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Old 21-05-2024, 04:19   #31
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Re: Choosing the the right VHF Coax

I have a stainless whip antenna that used to be sold by Vesper and itís bracket isolates the coax shield from the mount. Go figure.
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Old 21-05-2024, 08:28   #32
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Re: Choosing the the right VHF Coax

Quote:
Originally Posted by stormalong View Post
A counterpoise is needed on any antenna regardless of wavelength. It is the other half of the antenna.
Quote:
Originally Posted by Mike Burch View Post
The statement that any antenna requires a counterpoise should be read as meaning that any vertical antenna (other than a dipole) requires a counterpoise. And as the counterpoise is indeed the other half of the antenna, it should present a low impedance at the feed point.
Quote:
Originally Posted by Dockhead View Post
It is not true that all antennae need counterpoises. Dipoles (and other types of balanced antennae) don't need a counterpoise, and work well without grounding the antenna base or connecting the coax shield to the mast.
Quote:
Originally Posted by stormalong View Post
Half of a dipole is THE counterpoise. A "balanced" antenna is half radiator half counterpoise.
Quote:
Originally Posted by Mike Burch View Post
Are you trying to tell us that only half a dipole radiates?

That's a novel theory, but I don't think you'll find a lot of support for it.
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Originally Posted by stormalong View Post
No, I am telling you that each half of a balanced antenna pushes off of the other half. That is why it is BALANCED.

I am quite sure that I spent many a joyous evening in my misspent youth drinking beer with other radio geeks and contemplating such existential questions as whether one half of a dipole is actually a counterpoise, and if so whether it's the bottom half or the top half that is the counterpoise, and then (2 drink minimum) whether a theoretical dipole in empty space is half counterpoise, and then (3 drink minimum) how much microgravity it takes for the bottom half of the dipole to become a counterpoise.

I am too old and too sober for these questions. Could we please stop?
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Old 21-05-2024, 08:57   #33
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Re: Choosing the the right VHF Coax

Quote:
Originally Posted by stormalong View Post
Half of a dipole is THE counterpoise. A "balanced" antenna is half radiator half counterpoise.

Sorry, still not correct. Neither half of a dipole is a counterpoise. Both halves are radiators.


The statement "all antennae require a counterpoise" is simply not correct.
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Old 21-05-2024, 08:57   #34
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Re: Choosing the the right VHF Coax

Quote:
Originally Posted by Jammer View Post
I am quite sure that I spent many a joyous evening in my misspent youth drinking beer with other radio geeks and contemplating such existential questions as whether one half of a dipole is actually a counterpoise, and if so whether it's the bottom half or the top half that is the counterpoise, and then (2 drink minimum) whether a theoretical dipole in empty space is half counterpoise, and then (3 drink minimum) how much microgravity it takes for the bottom half of the dipole to become a counterpoise.

I am too old and too sober for these questions. Could we please stop?




OK.
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Cushion me soft . . . . rock me in billowy drowse,
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Old 21-05-2024, 09:21   #35
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Re: Choosing the the right VHF Coax

Dipoles don’t require a counterpoise. It’s as simple as that.

As to coax choices, particularly at VHF, the lower loss, the better. Discussions about gain is fundamentally wrong - gain of an antenna is a misnomer often used by people who conflate gain with directivity and radiation pattern.

Signal strength vs. coax type is an academic argument of little value. You can never know how weak your signal might be to the other station receiving your signal and every little bit might help under weak signal conditions especially in an emergency.
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Old 21-05-2024, 11:00   #36
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Re: Choosing the the right VHF Coax

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Dipoles don’t require a counterpoise. It’s as simple as that.
Can all of you who care deeply about this aspect of the topic start your own thread or something? You can also cover related matters like whether a counterpoise is sometimes a ground and even whether there really is such a thing as a ground. Or maybe whether there is more than one ground. Bonus question: is the frame of an aircraft a ground or a counterpoise? Why? 4 drink minimum for that one. 5 drink minimum for the same question on floatplanes. Does it change from a ground to a counterpoise when the aircraft takes off? Have fun. kthxbye

Quote:
Discussions about gain is fundamentally wrong - gain of an antenna is a misnomer often used by people who conflate gain with directivity and radiation pattern.
Maybe, just maybe, since every major antenna manufacturer and every major book on antennas all use the concept of "antenna gain" as a shorthand for the improvement in field strength in the preferred direction over some reference radiator, we could do that too.

Quote:
Signal strength vs. coax type is an academic argument of little value. You can never know how weak your signal might be to the other station receiving your signal and every little bit might help under weak signal conditions especially in an emergency.
I don't think that's true. I don't believe that "maximum effort" VHF installations on sailboats make sense. If the goal is to be received by other stations in an emergency at all costs we would, among other things, use more transmit power.

In the USA, the Rescue 21 system is used for emergency response. This system has excellent coverage with a design goal of being able to receive low-power transmitters 6 feet above the surface of the water. Coverage is well over 90% of coastal areas, great lakes, and inland rivers and is largely limited by terrain. Small improvements in boat-side radio system performance, such as by reducing feedline loss by 1-2 dB, do not translate into meaningful improvements in ability to communicate in an emergency. You might go from 90% to 90.5% coverage from a 2 dB improvement on an otherwise well-designed installation. For boats that need better coverage than what Rescue 21 provides, the best move is to spend the money for satellite communications of one kind or another.

When people with limited radio experience ask general questions about feedline in a sailboat forum, the right response is to emphasize: reliability, long life, and practicality for installation. Except in cases where weight aloft is paramount (racing), the best choice is an all-copper coaxial feedline with a solid dielectric with careful attention being given to: connector choice, connector installation, and bend radius. RG213 is a good choice for longer runs when it is feasible. RG58 is a good choice for shorter runs and for situations where RG213 is too bulky. The lightweight cables with foam dielectrics or aluminum conductors or both are not as reliable in the marine environment and should not be recommended. Exotic cables like RG393, RG214, and RG400 are expensive and unnecessary.

There are a handful of tragic stories of loss of life that could have been prevented had VHF communications with rescuers been able to be achieved, including the sequence of events that led to the deployment of Rescue 21. But in every one of these cases, the problems involved poorly installed and maintained boat-side and shore-side equipment that did not perform to its specifications, generally due to corrosion of antenna and feedline components, insufficient DC power to the transmitter, and failure of the feedline system due to moisture ingress.
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Old 21-05-2024, 11:27   #37
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Re: Choosing the the right VHF Coax

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Originally Posted by wholybee View Post
Note, LMR400 is aluminum and more sensitive to having the connectors installed correctly, and many recommend against it for that. If you opt for LMR400, you would be advised to have it professionally installed.
If you do use LMR400 make sure you get LMR-400-DB... This will help with water infiltration as its designed for direct burial. I do recommend not using any crimp connectors... A good correctly soldering in connector is the way to go. Get a professional if needed and he show up with crimpers, find a real professional.
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Old 21-05-2024, 12:12   #38
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Re: Choosing the the right VHF Coax

Quote:
Originally Posted by Jammer View Post
. . . I don't think that's true. I don't believe that "maximum effort" VHF installations on sailboats make sense. If the goal is to be received by other stations in an emergency at all costs we would, among other things, use more transmit power.

In the USA, the Rescue 21 system is used for emergency response. This system has excellent coverage with a design goal of being able to receive low-power transmitters 6 feet above the surface of the water. Coverage is well over 90% of coastal areas, great lakes, and inland rivers and is largely limited by terrain. Small improvements in boat-side radio system performance, such as by reducing feedline loss by 1-2 dB, do not translate into meaningful improvements in ability to communicate in an emergency. You might go from 90% to 90.5% coverage from a 2 dB improvement on an otherwise well-designed installation. For boats that need better coverage than what Rescue 21 provides, the best move is to spend the money for satellite communications of one kind or another.

When people with limited radio experience ask general questions about feedline in a sailboat forum, the right response is to emphasize: reliability, long life, and practicality for installation. Except in cases where weight aloft is paramount (racing), the best choice is an all-copper coaxial feedline with a solid dielectric with careful attention being given to: connector choice, connector installation, and bend radius. RG213 is a good choice for longer runs when it is feasible. RG58 is a good choice for shorter runs and for situations where RG213 is too bulky. The lightweight cables with foam dielectrics or aluminum conductors or both are not as reliable in the marine environment and should not be recommended. Exotic cables like RG393, RG214, and RG400 are expensive and unnecessary.

There are a handful of tragic stories of loss of life that could have been prevented had VHF communications with rescuers been able to be achieved, including the sequence of events that led to the deployment of Rescue 21. But in every one of these cases, the problems involved poorly installed and maintained boat-side and shore-side equipment that did not perform to its specifications, generally due to corrosion of antenna and feedline components, insufficient DC power to the transmitter, and failure of the feedline system due to moisture ingress.
Great advice here. And this: ". . . in every one of these cases, the problems involved poorly installed and maintained boat-side and shore-side equipment that did not perform to its specifications, generally due to corrosion of antenna and feedline components, insufficient DC power to the transmitter, and failure of the feedline system due to moisture ingress."


Might be a clue of what issues to concentrate on, in planning an installation.


We don't ever talk about radio power supplies, which can be a serious problem.
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Cushion me soft . . . . rock me in billowy drowse,
Dash me with amorous wet . . . . I can repay you."
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Old 21-05-2024, 13:36   #39
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Re: Choosing the the right VHF Coax

About the importance to get most of the power to the antenna: you have 25W and low power is 1W or 0.5W? In good conditions and a good installation, range will be practically the same.

It is in bad conditions that high power matters. Heeling in high winds, heavy rain, big waves etc. all reduce radio performance. Also, when a bad installation has trouble receiving a signal, a very loud signal has much more chance to get through.

I once assisted a boat during an emergency and they couldnít copy transmissions from our anchorage incl. mine. I then switched to a non marine radio configured for the channel and with 50W they could read me clearly and I could relay traffic to them.

If power wouldnít matter, radios would only have 1W.

So in this light, how much power would you rather loose in the antenna cable, 20% or 50%?
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Old 23-05-2024, 05:10   #40
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Re: Choosing the the right VHF Coax

Since I went down the path of ordering soldered connectors (and now have to get this done to get my boat in the water) I could use guidance on soldering. Iíve soldered electronics before but totally messed up my first attempt. It seems that my 40w iron isnít hot enough. I end of having to heat up the connector too much to get solder to flow. Do I need to be using a solder gun at 200w instead? I think that is likely the case? Any insight?
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Old 23-05-2024, 05:50   #41
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Re: Choosing the the right VHF Coax

Quote:
Originally Posted by s/v Jedi View Post
About the importance to get most of the power to the antenna: you have 25W and low power is 1W or 0.5W? In good conditions and a good installation, range will be practically the same.

It is in bad conditions that high power matters. Heeling in high winds, heavy rain, big waves etc. all reduce radio performance. Also, when a bad installation has trouble receiving a signal, a very loud signal has much more chance to get through.

I once assisted a boat during an emergency and they couldnít copy transmissions from our anchorage incl. mine. I then switched to a non marine radio configured for the channel and with 50W they could read me clearly and I could relay traffic to them.

If power wouldnít matter, radios would only have 1W.

So in this light, how much power would you rather loose in the antenna cable, 20% or 50%?
This is exactly it. A good install may not have much more usable range than a "decent" install, but it will be harder to encounter conditions that lead to it not working well enough.
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Old 23-05-2024, 06:12   #42
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Re: Choosing the the right VHF Coax

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Originally Posted by Timccarpenter View Post
Since I went down the path of ordering soldered connectors (and now have to get this done to get my boat in the water) I could use guidance on soldering. Iíve soldered electronics before but totally messed up my first attempt. It seems that my 40w iron isnít hot enough. I end of having to heat up the connector too much to get solder to flow. Do I need to be using a solder gun at 200w instead? I think that is likely the case? Any insight?
Soldering PL259 connectors is easy if you 1. Have an adequate soldering iron and 2. Use the proper technique. #1 is simple - a 40w iron is inadequate.

#2 takes some practice. There are a myriad YouTube videos from which you can find a description so not worth wasting space here reiterating. The braid soldering is often the more problematic as is proper waterproofing.
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Old 23-05-2024, 06:38   #43
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Re: Choosing the the right VHF Coax

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Ö.#1 is simple - a 40w iron is inadequate. .
Yep, I suspected that. Iím picking up a 260 watt. Seems the key on the braid is heating up fast, soldering and getting off so heat isnít building up throughout the connector. Is a 60/40 tin/lead solder with resin core ok to use?
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Old 23-05-2024, 07:01   #44
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Re: Choosing the the right VHF Coax

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Yep, I suspected that. Iím picking up a 260 watt. Seems the key on the braid is heating up fast, soldering and getting off so heat isnít building up throughout the connector. Is a 60/40 tin/lead solder with resin core ok to use?
Iíve used that solder for 60+ years on coax fittings. So far, so good
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Old 23-05-2024, 09:01   #45
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Re: Choosing the the right VHF Coax

Quote:
Originally Posted by s/v Jedi View Post
About the importance to get most of the power to the antenna: you have 25W and low power is 1W or 0.5W? In good conditions and a good installation, range will be practically the same.

It is in bad conditions that high power matters. Heeling in high winds, heavy rain, big waves etc. all reduce radio performance. Also, when a bad installation has trouble receiving a signal, a very loud signal has much more chance to get through.

I once assisted a boat during an emergency and they couldn’t copy transmissions from our anchorage incl. mine. I then switched to a non marine radio configured for the channel and with 50W they could read me clearly and I could relay traffic to them.

If power wouldn’t matter, radios would only have 1W.

So in this light, how much power would you rather loose in the antenna cable, 20% or 50%?
Well, sure.

My installation is overkill and 1 watt is enough for all routine comms.

I wouldn't buy a 1 watt radio set, though, because, as you say, you want the extra power for when you really need it.

I've never had to put out a distress call (thank God) but there was a case when I was relaying Mayday messages and Coast Guard responses to them, at the edge of my range, well over the horizon, and I was awfully glad to have the 25 watts then. I guess 50 would have been even better.

Of course you prefer to lose less rather than more in your feedline, BUT if you achieve this with foam insulation cabling which fails due to water intrusion or crushing or something, then you're screwed, and read the above post by someone about what the most common failures are.

So you'd certainly rather lose a bit more if it's necessary to have a robust coax feedline.
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Cushion me soft . . . . rock me in billowy drowse,
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