HF Radio Problems

[Dockhead]

I successfully used my reconfigured my M802 HF radio set and Pactor III modem (PTC-IIusb flashcd to Pactor III) last year to get gribs and weather, used successfully in a long distance ocean race we finished well in.


Last year I reconfigured the set to use a parallel backstay as the antenna and a heavy battery cable to a large bronze throughhull as a ground. The tuner is mounted in the lazarette; the radio is behind a settee near the nav table.


I reused a length of LMR400 (overkill I know) which was installed as part of the boat's original build for a sat phone antenna, to connect the radio to the tuner.


Everything worked well; I had transcontinental QSO's a great signal reports, and connected reliably to Winlink stations.


I had zero problem with noise from other onboard equipment.


HOWEVER, transmitting caused a lot of interference with other onboard equipment. The pilot would flip off so someone had to be hand steering whenever I was transmitting, and I think RFI killed my AIS and my Actisense NGT.


I'd be grateful for tips on how to solve this.


There are places where it is hard to separate the coax from other cabling -- going through bulkheads; the single wiring duct between the nav table and bilges. I will go through it again and see where I might achieve greater separation, but what else can I do? Will ferrite beads belp? Do they need to be ferrite beads specially tuned to HF frequencies?


I read somewhere that a ferrite bead on the coax between radio and tuner will help a lot; someone else said that will be a choke and degrade the signal. What's the truth?


Grateful for any tips.


The other thing I don't like is the parallel backstay antenna. It's in the way.


My backstay is too fat for economical insulators (they are a couple grand each, and I don't really fancy chopping my backstay anyway. What if I just use the uninsulated backstay? I guess it costs nothing to try it out, but anyone have experience? I thought I remember several on here having used that successfully.


I have one of the GAM antennas which clip to the backstay, which I got together with the radio when I bought it. I always thought that was nonsense -- won't it just inductively couple with the backstay, so might as well connect directly? But I've heard people say they get good results from them. I've never tried mine.


Tips?

[Jammer]

Originally Posted by Dockhead

HOWEVER, transmitting caused a lot of interference with other onboard equipment. The pilot would flip off so someone had to be hand steering whenever I was transmitting, and I think RFI killed my AIS and my Actisense NGT.

I'd be grateful for tips on how to solve this.

You will have to experiment. Read on.

There are places where it is hard to separate the coax from other cabling -- going through bulkheads; the single wiring duct between the nav table and bilges. I will go through it again and see where I might achieve greater separation, but what else can I do? Will ferrite beads belp? Do they need to be ferrite beads specially tuned to HF frequencies?

Ferrites could help but at HF you will need multiple turns through stacks of multiple cores which makes this a bulkly and expensive solution. LMR400 has a high bend radius which makes it a poor choice. Here's a photo of what I use at home:

[Jammer]

I read somewhere that a ferrite bead on the coax between radio and tuner will help a lot; someone else said that will be a choke and degrade the signal. What's the truth?

It depends, often both. A sufficient choking impedance (like in the photo above) will keep the RF flowing in a balanced way in the coax, so that the coax does not radiate. But sometimes having the coax radiate improves the overall performance of the antenna.


You may be better off filtering the RF out of your autopilot and other affected instruments, using ferrites, bypass capacitors, or a combination. See Jim Brown's excellent article:


http://www.audiosystemsgroup.com/RFI-Ham.pdf

The other thing I don't like is the parallel backstay antenna. It's in the way.

My backstay is too fat for economical insulators (they are a couple grand each, and I don't really fancy chopping my backstay anyway. What if I just use the uninsulated backstay? I guess it costs nothing to try it out, but anyone have experience? I thought I remember several on here having used that successfully.

If your hull is fiberglass you could place an insulator at the top of the backstay (only) and rely on the hull itself to insulate the bottom. Jim Cate uses an uninsulated backstay and says he gets good results. It is also possible to use the rig as a loop antenna, and connect the tuner to the forestay and backstay (instead of ground and backstay), which works for some people.

I have one of the GAM antennas which clip to the backstay, which I got together with the radio when I bought it. I always thought that was nonsense -- won't it just inductively couple with the backstay, so might as well connect directly? But I've heard people say they get good results from them. I've never tried mine.


Tips?

I am skeptical of those. Maybe they work on some boats. I doubt if they work much better than just connecting to the bottom of an uninsulated backstay.


If you're not going to insulate your backstay you might be better off with a hoistable tuned dipole. Usually people thread wire inside some rope, feed it with coax in the middle, and hoist the whole thing. Since you have a larger boat and often have crew that might work. They are band specific so you need two or three. There are several articles with details, if you are interested and can't find one I can post some links.

[Caleb_Grey]

Do you transmit with full power? Depending on conditions you shouldn't need the full 150 watts all the time. Try to start low and find a balance of interference and performance.
You could get an extension cable for the head unit, and move the radio body closer to the tuner.
As the gam is a $500 piece of kit you already have, give it a try, they work.

[Frankly]

When I installed my ICOM 802/ Pactor Modem set up (located the modem back with the radio), I installed a common mode choke right at the tuner (in the coax). Put some ferrites on the cables going fwd to the radio control unit, computer connections, and maybe the tuner connection and never had any interference problems. My Danfoss frig unit raises a lot of He## with the radio but just turn it off while operating.

Over the years I have replaced the jumbo Dynaplate ground with a connection to my centerboard system and done away with my lower backstay antenna insulator. HF radio still working fine but the Pactor is on the fritz so not sure if my changes have any effect on email operations.

You can buy the common mode chokes from MFJ, DX Engineering and a couple of other sources.


Frankly

[MicHughV]

While a backstay is most commonly used as an antenna, it does come with limitations.

My first boat, a ketch, had double backstays, which were located only inches away from the mizzen stays.

Cut a long story short, I was concerned that the proximity of other stays might interfere with the stay chosen as an antenna.

So I built my own. Basically a pvc pipe lashed to the stern rain, about 6' high. From the top of this pvc pole to the top of my mizzen was about 30', but the mizzen had no backstays to be concerned about. From the pvc pole to near the top of the mizzen I ran a lenght of 1/8" galvanized wire, appropriately fitted with finger size insulators at each end, these were attached by rope lashings to the pvc pole and top of mast.
The tuner was located at the base of the PVC pipe. From the tuner to the top of the pvc pole I used GTO wire, which was attached to the 1/8" cable.

The whole affair worked like a charm, and was inexpensive to install. Subsequent to that ketch, I did the exact same thing on sloop rigged boats, which worked as perfectly as the first.

Might be some ideas for you.

[Dockhead]

Originally Posted by Caleb_Grey

Do you transmit with full power? Depending on conditions you shouldn't need the full 150 watts all the time. Try to start low and find a balance of interference and performance.
You could get an extension cable for the head unit, and move the radio body closer to the tuner.
As the gam is a $500 piece of kit you already have, give it a try, they work.

I never use full power because of the interference problems, and don't miss it. I am getting good results with low and medium power; apparently the antenna and ground are both working well.


It would be nice to be able to use full power, however.


The GAM antenna would neatly solve the antenna problem, but I would like a scientific answer to the question of what if anything is different from just connecting directly to the backstay? The chainplate for the backstay is in the lazarette about 30cm from the tuner -- would be a cinch to hook it up. I guess I could just try it.

[Dockhead]

Originally Posted by MicHughV

While a backstay is most commonly used as an antenna, it does come with limitations.

My first boat, a ketch, had double backstays, which were located only inches away from the mizzen stays.

Cut a long story short, I was concerned that the proximity of other stays might interfere with the stay chosen as an antenna.

So I built my own. Basically a pvc pipe lashed to the stern rain, about 6' high. From the top of this pvc pole to the top of my mizzen was about 30', but the mizzen had no backstays to be concerned about. From the pvc pole to near the top of the mizzen I ran a lenght of 1/8" galvanized wire, appropriately fitted with finger size insulators at each end, these were attached by rope lashings to the pvc pole and top of mast.
The tuner was located at the base of the PVC pipe. From the tuner to the top of the pvc pole I used GTO wire, which was attached to the 1/8" cable.

The whole affair worked like a charm, and was inexpensive to install. Subsequent to that ketch, I did the exact same thing on sloop rigged boats, which worked as perfectly as the first.

Might be some ideas for you.

That's kind of what I already have -- alternate backstay rigged from spare main halyard to pushpit (to a length of cordage to insulate it from the pushpit). Problem is it's in the way, and the topping lift gets tangled in it when I let it off.


Perhaps I could rig it further back -- maybe to the end of one davit.


One complaint I don't have is performance -- it seems to work brilliantly.

[Dockhead]

Originally Posted by Jammer

You will have to experiment. Read on.

Ferrites could help but at HF you will need multiple turns through stacks of multiple cores which makes this a bulkly and expensive solution. LMR400 has a high bend radius which makes it a poor choice. Here's a photo of what I use at home:

So you've got your feedline looped through those ferrites? Ferrites are cheap; that would be brilliant if that could work for me. Only problem is I'm not sure I have enough extra length

[MicHughV]

As a side note....in my original antenna setup, I thought to extend my " long wire" from the top of the mizzen to the to the top of the main, again using the 1/8" cable, finger insulators and lashing.

I thought that having a longer antenna would give me better results, but thru' experimentation, discovered it didn't, as the angle between main and mizzen is rather flat and the radiation pattern might be useful to someone standing on the moon, so I removed it.

My first radio was a Stephens 222 SSB. It had an excellent tuner. As I progressed to get my Ham ticket, I installed a Kenwood Ham radio. I would use the SSB to tune the antenna and had an antenna switch to connect the Ham to the SSB antenna. The SSB had to stay on as it powered the tuner, but I could use the Kenwood without any problems.

At the time I was a member of a local Ham Club. There were some old timer guys there that knew every trick in the book, so would suggest you hook up with a local Ham club. to pick their brains

[denverd0n]

I have used EZNEC to model the propagation from both an insulated backstay, and the complete, uninsulated rigging for a sloop. I was surprised that using the complete rigging came out to be only slightly less efficient than an insulated backstay.

Now, mind you, this was all just computer modelling. I have not done extensive testing to see real world differences. So you might want to ask yourself how much you trust computer models. For myself, having worked for decades in the financial industry with some of the most sophisticated modelling software in the world, I see them as a valuable tool, but definitely NOT the be-all and end-all. But it certainly couldn't hurt to give it a try.

[Brian.D]

On the Common Mode currents is also my first thought. Those will kill you (not literally), but you can get a nasty RF burn if you are touching something metal.

A Common Mode Choke can be made or purchased. To make one, do a search on Ugly Balun. This is easy to make if you have any coax cable that is not being used.

If you can get some ferrite core type FT240-43 and some 18AWG wire you can make your own. Winding is simple and forgiving if you make a minor mistake. You will need some additional parts.

One other thought and I might be out in left field here, it is possible that your tuner is not handling the high impedance very well. You might need a 4:1 or 9:1 UnUn balun. This can also be made with FT240-43 cores but is a little tricky to wind, still doable.

Now, check your ground from the tuner to the thru hull. Is this connect by chance shared with a DC ground somehow? Remember that RF is an AC component and should have its own ground point and not shared with DC grounds. For testing I would make a DIY KISS, disconnect your current ground and connect the KISS and see if you are still getting RF in the electronics.

Good luck and as always, JMHO

[Dockhead]

Originally Posted by Brian.D

On the Common Mode currents is also my first thought. Those will kill you (not literally), but you can get a nasty RF burn if you are touching something metal.

A Common Mode Choke can be made or purchased. To make one, do a search on Ugly Balun. This is easy to make if you have any coax cable that is not being used.

If you can get some ferrite core type FT240-43 and some 18AWG wire you can make your own. Winding is simple and forgiving if you make a minor mistake. You will need some additional parts.

One other thought and I might be out in left field here, it is possible that your tuner is not handling the high impedance very well. You might need a 4:1 or 9:1 UnUn balun. This can also be made with FT240-43 cores but is a little tricky to wind, still doable.

Now, check your ground from the tuner to the thru hull. Is this connect by chance shared with a DC ground somehow? Remember that RF is an AC component and should have its own ground point and not shared with DC grounds. For testing I would make a DIY KISS, disconnect your current ground and connect the KISS and see if you are still getting RF in the electronics.

Good luck and as always, JMHO

Thanks, I'll check all that out.


My through hulls are not bonded, and there is absolutely nothing connected electrically to that big muffler water outlet throughull except my tuner ground, so I'm pretty sure that's not the problem.

[Brian.D]

What is a "big muffler water outlet"? Remember I only have an outboard. LOL

[MicHughV]

My girlfriend at the time had a dad that was an avid old time Ham. He insisted I get my Ham license before I traipsed off with his daughter.

His backyard was festooned with antenna's of every description, amongst which was a vertical long wire hanging from a frame he had concocted and was the antenna he most often used to contact us. He used the old style manual tuner. He was also a whizz with morse code, and could bang off code quicker than most people could talk.

It was handy to have his expertise whilst setting up my rig.

I was also a member of a local Ham club. About twice a year, we'd traipse off to a local farm and rig up every conceivable type of antenna one could think off. I found this all very interesting, though a lot went over my head.

I found it interesting that staying in touch with him sometimes depended on which compass direction my boat was pointed at. While communicating with him, I'd change compass direction, until he was happy with the signal strength, but this was a problem at times, because wave height and direction would cause my boat to pitch and down, or roll sideways, affecting the signal.

I also found it useful to have the engine running, so as to have maximum amperage at the batteries, as during transmission, a lot of amps are sucked out.

These are all little things that appear to influence performance.