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Old 01-06-2014, 18:10   #1
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Icom M802 & AT-140 Grounding???

I have an Icom M802 & AT-140 tuner that uses a wire mesh in the hull as an RF ground. The system works fine except I get some noise from the refrig & freezer compressors and the Simrad Autopilot. I have tried to isolate the noise at the compressors and autopilot computer without great success.

I was recently given advice to disconnect the RF ground from the M802 chassis & just connect the tuner to the RF ground. I was also given advice to connect the wire mesh RF ground to a bronze hull fitting to provide a better RF ground in contact with seawater. In the process of disconnecting the RF ground from the M802 chassis, I found that the M802 chassis is also common with the boats 12v DC ground so the original installation had the RF ground and ships DC ground tied together at the M802 chassis.

I have disconnected the M802 chassis from the RF ground and have connected the RF ground wire mesh to a brooze hull fitting and still have the RF ground connected to the tuner.

Am I on the right path or am I missing something. The ICOM manual says the the M802 chassis should be connected to the RF ground as well as the tuner????
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Old 01-06-2014, 18:49   #2
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Re: Icom M802 & AT-140 Grounding???

You are on the right track. Your M802 will be connected through the coax cable to the tuner and then to RF ground.

Have the changes you have made helped?
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Old 01-06-2014, 19:21   #3
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Re: Icom M802 & AT-140 Grounding???

HF frequencies actually propagate over the surface of materials rather than through them. The absolute need for a seawater conductive connection is actually an urban myth (poor physics). What actually happens with seawater coupling is that lower frequency noise in the negative/ground system is dampened by the seawater connection, consequently reducing the parasitic effect as a result of the higher frequency harmonics on the HF component of the system. Your copper mesh counterpoise connected to you engine block etc offers a good amount of surface area for your RF ground. Somewhere over 175sq.ft. of total surface area would be optimum but not always possible on a GRP boat.

You're probably fine with your current setup and you're going right direction and DeepFrz states. Decoupling your RF ground from your negative tie will go a long way to helping reduce the noise from your other devices. Typically, one of the worst offenders would be a PWM battery charger when it comes to SSB noise.

One of the reasons that people find that Kiss SSB works quite well is not because it's a perfect counterpoise solution, but because it is typically completely decoupled from the vessel's common negative/ground system and consequently not too noisy!
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Old 01-06-2014, 19:54   #4
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Re: Icom M802 & AT-140 Grounding???

We normally shut the fridge off when doing any HF radio communications. We have found we get noise from the auto pilot, some led lights, battery charger, cabin fans. Trying to eliminate all the noise well we put a number of chokes on the autopilot and that really helped but usually we just turn off the offending culprits when using the radio. We also have a 802 with a AT140 tuner and just run the ground to the nearest thru hull. Rock solid transmission.

Good luck
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Old 02-06-2014, 06:50   #5
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Re: Icom M802 & AT-140 Grounding???

BrightAyes,
Yes, you are in the right track in regards to "grounding" and wiring of the M-802 and AT-140...

But, this will typically have NO effect at all on radiated, on-board-generated, RFI (Radio Frequency Interference)....

Much of this is covered in the Sailmail Primer...
SailMail Primer


See detail here in red...
Quote:
Originally Posted by BrightAyes View Post
I have an Icom M802 & AT-140 tuner that uses a wire mesh in the hull as an RF ground. The system works fine except I get some noise from the refrig & freezer compressors and the Simrad Autopilot. I have tried to isolate the noise at the compressors and autopilot computer without great success.
Typical RFI/noises from Danfoss based refrigeration/freezers are lots of beeps, tones, and buzzes...(and this noise, as well as other noises from the Autopilot corepak/computer)
Typically these are RADIATED (i.e. "transmitted" thru the air) and received by your M-802/AT-140's antenna (backstay, I assume??)


So, the usual cures are mulit-fold (and most apply to BOTH the frig/freezer AND the autopilot):
a) Simply turn off the frig/freezer when using the radio (NOT such a great solution....but many times, just the a change in voltage and/or switching the frig off and then back on again a few minutes later is enough of a change to "move" the interference away from the frequency you're using, and you're good-to-go...)
Of course, turning off the autopilot is usually a non-starter...

b) Try to install your AT-140 and antenna as far away from your refrigeration compressors / controllers (and autopilot corepak) as possible (usually NOT very practical)

c) Make sure your GTO-15 antenna wire (that is the beginning of your antenna) that runs from the AT-140 output to your backstay is as far away as possible from the refrig compressors (and autopilot corepak) AND as short of length as possible....(do NOT lengthen it just to move it further away, as you want it to be as short as possible and run as directly as possibly to the backstay)

d) Do NOT ever run the GTO-15 wire along with any other wires!!!
ALWAYS keep the GTO-15 wire as far away from every other wire as possible....and never allow it to run parallel to other electronics wires....

e) Once you've done the above, then it may (usually) comes down to "choking-off" (and/or shielding) this radiated RFI at the source....
Understand that all the wiring that connects to these devices (refrig/freezer and autopilot corepak) act as ANTENNAS radiating/transmitting this noise/RFI....
Anything you can do to move these farther away, shield these devices, and "choke-off" this radiated RFI from these "antennas"....will go a long way in eliminating the RFI altogether....(but sometimes it is expensive to completely eliminate all RFI)

Clip-on ferrites are going to be your new best friend here!!
Buy a lot of them (maybe a dozen or more)....(all Raymarine electronics come with them, just for this purpose!)

Place them on ALL electronics wiring, especially on ALL autopilot wiring....and on all refrigeration wiring....
And, do this RIGHT AT THE devices, RIGHT as the wires leave the autopilot and refrig units...(thereby "choking-off" much of this radiated RFI...
Do NOT be stingy here....use a lot of ferrites and/or of you can loop the wiring thru the same ferrite 2 or 3 times that is even better (and their "choking" ability is multiplied exponentially (up to a point, anyway)....

I recommend DX Engineering and Radioworks....they both have the correct ferrite mix for HF RFI and both are used to dealing with HF radio users (mainly hams) who have RFI problems (although usually it's the HF radios causing the interference to other devices...

RF suppression snap-on Ferrite beads- DX Engineering

RFI


Also, take note that while it probably will be of little help in your specific problem described, using a "line isolator" on the coaxial cable (installed at the AT-140) is not only normal installation procedure, it is VERY practice to keep your radio's transmitted signal from causing interference to other devices on-board....and if you're ordering ferries anyway, you might as well buy/install a line isolator and coax jumper...

DX Engineering Maxi-CoreŽ Feedline Current Chokes DXE-FCC050-H05-A - Free Shipping on Orders Over $99 at DX Engineering

T-4

Line Isolator System



f) There are also "RFI shielded" refrigeration controllers....but they're expensive....(I think the Adler Barbour RFI-shielded BD50 controller is about $700....so, if all the above doesn't eliminate enough of the RFI, there is a rather expensive approach that will....and FYI, some have also done a DIY shield and using ferrites along with this DIY shield, has proven to be an excellent solution....but not one I'd recommend to a non-technical person)





I was recently given advice to disconnect the RF ground from the M802 chassis & just connect the tuner to the RF ground.
This is standard and normal practice, regardless of what the Icom manual says....(remember Icom manuals need to be "lawyer-proofed" and much is written that is not technically accurate)




I was also given advice to connect the wire mesh RF ground to a bronze hull fitting to provide a better RF ground in contact with seawater.
Yes, a direct sea water connection IS best (notwithstanding the misunderstandings of others)....
But, in most cases (99.9%) of RFI interfering with your RECEPTION on the radio, it will have NO effect at all...

BTW, I'm more concerned that there is "wire mesh" being used here...
This is very telling and NOT ever recommended for RF use (again notwithstanding that many laypersons seem to like its flexibility)....
"Wire mesh", unless it is contained within a jacket of some type so it cannot move AND protected from corrosion, can cause a LOT of RFI itself...
The "semi-conduction" of RF across all the small junctions as they move around, can cause a lot of RFI....and once these become corroded, they are no longer very conductive at RF and many times the problem gets worse....(and at best they cease to function as much of a ground connection...)

Copper strapping is used for RF grounding (both on-shore in all commercial environments, such as radio installations, cellular installations, etc. and on boats....), wire mesh is never recommended and I'd be happier recommending a large copper wire rather than "wire mesh"...

But, perhaps this is bronze mesh, or tinned copper mesh, that was glassed into the hull upon construction, so it does not move and is protected from corrosion???
If this is the case, just make sure the ends that you connect to are clean and shinny....and ignore my rant above...

Oh, and further, you should be using a water-resistant conductive grease on all your "ground" connections...
Penetrox-A is great stuff....its messy, but I've been using it for > 30 years and it works GREAT...
DX Engineering Penetrox A Anti-Oxidants DXE-P8A - Free Shipping on Orders Over $99 at DX Engineering





In the process of disconnecting the RF ground from the M802 chassis, I found that the M802 chassis is also common with the boats 12v DC ground so the original installation had the RF ground and ships DC ground tied together at the M802 chassis.
I have disconnected the M802 chassis from the RF ground and have connected the RF ground wire mesh to a brooze hull fitting and still have the RF ground connected to the tuner.
This is typical, and you disconnecting this is fine....(although some do find it works fine for them to have this connection, most do not...)
As you can see in the Sailmail Primer, having the RF ground connected to ONLY the AT-140 is the recommended way of doing it...
SailMail Primer




Am I on the right path or am I missing something. The ICOM manual says the the M802 chassis should be connected to the RF ground as well as the tuner??
Yes, you're on the right path....see all the above for details...
And, ask further questions as needed...


I hope this helps..

fair winds..

John
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Old 02-06-2014, 07:00   #6
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Re: Icom M802 & AT-140 Grounding???

Cavalier,
While I'm sure you're well intentioned here...but since I majored in Physics and have 40 years experience in RF, and have run my own electronics firm for over 30 years now....
Can I politely say your information is wrong...(and even if not flawed, is quite a ways beyond what anyone else here needs/desires..)


If you wish to be 100% accurate there is no "absolute need" for any ground at all....as the transmitter's signals will still radiate and the receiver will still work fine....
But, here we are trying to solve intricate RFI issues....
And, while "grounding" is a favorite internet subject to pontificate about, the fact is here in this situation it is almost irrelevant...

So, since this discussion / solution to "BrightAyes" problem has little to do with "grounding", I'm not going to ramble on about it, nor comment on the KISS....other than to say that your information and reasoning is wrong....sorry about that...



I do wish you fair winds and sunny skies..

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Old 02-06-2014, 09:04   #7
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Re: Icom M802 & AT-140 Grounding???

Quote:
Originally Posted by ka4wja View Post
..but since I majored in Physics ....
Excellent, at least there's two of us in this world!

Quote:
Originally Posted by ka4wja View Post
..Can I politely say your information is wrong...So, since this discussion / solution to "BrightAyes" problem has little to do with "grounding", I'm not going to ramble on about it, nor comment on the KISS....other than to say that your information and reasoning is wrong....sorry about that...
Just stating "you're wrong" doesn't serve much of an educational purpose for anybody other than to help lower your own elevated blood-pressure.

I'd agree with you that the RF interference being caused by all of the other motors, PWMs etc. in their boat most likely has little to do with the common grounding. However, it is always useful to go over the system to ensure that unnecessary noise isn't being introduced via the power supply and its vestiges.

Just on Friday of last week, I finished debugging the controller boards for a Pulsed-neutron Generator. We were having major issues with noise coming into the Analogue input channels of the system, especially from the feedback from the RF cavity we'd built for the pulser. Or so we thought. After endless modifications to cable screening, local filters up and down-stream of OPAmps, hardware rectification and software filtering. We hooked a scope on to the lab power supplies. There was a phenomenal amount of noise coming from the switching DC supplies. Once we put in DC-DC line conditioners our problems resolved themselves. Now, and as we originally thought, the source of the noise was external RFI or cross-talk even-though we'd laid out the PCBs specifically (through best practice) to reduce the possibilities of such occurrences. In the end of the day it was noise coming in through the output from the [relatively] low cost +/-12VDC power supplies.

To be useful, I'd recommend that the OP read a little further around the subject of RF, antennas, counterpoises etc.. Evidently, there's a small library available on the subject, but one recommendation would be:
Introduction to RF Propagation, John S. Seybold (John Wiley & Sons, Oct 3, 2005).
Pages 48 onwards are particularly well written and are very clear.

Will reading the book help the OP solve their current issue? probably not. Will the acquired understanding equip the OP with more knowledge to help debug a future problem? Most certainly.

I find that most of the threads on this forum give an OP a multitude of differing opinions and facts (some at odds with others), this may seem an unnecessary distraction. However, decisions are very easy when you're armed with everything you need to know - and very difficult when you're missing information.

I'm sorry if you felt that my comments in the prior post represented "a little too much information" for the thread - however, i'll continue to post in a similar manner, too much information (even if perceived as incorrect) is better than no information at all!
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Old 02-06-2014, 12:25   #8
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Re: Icom M802 & AT-140 Grounding???

John, I don't see what Cavalier originally posted could be construed as wrong. He advocated decoupling the DC ground from the RF counterpoise - which is widely considered a good practice. He stated that the absolute need for a conductive seawater coupling as a counterpoise was a myth, and is widely supported in that statement by pretty much everyone in HF radio (we don't have a direct connection to seawater either). He then states that PWM devices create a lot of noise - that too is established fact as far as I can tell.

Maybe it is because he mentioned the KISS? All he did was say that maybe the reason it works well for some people is because it forces a decoupling of the DC ground from the RF counterpoise on noisy boats. That is hardly a recommendation or endorsement of the system.

So what about that post is wrong?

His second post, however- there is a lot of fodder in that one! I'm personally surprised that someone working with RF cavities producing feedback didn't go immediately to the DC power supply to look for the cause. High quality DC power supply designs are critical in RF trapping cavity applications...

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Old 24-02-2018, 08:01   #9
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Re: Icom M802 & AT-140 Grounding???

I know this is an old thread, but this one hit the top of the list whilst googleing.. AND of course, I have a silly question-- I'm re-installing an AT-140 tuner and M-802 that had been removed by the person who sold me our boat (Tartan 37) and there are no instructions available (although I've read quite a bit on forums and downloaded the icom manuals). Most of the cables were ripped out of the boat, but I think I've figured out where to mount everything, there are two ground wires that I'm curious about. One end exits the tuner (and there is a short, 10" long green ground wire protruding from it) and the other endthat connects to the m-802 with a similar green wire along with the white plug for the radio. Is that the one everybody is talking about that should NOT be connected to the ground screw on the m-802 chassis? This cable (which is still attached along with rigging tape at the connectors) and has a green lead with crimped ring terminals at both ends (one where it comes out of the tuner and another at the end that plugs into the m-802) that I'm sure were originally connected to some grounded object in the boat. Should I defeat those leaving both boxes ungrounded (other than maybe with a KISS SSB, which I may buy)..?
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Old 24-02-2018, 13:54   #10
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Re: Icom M802 & AT-140 Grounding???

ICOM 802 & AT-140 Grounding.

With the advice for some experienced cruisers and ham radio guys this is what you should have:
1. A coax from the ICOM 802 to the AT-140.
2. A multi conductor control cable from the ICOM 802 to the AT-140 with disconnects on each end. The multi conductor control cable has a ground wire in it with a terminal on each end and these ground terminals should be attached to the ground terminal on the ICOM 802 and the grd terminal on the AT-140. Completes the control signal path.
3. At the advice of experts the ICOM 802 and AT-140 chassis are not connected to ships ground which can introduce noise.

I used the boat for many years with the copper grid that was molded into the hull but found it was connected somewhere to ships ground. I disconnected that and went with the KISS counterpoise and my performance improved on transmit and the receiver has less noise from boat systems like the refrig-autopilot- alternator.
Hope this helps.
PS. If you have an older ICOM 802 you should contact ICOM with your serial # and see if you need the clipping mod. It only affects voice but they will fix it for free.
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Old 24-02-2018, 14:39   #11
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Re: Icom M802 & AT-140 Grounding???

Thank you! I'm pretty sure I have a newer model m802- I think it was installed around 2013.. I'm emailing icom now to ask, so we'll find out about that soon, hopefully. So, the green ground wires are just attached to the boxes they interconnect-- not to any ground on the boat.. that's interesting, but understandable from what I'm reading. Does the KISS provide the ground?
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Old 24-02-2018, 15:10   #12
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Re: Icom M802 & AT-140 Grounding???

Irunbird,
BrightAyes got you the correct answer!!
(although, I disagree with him regarding the "KISS", he did answer your questions succinctly!)



Since you said you found this post thru Google, I'd like to point you to a thread here on Cruiser's Forum with a LOT of factual info / references...
Marine SSB Stuff (how-to better use / proeprly-install SSB, & troubleshoot RFI, etc.)

And, some updated info:
Marine SSB Stuff (how-to better use / proeprly-install SSB, & troubleshoot RFI, etc.)





As well as some other threads with some practical info, videos, etc...

Have a look at this YouTube playlist:
https://www.youtube.com/playlist?lis...rC-8QKVyMb4tVr

Icom M-802 Instr Videos(basic-adv) & LIVE DSC-Distress Call



And, don't forget the Sailmail Primer is one the most definitive sources of installation and set-up info for HF communications gear on boats!! Whether SSB Voice comms or digital data comms, it all applies equally! (and the App Notes have a lot of info, too)
https://sailmail.com/wp-content/uplo...2/smprimer.htm




{Please watch the videos in order on the playlist, as this way it will all make better sense!}
HF-DSC Comms
https://www.youtube.com/playlist?lis...ga2zYuPozhUXZX

New HF-DSC Explanation and LIVE Demonstration Videos

Maritime HF Comms
https://www.youtube.com/playlist?lis...ZDo_Jk3NB_Bt1y

Offshore Weather
https://www.youtube.com/playlist?lis...zdjTJjHlChruyY

VHF-DSC
https://www.youtube.com/playlist?lis...J6QugtO2epizxF




As for "ground"??
That's a very involved subject....and while I'm happy to delve into, I will do so only if you ask....'til then, here's the brief skinny...
Quote:
Originally Posted by Irunbird View Post
Does the KISS provide the ground?
The answer is actually, no, not really..
But, don't fret....'cuz the radio / antenna will work without any "ground" at all....it's all a matter of degree! An excellent (close-to-perfect) ground, copper strapping connected to the sea water, will generally be 3 to 6db better than the KISS, with almost unmeasurable difference between KISS and no "ground" at all...

There is a wealth of detailed test info, both scientific and real-world results, showing this...
https://www.ssca.org/forum/viewtopic...93838&start=75

But,. if you don't have the time and/or inclination to read all of this mumbo-jumbo....
Suffice to say that you can grab 2 or 3 pieces of scrap wire of almost any length and gauge (10' to 30' long), crimp then into one ring terminal, connect that to your tuner ground terminal, toss 'em in the lazarette / bilge / etc...it will cost you les than $5 (probably nothing at all!) and you will be better off than buying the KISS...(this is true, have a look at the above linked posting)



Sorry to be so brief, but I gotta' go..
I hope this helps.

Fair winds.

John
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Old 24-02-2018, 18:14   #13
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Re: Icom M802 & AT-140 Grounding???

Its wishful thinking that you are going "un-bond" your DC and RF ground. A reality check with a multimeter will soon confirm this!

Un-bonding is actually not the thing to do in my experience. What you should do is more bonding. Bond the noise emitters into your grounding system. Eliminating ground loops reduces common mode noise. Ground loops can be eliminated by more bonding not less, and this includes making sure the items that causes the noise are bonded to the same ground reference point.

As others have alluded, noise has 2 paths. The first path is direct radiated emissions that bonding or un-bonding is not going to fix.

The other path for noise is conducted, commonly referred to as common mode noise. This path can normally be fixed by using things like good chokes. Chokes wont and cant cure radiated emissions.

Radiated emissions can be fixed by getting rid of the noisy item which probably does not comply to the EMC regulations or finding equipment that is certified to a high standard like FCC class B standard. Try to fix radiated emissions from a poorly designed piece of equipment is a very tough task that takes a lot of engineering at the design stage of the product. I would also call the manufacturer an complain about the device causing interference they might have a fix.

I can assure you from trying to do this by pulling equipment apart and using EMC probes to measure noise and bypass and filter this noise, success is very limited. EMC design is a complicated business thats more about PCB board layout and things like ground planes being designed into the product. Even things like conductive spray to try and reduced radiated emissions is an exercise in futility.

The 2 attached pictures are of my professional Near Field and RF current probes used to diagnose such issues. Thats 10,000 dollars worth of professional EMC current probes sitting in that case that can be used to measure common mode, differential mode, rf and noise currents. When you use such equipment for year after year you quickly know when equipment is badly designed just like most yacht electronic equipment, thats why they cause so much noise to HF. It might be worthwhile making such a simple clamp on probe to clip around the cables to isolate the worst of your equipment.


Quote:
Originally Posted by BrightAyes View Post
I have an Icom M802 & AT-140 tuner that uses a wire mesh in the hull as an RF ground. The system works fine except I get some noise from the refrig & freezer compressors and the Simrad Autopilot. I have tried to isolate the noise at the compressors and autopilot computer without great success.

I was recently given advice to disconnect the RF ground from the M802 chassis & just connect the tuner to the RF ground. I was also given advice to connect the wire mesh RF ground to a bronze hull fitting to provide a better RF ground in contact with seawater. In the process of disconnecting the RF ground from the M802 chassis, I found that the M802 chassis is also common with the boats 12v DC ground so the original installation had the RF ground and ships DC ground tied together at the M802 chassis.

I have disconnected the M802 chassis from the RF ground and have connected the RF ground wire mesh to a brooze hull fitting and still have the RF ground connected to the tuner.

Am I on the right path or am I missing something. The ICOM manual says the the M802 chassis should be connected to the RF ground as well as the tuner????
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Old 25-02-2018, 15:06   #14
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Re: Icom M802 & AT-140 Grounding???

Man- thanks, guys! I think I have enough here to read and watch to keep me busy for a long time to come.. I installed most of the things on the boat (I think) as the previous owner had and discovered a 3" wide copper strap that winds all along the hull surface and is neatly close to where the AT-140 is located, so I attached that to the ground terminal. I have left the antenna disconnected, but will attach that right before connecting power. I located a suitable place for the radio adjacent to the house bank and mounted it there. All the wiring is run with the exception of a sat antenna (although that cable is connected to the radio via bnc connector and is coiled on top of the unit) and none of the DSC cables are yet connected.. I have two 10' sections of Rg-8u (Radio-shack brand) and one of the pl-259 connectors is heavily corroded.. I'm obviously going to replace these as I'd really like to have DSC use via the m802 (I have it with the current VHF), but also need to figure out how to connect the gps antenna- I'm guessing this might plug into a t-connector with the nmea 0183? This white cable is shielded and has two wires-- one black and one red.
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Old 27-02-2018, 22:44   #15
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Re: Icom M802 & AT-140 Grounding???

I have heard this argument about getting a bunch of wire and making a KISS counterpoise many times. It would be interesting to have A/B comparison with a KISS system. Has anyone done this?

As most on this forum know, reliable HF communications, particularly for offshore boaters, is not a matter of a hobby, or of convenience, it is something that must work well and reliably in the worst of conditions. I used multiple lengths of 3" copper ribbons in the bilge for an RF ground on our last boat, an O'Day 35. it never worked very well and eventually corroded badly with the salt water. Yes epoxy paint would help to mitigate corrosion but I would not trust it over the long term and it is a lot of painting and routing of copper yet again. I had read that marine growth was a continual problem with sintered grounding plates which require through-hull mounting. So with our new boat, a Beneteau 46, i decided to try the KISS counterpoise given the feedback from many of boaters who have tried it (boaters both with and without a strong HF radio experience). I personally use 20 and 40 meters 95 % of the time. The KISS system works so much better than my last setup. Ham friends who I have kept in touch with on regular schedules over the years say consistently that I now have a "booming" signal. One of these friends on land got curious and decided to test the KISS system himself. His results using autotune on his transceiver for all tests were informative. He demonstrated that for his antenna the KISS system performance was equal to his existing 500' of copper ground radials on 20 and 40 meters. That is perhaps hard for many to explain, but it is consistent with what other boaters have reported, i.e. excellent results with the KISS system especially in the mid HF range.

Freq (kHz) A/B signal report comparison
1900 A > B by three S-units
3970 A > B by two 2 S-units
7100 A = B, no difference observed
14020 A = B, no difference observed
21020 A > B by one S-unit
Notes: A = with 500' of ground radials;
B = with KISS-SSB counterpoise.

Now in addition to the cheap bundle of wires argument, there are also arguments based on radio theory, ground current measurements, spectrum analyzer results, etc. This all misses the point for most boaters. To them, the cost of KISS, about $150, is not at all an issue, especially compared to the routine costs of boat ownership. A high performing, clean, compact, reliable, corrosion-free, and marine growth-free solution to the "grounding" problem is what many boaters are after. This is what the KISS system provides, in my opinion. And to have a counterpoise on board that appears to work as well as 500 feet or radials on land, sounds good enough for me. Anyway, I feel that there is more analysis that can and should be done, but for now the KISS onboard simply works, and it works more reliably partly because it is...well...simple.
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