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Old 10-09-2016, 19:44   #16
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Re: Ground Plane for ICOM M802

For what its worth:

The reason flat ribbon is better than round wire is that HF frequency currents travel only on the surface of conductors.

Thus, thin flat conductors offer more surface area for transductance that do round wires, for the same amount of copper. You can certainly gain the same effect with wire, it just needs a lot more copper to achieve the same effect.

To estimate the difference, calculate the area (per linear foot) for each option, and "just" use an area-equivalent amount of wire to replace the aging foil.
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Old 10-09-2016, 20:54   #17
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Re: Ground Plane for ICOM M802

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Originally Posted by CampDavid View Post
Buy a KISS SSB ground and all it a day. Not expensive and they work

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This is correct. Or you can use 1940's technologies and try and find the headwaters of the Nile with useless old wives tales and achieve the same result.
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Old 11-09-2016, 00:59   #18
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Re: Ground Plane for ICOM M802

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Originally Posted by Dockhead View Post
The total run is probably 4 meters.
4 meters is a bit too long for a good connection between tuner and ground plate/thruhull then water. It is a fifth of a wave in 20m. You can use radials or capacitive foil but those are different approaches.

For direct connection to water the tuner should be directly below the antenna and close to the ground plate/throughhull.


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Old 11-09-2016, 02:13   #19
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Re: Ground Plane for ICOM M802

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Originally Posted by transmitterdan View Post
4 meters is a bit long for a ground strap IMO. Is there no thru hull nearer?

What you might do is use a short piece of copper tubing to get through the bulkhead. Attach copper strap for the rest of the run on either side. Strap can either be soldered to the copper tubing or clamped.
It's a 54' boat, so the distances are fairly great. Nearest through hull is in the after heads.

I had never heard that this distance was critical.

So maybe I should try the lifelines?
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Old 11-09-2016, 06:04   #20
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Re: Ground Plane for ICOM M802

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The way it has to be routed makes it almost impossible to use a strap. How much worse is the heavy cable?
Heavy cable is ineffective.

For a ground plane, you need surface area. Copper foil 75 mm wide and of thin gauge is ideal as RF current flows on conductor surface mostly. https://en.wikipedia.org/wiki/Skin_effect
The copper foil should be connected to an external dynaplate through bolted to the hull and it can also be extended for more surface area if connected to metal water tanks. I would not connect a ground plane to a through hull fitting.

A wire counterpoise https://en.wikipedia.org/wiki/Counte...(ground_system) is an effective alternative and is a commercial rendition of this is the KISS system http://www.kissssb.com/
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Old 12-09-2016, 03:33   #21
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Re: Ground Plane for ICOM M802

Why is heavy battery cable not so good?

Answer: Battery cable is made up of many small copper wires sort of twisted much like 3 strand rope except all the wires turn the same direction. RF current (unlike DC) does not like to go round those turns. It wants to go straight through. Thus the current will "jump" from one strand to its neighbor in an effort to go straight. Copper wires that are just touching one another have fairly high resistance where they touch compared to the copper itself. So while a battery cable will appear to work and it may show great VSWR it is likely the real reason is the wire is acting as a reaistive dummy antenna. This is much like the KISS which has significant resistance thus improving VSWR but not antenna efficiency. A good tuner ground is needed to improve antenna efficiency. Improved VSWR is no proof of higher efficiency. Usually it means the opposite.
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Old 12-09-2016, 06:14   #22
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Re: Ground Plane for ICOM M802

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Why is heavy battery cable not so good?

Answer: '.
--
-.
. Improved VSWR is no proof of higher efficiency. Usually it means the opposite.
This view on the VSWR is incorrect. VSWR is a direct measure of antenna efficiency
In an ideal scenario all of the RF energy produced by the radio would be fed into the antenna with no transmission losses. This would be perfect matching and a VSWR of 1.0
Higher ratios, greater than 1 show losses between the radio and antenna and if a VSWR is greater than 1.5, most of the radio's output is lost before it arrives at the antenna.
That is the function of the tuner, to match the impedance of the radio to the impedance of the antenna at the frequency in use.
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Old 12-09-2016, 06:27   #23
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Re: Ground Plane for ICOM M802

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This view on the VSWR is incorrect. VSWR is a direct measure of antenna efficiency
This is something that is often misunderstood. A dummy load radiates no power but has really good VSWR. So it is easy to see that VSWR is not sufficient to determine antenna efficiency. If you put a lossy element into the ground return of the tuner that will improve VSWR. But it will not improve antenna efficiency.
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Old 12-09-2016, 06:34   #24
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Re: Ground Plane for ICOM M802

Quote:
Originally Posted by transmitterdan View Post
Why is heavy battery cable not so good?

Answer: Battery cable is made up of many small copper wires sort of twisted much like 3 strand rope except all the wires turn the same direction. RF current (unlike DC) does not like to go round those turns. It wants to go straight through. Thus the current will "jump" from one strand to its neighbor in an effort to go straight. Copper wires that are just touching one another have fairly high resistance where they touch compared to the copper itself. So while a battery cable will appear to work and it may show great VSWR it is likely the real reason is the wire is acting as a reaistive dummy antenna. This is much like the KISS which has significant resistance thus improving VSWR but not antenna efficiency. A good tuner ground is needed to improve antenna efficiency. Improved VSWR is no proof of higher efficiency. Usually it means the opposite.
That sounds reasonable. So what do you think about lifelines instead of a through-hull?
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Old 12-09-2016, 06:38   #25
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Re: Ground Plane for ICOM M802

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That sounds reasonable. So what do you think about lifelines instead of a through-hull?
If it is far to a through hull then run from the tuner to as many things as you can. I'm not a big fan of lifelines but it can't hurt to try. Make sure no one can touch a lifeline and the antenna cable at the same time when transmitting.

It almost never degrades performance to run multiple ground runs to various places.
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Old 12-09-2016, 09:52   #26
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Re: Ground Plane for ICOM M802

Quote:
Originally Posted by transmitterdan View Post
If it is far to a through hull then run from the tuner to as many things as you can. I'm not a big fan of lifelines but it can't hurt to try. Make sure no one can touch a lifeline and the antenna cable at the same time when transmitting.

It almost never degrades performance to run multiple ground runs to various places.
We have changed out our lifelines for 1" rails, and have a large arch. We use a whip, copper strapping from Nav to Tuner (which is immediately under the antenna), and copper strapping to bridge the gates (which have SS chain guards, but just-in-case), plus 30x60" copper flashing under the workbench and a large dynaplate immediately under the Nav.

The strapping includes the motor mounts and the arch, which due to the rails is integral to all that (continuous circuit from arch/pushpit entry starboard around pulpit and back to port entry; even THAT gap is bridged with strapping.

Most of the time I get booming reports; there's a LOT of surface area in ~400 lineal feet of 1" tube and about 80LF of 2" arch tube, all connected to the sea via the dynaplate and propshaft...
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Old 13-09-2016, 04:40   #27
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Re: Ground Plane for ICOM M802

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Originally Posted by kish View Post
This view on the VSWR is incorrect. VSWR is a direct measure of antenna efficiency
A good, or low VSWR only indicates efficient transfer of RF energy out of the transmitter. What happens to that energy when it leaves the transmitter and enters the feedline and antenna system is a very important factor. As transmitterdan illustrates, the efficency of the radiator of RF energy - the antenna/ground(counterpoise) is a large variable independent of the VSWR and can vary greatly.

You can attach an antenna which presents a very high VSWR at a given frequency to a length of water-logged coax which has turned into a resistive load, and find a nice low VSWR at the transmitter - but most of the energy is being dissipated within the coax. This is not a rare occurence!

Conversely, you can attach an antenna with relatively high VSWR directly to a transmitter so that there are no feedline losses, and despite that high VSWR almost all of that RF energy will get radiated anyway - minus a portion of it that will be dissipated in the amplifier final stage.

VSWR is but one component of the system efficiency equation, albeit an important one!
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Old 13-09-2016, 05:12   #28
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Re: Ground Plane for ICOM M802

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Originally Posted by CampDavid View Post
Buy a KISS SSB ground and all it a day. Not expensive and they work
Yes, a KISS will "work". It is expensive for what it is. Despite the misleading explanation of how it works (hey, its on the internet, it must be true!), it functions no differently than a fat 14 foot wire. This has been amply demonstrated by KA4WJA (John) using 21st century RF test gear and documented in these forums. Before his more rigorous analysis I did similar testing with the KISS and an antenna analyzer with equivalent results.

You can easily duplicate its function with $10 worth of wire made into a 14 foot bundle and attached to the tuner ground lug just like the KISS. You can even improve efficiency over the KISS by taking that same quantity of wire and running lengths of it in different directions from the tuner ground lug and laying them in the bilge or attaching to bronze sea cocks, lifelines or whatever.

The advantages of the KISS counterpoise are that it is a very simple to install solution that is well sealed from the elements, and provides a modicum of function. If that is good enough for your peace of mind, go for it! The disadvantage is that it is $10 worth of wire sealed into a garden hose being sold for $160 while being hawked as more than it really is.
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