm also installing a dual needle SWR meter (Daiwa CN-101).

My installation is coming along. Today, I fished the control cable from transceiver to tuner, hooked up DC power, and started soldering PL259 connectors on feedlines. Also got a good deal on large dynaplate, 18" X 6". I plan to cut it in half and use one half for RF ground and the other half for grounding the arch and other electronics.

[svcattales]

I completed our SSB installation except for installing dyna plate (hauling out in December). Would like some additional advice on the dyna plate install.

I got a deal on the jumbo dyna plate, 6" X 18", and I'm trying to decide whether or not to cut in half lengthwise to get two 3" X 18" plates so I can use one for SSB and the other for a normal electronics grounding plate in the other hull. I don't want to cut the plate, however, if it degrades my SSB performance. To cut or not to cut, that is the question??

The second question os whether or not to put bottom paint on the dyna plate. I know it is not supposed to be painted, but we are in heavy barnacle area and they add a thicker cover than bottom paint. Which is less harmful to the groundplane; bottom paint or barnacles?

FYI. I jury-rigged a groundplane using Rick's bundled wire concept instead of 3" copper strap and it worked well. Used three lengths of triplex copper house wire and placed the dyna plate inside the hull just touching a small dyna plate already mounted in the hull. With this setup I was able to get good signal checks in N. Carolina (we're located in St Pete, Fl).