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Old 01-10-2009, 21:02   #16
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Originally Posted by fairbank56 View Post
and yet inside their tuner's the connection from the ground stud to the circuit board ground plane is a 4" piece of 16 gauge round wire.
So now we are more knowledgeable than the Icom engineers that designed the tuner? If you look where that internal wire connects to, you will probably find an output transformer with even thinner solid wire and if you follow the path further back you will find CMOS semiconductor stages etc. That has nothing to do with what you connect to the tuner.

As I wrote before, the RF resistance of a conductor is measured in ohms per length unit, just like for any wiring. The 4 inches inside the tuner make no difference and believe me, it's much easier to solder a wire onto a printed circuit board than a 3" wide copper foil. I think it's getting ridiculous. Throw out solid engineering knowledge, it's all crap and instructions written down are all wrong, we know better, anyone knows plain wire works as well as foil, who needs an electrical engineering study for that??! Come on, I challenge you: build your own tuner and demonstrate you're better!

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Old 01-10-2009, 23:36   #17
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Hey Bill, and other marine-SSB/ham geeks... I have a question for you.

I'm just about install the classic M802/AT140/backstay rig, and I have a steel hull. I'm concerned about the DC ground loop implications of the tuner-foil-hull connection at the stern, and have on hand a WWII-era big honkin' high-voltage mica capacitor that's transparent at HF. I haven't tested this, but sure like the DC-blocking approach... do you have any experience with this?

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Old 02-10-2009, 00:08   #18
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A mica capacitor is the best choice for this and has negligible aging. The only concern is when they get wet. A true RF mica capacitor is expensive and cast in epoxy inside a metal housing. I suspect that this is what you have, great!

You should just try it. If you have winlink or sailmail, select a station that is weak but works. Now, put the capacitor in and first check if the tuner tunes well on all bands. If so, try pactor mode again and compare connect speeds. I think that if the tuner tunes well it will be good.

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Old 02-10-2009, 04:27   #19
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Originally Posted by s/v Jedi View Post
So now we are more knowledgeable than the Icom engineers that designed the tuner? If you look where that internal wire connects to, you will probably find an output transformer with even thinner solid wire and if you follow the path further back you will find CMOS semiconductor stages etc.
Your assumptions are wrong again Nick. The wire connects directly to the large surface area ground backplane of the circuit board right where the shield of the coax input connects. Other tuner's that Iv'e worked on over the years have had a metal strap or braid of varying widths going from the stud to an internal ground plane. I don't recall ever seeing one using round wire. I have lots of issues with the way Icom "engineers" design their marine gear. As a technician who has worked on their gear for many years I have found myself shaking my head and snickering to myself at their design work. So, with your infinite knowledge Nick, how long can we extend this round wire?. Do we have to connect the strap directly to the ridiculously small stud on the tuner (Icom engineer's again) or can we just use round wire to the strap at a more convenient connection point? Please enlighten us.

Eric
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Old 02-10-2009, 08:00   #20
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Pardon my ignorance but does it matter?

I have always just bent it or folded as required to change direction. As we are only talking HF frequencies a piece of wet string will ALMOST suffice - OK it won't work that well but I have seen so many many poor HF installations that work some of the time, that I truly believe we worry too much at times about getting perfect.

Sure some people should worry more and do more to get it right but if one follows the general recommendations of manufacturers and professionals like say Bill, and then just do the best they can with what they have, the HF will work.
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Originally Posted by GordMay View Post
Here’s some different takes on the subject:

Gordon West ➥ http://www.kp44.org/ftp/GroundingCou...stChapter8.pdf

Icom ➥ http://www.icomcanada.com/techbullet..._grounding.pdf

Dr. John Gregory ➥ Installation Procedure
These references support the general consensus of using foil; my point was that one does NOT have to have a perfect ground installation, rather just one that meets most of the recommendations such as those cited above. This will get the job done .

On re-reading my post I see that my question "what does it matter" is possibly ambiguous. I was asking in relation to Gord's question of the right way to bend foil rather then good ground techniques in general.

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Originally Posted by fairbank56 View Post
It's interesting to note that Icom's instruction manual on grounding and antenna considerations states; "Now here’s another very important point, no round wires for RF ground!" and yet inside their tuner's the connection from the ground stud to the circuit board ground plane is a 4" piece of 16 gauge round wire.
I can't see an issue with this. The whole idea of using foil is to get surface area and thus a lower impedance path for the RF (mainly lower inductive reactance). Anyway of getting a low RF impedance is good, foil is just an easy way . So 4 inches of 16 AWG is not going to add much in the way of impedance compared with say 4 to 6 feet of round wire. If you could mount the tuner so that the ground feeder was only 4 inches, then using sound round wire would be fine.

Most of us have at least several feet of ground feeder so then we have use something with a lower impedance to get a good antenna system.

Icom have to balance the physical and practicable aspects of the circuitry within the tuner with the "perfect" aspects. That they choose a 4" round wire seems to be common sense to me.

IMO, a lower inductance ground feeder would be had using a ROUND thin wall copper tube say 1.5 inches in diameter but most of us would find this physically quite difficult to run and terminate but it would be electrically better than say 3" foil.

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Originally Posted by fairbank56 View Post
The problem with all this is that it is difficult to prove what works best. Just being able to make a contact with a station hundreds or thousands of miles away is NOT an indication of your antenna systems efficiency. I have a very inefficent antenna system on my trailblazer (auto-tuner with 8' whip on back bumper) and make these contacts all the time. I made a contact with a New Zealand station early this morning on the 40 meter ham band from Maryland on a boat on the hard with nothing but 12' of GTO-15 coiled up on the deck for an antenna. The one area where you may see a difference with one ground plane system over another is with how your transmission affects your other onboard electrical/electronics system with interference.

Eric
Oh so true .

FWIW, the HF antenna feeder in an Embraer aircraft (EMB-120) uses 1" diameter Al tube (about 4' long) to carry up to 50 amps of HF RF current. At these current levels, the impedance has got to be low.
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Old 02-10-2009, 08:06   #21
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Originally Posted by fairbank56 View Post
...... Do we have to connect the strap directly to the ridiculously small stud on the tuner (Icom engineer's again) .......

Eric
I hate that small stud, I have never understood WHY they made it so tiny. Other manufacturers manage to do much better.
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Old 02-10-2009, 09:14   #22
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Round copper tubing is an excellent way to carry RF onboard. It's often easier to feed thru holes and other obstructions. Easy to terminate: just flatten one end, and use small bolts/ring terminals, etc. Just need to be sure that it doesn't touch anything which would be harmed by the RF voltages and currents carried.

I agree with Eric and Wotname re: Icom engineering. Sometimes, you just gotta wonder. There are lots better tuners out there (like the SG230, the SEA series, Kenwood, etc.). And, why in heaven use a capacitor to "keep the memory" for a max of 1 month? The SG230 has lots more memories and they're non-volatile.

BTW, the engineers who design these tuners, and these radios are usually NOT the same folks who write the manuals and the install books.

Moreover, the "best practices" cited by the "authorities" often change over time, as they become aware of new information. Gordon West was an early affectionado of the 100sq ft of copper theory but, after some on-the-air testing he concluded that a short connection to the nearest bronze thru-hull is often as good as more extensive RF grounding.

Also, the idea of "never couple to an unbonded thru-hull" has evolved into the opposite: couple ONLY to thru-hulls which are otherwise unbonded. The SG230, and the Icom tuners -- and probably others -- have built-in DC blocks on their ground lugs, i.e., they do not pass DC to the external RF ground.

Ditto for the "connect to everything metal" school of thought. It's a much better idea to keep the RF grounding separate....do NOT connect to engine or other parts of the DC grounding system.

Finally, there are tons of entire books on wire antennas. Usually, in these books there is no mention of copper straps for grounding. Wires are fine, provided they're properly sized and arrayed. Wotname is right: the copper straps are just convenient sometimes, not mandatory.

BTW, I worked on a boat in Annapolis the other day which had the most unusual RF grounding system I've yet run across: the lower part of the standing backstay was split, but electrically connected at the split (the upper part of the backstay was insulated and fed with GTO-15 in the traditional manner). Copper foil and wire (a combination in series) was used to connect between the two chainplates under deck, and the nearby tuner ground lug. Sort of a "delta RF ground". Wild!

Bill
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Old 02-10-2009, 09:35   #23
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Originally Posted by fairbank56 View Post
Your assumptions are wrong again Nick. The wire connects directly to the large surface area ground backplane of the circuit board right where the shield of the coax input connects.
Eric,

You've been in my hair since the first message I posted on this forum. After all this time and what, 1,200+ msgs I posted you must have read enough of them to find that I am not dreaming up what I post and am actually quite a nice guy??!!

Anyway, I never studied the Icom tuner design but I am sure that this PCB ground plane connect many more components than the coax shield and the 4" AWG 16 ground wire. Every RF PCB implements ground as a plane taking up most of the surface area of the PCB but it still has the primary function of interconnecting components on the PCB.

Quote:
Other tuner's that Iv'e worked on over the years have had a metal strap or braid of varying widths going from the stud to an internal ground plane. I don't recall ever seeing one using round wire. I have lots of issues with the way Icom "engineers" design their marine gear. As a technician who has worked on their gear for many years I have found myself shaking my head and snickering to myself at their design work.
So, do you state that the Icom tuner doesn't work as good as the other ones? Because if you do, your negative comments on it's design make sense.
I believe that the Icom tuner works just as fine as the others. It is the high level of engineering knowledge at Icom that makes it possible to create a good functioning tuner that looks "less well done" on the inside. They do this to save money on components and assembly time. It is very difficult to get away with that so well, while it is much easier to create a good functioning product with straps and bolts etc. You can be sure that every wire inside the tuner and every trace on it's PCB, had it's length and diameter/width and path exactly calculated to make this work, plus many prototypes to work out the problems, before getting to this product. Making it look that shabby on the inside is what makes it the big design challenge and the fact that it works so well is why an RF designer will respect it. It even copes with the environment well enough as my Icom tuner is older than I remember.

Quote:
So, with your infinite knowledge Nick, how long can we extend this round wire?. Do we have to connect the strap directly to the ridiculously small stud on the tuner (Icom engineer's again) or can we just use round wire to the strap at a more convenient connection point? Please enlighten us.
I have only 6 years of RF design to look back at, I switched to micro-computer design after that (for the money, RF design is more fun). I know you're mocking me but I'll give a serious answer anyway: My knowledge is much more finite than that of the Icom engineers and they tell us that you should not use wire but foil. You are not extending an internal wire, you are connecting an RF ground plane system to a highly & precisely designed and tuned product. If you connect wire, you might well throw the RF impedance off loosing much of the "room" the system allows you. This will result in many bad things happening but one that is easily recognized is the inability to tune to a frequency or that it takes much longer to tune to that frequency.

A short piece of wire connecting to foil: it probably isn't that short piece of wire that will cause a problem; it's the extra insertion losses. If you crimp terminals on both ends of the wire, you create 4 insertion points (with loss) whereas a direct connection of the foil is only one insertion point.

People who have trouble connecting the foil to the tuner, don't use the right technique so I attached a photo that shows it's easy to connect it to even the tiniest stud.

First, you fold the foil double onto intself for a couple of inches. Next, you fold the sides at the end so that it tapers to however narrow you need it to be to access the connection stud on the tuner.

Yes, I know the photo isn't an Icom tuner; it's my SGC tuner which is much easier to take a photo of as my Icom is buried deep...

cheers,
Nick.
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Old 02-10-2009, 09:53   #24
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The whole idea of using foil is to get surface area and thus a lower impedance path for the RF (mainly lower inductive reactance). Anyway of getting a low RF impedance is good, foil is just an easy way . So 4 inches of 16 AWG is not going to add much in the way of impedance compared with say 4 to 6 feet of round wire. If you could mount the tuner so that the ground feeder was only 4 inches, then using sound round wire would be fine.
I fully agree. Mentioning "inductive reactance" is correct of course, but I try to stay away from these terms because too many readers will give up at that point, making this an engineers-only thread. I even shy away from "impedance" and try to use "RF resistance" instead.

And yes, copper piping is great. If you go that way, bend it instead of soldering knees.

Bill writes:
Quote:
re: Icom engineering. Sometimes, you just gotta wonder. There are lots better tuners out there (like the SG230, the SEA series, Kenwood, etc.). And, why in heaven use a capacitor to "keep the memory" for a max of 1 month? The SG230 has lots more memories and they're non-volatile
Oh indeed, Icom isn't the best tuner when you look at the features, I agree with that. But those features come with a price tag too. But I don't think an SGC tuner will give you better range compared to an Icom tuner. Overall, I see a slightly better SWR with it and tune-times are shorter but if all you care about is talking on the nets and using your Pactor modem, the Icom tuner does that fine at a lower cost.

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Old 02-10-2009, 10:00   #25
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......but I try to stay away from these terms because too many readers will give up at that point, making this an engineers-only thread. I even shy away from "impedance" and try to use "RF resistance" instead.....
.
Good point , I will try to remember that. Hey aren't the sailors out there sailing while the engineers (without a life) are posting stuff on the internet .
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Old 02-10-2009, 10:11   #26
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In this thread, we're also completely mixing up a general ground plane with ground radials. Whenever something like 100 sq. ft. is mentioned, we're talking about a general ground plane. But when several lengths of foil (or wire) of certain lengths are discussed, we're talking about tuned (resonant) radials. Some call that a "counter poise" to differentiate it from a regular ground plane.

A good document is here: http://www.bencher.com/pdfs/00361ZZV.pdf
Tuned radials work best when the vertical is elevated at least 1/2 wavelength above ground. Boats don't have that.

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Old 02-10-2009, 10:59   #27
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The SG230, and the Icom tuners -- and probably others -- have built-in DC blocks on their ground lugs, i.e., they do not pass DC to the external RF ground.
Icom and SEA tuner's do not have DC blocking capacitors on their ground lugs.

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Originally Posted by s/v Jedi
You've been in my hair since the first message I posted on this forum. After all this time and what, 1,200+ msgs I posted you must have read enough of them
I only read topics of interest to me, and reply infrequently (150 posts in 2 1/2 years). If you didn't quote me and then start off with snide remarks, it wouldn't be a problem.

Quote:
So, do you state that the Icom tuner doesn't work as good as the other ones? Because if you do, your negative comments on it's design make sense.
No, I do not state that, and my only negative comment was about the small ground stud. These tuner's actually work too well. In fact, they will tune just fine on all bands with no antenna or ground attached whatsover. Which makes it that much more difficult to determine whether your efforts at installing a decent antenna/ground system is working.

I apologize for mocking you Nick. As before, I'm a little too quick on the keyboard sometimes.

Eric
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Old 02-10-2009, 13:54   #28
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If you didn't quote me and then start off with snide remarks, it wouldn't be a problem.
Hmm... snide: "critical in an unfair and nasty way". What I wrote was "So now we are more knowledgeable than the Icom engineers that designed the tuner?" This was in defense of the Icom engineers and it doesn't really sound nasty/unfair to me. I also meant this in a broader sense which is why I used the word "we" instead of "you". I think it's very easy for "us" to write things like "wire works as good as foil so those designers don't know what they are talking about and we know better". But that isn't true; the engineers at Icom know much more than we do and it is they that know better what they are talking about.

Quote:
No, I do not state that, and my only negative comment was about the small ground stud. These tuner's actually work too well. In fact, they will tune just fine on all bands with no antenna or ground attached whatsover. Which makes it that much more difficult to determine whether your efforts at installing a decent antenna/ground system is working.
Exactly, the Icoms tuners work well. I can't tune mine on the 2 Mhz band without antenna though...
I think what you and others really mean is that we would like to see a more robust appearance and more advanced features in a tuner. But we can get that from the other brands mentioned earlier. Most cruisers don't really care about that but they do care about the cost which leads them to Icom, which is a design goal that the Icom engineers work with: design something that works well enough at the lowest possible price. It's a mass market product and a successful one.

It's always hard to test the efficiency of an antenna. Even an SWR meter doesn't help much except to find big problems. The tuners we use make it hard or even impossible to use an antenna analyser. What's left is field strength measurements and that ain't much fun!

When the tuner is located at the stern, we're hip deep in trouble anyway because it's nearly impossible to create an effective tuned radial system when we have less than 180 degrees to work with. I find it amazing that it works so well, but I also think every series-built plastic boat should have a copper mesh in the laminate of the aft section for RF ground.

Quote:
I apologize for mocking you Nick. As before, I'm a little too quick on the keyboard sometimes.
No problem, I think we'll be fine from here on ;-)

ciao!
Nick.
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Old 02-10-2009, 15:55   #29
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A mica capacitor is the best choice for this and has negligible aging. The only concern is when they get wet. A true RF mica capacitor is expensive and cast in epoxy inside a metal housing. I suspect that this is what you have, great!
That't the animal, Nick - thanks! It's on the boat and I'm not, or I'd post a photo... but I'll try to remember to come back to this thread when the install is done (or will post somewhere, I'm sure; I tend to be a wordy sort).

Best 73,
Steve
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Old 02-10-2009, 16:05   #30
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Lifelines as Counterpoise

I use the lifelines on my boat as the counterpoise and can talk 5 by 5 to Fla from the Chesapeake on the Waterway Net. Since it's so easy, I'd try this first before taking a more difficult approach.
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