Ferrite Beads on HF Radio Installation

[Dockhead]

Originally Posted by Jammer

Yes.

The basic antenna serving as a starting point for understanding is a dipole, that is, two pieces of conductive material (wire, rod, tubing, etc) extending in opposite directions. One would be connected to each terminal on the transmitter.

It is possible to substitute a conductive disc for one of the pieces, with the other conductor perpendicular. RF performance is nearly identical. The ocean is electrically the same as a conductive disc, or nearly so, with the soil on dry ground being similar but less ideal (because it is more resistive).

Backstay antennas are, well, terrible antennas, particularly when used for the entire HF band. The only reason they work at all is that a sailboat in the ocean benefits from a fantastic ground plane (salt water) and a lack of man-made noise (as long as sources on the vessel itself are controlled). I have experimented with backstay-like vertical antennas on my house and can confirm this experimentally.

You can build a simple dipole for a specific band and hoist it when needed and it will far outperform (by 10dB) a backstay antenna, and at a tiny fraction of the cost. No tuner needed. No ground plate needed. No RF in the boat. And some sailors do that. But they're fiddly and not suitable to rely on in an emergency, so they aren't the established practice.

Then why are we so hung up on how we connect the ground? If what you say here is true, we could just as well use GTO-15, no?

[Jammer]

Originally Posted by Dockhead

Then why are we so hung up on how we connect the ground? If what you say here is true, we could just as well use GTO-15, no?

::shrug:: Or we could obsess more over the connection to (and conductivity of) the backstay.


I think some of this is driven by what is practical for installation in particular cases (as s/v Jedi posted upthread). Some of it is influenced by the thinking for lightning protection grounds. Some of it is an adaptation of radio technique on land, where flat braid is ordinarily used wherever possible because it is practical in that environment; solid flat copper strap is more resistant to salt but performs similarly.


Rather like the story of people sawing the bone off the ham before cooking it.

[s/v Jedi]

If your only choice is to use a cable in a duct with your other wiring (outrageous!) then I recommend to sell the rig and just use satellite. I am sure you will have interference and also sure you won’t get rid of it with ferrite beads.

[Dockhead]

Originally Posted by s/v Jedi

If your only choice is to use a cable in a duct with your other wiring (outrageous!) then I recommend to sell the rig and just use satellite. I am sure you will have interference and also sure you won’t get rid of it with ferrite beads.

If it doesn't work, that's exactly what I'll do!


But that's not the only choice. I can connect to lifelines or rudder post without the duct.

[Wotname]

Originally Posted by Dockhead

If it doesn't work, that's exactly what I'll do!


But that's not the only choice. I can connect to lifelines or rudder post without the duct.

Or use your earlier consideration, namely

I could do one of those sintered plates, but I really don't want to drill a hole in my fully cored hull.

No????

[s/v Jedi]

Rudder post is your best bet when you don’t want to drill holes.

[Jim Cate]

DH, I think your general sense of perfectionism is causing you to overthink this issue. I suggest that you ignore all the "best practice" advice and hook it up with whatever cable you have to the through hull fitting (and with something better than a hose clamp). Give it a try. The advantage of a superior ground is perhaps real, but small in extent. With the inherent vagaries of HF comms, you will likely never realize any disadvantage.

If the RFI issues persist, continue with attempts to minimize the effects. I had good results with ferrites on the control cables to the A/P and bypass caps on the power leads.* I suspect that your boat has much more digital complexity than mine have had, and that could well make the problem more persistent.

*At present I have no RFI issues beyond the touchpads on our laptops not working when I'm transmitting. A/P works normally, no feedback into VHF or FM radios, no unexplained electrical .

One final thing: you might try transmitting a lower power levels. I typically run 30-50 watts and distant stations don't find perceptible differences in sig strength as I power down from full (100 W) power.

good luck...

Jim

[Dockhead]

Originally Posted by Wotname

Or use your earlier consideration, namely

No????

Yes, the plate is probably the best option of all. But it will require being out of the water for a week, which I can't do now. I need the radio set for a long distance race I'm participating in, to get weather data for routing.

I normally use Iridium for this, but I sold my Go! after my Greenland trip, and I promised myself I would not buy another Go! so long as I had this inoperable M802 staring at me from my nav station. So it was a kind of challenge to myself.

If I fail to get this working in the next couple of weeks, I will buy another Go!, as I told Jedi. If the ground is the reason for this failure, then maybe the plate is the right solution. I could install it directly under the tuner so the lead would be only centimeters long.

But with a fully cored hull -- I will have a professional do that, a trusted shipwright, with the boat on the hard in Cowes next year. It's not such a big job, but it has to be done right (otherwise awful consequences), and it takes some time out of the water.

[ka4wja]

Sorry I've been tied up....and, didn't see this until now....and, I still need to be brief, as I'm still tied up, and I do not have the time to read 4 pages of posts....(so, sorry if others have already written all of this....my response here is just based on our original post!)


So, here goes....btw, all of this is covered in the "Stickies" above...

And, remember, I've been doing this for > 45 years....and, I do realize that most have not....so, no worries!
Just don't over-think it....just use the accepted / best practices (mine and Sailmail's, etc.) and, you should be good-to-go!



1) First off, anything metallic / conductive works....works for an antenna, and/or a "antenna ground".

It's just all a matter of degree....and where/how the RF is radiated (and/or is causing RFI).

{heck, even having no antenna ground at all, works...to some extent.....operator skill and understanding of radiowave propagation can compensate for a great deal of antenna system deficits!}

a) Your "antenna ground" IS the other-half of the antenna circuit, and it allows the other half (or more) of your transmit power to be radiated by the antenna itself....(better antenna ground = more transmitter power is radiated from the antenna)


b) AND, it is also where / how your antenna tuner/couple makes as low-loss match as possible to your antenna....(better antenna ground = lower tuner/coupler losses....without an antenna ground, tuner/coupler losses are much higher.)

c) Your antenna ground also allows whatever RF is not radiated to be shunted-to "ground", thereby reducing transmit RFI (reducing/eliminating your HF transmit signal from interfering with other systems on-board)

d) Further, your antenna ground can also improve your reception in multiple ways....improved received signal strengths and lower local noise reception....(better antenna ground = better receive S/N [Signal-to-Noise Ratio]...)

BUT....
But, again.....this is all matter of degree....and in the real-world there are variables on boats that cannot be precisely predicted ahead of time....so..
So, we make our decisions and do the best we can....and if there is poor performance, we can make changes....




2) Secondly (but, should be first), do NOT place any ferrites on any radio or antenna ground cable, ever!!! (this defeats it purpose!).....it would be like placing ferrites on your GTO-15 wire....this is like squeezing a hose with a pair of vice grips, closing off the flow of water inside....ferrites close-off the flow of RF current on the surface of the wire they are on, but this usually confuses folks, 'cuz they read to use ferrites on coaxial cable, control cables, USB cables, etc....so, please understand that the RF current in a coaxial cable is on the outside of the inner conductor and the inside of the outer conductor!!!! Now, you see why RF [Radio Frequency energy] is confusing to laypersons!!! LOL

Let me repeat, do NOT place any ferrites on any radio or antenna ground wire / cable / strap!




3) The confusion about using "wire" versus using wide copper strapping is because the two "camps" are talking about two completely different concepts / applications....and, unfortunately egos got involved and neither camp wanted to admit the other was correct in their own application!


Let me give a brief explanation:

a) If desiring to use the sea water as your antenna ground (all agree this is good, and most agree it is the overall best approach for a wide-band HF antenna ground on a fiberglass boat), then THE CONNECTION TO THIS antenna ground should be of low-impedance / low-inductance.....which usually necessitates use of a wide copper strap, as the RF impedance of even a 2" wide copper strap is lower than that of a 4/0 (0000 ga) copper wire (I did the calculations for the SSCA years ago, and posted it on their discussion boards, but they now refuse to even allow me to read, and I'm away from my references here)....BUT...

But, remember that the distance is additive....meaning if you have a shorter run of wire (say, a couple feet), and it is large enough, you may in fact have as low of impedance connection of a boat with a longer run (15' to 20') of copper strapping...

Remember, the copper strapping is not your antenna ground (or rather is not designed to be your antenna ground), but rather just the low-impedance way of connecting to the antenna ground / sea water!!

{Although, in actual real-world installs, if the length of this connection, from tuner to sea water, is more than 1/4-wavelength, then the strap IS, to some extent, acting like an artificial antenna ground, as well as a connection to the sea water....so, as you see their actual performance / application varies depending on what freq you're using, their length, and their location/position in the bilge, etc....}

Also, please understand the "weirdness" of RF....as it is the surface area of the antenna ground that is closest to the antenna feed that makes the most difference!! {what this means is: if you can use wide copper strapping close to the tuner, but need to use wire to pass thru some weep-holes, etc., in order to get a connection to a underwater thru-hull, etc...then this is much better than using wire for the whole run from tuner to underwater thru-hull...)

Further, remember that assuming similar size / surface area the differences between a bronze thru-hull and a dedicated antenna grounding plate, are rather small (inconsequential?)....but the differences between having a "clean" connection versus a fouled connection are much more consequential! But, also...the fact that most dedicated HF antenna grounding plates are rather large compared to a 1.5" thru hull, this does give the dedicated grounding plate an advantage (albeit, when clean, this advantage is minor....but, when fouling is present, it can be an important advantage!)

Finally, fyi....you can curl / roll the strap into a large round tube or curved conductor (to allow it to more easily routed thru a hole, etc....and it will still have the low-impedance you desire (as long as you don't fold-it-over / have it over-lap....but, even if you do fold-it-over itself, the reduction in surface area is only for that short length where it its folded-over / over-lapping, so if only a few inches to get through a hole, etc., the performance is barely effected....so....so, many find that they actually can use wide copper strapping, just that they prefer not to, due to the difficulty.



b) If desiring to use an artificial antenna ground (typically refereed to as a "counterpoise"), then of course normal round wire is fine.....as this wire is the antenna ground, not the sea water!

Also, while using a "tuned" ground, aka "tuned radials" is good, it is impossible to really do so on our boats....and this is not only because the lengths needed (at least three to four "radials" symmetrically arranged around the antenna base, for EACH freq/band we use, and each 1/4-wavelength on each/every band we operate on), but also 'cuz as the name implies, these need to be "tuned" which is all but impossible to do so in the confines of our bilges and in close proximity to the hull, tanks, engines, keel, pumps, all the other wiring, etc., as well as the close proximity of the OTHER radial wires themselves....remember the other word here "radial", which as the name implies, means these need to be arranged symmetrically around the antenna base "radially", in order for them to adequately return all the antenna ground currents to be radiated by the backstay (and not radiate themselves!) {and, btw, a "tuned radial" is always isolated from ground, and must be separate from other connections....or, it is no-longer "tuned".....but, all is not lost....as not being "tuned" is not a major problem at all...}

Further, if desiring to use an artificial antenna ground, and desiring to use whatever metallic structure you have, such as toerails, rub rails, lifelines, etc....it perfectly fine to connect to them using wire....(although I still recommend trying to use as low impedance connection as practical, use of wire is okay here)

Finally, if desiring to use an alum toe rail, etc. as an artificial antenna ground, remember than anodizing is a very poor conductor (especially at RF), and as such you must make connection to the alum toe rail below the anodizing (preferably drilled and tapped into the alum, with a SS machine screw, and use Penatrox-A conductive grease to allow good connection between dissimilar metals (the opposite of tef-gel, which attempts to isolate the dissimilar metals)...



4) So, as you can see the two "camps" actually do not contradict each other....it's just their egos that don't wish to admit the other application is different!




5) As for details of RFI, and how-to reduce/eliminate it, etc....please have a look at the "Stickies"...



6) As for the LMR-400....well, not my recommendation....but if new and if connectors are properly installed and weather-proofed, it will work...BUT....I would recommend just about any other cable, other than the LMR-400....and for the cost (money and time) to pull a proper cable, it just doesn;t make sense to me to try and use it....(pull a hunk of RG-8x, or RG-213, thru and either leave the LMR alone, or use it to pull new cable thru)


Hope this helps?
fair winds
John


P.S. Again, my response here is just based on your original post....so, perhaps others have already written all of this?

[Jammer]

Originally Posted by ka4wja

a) If desiring to use the sea water as your antenna ground (all agree this is good, and most agree it is the overall best approach for a wide-band HF antenna ground on a fiberglass boat), then THE CONNECTION TO THIS antenna ground should be of low-impedance / low-inductance..

Why do you think this is a bigger deal than the impedance of any other part of the antenna system?

[ka4wja]

Dockhead,
I've read some more of this thread, but still not all of it..
And, still need to be brief.
So...

1) Just run a wire from the tuner ground lug to your lifelines (and alum toe rail?, if possible), and if you have the copper strapping and can simply lay it flat against the hull, near the tuner, then connect that to the tuner ground lug as well....
Doing these things will (should) get you a workable set-up!


And, read the "Sticky" above, about proper install techniques...., it should answer all your questions.




2) Forget trying to run an antenna ground system thru the boat, thru conduits with other wiring, etc..
This is just asking for issues....and, quite frankly a waste of your time / effort!

3) If I understand correctly, your primary use will be to receive weather info during a rally?
If this is correct, no worries....
Don't sweat the set-up.....
Do what I recommend above in #1, and you'll be fine...BUT...
BUT, also do #4!


4) Rid your boat of RFI producing devices...and/or power them completely off when using the HF radio!
This will improve your receive S/N....

And, keep both your GTO-15 wire and your new antenna ground wire (going to lifelines) as far away from other wiring as possible, and keep them from running parallel to other wires as best you can....
Also, use ferrites on any/all other cables that are near the GTO-15 and antenna ground wire (such as autopilot, NMEA wiring, etc.)...
This will improve (eliminate?) your transmit RFI..

I hope this helps?




Jammer, et al,
I don't have the time to delve into the details here...

Originally Posted by Jammer

Why do you think this is a bigger deal than the impedance of any other part of the antenna system?

But, in brief...

I don't think there is much debate that our antennas (backstays, 23' whips, etc.) are not that great....they are compromise antennas, that need to work between 1.6mhz thru 26mhz, rain or shine, for comms from 50-100nm, out to 5000 to 10,000 miles, and be best / most efficient as we can make 'em for 4mhz thru 12mhz, for ~ 200-300 miles, out to 2000-3000 miles...
And, in my opinion, we should try to optimize our antenna system as best we can....or at least don't do things to make it worse.



So, without getting into a debate...


I'd rather have as much of my antenna ground currents returned to the feed for radiation as possible, so I'd rather not put an RF choke inline with the antenna ground system (which is what introducing additional inductance into the antenna ground / ground connection, in effect does).


While this isn't technically a "bigger deal" than losses in other parts of the antenna system, it is what was being discussed here, yes? (The antenna ground system and its connections?) If someone was considering placing an RF choke inline with the antenna wire itself, I'd of course mention this as problematic as well.

Now, to be clear here...
a) this is a sailing forum, and I've been accused over the years of being too much of a "radio nut" (what I prefer to call more of a purist), but I'm trying to mellow out a bit and understand that there is a big difference between "what works" versus what I might actually do for my own boat...and, I'm trying to stress the "what works" and "what is good practice", rather than "this is what I do"...but...but, sometime my purist tendencies do ooze out....


{I mean, while I might use a few feet of 12ga GTO-15 wire from the tuner antenna terminal to the backstay, and have it attached to the backstay twice (for redundancy), a couple inches apart, on the new/clean 1/2" SS rigging, using a liberal coating of Penetrox-A...and two runs of 6" wide (and 0.32" thick) copper strap (~ 7' long) running from the tuner ground lug to two Super Dynaplates (18" x 6") that are always submerged....plus < 1' run of 3" wide copper strap to two large flat metal tanks (~ 2' x 6' each)....plus an additional 3" wide copper strap (15' long) from tuner ground lug forward to keel bolts (supporting ~ 9550lbs of external lead ballast)..... and, all RG-213 cabling, including a 2kw line isolator (at the tuner).....and, ferrites (both clamp-on and torroids) on all M-802 and AT-140 control / interface cables....











[BTW, I have two M-802's (one stowed away, except for this HF-DSC testing, to make videos, etc.) and two remote tuners, one AT-140 and one SGC, and dedicated coax, power/control wiring, isolators, etc., for each]






As well as using a 3' run of 2ga 12vdc power cable to a high-current breaker/switch, and then 4' of 00ga wire to the main house bank....but....but, I'm a radio nut....
And Fyi, it was Icom that (back in 2004 / 2005) suggested much of this extreme stuff (and/or myself suggesting this to get Icom to grasp that there was a problem with the early M-802's), to eliminate all possible external issues when I was working with them in tracking down the dreading "M-802 Clipping Issue", the M-802's APC circuit was faulty on early units...(which they initially dismissed as something we were doing wrong on installs....until they actually had one of their tech down in Mexico actually see the problem on-board....and, then working with myself, and a few others {primarily in California and Mexico}, with me being the only one in Florida / Caribbean), but I digress...}




b) Dockhead (and others here) do grasp the basics pretty well....and, while he (they) might be a little less into radio than I am (okay, I LOT less into radio!), he's not a dumb guy....


c) If I delved too much into the weeds, most sailors will get disillusioned with the tech and start thinking of HF comms as a "black art"....so, I'm trying to keep it basic, without making errors...as this will allow most of my fellow sailors to get an HF system on-the-air and working well, without a lot of hassle....and that last part, lack of hassle, is what seems to be a rather important part of the puzzle for non-radio sailors...


So, I hope this helps clarify my position a bit....
(btw, I still haven't had the time to read the whole thread....maybe tonight? But, I did see that Brian rescued my long-winded and lengthy debunking of the KISS Ground....so, Thank You Brian!!!)


fair winds.


John


P.S. I try not to mention this much, 'cuz when I read someone else bragging about their radio accomplishments I generally roll-my-eyes....so, please note that I'm just adding this for context and clarity, not to show-off....LOL

I assisted in my first marine HF (SSB) install in 1973....and, in addition to ~ 50 years of experience / training in both maritime and ham, on-board and on-shore, I have also studied (and taught) radiowave propagation, and antenna system design, etc. for > 45 years.....so, to be clear, I have never been an advocate of the snake-oil of the KISS, and I did want to debunk it....but, I tried to go in with an open mind....but, in case it gets lost in all the mumbo-jumbo of the KISS Ground evaluation I did years ago (most lost site of it, in the original SSCA discussion), in addition to the math/theory showing a copper-strap-fed direct sea-water antenna ground to be much better than the KISS, I found about 5 to 6 times the antenna current (using my Delta TCT rf current transformer and Tek scope), versus the KISS...but since these are rather old-tech test devices, I don't have nice color images to post....what that means is that I proved in the real-world that I had 7db to 8db of transmit improvement using the direct sea water antenna ground versus the KISS, as well as anecdotal signal report improvements....but, I don't have cool color pics / images to share, but then again, neither did Gordo when he did his tests comparing direct sea-water connection to capacity-coupled antenna ground, decades ago, so I do hope all simply take me at my word...

[Jammer]

Originally Posted by ka4wja

Jammer, et al,
I don't have the time to delve into the details here...

But, in brief...
[... lengthy text snipped ...]

So, I hope this helps clarify my position a bit....
(btw, I still haven't had the time to read the whole thread

Wow. Um,
1) Thanks for trying to be helpful
2) I cared enough to read the whole thing, as part of the "listen first" approach I strive for
3) No, it didn't clarify your position

P.S. I try not to mention this much, 'cuz when I read someone else bragging about their radio accomplishments I generally roll-my-eyes....so, please note that I'm just adding this for context and clarity, not to show-off....LOL

I assisted in my first marine HF (SSB) install in 1973....and, in addition to ~ 50 years of experience / training in both maritime and ham, on-board and on-shore, I have also studied (and taught) radiowave propagation, and antenna system design, etc. for > 45 years.....so, to be clear, I have never been an advocate of the snake-oil of the KISS, and I did want to debunk it....but, I tried to go in with an open mind....but, in case it gets lost in all the mumbo-jumbo of the KISS Ground evaluation I did years ago (most lost site of it, in the original SSCA discussion), in addition to the math/theory showing a copper-strap-fed direct sea-water antenna ground to be much better than the KISS, I found about 5 to 6 times the antenna current (using my Delta TCT rf current transformer and Tek scope), versus the KISS...but since these are rather old-tech test devices, I don't have nice color images to post....what that means is that I proved in the real-world that I had 7db to 8db of transmit improvement using the direct sea water antenna ground versus the KISS, as well as anecdotal signal report improvements....but, I don't have cool color pics / images to share, but then again, neither did Gordo when he did his tests comparing direct sea-water connection to capacity-coupled antenna ground, decades ago, so ...

Great are your achievements. As you request, I will not share mine.

Stop by the former corporate headquarters and engineering offices of E.F. Johnson sometime, though. There's a startup that is doing some cutting edge millimeter wave work there. I'll show you around the lab.

I do hope all simply take me at my word...

Respectfully, that isn't how we do science.

[Bycrick]

Just to correct some of the mis-leading information about the LMR400 cable family.

It’s NOT just a single cable. There are at least 5 different cables.

Some have a polyethylene outer jacket (just like RG213). Others use PVC. There are pluses and minuses with both.

All the LMR400 cables are double shielded. An primary shield of braided copper with about 95% coverage (just like RG213). Then there’s a second shield of aluminum foil. It isn’t even connected at the ends.

All of them use a foam PE dielectric. Yes, it will potentially absorb more moisture than a solid dielectric, but you’re unlikely to see the difference in the normal 15-20 year specified life. But it has lower loss than a solid dielectric.

The center conductor can be stranded copper wire (400UF) or copper-coated solid aluminum. The solid wire is lighter, slightly lower loss, but not as flexible or vibration resistant. But you can solder to both of them just fine.

Would I buy LMR400UF for a 30’ run of HF cable that might sit in water? No. I’d want a PE jacket. But if you have it installed, I don’t think it will improve things a bit to replace it.

[Dockhead]

Originally Posted by ka4wja

Sorry I've been tied up....and, didn't see this until now....and, I still need to be brief, as I'm still tied up, and I do not have the time to read 4 pages of posts....(so, sorry if others have already written all of this....my response here is just based on our original post!)

So, here goes....btw, all of this is covered in the "Stickies" above...

And, remember, I've been doing this for &gt; 45 years....and, I do realize that most have not....so, no worries!
Just don't over-think it....just use the accepted / best practices (mine and Sailmail's, etc.) and, you should be good-to-go!

1) First off, anything metallic / conductive works....works for an antenna, and/or a "antenna ground".

It's just all a matter of degree....and where/how the RF is radiated (and/or is causing RFI).

{heck, even having no antenna ground at all, works...to some extent.....operator skill and understanding of radiowave propagation can compensate for a great deal of antenna system deficits!}

a) Your "antenna ground" IS the other-half of the antenna circuit, and it allows the other half (or more) of your transmit power to be radiated by the antenna itself....(better antenna ground = more transmitter power is radiated from the antenna)

b) AND, it is also where / how your antenna tuner/couple makes as low-loss match as possible to your antenna....(better antenna ground = lower tuner/coupler losses....without an antenna ground, tuner/coupler losses are much higher.)

c) Your antenna ground also allows whatever RF is not radiated to be shunted-to "ground", thereby reducing transmit RFI (reducing/eliminating your HF transmit signal from interfering with other systems on-board)

d) Further, your antenna ground can also improve your reception in multiple ways....improved received signal strengths and lower local noise reception....(better antenna ground = better receive S/N [Signal-to-Noise Ratio]...)

BUT....
But, again.....this is all matter of degree....and in the real-world there are variables on boats that cannot be precisely predicted ahead of time....so..
So, we make our decisions and do the best we can....and if there is poor performance, we can make changes....

2) Secondly (but, should be first), do NOT place any ferrites on any radio or antenna ground cable, ever!!! (this defeats it purpose!).....it would be like placing ferrites on your GTO-15 wire....this is like squeezing a hose with a pair of vice grips, closing off the flow of water inside....ferrites close-off the flow of RF current on the surface of the wire they are on, but this usually confuses folks, 'cuz they read to use ferrites on coaxial cable, control cables, USB cables, etc....so, please understand that the RF current in a coaxial cable is on the outside of the inner conductor and the inside of the outer conductor!!!! Now, you see why RF [Radio Frequency energy] is confusing to laypersons!!! LOL

Let me repeat, do NOT place any ferrites on any radio or antenna ground wire / cable / strap!

3) The confusion about using "wire" versus using wide copper strapping is because the two "camps" are talking about two completely different concepts / applications....and, unfortunately egos got involved and neither camp wanted to admit the other was correct in their own application!

Let me give a brief explanation:

a) If desiring to use the sea water as your antenna ground (all agree this is good, and most agree it is the overall best approach for a wide-band HF antenna ground on a fiberglass boat), then THE CONNECTION TO THIS antenna ground should be of low-impedance / low-inductance.....which usually necessitates use of a wide copper strap, as the RF impedance of even a 2" wide copper strap is lower than that of a 4/0 (0000 ga) copper wire (I did the calculations for the SSCA years ago, and posted it on their discussion boards, but they now refuse to even allow me to read, and I'm away from my references here)....BUT...

But, remember that the distance is additive....meaning if you have a shorter run of wire (say, a couple feet), and it is large enough, you may in fact have as low of impedance connection of a boat with a longer run (15' to 20') of copper strapping...

Remember, the copper strapping is not your antenna ground (or rather is not designed to be your antenna ground), but rather just the low-impedance way of connecting to the antenna ground / sea water!!

{Although, in actual real-world installs, if the length of this connection, from tuner to sea water, is more than 1/4-wavelength, then the strap IS, to some extent, acting like an artificial antenna ground, as well as a connection to the sea water....so, as you see their actual performance / application varies depending on what freq you're using, their length, and their location/position in the bilge, etc....}

Also, please understand the "weirdness" of RF....as it is the surface area of the antenna ground that is closest to the antenna feed that makes the most difference!! {what this means is: if you can use wide copper strapping close to the tuner, but need to use wire to pass thru some weep-holes, etc., in order to get a connection to a underwater thru-hull, etc...then this is much better than using wire for the whole run from tuner to underwater thru-hull...)

Further, remember that assuming similar size / surface area the differences between a bronze thru-hull and a dedicated antenna grounding plate, are rather small (inconsequential?)....but the differences between having a "clean" connection versus a fouled connection are much more consequential! But, also...the fact that most dedicated HF antenna grounding plates are rather large compared to a 1.5" thru hull, this does give the dedicated grounding plate an advantage (albeit, when clean, this advantage is minor....but, when fouling is present, it can be an important advantage!)

Finally, fyi....you can curl / roll the strap into a large round tube or curved conductor (to allow it to more easily routed thru a hole, etc....and it will still have the low-impedance you desire (as long as you don't fold-it-over / have it over-lap....but, even if you do fold-it-over itself, the reduction in surface area is only for that short length where it its folded-over / over-lapping, so if only a few inches to get through a hole, etc., the performance is barely effected....so....so, many find that they actually can use wide copper strapping, just that they prefer not to, due to the difficulty.

b) If desiring to use an artificial antenna ground (typically refereed to as a "counterpoise"), then of course normal round wire is fine.....as this wire is the antenna ground, not the sea water!

Also, while using a "tuned" ground, aka "tuned radials" is good, it is impossible to really do so on our boats....and this is not only because the lengths needed (at least three to four "radials" symmetrically arranged around the antenna base, for EACH freq/band we use, and each 1/4-wavelength on each/every band we operate on), but also 'cuz as the name implies, these need to be "tuned" which is all but impossible to do so in the confines of our bilges and in close proximity to the hull, tanks, engines, keel, pumps, all the other wiring, etc., as well as the close proximity of the OTHER radial wires themselves....remember the other word here "radial", which as the name implies, means these need to be arranged symmetrically around the antenna base "radially", in order for them to adequately return all the antenna ground currents to be radiated by the backstay (and not radiate themselves!) {and, btw, a "tuned radial" is always isolated from ground, and must be separate from other connections....or, it is no-longer "tuned".....but, all is not lost....as not being "tuned" is not a major problem at all...}

Further, if desiring to use an artificial antenna ground, and desiring to use whatever metallic structure you have, such as toerails, rub rails, lifelines, etc....it perfectly fine to connect to them using wire....(although I still recommend trying to use as low impedance connection as practical, use of wire is okay here)

Finally, if desiring to use an alum toe rail, etc. as an artificial antenna ground, remember than anodizing is a very poor conductor (especially at RF), and as such you must make connection to the alum toe rail below the anodizing (preferably drilled and tapped into the alum, with a SS machine screw, and use Penatrox-A conductive grease to allow good connection between dissimilar metals (the opposite of tef-gel, which attempts to isolate the dissimilar metals)...

4) So, as you can see the two "camps" actually do not contradict each other....it's just their egos that don't wish to admit the other application is different!

5) As for details of RFI, and how-to reduce/eliminate it, etc....please have a look at the "Stickies"...

6) As for the LMR-400....well, not my recommendation....but if new and if connectors are properly installed and weather-proofed, it will work...BUT....I would recommend just about any other cable, other than the LMR-400....and for the cost (money and time) to pull a proper cable, it just doesn;t make sense to me to try and use it....(pull a hunk of RG-8x, or RG-213, thru and either leave the LMR alone, or use it to pull new cable thru)

Hope this helps?
fair winds
John

P.S. Again, my response here is just based on your original post....so, perhaps others have already written all of this?

Wow! Tremendously helpful, as usual, John. Thanks!

So let me see if I got the practical points (which is ALL I'm interested in, at the moment!) straight:

1. Seawater ground really wants a low impedence connection, because the connection is NOT part of the ground. Therefore, copper strap is very desirable. However a short connection with wire and/or very heavy wire MIGHT be ok.

2. Radial pseudo-ground (lifelines) is not as good as seawater ground, but might work. For this kind of ground, copper strap is not needed -- wire is ok.

3. Don't put ferrite beads on ground or antenna wires. I did actually know that. Ferrite beads on the other cables; someone posted a good guide to this practice; I'll read it.

4. Don't use the LMR-400 for the tuner connection (why?). I have some RG-58 I could pull -- that's better?

Does that sum it up?

So which do you think, of my two realistic (in the short term, before my race) options do you think is best?

1. 16mm2 battery cable connecting tuner to massive through hull. Wire is about 4 meters long. I can rearrange other wires (rudder sensor, power supply to hydraulic bathing platform lift, coax to Navtex antenna) so that this cable is not in the same duct, but they are not far away, and inevitably cross here or there.

or

2. 16mm2 battery cable connecting the tuner ground to my lifelines (my toerail is teak, so all I have is pushpit and lifelines).

Which of these is more likely to work acceptably well?

Thanks again for your help. And thanks again to Jammer, Jedi, and everyone else.


P.S. -- what does this installation need to do, in the short run? Use case should always first question, for this kind of task.



I need to connect to WinLink stations with a Pactor III modem to get GRIBS over SailDocs to put into my routing system for this long distance race I'm participating in at the end of this month. That is job 1, 2 and 3 for the short term. I might try to make some ham contacts if the weather is calm and it gets boring out there, but I am not using this station for DX contest, probably never and certainly not this summer. So if it is only good enough to do this successfully, then this install will be a success. If over the rest of the year I'm not satisfied with how it works, then I'll just install a plate right under the tuner, when I'm out of the water in Cowes over the winter. That I can connect with probably 30 or 40cm of copper strap, which I hope will settle the matter once and for all, if the present solution is unsatisfactory.

[Dockhead]

Originally Posted by Bycrick

. . .Would I buy LMR400UF for a 30’ run of HF cable that might sit in water? No. I’d want a PE jacket. But if you have it installed, I don’t think it will improve things a bit to replace it.

The disused run of LMR400 is the UF version.


It is in good condition and has never been sitting in water. It runs through areas which are bone dry.