Ferrite Beads on HF Radio Installation

[Dockhead]

Originally Posted by 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

Thanks, Jim!


Yes, I hear you about the lower power levels.



I did actually used this rig successfully for some time with the tuner in the salon, and the uninsulated shroud as an antenna, and the a ground battery cable to a through-hull. At lower power settings, it crashed the network less often and still got through.


I am actually a big fan of QRP. Seems like an art to me. My VHF has a really good antenna installation -- probably the greatest moment in my exceedingly modest radio life. I use it set on 1 watt almost all the time

[ka4wja]

Dockhead,
You're welcome...

Now, here are the short / practical answers....

Remember a good understanding of radiowave propagation and reducing your on-board RFI / RF Noise will go a LONG WAY to improving your success in HF comms, and can (usually will) compensate for installation deficiencies, etc...

Originally Posted by Dockhead

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.
It's not designed to be part of the antenna ground, but in many cases it does contribute to the ground system, and as such being a wide strap helps here too, as fiberglass is damn lossy at RF.
Therefore, copper strap is very desirable. However a short connection with wire and/or very heavy wire MIGHT be ok.
Yep...It will be okay!

2. Radial pseudo-ground (lifelines) is not as good as seawater ground, but might work.
It will work....no "might" involved here.
For this kind of ground, copper strap is not needed -- wire is ok.
Yep, wire is fine...

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.
Yep, ferrites choke off RF....I guess I read your plan wrong...
You're good-to-go..

4. Don't use the LMR-400 for the tuner connection (why?). I have some RG-58 I could pull -- that's better?
Well, LMR per-se isn't always bad....just that I don't recommend it on-board...(both due to the dissimilar metals inside, that will corrode quickly if they get moisture intrusion....and its low-density-foam dielectric that can wick and hold the moisture well....as well as the stiffness of the cable, even the "uf" version, which makes proper connector assembly difficult, and as such makes waterproofing critical....)

But, to be clear, if the LMR-400uf that you have installed was for a sat comm antenna, it will have N-connectors on it (or possibly TNC's), and are likely well installed...

So, if the connectors look good, and you have the adapters at hand, go-for-it...
It should be fine...


Does that sum it up?
Yep, with my clarifications here in red....that sums 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.
Not really a good approach...
It might work...but, more likely to cause transmit RFI issues into other systems on-board, AND add to your receive RFI...

If it was the only option, I'd still say "no", and just try to run the radio without any antenna ground at all...
But, since you do have another option, just go for the other option.


or

2. 16mm2 battery cable connecting the tuner ground to my lifelines (my toerail is teak, so all I have is pushpit and lifelines).
Yes, do this!!!
it WILL work better that the "KISS-Ground", and from antenna efficiency point-of-view it will likely be better that your #1 approach...
(remember, the radio will work without any antenna ground at all....and all of this is a matter of degree, and adds to other advantages as well...)



Which of these is more likely to work acceptably well?
Do #2...
It will work.

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 understand that there are a LOT more imperative things to take care of before a long offshore race....but, a brush-up on radiowave propagation (watch a couple videos?) and testing how the system works at anchor, when switching various other systems / devices on and off (checking your rec S/N, and RFI levels), are somethings I highly recommend!
{I'm not a big fan of relying on computer modeled "propagation tables", nor do I think listening to lots of noise is acceptable just 'cuz someone left their phone charger or iPad charge plugged-in!}
Hint:
Many times it is not a local WINLINK or Sailmail station that will provide the best signals, but rather it can be a couple stations a couple thousand miles away...
Of course use the station with the best signal (S/N), and sometimes that IS the closest one....but sometimes it's not!

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.

Hope this helps...gotta' go.

fair winds and good luck in the race!!!

John

[hasse_A]

This is my setup:

1) Antenna is a backstay antenna. I have dual backstays with insulators 1.5 meters from the masthead. No insulators at the deck. The backstays are shorted at the top below the insulators and beneath deck. This gives me a lot of wire in the air and a wide bandwith antenna easy to for the tuner to handle.

2) The antenna tuner is placed aft just beneath deck connected to one of the chain plates.

3) I have a Dynaplate 10 m2 as close to the tuner as being practical in regards placing it deep in the water enough.

To be safe you need a DC block between the tuner ground and the Dynaplate. At the moment this consist of multiple 1.5 meters of coax cables. Shield connected at one end and center wire at the other end.

I am not sure this is a good solution so I am going to replace this with capacitors on a pcb I designed and use 25 mm copper strap instead.
There are 16 capacitors 150 nF each adding up to 2.4 uF which should be enough for the HF bands.

Since I have a number o these boxes I will also connect the external iron keel and the engine to the tuner ground.

Attaching box with the pcb I designed.

[ka4wja]

Hasse,

That's a nice box...but fyi (unless on an aluminum-hulled boat) DC-isolating your RF antenna ground is almost always unnecessary...


In many decades past (1960's and 70's), before most boats were built to ABYC standards, there was some concern of underwater galvanic corrosion if there was current flowing between bronze thru-hulls / keel and a Dynaplate, but few (if any) issues have ever been reported....Dynaplates are bronze, thru-hulls are bronze (well, mine are Marelon), props are bronze, zincs on SS shafts, and big lead keels....so, unless there was some weird current issues on-board, there really is no issue at all...as there is is little current (no real harmful DC current) on the antenna ground....(and, over my own 45+ years doing this, I've never seen any issues, on any boat, ever....of course, with an aluminum-hulled boat, DC-isolating everything is de rigueur, but on fiberglass boats it's almost unheard of these days)


But, even more efficiently....if someone does desire to DC-isolate their antenna ground, why not just install one cap (a 0.01uf to 0.1uf cap ---- ceramic disc or silver mica, either will do ---- with a voltage rating of 500v to 1500v), inside the tuner....just solder in the leads of the cap between the PC board and the ground lug stud (either in place of, or in series with, the wire that connects the ground lug to the tuner's PC board)....this is what SGC tuners have had for many decades, AND what I've done to a few Icom tuners that were to be used on aluminum-hulled vessels! This works perfectly, and is cheap, quick, and totally weather-proof...(but, again, except for aluminum-hulled boats, unnecessary)



BTW, this is another "tradition" that gets way, way over-used....just like the "backstay stand-offs" (also unnecessary, unless the lower part of the stay is grounded to the sea water or metal hull....and, even then almost all of the transmitted energy is radiated / damn little is shunted to ground)



Fair winds


John

[SoonerSailor]

Dockhead et al-

This is how I look at RF grounding issues, and using those principles you can work out what is likely to work best. On top of it all, experimenting a bit to find what actually works on your boat is going to help a lot.

Interference by your radio affecting other electronics on the boat is a result of high impedance (RF resistance) ground issues. The return current that is part of your antenna system will take any route it can to get back to your ATU RF ground connection. That path can include almost any other electrical conductors on your boat. The amount of RF current that any of those conductors will carry is going to be inversely proportional to the impedance of those conductors relative to the other routes on the path back to the ATU ground connection. Adding proper ferrites to wiring increases the impedance of that conductor to RF, and reduces current flow on that path, and hence interference potential. The more low impedance ground path you provide to your ATU, the less RF will flow through higher impedance connections like the wiring of your other electronics, and the less interference these devices will experience.

Copper strap is desirable as a ground path because it has low impedance to RF, so will allow a greater proportion of return current to take that path. It doesn't necessarily make it easier for your ATU to achieve a match, but it will result in less RF current flow in other wiring. You can perhaps make up for the lack of a wide strap ground path by supplying multiple other return paths, like wires to multiple bronze sea cocks, bronze hull plates, multiple wires along the boat hull, or even lifelines. The idea is to provide return paths to ATU ground that don't travel through your other electronics. Again, this doesn't necessarily improve the performance of your radio appreciably, but does reduce undesirable RF current paths.

Again, I would experiment with what is available to you, and do it on multiple bands.

Chip

[hasse_A]

If you connect shore power with ground and you have a water heater you may well get problems if you do not have your system DC-isolated from anything in contact with the water. There is a risk that the shore power ground does not have the same DC-level as the water and you will have a current through your system out to the item in contact with the sea water.
I have friends that have consumed 2 propellers this way.

[Dockhead]

Originally Posted by hasse_A

If you connect shore power with ground and you have a water heater you may well get problems if you do not have your system DC-isolated from anything in contact with the water. There is a risk that the shore power ground does not have the same DC-level as the water and you will have a current through your system out to the item in contact with the sea water.
I have friends that have consumed 2 propellers this way.

Yeah, I have never had that problem, but I do have a 3.6kW Victron isolation transformer which I am going to bring back to life with the help of Jedi's excellent blog post. That will exclude such a thing entirely.

[Brian.D]

@hasse A, if you feel more comfortable with the DC Isolation capacitors, go for it. It will not hurt your system in anyway, shape, or form.

[s/v Jedi]

I’m thinking you can use the PCB itself as a capacitor using top and bottom copper layers? I made stripline inductors by etching and always had to deal with capacitance so shouldn’t be too hard.

[Jammer]

You know, you can buy mylar film capacitors suitable for 3000 volts from Digikey for, like, $5 each.

[s/v Jedi]

Originally Posted by Jammer

You know, you can buy mylar film capacitors suitable for 3000 volts from Digikey for, like, $5 each.

That’s cheating

[Bycrick]

Capacitance isn’t the only issue. There will be some inductance from the PC board itself, as well as internal to the capacitors themselves. The various inductance scan cause the whole assembly to be resonant at some frequency(s) and thus present a high impedance at some frequencies even though it may work fine at other frequencies.

The easy solution suggested by a good RF engineer was to use several different types and values of capacitors in parallel.

In one case, we built a prototype using some really cheap capacitors with widely varying specs, which worked wonderfully. Then somebody decided to replace the cheap caps with some really, really good ones. The system oscillated like mad, completely unworkable. It turned out that the really cheap caps were series-resonant at the frequencies of interest and worked far better than the "high-quality" caps did.

Not all caps are equal, some are more equal than others.

[Wireless1]

Originally Posted by Dockhead

Fine, but all I care about is that it works.

There is no way I'm getting copper strapping through that bulkhead.
.

Actually there is a very easy way to pass 2” wide copper foil through a bulkhead. I’ve done it numerous time on boats I’ve owned. All you have to do is make one thin plunge cut through the bulkhead with your jigsaw (slightly wider than your foil). The foil can then be easily be fed through the slit. Then to hold the foil in place put a small fender washer screwed through the foil into the bulkhead on each side and go on to your next bulkhead. Easy peasy.
Hope this helps...

[Dockhead]

Originally Posted by Wireless1

Actually there is a very easy way to pass 2” wide copper foil through a bulkhead. I’ve done it numerous time on boats I’ve owned. All you have to do is make one thin plunge cut through the bulkhead with your jigsaw (slightly wider than your foil). The foil can then be easily be fed through the slit. Then to hold the foil in place put a small fender washer screwed through the foil into the bulkhead on each side and go on to your next bulkhead. Easy peasy.
Hope this helps...

If what I had was a normal bulkhead, that might be ok. But I have ring frames and no access to the bulkhead itself which is behind furniture. There are three ducts through the ring frames -- the only way to pass anything through that bulkhead. I am NOT going to rip up my teak furniture for a stupid ground strap

[s/v Jedi]

You mean ring frames like this? You can just go through them...

It sounds like the boat has an inner lining/shell? Those will stop most projects, turning them into h@ll