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Old 20-08-2013, 07:38   #61
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Re: Amazing Power of Good Antennas

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Originally Posted by Dockhead View Post
Mine is a Galaxy XP, specifically, the Galaxy 5400-XP:

Shakespeare Galaxy XP High Performance Antennas
I personally find Banten Antennas to be very good, the GMDSS professional series are very good , with N connectors on the body and gold plated elements.

Dave
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Old 20-08-2013, 07:39   #62
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Re: Amazing Power of Good Antennas

Again, I think that most people who report amazing results from their antenna after replacing old coax, old connectors and antenna are actually getting those results due to the new coax and connectors, and the actual antenna is secondary. I bet that if the old antenna was used with the same type of new coax and connectors as the old, amazing results would still be found.

There is a lot of old coax and connectors that have gone bad out there. More so than antennas.

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Old 20-08-2013, 08:58   #63
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Like I wrote before, everything done right makes it better and when enough things have been done right you will get those amazing results.

Cables and connectors need to be done right but that doesn't mean the antenna isn't a factor. Like always there are good ones and not so good ones. People who say that it doesn't matter because as long as the VSWR is right the antenna performs optimal, have missed a clue. When you swap antenna with a dummyload you get good VSWR but not amazing results when you try to use the radio for communications.

About good antennas: there are several factors that make an antenna good, like it's design and it's durability. Some designs are easier to implement physically while others are more complicated. Yes, this affects price. A stainless whip is just that and it is durable. But if you want a vertical dipole design, you need a fiberglass tube to hold the elements and create a center feed to them. A fiberglass tube will quickly break down under UV exposure so it needs a quality finish. More things that affect price. The reason all that exists is because the whip is a ground plane design but where is the ground plane at the masthead? This design works very good on the roof of a (metal) car, but not as well at the masthead. So some designs are more suitable for application A while other designs make better sense for application B. Now it isn't as simple as buying that "sailboat masthead" antenna anymore, isn't it?

So, how good does the antenna need to be? What is good enough? The stainless whip is considered good enough, because it allows communication in GMDSS sea area A1, which is covered by the VHF radio. So there it is, the reason that these are used so often.

Of course, the GMDSS system dictates that as soon as you leave A1 and enter the A2 area, you switch to MF communications. Like for VHF, your MF radio needs to be equipped with DSC. Don't have that? I don't have that... well, you can switch to using your A3 area communications while in an A2 area and this would be your Inmarsat C terminal. Don't have that? I don't have that... hmmm... may be it is a good idea to have a VHF installation that allows communications well into A2 areas; it's your call

I did my first marine VHF installation in 1978. The boat was on Dutch inland waters. My radio check on 25W was answered by both Dutch and English coast stations. The Dutch station was 30nm away and the English station over 100nm away, meaning my signal went through the A1 areas of both Holland and England, plus the piece of A2 area in between those two. We then decided that we did not need MF, which was a dedicated Sailor radio in those days.

And this brings me to the most important factor: what do you intend to do with your radio? When you sail around the buoys in from of the clubhouse every weekend, you will have different requirements than when you're anchored in the San Blas Islands and want to talk to your buddy 30nm or more away. Not every boat needs to maximize VHF range, but for some it enables new possibilities.

About power: for VHF communications, power is very important. People who say it isn't and that a couple of dB loss here and there doesn't matter, are confusing this with SSB. On short wave radio, I can talk around the world on 5W and this must be what they think. I have the ability to Tx with 50W instead of the regular 25W and it makes a big difference. Not for links with friends 10nm away. But huge for longer than normal distances. The effort to bring as much power to the antenna as possible is worth it for your VHF radio.
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Old 20-08-2013, 10:19   #64
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Re: Amazing Power of Good Antennas

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Originally Posted by s/v Jedi View Post
Like I wrote before, everything done right makes it better and when enough things have been done right you will get those amazing results.

Cables and connectors need to be done right but that doesn't mean the antenna isn't a factor. Like always there are good ones and not so good ones. People who say that it doesn't matter because as long as the VSWR is right the antenna performs optimal, have missed a clue. When you swap antenna with a dummyload you get good VSWR but not amazing results when you try to use the radio for communications.

About good antennas: there are several factors that make an antenna good, like it's design and it's durability. Some designs are easier to implement physically while others are more complicated. Yes, this affects price. A stainless whip is just that and it is durable. But if you want a vertical dipole design, you need a fiberglass tube to hold the elements and create a center feed to them. A fiberglass tube will quickly break down under UV exposure so it needs a quality finish. More things that affect price. The reason all that exists is because the whip is a ground plane design but where is the ground plane at the masthead? This design works very good on the roof of a (metal) car, but not as well at the masthead. So some designs are more suitable for application A while other designs make better sense for application B. Now it isn't as simple as buying that "sailboat masthead" antenna anymore, isn't it?

So, how good does the antenna need to be? What is good enough? The stainless whip is considered good enough, because it allows communication in GMDSS sea area A1, which is covered by the VHF radio. So there it is, the reason that these are used so often.

Of course, the GMDSS system dictates that as soon as you leave A1 and enter the A2 area, you switch to MF communications. Like for VHF, your MF radio needs to be equipped with DSC. Don't have that? I don't have that... well, you can switch to using your A3 area communications while in an A2 area and this would be your Inmarsat C terminal. Don't have that? I don't have that... hmmm... may be it is a good idea to have a VHF installation that allows communications well into A2 areas; it's your call

I did my first marine VHF installation in 1978. The boat was on Dutch inland waters. My radio check on 25W was answered by both Dutch and English coast stations. The Dutch station was 30nm away and the English station over 100nm away, meaning my signal went through the A1 areas of both Holland and England, plus the piece of A2 area in between those two. We then decided that we did not need MF, which was a dedicated Sailor radio in those days.

And this brings me to the most important factor: what do you intend to do with your radio? When you sail around the buoys in from of the clubhouse every weekend, you will have different requirements than when you're anchored in the San Blas Islands and want to talk to your buddy 30nm or more away. Not every boat needs to maximize VHF range, but for some it enables new possibilities.

About power: for VHF communications, power is very important. People who say it isn't and that a couple of dB loss here and there doesn't matter, are confusing this with SSB. On short wave radio, I can talk around the world on 5W and this must be what they think. I have the ability to Tx with 50W instead of the regular 25W and it makes a big difference. Not for links with friends 10nm away. But huge for longer than normal distances. The effort to bring as much power to the antenna as possible is worth it for your VHF radio.
As usual, very valuable thoughts from Nick. For those of you who didn't follow the thread last year, Nick was a major influence on my VHF installation, which was my first real foray at fiddling with radios. Thanks again, Nick.

In my opinion, VHF is going to be the most important means of communication even on boats which spend a lot of time far out to sea. Even if you have a good SSB installation, you're always going to use VHF if you can make reasonable contact. I bet hardly anyone, even extremely good HF operators, uses SSB for more than 10% or 15% of practical communications. Even circumnavigators are spending most of their time near shores.

So in my opinion, it really pays to take some trouble getting the VHF installation right. The cost is ridiculously little compared to what we spend on other things. My top-of-the-line VHF transceiver only cost me about $500, as far as I recall, and a fantastic antenna is only $120 or so. A roll of RG213 is more expensive -- I think it was about $160. But these are trivial sums of money compared to other systems on the boat. I can't believe people would seriously care that PL259 connectors cost $7 (the good ones) compared to $12 or $15 you pay for Type "N" connectors. Saving $8 on something like that? Give me a break! I think I paid 8 pounds for a plastic dinghy bailer last week.


Nick's remarks on power over VHF are interesting. I have a place to install a mobile ham VHF/UHF transceiver, and I have the antenna and power supply already fixed up. These things put out 50 watts, or even 75 watts, and can be "opened" to marine VHF frequencies. It is perfectly legal to use them on the marine band for a genuine distress situation. Hmmm.

Concerning power another point: Someone pointed out that FM radio is subject to "capture effect" (marine VHF uses FM -- frequency modulation). That means power of your signal is crucially important -- if two FM signals are on the same frequency at the same time, the stronger one will be "captured" by receivers, and the weaker one will be heard not at all. So even a little bit more power may make the difference between being heard and not being heard, which can be a matter of life and death in a distress situation. This is different from SSB, since the modulation scheme used (basically AM) ensures that weak signals are always heard if they are at all readable, and they will be heard simultaneously with a stronger one. Another reason why power is more important on VHF than it is on SSB.
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Old 20-08-2013, 10:30   #65
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Re: Amazing Power of Good Antennas

Quote:
Originally Posted by goboatingnow View Post
I personally find Banten Antennas to be very good, the GMDSS professional series are very good , with N connectors on the body and gold plated elements.

Dave
Looks really great -- I especially like the "N" type socket. The model 0008 looks very similar to the Shakespeare Galaxy XT -- internal dipole etc.

I also like the Danish Procom antennas.
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Old 20-08-2013, 13:23   #66
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Re: Amazing Power of Good Antennas

Dockhead-
I would suggest that TypeN is the wrong fitting to use with marine VHFs, even if it is a better technical solution, simply because it is not the norm. If you grab an SWR meter, or a patch cable (UHF male-to-male) to try swapping out a section while looking for a problem, they'll all be UHF fittings. If you have TypeN, you're SOL.

Amphenol RF- UHF Connector Series&

Amphenol have lots of specs up on their web site and when a spec is missing, they'll gladly talk to you or email to supply it. For instance, they do document the insertion less for every TypeN fitting, but they don't show any insertion loss at all for UHFs. Perhaps that's an omission, perhaps there is no power loss at what we now call VHF frequencies for the "UHF" fittings. In which case, the inferior part might actually be better for the job. But while most of us can only guess, they'll know for certain.
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Old 20-08-2013, 17:47   #67
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Quote:
Originally Posted by Dockhead View Post

Looks really great -- I especially like the "N" type socket. The model 0008 looks very similar to the Shakespeare Galaxy XT -- internal dipole etc.

I also like the Danish Procom antennas.
Just remember the only difference between type N and BNC is the threaded outer shell. Electrically they are identical. For those that don't believe try to plug a type N into a BNC. It fits perfectly. SO-239 (so-called UHF) is more rugged and can handle more power than type N.
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Old 21-08-2013, 02:19   #68
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Re: Amazing Power of Good Antennas

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Just remember the only difference between type N and BNC is the threaded outer shell. Electrically they are identical. For those that don't believe try to plug a type N into a BNC. It fits perfectly. SO-239 (so-called UHF) is more rugged and can handle more power than type N.
Although I use plenty of BNC connectors, the N type is a far superior mechanical fit.

I am not sure if your power statement is correct but even if it is, I seriously doubt any of us here will have so much power to Tx that a N type won't handle it (with bells on).
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Old 21-08-2013, 07:10   #69
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Re: Amazing Power of Good Antennas

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Originally Posted by s/v Jedi View Post
Like I wrote before, everything done right makes it better and when enough things have been done right you will get those amazing results.

Cables and connectors need to be done right but that doesn't mean the antenna isn't a factor. Like always there are good ones and not so good ones. People who say that it doesn't matter because as long as the VSWR is right the antenna performs optimal, have missed a clue. When you swap antenna with a dummyload you get good VSWR but not amazing results when you try to use the radio for communications.

About good antennas: there are several factors that make an antenna good, like it's design and it's durability. Some designs are easier to implement physically while others are more complicated. Yes, this affects price. A stainless whip is just that and it is durable. But if you want a vertical dipole design, you need a fiberglass tube to hold the elements and create a center feed to them. A fiberglass tube will quickly break down under UV exposure so it needs a quality finish. More things that affect price. The reason all that exists is because the whip is a ground plane design but where is the ground plane at the masthead? This design works very good on the roof of a (metal) car, but not as well at the masthead. So some designs are more suitable for application A while other designs make better sense for application B. Now it isn't as simple as buying that "sailboat masthead" antenna anymore, isn't it?

So, how good does the antenna need to be? What is good enough? The stainless whip is considered good enough, because it allows communication in GMDSS sea area A1, which is covered by the VHF radio. So there it is, the reason that these are used so often.

Of course, the GMDSS system dictates that as soon as you leave A1 and enter the A2 area, you switch to MF communications. Like for VHF, your MF radio needs to be equipped with DSC. Don't have that? I don't have that... well, you can switch to using your A3 area communications while in an A2 area and this would be your Inmarsat C terminal. Don't have that? I don't have that... hmmm... may be it is a good idea to have a VHF installation that allows communications well into A2 areas; it's your call

I did my first marine VHF installation in 1978. The boat was on Dutch inland waters. My radio check on 25W was answered by both Dutch and English coast stations. The Dutch station was 30nm away and the English station over 100nm away, meaning my signal went through the A1 areas of both Holland and England, plus the piece of A2 area in between those two. We then decided that we did not need MF, which was a dedicated Sailor radio in those days.

And this brings me to the most important factor: what do you intend to do with your radio? When you sail around the buoys in from of the clubhouse every weekend, you will have different requirements than when you're anchored in the San Blas Islands and want to talk to your buddy 30nm or more away. Not every boat needs to maximize VHF range, but for some it enables new possibilities.

About power: for VHF communications, power is very important. People who say it isn't and that a couple of dB loss here and there doesn't matter, are confusing this with SSB. On short wave radio, I can talk around the world on 5W and this must be what they think. I have the ability to Tx with 50W instead of the regular 25W and it makes a big difference. Not for links with friends 10nm away. But huge for longer than normal distances. The effort to bring as much power to the antenna as possible is worth it for your VHF radio.
I'm one of those people who say a couple dB loss doesn't matter, and I'm not confusing it with HF atmospheric propagation either. It's about weighing the benefits over the cost and effort required to gain a dB or two. Most would consider it ludicrous to suggest that Dockhead change out his RG213 for LDF7, because it's nearly 2 inches in diameter, but the insertion loss would be around 0.25db/100'. That's a couple of dB and then some over his current configuration, but it's $7-10 per foot, connectors are expensive, and the size is impractical. So, a compromise is made where the 3dB loss is acceptable as it meets many of his other requirements. I know this is an extreme example, but 3 dB loss between a transceiver and antenna is fine and is not going to be noticeably any worse performing than the same setup with 1.5-2dB loss to the ant. RG8 sized cables can present similar installation issues for some and added expense producing little bang for the buck.

Not to be nitpicking, but I thought marine VHF transmit power was limited to 25 watts at the transceiver?
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Old 21-08-2013, 08:04   #70
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Re: Amazing Power of Good Antennas

Hopefully, no one who minimizes the effect of a 3dB loss using poor connections and cheap coax will find himself in panic mode lamenting that decision because no one hears his mayday call.

Personally, I find it curious when some are so willing to sacrifice so much for a few extra dollars and/or effort. This discussion seems ludicrous given the consequences, unlikely as it may be. But the, this is the Internet...

I won't sacrifice one DBto make a ham radio contact from home. Doing it on a boat is ridiculous.
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Old 21-08-2013, 09:29   #71
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Re: Amazing Power of Good Antennas

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Not to be nitpicking, but I thought marine VHF transmit power was limited to 25 watts at the transceiver?
Exactly, and this is the reason that you should not use RG8x or RG58 cable (or any equivalent) but step up to RG213/LMR400 type. With a limit of 25W you can not afford to throw half away like you seem to think. With higher output power you can compensate for losses in transmissions, but you only have 25W plus it does not help for receiving far away stations (except coast guard who use very high antennas and high output power).

I can simply check the 3dB difference by switching from 25W to 50W and find that the difference for long range communications is enormous. I can do this with one of my HAM radios.

For VHF cruisers nets I can relay for boats underway that nobody else even hears in the noise. This means that my antenna and cable is much better than theirs and this should be reason enough for anybody to do this. Every boat can install LMR400 size cable and the extra cost is marginal for such a primary safety device
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Old 21-08-2013, 09:37   #72
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Re: Amazing Power of Good Antennas

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For VHF cruisers nets I can relay for boats underway that nobody else even hears in the noise. This means that my antenna and cable is much better than theirs and this should be reason enough for anybody to do this. Every boat can install LMR400 size cable and the extra cost is marginal for such a primary safety device
VHF is our primary communication tool on board, and its importance cannot be overemphasized. Good VHF comms can easily be a matter of life and death for someone.

I recently had to relay VHF comms for a helicopter rescue because the victim could not be heard, either by the coast guard nor by the helicopter. The coast guard ordered me to heave to and manage communications until the injured person was lifted away! Imagine if I had not been there!

This is not a system where you want to save $50 on an antenna, or $80 on cables, or for God's sake, $7 each on coax connectors.
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Old 21-08-2013, 10:21   #73
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Re: Amazing Power of Good Antennas

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I recently had to relay VHF comms for a helicopter rescue because the victim could not be heard, either by the coast guard nor by the helicopter. The coast guard ordered me to heave to and manage communications until the injured person was lifted away! Imagine if I had not been there!
Good Kit is good Kit end of story and one should do as much as one can afford. However there is a danger that this can end up , with angels and pins.

The vast majority of VHF installations suffer from poor connectors, thats my experience, either badly installed to begin with or allowed to deteriorate over time .

Using reasonable quality co-ax and PL crimped on connectors will provide an install that is proven to work well, yes its not the optimum, but its works well.

I have a good quality setup with crimped PL connectors, reasonable cox-ax and the connectors are maintained etc. I regularly reach long(er) distances then the neighbours, That may be because of their poor systems , rather then mine being brilliant.

Ive also done N series installs ( previous boat) and to tell you the truth Its very hard to quantify the results in voice clarity or distance reached. No point you reaching someone if they can talk back. ( youll always reach the CG radio station).

Great work Dockhead ( one day I will hit the 'i' by mistake, its right there beside the 'o')

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Old 21-08-2013, 10:25   #74
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Boys,

Unless you are doing the proper analysis you may be overlooking some pretty basic stuff. The "cheap" coax and antennas are good enough. And when we try to measure the "quality" of our systems by how far away we can hear and be heard it is possible to create a situation where safety is compromised. Expensive high gain antennas may reach further but they do that at the expense of elevation gain. So on a flat sea things seem great but when things get roiling comms suffer. In an emergency you want power radiated upward so you can talk to that aircraft overhead. Low gain antennas are better for that.

My message is not intended to denigrate best practice but just that we should beware of limited empirical data and keep all requirements in mind. It's often not possible to get the most important empirical data until TSHTF.
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Old 21-08-2013, 10:30   #75
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Re: Amazing Power of Good Antennas

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Boys,

Unless you are doing the proper analysis you may be overlooking some pretty basic stuff. The "cheap" coax and antennas are good enough. And when we try to measure the "quality" of our systems by how far away we can hear and be heard it is possible to create a situation where safety is compromised. Expensive high gain antennas may reach further but they do that at the expense of elevation gain. So on a flat sea things seem great but when things get roiling comms suffer. In an emergency you want power radiated upward so you can talk to that aircraft overhead. Low gain antennas are better for that.

My message is not intended to denigrate best practice but just that we should beware of limited empirical data and keep all requirements in mind. It's often not possible to get the most important empirical data until TSHTF.
nobody is talking about high gain antennas, just the insertion loss in connectors , co-ax and a good quality standard antenna.

Dave
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