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Old 21-01-2013, 08:16   #76
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Re: Installing an ICOM IC-M802

I am thinking about splitting my backstay into two backstays, one to the port and one to the starboard quarter, and using the two stays as a inverted vee. Feedpoint of course at the masthead. Maybe even locating the tuner up there, too, right at the feedpoint. Anybody here seen an installation like that? Not really so far off topic... it would make the problems with RF ground sorta moot.
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Old 21-01-2013, 10:40   #77
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Re: Installing an ICOM IC-M802

I had a CAT with a short stay on the port side as the antenna. It looked feasible for an antenna and may have been interesting. However, as you suggest there are many other implications on a boat that can make it a lot more challenging than ashore.

As stated earlier I check over 40 boats a year here in the Sea of Cortez. While we have been really talking about theory of installations. The reality is quite different.

The average cruiser typically does not understand HF SSB. They were an expert in another field before they retired. When faced with the option of cutting the back stay and putting holes in the boat to make it work, they resist and look for other options. Isolated backstay and dynaplate maybe the best around solution. However I think the boat has a lot to do with it. Here in PV, we have a local SSB net. It is all ground wave.

The boats in La Cruz have various configurations. One of the boats has copper plates connected by copper strips (all isolated from DC ground) with an isolated backstay. They seem to be able to hear better than even the shore stations in the net. As far as transmitting they are always good. However the Cat with a Kiss Ground on the other side of the same dock with a 24 foot fiberglass pole was stronger today, but could not hear the contact south of us.

One of the boat with the dynaplate and Isolated backstay has been the weakest in the Sea of Cortez. Seems to hear OK, but the boats in the same anchorage, some may even have Dynaplates, are 2-3 bars stronger.

About 30-40% of the installations down here are by the owners. Another 30-40 are by individuals that define them selves as experts and the rest are by good technical folks, maybe even real experts.

e.g. Last spring in Mazatlan I found one of the "defined expert installations" with max SWR on my meter. Long story short, he used GTO15 high voltage cable between the transceiver and the antenna tuner. The boat was using a Gamm antenna. The extra HV wire had been coiled into a 5" loop and tie wrapped to a metal bracket.

A boat I checked 2 days ago because of poor output here in the marina had inserted a piece of # 6 wire with about 10 MOVs in Parallel, that in series with another piece of wire and then to the Dynaplate ground connection on the AT 140 tuner. The Dynaplate was also hooked into the boats bonding system.

I could go on for hours.

Most of the ones installed by the owners are OK, some not great, but OK.

With the use of a Gamm and Kiss ground, there are usually minimal technical issues. They are installed they way the manufacture has specified. While communicating within the nets, the boats that do not communicate well are ones with issues. The ones that excel, strong transmission and reception, vary with products used.

As a result I typically do not badmouth any of the products used, except using a Ham radio instead of a Marine radio. Even that works for the Ham that put the radio in, but the second owner on those boats seem to always have issues. The Ham radio is never straight forward to do the marine things like Airmail. (Airmail does support a few Ham radios, but not Icom which seems to be the most popular, probably a cost factor.)

In saying all of this, while it may work fine to do an inverted V using 2 stays, with a 50 foot mast and 14 foot beam, the length of the wire is probably to short for anything below 4.4 MHz and ~16 degree angle between the elements would be to small for a typical inverted V. The tuner at the top of your mast would be interesting and would probably require a special control cable with larger wire. Alternatively you could run transmission line from the tuner to the top of the mast, but there you have losses and the standard Marine grade tuner below would not compensate for transmission line and the antenna so you may well have high losses from cable length and SWR.

Bottom Line the systems now being used on boats work reasonably good. Nothing like our MARS station back home, but good. Because it is typically a back stay antenna, it is slightly directional from the stern. The key is make sure your connections are not corroded and use lots of snap on cores to keep the RF out of the transceiver, modem and computer.

73s
TL Sparks
AD7XL

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Originally Posted by GrowleyMonster View Post
I am thinking about splitting my backstay into two backstays, one to the port and one to the starboard quarter, and using the two stays as a inverted vee. Feedpoint of course at the masthead. Maybe even locating the tuner up there, too, right at the feedpoint. Anybody here seen an installation like that? Not really so far off topic... it would make the problems with RF ground sorta moot.
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Old 21-01-2013, 14:47   #78
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Re: Installing an ICOM IC-M802

SWR by itself does not say anything about how well an antenna system will radiate power. A low SWR is important primarily to the radio to minimize reflected power that can damage the radio's final amplifier. Radios with tube finals are typically tolerant of much higher SWRs than transmitters with transistor finals, and they can transmit very efficiently at those higher SWRs. Most modern radios begin to cut back power if they see an SWR of greater than 2:1. This is simply to protect the radio, and is the reason you don't want your radio to see an SWR higher than 2:1. The antenna tuner takes care of this problem for the radio.

A high SWR doesn't even mean that a lot of power is wasted. At an SWR of 2:1, only 10% of output power is being reflected back into the radio, but of that most is being reflected back out of the radio to the antenna again for radiation, so in practical terms very little is actually being lost. A higher SWR does mean that transmission line losses will be greater between the radio and ATU or antenna, but with the lengths of coax we use on a boat, and at HF (as opposed to VHF) these losses also are relatively small.

An monopole (backstay) antenna with a 50 ohm nominal impedance at a given frequency may give a 1:1 SWR to the radio, but that does not mean that it is radiating all of the power delivered to it. If the radiation resistance of the antenna is low relative to the ground resistance of the ground/counterpoise, then much of the power delivered to it will be dissipated as heat in the ground/counterpoise. This is most apt to be a factor when the antenna length is less than 1/4 wavelength of the frequency in question. On a 40 foot boat with a 55 foot backstay antenna, we are talking about frequencies below about 8 mHz. Even a relatively poor counterpoise at lower frequencies can be plenty good enough at higher frequencies.

The KISS counterpoise can certainly let you get a signal out and let your ATU match your antenna system to your radio, but it is not a tuned multiband radial and not likely to work much better than an equivalent length of 14 ga wire attached and placed in the same way. It is sealed to reduce the chance of corrosion, which is probably the biggest enemy of any blue water counterpoise system, so that is a good thing. It also keeps one from attaching the counterpoise system to the wrong things, like the boat's DC ground.

If I were to predict where the KISS would come up short compared to a true tuned radial system, or copper strapping run the length of the boat, I would expect it to be in the lower frequencies where high quality of ground with low ground resistance becomes most important.

Chip
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Old 21-01-2013, 16:26   #79
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Re: Installing an ICOM IC-M802

Chip,

I agree with everything you said other than a 1:1 SWR is very hard to find. The KISS comes the closest as does the radials I installed except on 18MHz where it typically goes up to about a 1.8:1.

To clarify what I mean, I do not generally systems. I check systems that are not working. They frequently have a high SWR when they can not talk, usually because of corrosion. KISS never corrodes so it always has a good SWR. It seems to be the only ground system that does not have negative effects as a result of the environment.

Our lowest frequency net here is 3968.0 so I have no idea how KISS would work in the 2 MHz band. None of the KISS boats seem to have a weak signal in the Sea of Cortez. However Copper and Dynaplate boats do and it is usually corrosion.

Everyone has something they like, but no real testing has been done on boats. The only realistic test in my opinion would be to have a boat with copper, a Dynaplate, and a Kiss transmit a tone out at sea with another boat going around it at a significant distance to establish field strength and pattern. Change the ground and do it again.

The standard test seems to be I talked to some station far away so my radio is better. There are to many variables in that test to pass the snicker test. e.g. I have talked to the Bahamas, North Dakota, New York, Minesota etc. on 14300 when I was in La Paz. Does that mean I have a great ground, antenna, radio. I do not think so. It is probably an OK system. I wish there was a formula to stick it all into to determine the prefect solution. However, all the boats are different.

What I know to be true at least here is that all of the systems seem to work OK when they are not broken, and the kiss guy is not a crook as was implied earlier by another gentleman.

73s
TL Sparks
AD7XL


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Originally Posted by SoonerSailor View Post
SWR by itself does not say anything about how well an antenna system will radiate power. A low SWR is important primarily to the radio to minimize reflected power that can damage the radio's final amplifier. Radios with tube finals are typically tolerant of much higher SWRs than transmitters with transistor finals, and they can transmit very efficiently at those higher SWRs. Most modern radios begin to cut back power if they see an SWR of greater than 2:1. This is simply to protect the radio, and is the reason you don't want your radio to see an SWR higher than 2:1. The antenna tuner takes care of this problem for the radio.

A high SWR doesn't even mean that a lot of power is wasted. At an SWR of 2:1, only 10% of output power is being reflected back into the radio, but of that most is being reflected back out of the radio to the antenna again for radiation, so in practical terms very little is actually being lost. A higher SWR does mean that transmission line losses will be greater between the radio and ATU or antenna, but with the lengths of coax we use on a boat, and at HF (as opposed to VHF) these losses also are relatively small.

An monopole (backstay) antenna with a 50 ohm nominal impedance at a given frequency may give a 1:1 SWR to the radio, but that does not mean that it is radiating all of the power delivered to it. If the radiation resistance of the antenna is low relative to the ground resistance of the ground/counterpoise, then much of the power delivered to it will be dissipated as heat in the ground/counterpoise. This is most apt to be a factor when the antenna length is less than 1/4 wavelength of the frequency in question. On a 40 foot boat with a 55 foot backstay antenna, we are talking about frequencies below about 8 mHz. Even a relatively poor counterpoise at lower frequencies can be plenty good enough at higher frequencies.

The KISS counterpoise can certainly let you get a signal out and let your ATU match your antenna system to your radio, but it is not a tuned multiband radial and not likely to work much better than an equivalent length of 14 ga wire attached and placed in the same way. It is sealed to reduce the chance of corrosion, which is probably the biggest enemy of any blue water counterpoise system, so that is a good thing. It also keeps one from attaching the counterpoise system to the wrong things, like the boat's DC ground.

If I were to predict where the KISS would come up short compared to a true tuned radial system, or copper strapping run the length of the boat, I would expect it to be in the lower frequencies where high quality of ground with low ground resistance becomes most important.

Chip
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Old 21-01-2013, 16:47   #80
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Re: Installing an ICOM IC-M802

Quote:
Originally Posted by GrowleyMonster View Post
I am thinking about splitting my backstay into two backstays, one to the port and one to the starboard quarter, and using the two stays as a inverted vee. Feedpoint of course at the masthead. Maybe even locating the tuner up there, too, right at the feedpoint. Anybody here seen an installation like that? Not really so far off topic... it would make the problems with RF ground sorta moot.
Hi GM although that design would indeed not require a ground, an inverted vee is not a very good antenna despite its widespread use by hams. The legs of a dipole are out of phase so the fields begin to destructively interfere when it is bent. When the apex angle is less than 90 degrees the cancellation becomes extreme and the feed impedance would be beyond the ability of a tuner to efficiently tune.
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Old 22-01-2013, 19:24   #81
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Re: Installing an ICOM IC-M802

"the kiss guy is not a crook as was implied earlier by another gentleman"

I am not saying the guy is a crook (either expressed or implied), but I will observe the following:

The KISS-SSB website implies this is an Icom endorsed product - I am yet to find anyone within the Icom organisation that has endorsed this product. This statement is thus misleading.

KISS-SSB may argue that Icom have not endorsed the product but that Icom have endorsed the principle of its operation. This is stretching the truth as well.

Certainly in the Icom m802 manual, Icom itself recommends the use of a counterpoise system but only as a supplement or an adjunct to a grounding plate or a copper foiling arrangement. At no point does Icom itself say that the attachment of a few counterpoise wires constitutes an acceptable grounding system.

Grounding to the conductive sea water around the boat works because the sea water acts as a reflective surface for radio waves and particularly enhances long distance communication via a lower angle of radiation for the transmitted radio signal.

A counterpoise operates in the same manner as a tuned radial system for a vertical antenna - if you have few radials - ie one per band like the KISS-SSB system, the resulting antenna system is pretty inefficient - ie akin to a dipole with one leg raised vertical in the air with the second leg lying on the deck of the boat. If you add many (50 or more) radials (counterpoise wires) for a given frequency the counterpoise will eventually start acting like a reflective surface for radio signals and this combined with a capacitive coupling to the surrounding sea water will do a similar job to bonding directly with the sea water via a dynaplate or metal keel. For this latter system to work you either need lot of counterpoise wires or a significant surface area of metal such as copper sheet. This is actually the system recommended by Icom in the m802 manual.

Of course I am always happy to be proven wrong. If someone can show me a specific Icom endorsement for the KISS-SSB product I would most happily defer to the expertise of the Icom RF engineers. If such an endorsement does not exist then I stand by my comments re a possible misrepresentation of this product.

This certainly does not mean the KISS-SSB guy is a crook but it probably does suggest he has been a little over zealous in the promotion of his product.

Cheers
Paul - vk4ma
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Old 22-01-2013, 20:36   #82
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Re: Installing an ICOM IC-M802

Paul – I’m afraid you (and many others) are mistaken in the belief that radials or a counterpoise reflects RF radiated from the monpole antenna. All reflection takes place in the far field well away from any radials, in the Fresnel zone surrounding the antenna out several hundred wavelengths.
The SOLE purpose of radials or a counterpoise is to collect and return the near field radiated RF to the shield side of the feedline or tuner in the most efficient manner possible, and even one or two radials are sufficient over the low loss ground that the surface of salt water provides, if a direct low impedance connection to the SURFACE of the sea is not possible. The second leg of a dipole, consisting of only a single wire, does exactly that with nearly 100% efficency and the radials or counterpoise of a monopole serve this same function.
It is totally unneccessary for either the monopole radiator or the radials to be wavelength since resonance has no bearing whatever on antenna efficiency and the ATU simultaneously tunes the entire system to resonance in order for the transmitter to load properly. In fact ground radials cut to formula for wave are totally detuned by the nearby ground.
73 Bob N6BK HS0ZIA
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Old 22-01-2013, 21:30   #83
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Re: Installing an ICOM IC-M802

One additional note - the skin depth of sea water at 5 mHz is about 10cm/4", and is LESS at higher frequencies. This means that any connection (either direct or capacitively coupled via a plate) to sea water at a deeper depth is USELESS as an RF return current ground.
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Old 22-01-2013, 21:49   #84
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Re: Installing an ICOM IC-M802

Hello Bob

So are you advocating that one single (long) counterpoise wire is all that is required for a highly efficient grounding system in a marine installation, and - if not - why not? As all cruisers sit overly a highly conductive SURFACE and if a random length wire of reasonable length is near 100% efficient in returning near field radiated RF why would we bother doing anything more?

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Old 22-01-2013, 22:32   #85
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Re: Installing an ICOM IC-M802

Yes Paul that is exactly correct, and this has been borne out with lots of emperical field strength research by ON4UN, K3LC and others as well as NEC4 antenna modeling software. And no radials whatever are needed if a direct connection to the sea SURFACE or a metal hull (via a DC blocking cap) can be achieved. Radials and counterpoises are not necessary at all against a perfect (or sea water) ground, they are only needed to enhance the less than ideal grounds found on land. 73
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Old 22-01-2013, 22:56   #86
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Re: Installing an ICOM IC-M802

Hello Bob
I am not sure that you have answered my question.
For new installs it is far easier to simply attach one counterpoise wire of reasonable length than making a contact point with the surrounding seawater (via dynaplate or metal hull etc).
Are you advocating that we can dispense with a grounding point to the surrounding sea water altogether and simply use this one counterpoise wire.
I agree that counterpoise wires are not required if you have decent dynaplate. But what you appear to be saying is that a dynaplate (or grounding point to the sea) is not required at all and that a single wire counterpoise of reasonable length is all that is required.
If a grounding point to the sea is required then why? - as your earlier post would suggest that a single wire counterpoise is all that is required to achieve maxium system performance.
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Old 22-01-2013, 23:15   #87
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Re: Installing an ICOM IC-M802

If a direct low impedance ground connection cannot be made to the sea SURFACE for whatever reason (I know nothing about dynaplates) then one or two radials of reasonable length will provide adequate return current and adding more will not result in a noticeable improvement in field strength.
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Old 22-01-2013, 23:44   #88
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This thread is heavy with jargon and hype. Constructing an effective antenna on a yacht is not difficult. Most problems arise from simple things: using the wrong parts, corrosion, weird beliefs. Follow any guides by the radio manufacturers or from informed practical sailors like the folks at Sailmail and it will work just fine.

All this talk of "radial" and "counterpoises" is simply nonsense in the context of the typical yacht: fancy names for an RF ground. Same with a KISS which is simply a market hyped RF ground no different than a newly installed corrosion free piece of wire.

Connect the antenna tuner ground terminal to something that is intimate with the seawater and metallic hull parts. Then the antenna terminal to a long wire aerial that is not. Simple. Check for corrosion several times per year.
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Old 23-01-2013, 00:32   #89
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Re: Installing an ICOM IC-M802

Hello Bob
Your answer still suggests that a ground connection to the sea is the most preferable option - ie "If a direct low impedance ground connection cannot be made to the sea SURFACE......" - why is this the preferred option when you claim a single wire counterpoise is a perfectly good substitute.

I am not trying to be difficult, but your claim goes right to the heart of whether the KISS-SSB product is a perfectly good substitute for a dynaplate.

The question is important because I can guarantee that given a choice, 99% of marine radio installers would prefer to simply run out a single counterpoise wire as compared to pulling the boat out of the water and drilling holes through the hull to mount a dynaplate.

If the dynaplate is adding absolutely no value to the antenna system then I am wondering why for 30 years or more installers have been putting themselves through the pain of dynaplate installation.

I am not saying your wrong, as your logic is quite sound, but even you seem to be quite reluctant to dismiss the benefit of a grounding point to sea and the single wire counterpoise is now only providing "adequate" return current.

One practical reason why a single wire counterpoise may not do a reasonable job is because there is insufficient space in an average pleasurecraft to run out a counterpoise of sufficient length for efficient operation of the antenna system on low frequencies. Although I agree that the counterpoise does not have to be a resonant quarter wave, for commonly used frequencies such as 2.182mhz, it probably still needs to be at least 25 metres (straight line) to perform effectively. There are few vessels with this type of space available.

The bottomline therefore is that grounding to infinite conductive surface of the surrounding sea water is much more efficient than using an electrically short counterpoise and this is probably why the installation of groundplates has been favoured over counterpoise for the last 30 years or so.

If my theorising is correct, then I would stick to my guns in saying that the KISS-SSB system will not provide as optimal system performance as mounting a decent dynaplate. Unfortunately measuring the difference in performance is nigh impossible and thus products such as KISS-SSB can be marketed with very little credible evidence to justify performance (or diminution thereof).

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Old 23-01-2013, 01:51   #90
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Using a Dynaplate or (better on my opinion) capacitively coupling thru the hull makes a good RF connection to the sea. It also satisfies perfectly the concern with a sea surface connection. The hull is the surface of the sea on all floating boats, right?

I don't know if my several installations have been "optimal", however they worked better than necessary in that even in remote areas poorly covered by Sailmail stations I could always contact more than one during a 24 hour period.

Antennas were properly insulated backstays. The antenna tuner was properly placed at the base and grounded to toerails, lifelines, encapsulated lead keels, via copper foil bonded to the underwater FRP hull where possible. Textbook. No technical understanding necessary. Some of the connections go bad of course, it's a boat, but they are easy renewed.

Considering the goofy non-textbook installs have seen on other boats its no wonder people have problems.
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