HF in marinas

[findus]

Dread thrift...

I have used HF for 50 years. There is 1 piece of communication eqpt which will not be on my next boat and this is HF!

However, I will have a proper Satcom and Sat data.

FWIW

Monique, can you elaborate, why not HF on the next boat?

Thanks!

Findus

 

[cornell_b]

HF radio

if you can find a ham radio operator in your area, he could take a look at your system andperhaps find your problem....would check the SWR meter on your radio while transmitting, the answer might be in the reading of the meter....KD4NKL

 

[Mirror Painter]

I said before '. This discussion is pointless until we know what the OP is using as an aerial (and ground?) and what he is trying to achieve '.

I was wrong because it is not pointless but enjoyable. However the OP does still need to let us know what he has for an aerial and 'ground' and what he is trying to do before people can hope to advise him.

 

[PITCAIRN]

You are probably right.

I assume you are using a backstay or other vertical antenna.

Your signal will be warming up all the masts in the marina.

Not much you can do about it really except to find somewhere with a bit of space around you and drop the hook.

Or maybe try a "lash-up" inverted V antenna

Longish length of wire - tie the insulated end to the front of the boat, hoist the middle up the mast with a spare halliard and connect the other end to the ATU - or transceiver if it has an integral tuner.

Worth a try for a length of wire and 10 mins work

Just for the sake of clarity, what you have described is not an 'inverted V' antenna, (albeit as you have described it, the antenna does in appearance look like an upside down 'V' shape).
In fact what you have described ( ''connect the other end to the ATU '' ) is an 'end fed long wire or, 'marconi' antenna, just as the end of the back -stay hooked up to the ATU is a 'marconi'. Ground plane and counterpoise are critical, this type of antenna wont work without same.
The 'inverted V' is a quite different antenna, centre fed haf wave dipole , the ground plane not as critical and no counterpoise needed.

 

[Mirror Painter]

Just for the sake of clarity, what you have described is not an 'inverted V' antenna, (albeit as you have described it, the antenna does in appearance look like an upside down 'V' shape).
In fact what you have described ( ''connect the other end to the ATU '' ) is an 'end fed long wire or, 'marconi' antenna, just as the end of the back -stay hooked up to the ATU is a 'marconi'. Ground plane and counterpoise are critical, this type of antenna wont work without same.
The 'inverted V' is a quite different antenna, centre fed haf wave dipole , the ground plane not as critical and no counterpoise needed.

Good explanation. Just for the sake of pedantry, the term 'long wire' should strictly speaking be used for a wire of at least one wavelength long.

I'm going to PM the OP and ask him to get back here and tell us what he is using

 

[KellysEye]

>The fact that people can talk to each other on HF halfway round the world? Seems pretty conclusive to me. They certainly can't see each other.

You need a clear line of site to get the signal out, surrounding masts block it, then it bounces off the ionosphere and indeed can reach halfway round the world.

>This will have two effects - first it will absorb power from the transmitted signal ie it will "heat up" the mast.

SSB doesn't heat up the mast because of the insulators, the top insulator should be at least twelve inches from the masthead wire fitting. And a mast doesn't affect the signal. However you can light a cigarette on the aerial, a good party trick.

>Just for the sake of pedantry, the term 'long wire' should strictly speaking be used for a wire of at least one wavelength long.

The aerial doesn't have be any particular wavelength, the normal length is about 34 feet and the frequencis are set by an Automatic Tuner Unit that ' tricks' the aerial/radio into thinking it's the correct wavelength.

>I did suggest trying an inverted V initially.

An inverted V won't work it needs to be a straight wire or if you have a ketch the a Z shape aerial using a main mast backstay and the triatic (mizzen to mast) stay. The latter has a much stronger signal than a single wire, that's what we had.

The ground is the sea and makes up half the aerial, as said it is critical to have a good ground, many boats who have SSB don't have a good signal because of the limited amount of metal that can be linked inside a boat. Obviously a metal boat has the best signal. The only thing that can beat it is a cat with copper foil glassed the whole length of both hulls, which we have seen.

 

[MM5AHO]

If you were to carefully position the boat, such that on one side there's a boat with mast longer than the transmitting boat, by about 10%, and on the other side, a series of shorter masts (and therefore stays), then a gain antenna might (in theory) be created. This directional antenna could be used to break out of the described difficulty.

In practical terms, the above would be almsot impossible to acheive, but I did like the mental image of a vertical yagi of 50 elements for the marine ssb band!

 

[john_morris_uk]

Just for the sake of clarity, what you have described is not an 'inverted V' antenna, (albeit as you have described it, the antenna does in appearance look like an upside down 'V' shape).
In fact what you have described ( ''connect the other end to the ATU '' ) is an 'end fed long wire or, 'marconi' antenna, just as the end of the back -stay hooked up to the ATU is a 'marconi'. Ground plane and counterpoise are critical, this type of antenna wont work without same.
The 'inverted V' is a quite different antenna, centre fed haf wave dipole , the ground plane not as critical and no counterpoise needed.

I am glad someone else has explained it properly! I thought of typing out the explanation of what an inverted 'V' really is, but sort of lost the will to live with some of the discussions going on in the topic.

The answer (by the way) to the OP is almost certainly that the surrounding masts ARE interfering/absorbing some of your transmitted (and received) signals. I have suffered the same problem when we have been in the middle of a Marina. Too much other metalwork around and lots of it getting in the way of the low angle radiation that you need to achieve good results.

The posters who talk about signals bouncing off the ionosphere ought to know that the angle of radiation is critical and hence local metal work does sort of 'get in the way. They also ought to know that its not just a question of 'bouncing off some imaginary layer and you get MUF's etc and LUF's for ionospheric propagation and different F layers in the ionosphere as well as ground radiation etc etc. RF propagation at HF is not always straightforward. At low frequencies its very difficult to achieve antennas that have low angles of radiation, although a reasonably tall vertical is one of the best bets. Its all to do with the wavelength vs height of the antenna and at longer wavelengths that means very high! (Its one of the reasons that the BBC transmitter masts for their 198 kHz transmitter at 700 feet tall, and even then they have to put a 'T' on the antenna to electrically shorten it as 700 feet is only a fraction of the 1500 metre wavelength.)

Anyway, before I get carried away, the answer is that all the local metalwork is almost certainly interfering with the correct operation of the backstay antenna, and you've got nothing much to worry about if the setup works perfectly well when you are at anchor away from other boats.

 

[Beadle]

I would contend that it IS an inverted V

I know that traditionally the antenna is fed at the low impedance (high current) point in the centre.

There is no good reason why it cannot be fed at the high impedence (high voltage) end - provided of course that the feed is at a suitable impedance. The voltage and current distribution along the radiating part of the aerial would be the same - which would give the same radiation pattern.

There is no law that I am aware of that says it has to be centre fed, although I concede it almost always is. But that is a matter of convenience more than electrical design properties.

 

[john_morris_uk]

Just for the sake of clarity, what you have described is not an 'inverted V' antenna, (albeit as you have described it, the antenna does in appearance look like an upside down 'V' shape).
In fact what you have described ( ''connect the other end to the ATU '' ) is an 'end fed long wire or, 'marconi' antenna, just as the end of the back -stay hooked up to the ATU is a 'marconi'. Ground plane and counterpoise are critical, this type of antenna wont work without same.
The 'inverted V' is a quite different antenna, centre fed haf wave dipole , the ground plane not as critical and no counterpoise needed.

I would contend that it IS an inverted V

I know that traditionally the antenna is fed at the low impedance (high current) point in the centre.

There is no good reason why it cannot be fed at the high impedence (high voltage) end - provided of course that the feed is at a suitable impedance. The voltage and current distribution along the radiating part of the aerial would be the same - which would give the same radiation pattern.

There is no law that I am aware of that says it has to be centre fed, although I concede it almost always is. But that is a matter of convenience more than electrical design properties.

In defence of Pitcairn but I'm not going to die in a ditch over the definition - I think that the inverted V traditionally referred to a half wave dipole with the ends dropped to improve the radiation pattern and matching to a 50 ohm impedance line. I would still argue that an end fed wire however its slung is just an 'end fed wire' (and that it shouldn't be called a 'long wire' until its more than a wavelength or so long. Ideally multiple wavelengths long in which case it exhibits gain in lobes off either end, but I am getting carried away again with reminiscing about RF theory).

 

[wotayottie]

If you have got this far Dromio you are doing well.

Like you I have found it difficult more often than not to use SSB in a marina. Many marinas are sited in such a way as to give you good shelter which in turn often means using old harbours with lots of building around. Not to mention the masts. Furthermore, many marinas seem to have a lot of badly shielded electrical machinery which adds to the problem. Plus of course there are often issues with internal boat kit like fridges.

I have often found that my reception in marinas was either bad or useless particularly on 80m and in the last 12 months. Conditions have been poor - for example I could not even hear most of my morning sked from no more than 100 miles away. But I could often hear the USA on 20m in the same marina.

Transmission is a bit of a different issue since local electrical equipment should not affect it. Much more likely you have some sort of installation problem. Are you getting lots of tramp RF around the boat? Or feedback via the mike lead? Before now I have found myself triggering the engine alarm when transmitting on 20m . You need to check the basics.

Dont bother trying hoisting a wire up the mast to make a different aerial . Tried that one and you get endless problems with the relationship of the wire to your standing rigging.

 

[Mirror Painter]

"I have often found that my reception in marinas was either bad or useless particularly on 80m and in the last 12 months. Conditions have been poor - for example I could not even hear most of my morning sked from no more than 100 miles away. But I could often hear the USA on 20m in the same marina. "

That's a good illustration of why, (despite what somebody else suggested), the length of the aerial wire is very important. For example a 34' wire is half wave on 20Mtrs. A half wave on 80 Mtrs would need to be about four times that - i.e. around 130'. An A.T.U. may 'trick' the transceiver in to seeing an impedance match but it wont make a bad aerial in to a good aerial.

 

[Beadle]

" An A.T.U. may 'trick' the transceiver in to seeing an impedance match but it wont make a bad aerial in to a good aerial."

Yes - that's quite true - although I could take issue with the word trick.

My suggestion was based on the probability that if he is using a vertical antenna surrounded by scores of vertical conductors some more or less connected to earth then any vertical antenna is going to suffer from those vertical conductors absorbing and reflecting the power from his antenna.

The fact is that in an average sized boat the only antenna that could be remotely described as "good" is a vertical - and even a vertical will require an ATU to "trick" the wireless into thinking its a suitable impedance.

In almost all amateur installations the antenna is a compromise made to match space, effectiveness, cost and tolerance from neighbours (and wives!)

That is what explains the widespread use of the "inverted V" - It fits nicely over your average suburban house with the middle on a short mast on the chimney and anything handy in front and back garden.

Earthing is important whatever the aerial, but especially so on end fed and vertical (same thing in a way) Since the OP appeared to have a station that works satisfactorily at sea I assumed that such things as earthing, power supply ATU etc were working properly.

 

[KellysEye]

>The fact is that in an average sized boat the only antenna that could be remotely described as "good" is a vertical

All the SSB rigs I've seen on boats (150+) are on a backstay which is not vertical. With a good ground they work fine. As I mentioned ours is Z shaped the bottom being the steel hull.

 

[tawhiri]

SSB problems

I am experiencing similar problems to OP, and I can describe my setup.
Icom 710 tranceiver connected to AT120 antenna tuner via 6 meters of RG58 coax, then 9m of wire hoisted up with the topping lift. The ground is about one square mter of alu foil in the stern locker, no direct contact to sea water.
When I connected to a shore station in Italy about 300 miles away, the uplink transmitted 150 bytes/minuet and the downlink received 600 bytes/minuet.

 

[wotayottie]

"I have often found that my reception in marinas was either bad or useless particularly on 80m and in the last 12 months. Conditions have been poor - for example I could not even hear most of my morning sked from no more than 100 miles away. But I could often hear the USA on 20m in the same marina. "

That's a good illustration of why, (despite what somebody else suggested), the length of the aerial wire is very important. For example a 34' wire is half wave on 20Mtrs. A half wave on 80 Mtrs would need to be about four times that - i.e. around 130'. An A.T.U. may 'trick' the transceiver in to seeing an impedance match but it wont make a bad aerial in to a good aerial.

That's true Moxon but it's no help on a typical sized sailing boat and it's only a minor part of the issue anyway. I might have very poor reception in most marinas but I have reasonable reception with the same aerial at sea or at anchor in a quiet bay. Sure the backstay aerial is not ideal but modern com radios are so sensitive that that aerial length mismatch is only normally an issue on QRP from a long way away. Ambient electrical noise is a bigger issue. As indeed it is at home. Transmission is different

I've just checked my noise level at home with an 80 m dipole and in a country area with the house bordering fields. At 1600 hrs its s4 to s5. So how much worse is it going to be in an industrial area like most marinas / harbours?

 

[wotayottie]

"I have often found that my reception in marinas was either bad or useless particularly on 80m and in the last 12 months. Conditions have been poor - for example I could not even hear most of my morning sked from no more than 100 miles away. But I could often hear the USA on 20m in the same marina. "

That's a good illustration of why, (despite what somebody else suggested), the length of the aerial wire is very important. For example a 34' wire is half wave on 20Mtrs. A half wave on 80 Mtrs would need to be about four times that - i.e. around 130'. An A.T.U. may 'trick' the transceiver in to seeing an impedance match but it wont make a bad aerial in to a good aerial.

That's true Moxon but it's no help on a typical sized sailing boat and it's only a minor part of the issue anyway. I might have very poor reception in most marinas but I have reasonable reception with the same aerial at sea or at anchor in a quiet bay. Sure the backstay aerial is not ideal but modern com radios are so sensitive that that aerial length mismatch is only normally an issue on QRP from a long way away. Ambient electrical noise is a bigger issue. As indeed it is at home. Transmission is different

I've just checked my noise level at home with an 80 m dipole and in a country area with the house bordering fields. At 1600 hrs its s4 to s5. So how much worse is it going to be in an industrial area like most marinas / harbours?

 

[Mirror Painter]

I am experiencing similar problems to OP, and I can describe my setup.
Icom 710 tranceiver connected to AT120 antenna tuner via 6 meters of RG58 coax, then 9m of wire hoisted up with the topping lift. The ground is about one square mter of alu foil in the stern locker, no direct contact to sea water.
When I connected to a shore station in Italy about 300 miles away, the uplink transmitted 150 bytes/minuet and the downlink received 600 bytes/minuet.

I have a plastic boat with no mast on a river no experience of marine H.F. - but:

1. What frequency are you using, (A 9 Mtr wire is roughly a 1/4 wave on 8Mhz)?

2. What can you do to increase your ground or counterpoise? On any H.F. band 1Mtr of foil is inadequate.

 

[KellysEye]

>That's a good illustration of why, (despite what somebody else suggested), the length of the aerial wire is very important. For example a 34' wire is half wave on 20Mtrs. A half wave on 80 Mtrs would need to be about four times that - i.e. around 130'. An A.T.U. may 'trick' the transceiver in to seeing an impedance match but it wont make a bad aerial in to a good aerial.

So what aerial size are you recommending?

Most boat aerial lengths are determined by the length of the backstay and have nothing to do with the any particlar wavelength, the ATU handles that. As I said the average I've seen is around 34 feet, although ours was longer than that with the triatic stay connected to the backstay. Some people use all of their backstay, some part of it. Because of the ATU there are no such things as bad a aerials only bad grounds.

>Icom 710 tranceiver connected to AT120 antenna tuner via 6 meters of RG58 coax, then 9m of wire hoisted up with the topping lift. The ground is about one square mter of alu foil in the stern locker, no direct contact to sea water.

A couple of thoughts about what might improve things. The ATU should be as close the the aerial as possible and connected with copper foil as close to the aerial as possible.
The ground doesn't need to be in the water but it does need to be on the inside surface of the hull if using foil. Copper foil is much better than Aluminium and the more of it the better. Most people with GRP boats link the ground to the engine and anything else metal they have below deck.

 

[Mirror Painter]

>

So what aerial size are you recommending?

I'm not recommending anything to you because you'd only argue about it!

In fact I don't think I'm recommending anything to anyone - just trying to share some very basic aerial theory. Basic because it's all I've got