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Old 18-08-2013, 21:43   #46
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Re: Amazing Power of Good Antennas

Quote:
Originally Posted by btrayfors View Post
I cannot agree that a 50% loss of radiated power is insignificant....at VHF or HF or MF or even UHF frequencies.

Bill
I agree with this. It is important to choose the right cable for you situation. A cable may be ok for HF but have horrible characteristics when it comes to VHF or higher. For HF, propagation could be favorable where 50% loss could be unnoticed by the receiver but why chance it? It's good to get the best quality and lowest loss cable you can afford to make sure as much power is getting to the antenna to maintain as reliable communications as possible. It's especially important the higher in frequency you go. It could be your life or the life of others on the line
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Old 19-08-2013, 06:52   #47
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Re: Amazing Power of Good Antennas

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Originally Posted by El Rubio View Post
There's quite a bit of hair splitting regarding antenna line/cable losses and their actual affect on real life operating. For example, I often recommend LMR240 over LMR400 or RG213 in most installations because the difference in loss is negligible and almost totally imperceivable. One poster here said he ran "fat" RG213. 213 is great for VHF, but "fat" is the key term here. If he pulled 100', then he saved 0.2dB of loss over 1/4 inch LMR240. The 240 would probably have been significantly easier to route to the radio.

N connectors were designed to be weatherproof, but not very well. If it's exposed, it WILL get wet. You never see commercial operators use N connectors that aren't sealed. If you think sealing with various tapes "traps water", you're not doing it right and possibly unnecessarily spending more money for water proof connectors. At VHF frequencies, the insertion loss of N type connectors is so miniscule and similar to PL259's, that it isn't worth noting. N's are typically made better, but even the cheap PL-259's are effective and low loss when installed properly. The advantage of N's appears at UHF freq's.

My point is, that the average non-engineer reading this thread and planning a VHF installation might spend $$$ & extra work to save fractions of losses, that are insignificant in real world applications. I'm not denying that less loss=better signal, but in situations where the difference is <2 or 3dB, it may not be worth the effort and expense for minimal performance improvement.
In my humble opinion -- very humble, since I'm relatively new at this -- this is bad advice.

First of all, the cable. LMR240 has foam dielectric and like LMR400 is not really recommended for outdoor, much less marine duty. If water gets into it, then it's all over. Most cruisers don't have their masts out more than once every ten years or more, and replacing coax for VHF could cost thousands in labor. Here really marine grade tinned-copper shield RG213 (or at least, RG8X) is doing it the right way. I know people get away with using foam core coax, but why would you even want to risk it, considering how hard it is to replace your coax if it goes wrong?

I had no big trouble pulling the "fat" RG213 up my mast and back to my nav table. With the mast down, of course! Different masts with different conduits may give different results. Of course, I could not have done it with the mast up, but I couldn't have done thin cable, either.

Here is the cost of the question in dB for my installation:

100 feet

RG213/U 2.5dB
LMR240 3.1dB
RG8X 4.6dB

So foam-dielectric LMR240 would be a loss of 0.6dB; proper marine rated RG8X 2.1dB.

Now connectors.

PL259/SO239 a/k/a "UHF" connectors are a prehistoric technology, from before WWII. It is true you can hardly get rid of them altogether, since most radios use them for their rear panel connections, but you are not required to multiply the number of them in your antenna system. The problems with UHF connectors are many, and cannot be expressed just in dB of attenuation. Here is a good summary: 'UHF' Connector Test Results. Note that the SWR of a set of UHF connectors is nearly 2.0 for the el-cheapo ones. That's just the connector, not the whole antenna system!! Even the good ones are over 1.5. Type "N" connectors are basically 1.0. This is awful!

The insertion loss of el-cheapo UHF connectors is about 1dB each. This is not "miniscule"! So this: "even the cheap PL-259's are effective and low loss when installed properly" is really bad advice. Good ones like the Amphenol ones I use (for back panel connections) are more like 0.5dB. Type "N" connectors, on the other hand, are quite close to 0 at VHF frequences -- say 0.1dB at most. Interestingly, BNC, SMA, and TNC connectors are also far superior to UHF connectors in terms of insertion loss (and everything else).

So if I had wired my antenna back up the way it was, with two pairs of UHF connectors rather than one pair of Type "N", I would lose 2dB (or at least 1dB, using good ones) compared to 0.1dB. A difference? It all adds up. If I had used easy to install but marine-grade RG8X and el-cheapo UHF connectors, and if I had used a pair of connectors at my mast base as originally installed, I would have a total loss of 4.6 + 2 = 6.6, not counting the connector at the rear panel of the radio. That means that less than 20% of the power which makes it past the rear panel connectors of my radio would make it to the antenna. If we presume that Icom used a "good" SO239 on the back of my M604, then the total loss is 7.6dB, and the antenna will be getting only 4.3 watts out of the 25 watts put out by the radio. 4.3 watts! That's less than a handheld!

The way I did it, I lose 2.5dB + 0.1dB =2.6dB. That's it. Plus the rear panel connector, it's 3.1dB. That means 55% of the power gets through from the back panel to the antenna. That means that even with the extra 0.5dB of loss from the rear panel connectors, 12.2 watts get to the antenna. That's more than 2.8 times as much, nearly half of the radio's full output.

Of course the thin cable variant would be much better with good quality UHF connectors rather than el-cheapo ones and the difference correspondingly less. But we're still talking about 6.1dB of total attenuation. That would still leave me with only 6.1 watts of power getting to the antenna, hardly more than my 6 watt SH handheld puts out.


Is it worth pulling fat cable and using Type "N" connectors to get 2.8x as much power to the antenna? Everyone will have to decide for himself, of course, but I can't imagine how it wouldn't be worth it for anyone. The difference in cost and trouble to do it right, is simply not that great.
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Old 19-08-2013, 08:19   #48
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Re: Amazing Power of Good Antennas

While there's much to be said for Type N connectors, the venerable PL-259's are perfectly adequate for VHF as well as MF/HF antenna connections.

The figures cited above and in the referenced "research" article are WAY WAY overblown. Many other published tests have documented insertion losses far lower.

Bottom line: a good quality PL-259, properly terminated, has an insertion loss of less than 0.2db. Add up the 4-6 PL-259/SO-239 connections in a typical VHF antenna system and you come up with plus or minus 1db total insertion loss, plus coax losses.

I agree that in a marine installation RG-213 or my favorite RG-214 are preferable to LMR-400 and such products, due to possible water intrusion. I know of one very experienced sailor/ham who prefers LMR-400, but he's a meticulous worker who is able to ensure the watertight integrity of connections.

Bill
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Old 19-08-2013, 09:09   #49
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Re: Amazing Power of Good Antennas

"The insertion loss of el-cheapo UHF connectors is about 1dB each. This is not "miniscule"! So this: "even the cheap PL-259's are effective and low loss when installed properly" is really bad advice. Good ones like the Amphenol ones I use (for back panel connections) are more like 0.5dB. Type "N" connectors, on the other hand, are quite close to 0 at VHF frequences -- say 0.1dB at most"

Good point, Dockhead. There is something to be said about simply matching cable types and fittings and following standard practices. A couple of years ago I spoke with someone at Amphenol about fittings and cables for a cellular phone antenna. In the US, they tend to use thin cable and FME connectors, sometimes SMA. And of course you can adapt and couple but that's just 'more stuff'. The engineer who took my question patiently explained that it wasn't obvious, but there was an "impedance bump" every time the physical diameter of the cable and fitting changed, an insertion loss for every fitting, in short, selecting and matching the fittings to the cable type as much as to the frequency, makes a difference in the signal strength and quality in any installation. And simply reading specs (for loss or anything else) may not provide the whole picture, or explain why a particular standard is, after all, standard.

With VHF cables there's something else to consider. When they go up the mast, they go vertical. One hopes. If a cable with foam dielectric goes vertical, it will be pulled by gravity, it will stretch, the dielectric will get thinner and crush down on itself and guess what? The impedance changes. In order to avoid this, the cable needs to be properly (frequently) tied off to a support, but if you just clamp it tight, again, the dielectric gets crushed and the impedance changes. Catch-22, if the cable is not lovingly installed, in the real world an "inferior" solid dielectric material will be in better shape than foam after just a couple of months, and performing better for the rest of the years.
But again, just reading cable specs won't tell you that.
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Old 19-08-2013, 10:20   #50
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Originally Posted by btrayfors View Post

Well, then, we do not agree.

While I certainly agree that fretting over insertion loss of connectors (essentially negligible if installed correctly) is silly, I cannot agree that a 50% loss of radiated power is insignificant....at VHF or HF or MF or even UHF frequencies.

At the fringes of reception area, it may make the difference between capture and no-capture for VHF/FM, or between intelligible and non-intelligible voice with the squelch open....as in an emergency situation.

Small point, perhaps, but I don't think it's a good idea to give up 1/2 of whatever power output you have available because of an inferior installation.

Sorry, but more than 50 years of hamming and many years of boating and professional radio installation, testing, and certification make me just a bit cautious about throwing power away.

Bill
Inferior to what degree? In an earlier post, I compared LMR240 to RG213 and made the case that 240, being smaller, was easier to route through tight areas like a mast, headliner, etc. It's also cheaper and rated for higher power, not that power is an issue really. The difference in loss would be -0.2dB and an easily acceptable compromise. Would you suggest I run LMR600 instead because I could gain another 2dB? I doubt you would for the same reasons I suggested LMR240 over RG213, but it would still be superior performance. I think you're focusing on "3dB" which I still contend is minimal, not undetectable, but minimal.
On your ham transceiver, have you ever used attenuation to cut noise and bring out a low signal on HF, by reducing RF gain, or switching in attenuation. 3dB does almost nothing to the signal or noise, but 6dB or more becomes effective. I'm trying to illustrate the minimal effect 3dB has on rx'd signal.

I'm all for getting the most out of a system, but not at any cost.
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Old 19-08-2013, 10:30   #51
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Re: Amazing Power of Good Antennas

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Originally Posted by btrayfors View Post
While there's much to be said for Type N connectors, the venerable PL-259's are perfectly adequate for VHF as well as MF/HF antenna connections.

The figures cited above and in the referenced "research" article are WAY WAY overblown. Many other published tests have documented insertion losses far lower.

Bottom line: a good quality PL-259, properly terminated, has an insertion loss of less than 0.2db. Add up the 4-6 PL-259/SO-239 connections in a typical VHF antenna system and you come up with plus or minus 1db total insertion loss, plus coax losses.

I agree that in a marine installation RG-213 or my favorite RG-214 are preferable to LMR-400 and such products, due to possible water intrusion. I know of one very experienced sailor/ham who prefers LMR-400, but he's a meticulous worker who is able to ensure the watertight integrity of connections.

Bill
I did quite a bit of reading on connectors when I was designing my installation, and never read anything good about UHF connectors, which are by general agreement the worst coax connectors made. Even if the insertion loss is only 0.2dB (and more of the tests I've read show more than that), why would you put up with that if you can have 0.1dB or 0.01dB, plus at least an attempt at weatherproofness, plus 1.0SWR, plus other good qualities, for just a few dollars more per connector? Is it pure inertia on the part of sailors who at some point mastered soldering PL259's and just don't want to buy a crimper or deal with a different type of connector?

Speaking of soldering -- my own problems soldering have probably skewed my views, but I've kind of come around to the idea that crimping is better. I saw a lot of photos of cut up PL259's where the dielectric was melted, and read a lot about how hard it is to get a good solder joint and yet avoid damaging the dielectric, and after that I bought a couple of good crimpers.

Why is RG214 your favorite?? Interesting -- do tell. I considered it for my installation but couldn't figure out any real advantage. What does the silver plating do? In the end I was worried that it would be more susceptible to corrosion than the regular tinned RG213.
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Old 19-08-2013, 10:59   #52
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Re: Amazing Power of Good Antennas

Doesn't anyone else use coaxseal and self-amalgamating tape? Pretty easy to make a waterproof connection with it.

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Old 19-08-2013, 11:23   #53
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Re: Amazing Power of Good Antennas

Dockhead, Ive never seen tinned RG213/U , where did you get it.


realistically unless we measure looses between too different cable/connector strategies this argument is a theoretical one

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Old 19-08-2013, 12:31   #54
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Originally Posted by Dockhead

In my humble opinion -- very humble, since I'm relatively new at this -- this is bad advice.

First of all, the cable. LMR240 has foam dielectric and like LMR400 is not really recommended for outdoor, much less marine duty. If water gets into it, then it's all over. Most cruisers don't have their masts out more than once every ten years or more, and replacing coax for VHF could cost thousands in labor. Here really marine grade tinned-copper shield RG213 (or at least, RG8X) is doing it the right way. I know people get away with using foam core coax, but why would you even want to risk it, considering how hard it is to replace your coax if it goes wrong?

I had no big trouble pulling the "fat" RG213 up my mast and back to my nav table. With the mast down, of course! Different masts with different conduits may give different results. Of course, I could not have done it with the mast up, but I couldn't have done thin cable, either.

Here is the cost of the question in dB for my installation:

100 feet

RG213/U 2.5dB
LMR240 3.1dB
RG8X 4.6dB

So foam-dielectric LMR240 would be a loss of 0.6dB; proper marine rated RG8X 2.1dB.

Now connectors.

PL259/SO239 a/k/a "UHF" connectors are a prehistoric technology, from before WWII. It is true you can hardly get rid of them altogether, since most radios use them for their rear panel connections, but you are not required to multiply the number of them in your antenna system. The problems with UHF connectors are many, and cannot be expressed just in dB of attenuation. Here is a good summary: 'UHF' Connector Test Results. Note that the SWR of a set of UHF connectors is nearly 2.0 for the el-cheapo ones. That's just the connector, not the whole antenna system!! Even the good ones are over 1.5. Type "N" connectors are basically 1.0. This is awful!

The insertion loss of el-cheapo UHF connectors is about 1dB each. This is not "miniscule"! So this: "even the cheap PL-259's are effective and low loss when installed properly" is really bad advice. Good ones like the Amphenol ones I use (for back panel connections) are more like 0.5dB. Type "N" connectors, on the other hand, are quite close to 0 at VHF frequences -- say 0.1dB at most. Interestingly, BNC, SMA, and TNC connectors are also far superior to UHF connectors in terms of insertion loss (and everything else).

So if I had wired my antenna back up the way it was, with two pairs of UHF connectors rather than one pair of Type "N", I would lose 2dB (or at least 1dB, using good ones) compared to 0.1dB. A difference? It all adds up. If I had used easy to install but marine-grade RG8X and el-cheapo UHF connectors, and if I had used a pair of connectors at my mast base as originally installed, I would have a total loss of 4.6 + 2 = 6.6, not counting the connector at the rear panel of the radio. That means that less than 20% of the power which makes it past the rear panel connectors of my radio would make it to the antenna. If we presume that Icom used a "good" SO239 on the back of my M604, then the total loss is 7.6dB, and the antenna will be getting only 4.3 watts out of the 25 watts put out by the radio. 4.3 watts! That's less than a handheld!

The way I did it, I lose 2.5dB + 0.1dB =2.6dB. That's it. Plus the rear panel connector, it's 3.1dB. That means 55% of the power gets through from the back panel to the antenna. That means that even with the extra 0.5dB of loss from the rear panel connectors, 12.2 watts get to the antenna. That's more than 2.8 times as much, nearly half of the radio's full output.

Of course the thin cable variant would be much better with good quality UHF connectors rather than el-cheapo ones and the difference correspondingly less. But we're still talking about 6.1dB of total attenuation. That would still leave me with only 6.1 watts of power getting to the antenna, hardly more than my 6 watt SH handheld puts out.


Is it worth pulling fat cable and using Type "N" connectors to get 2.8x as much power to the antenna? Everyone will have to decide for himself, of course, but I can't imagine how it wouldn't be worth it for anyone. The difference in cost and trouble to do it right, is simply not that great. to get 2.8x as much power to the antenna? Everyone will have to decide for himself, of course, but I can't imagine how it wouldn't be worth it for anyone. The difference in cost and trouble to do it right, is simply not that great.
Times Microwave, rates almost all LMR series cable for outdoor use and standard LMR is rated 20 years for UV. If water gets into any cable, it will most likely be all over by the time it's noticed. Braided shield will wick moisture too. It's not always necessary to pull a mast to replace coax and is certainly easier with smaller diameter cable. I have never seen LMR 240 or 400 stretched and elongated. I don't think that's possible with just the 50 feet or so inside of a mast.


My comparison was not a knock on your installation, but the size of the cable. The fact that you used the term "fat" fit in with my point. I hope I didn't offend you, as it's obvious you put a lot of thought into your setup and made good choices.

Your reference on connectors is suspect. The reason I say this is primarily the SWR measurements where the connectors are listed with high vswr. I have made many, many measurements with properly calibrated test gear and have never, ever seen those kinds of results. One test I recall, I had a length of RG214, maybe 200'. I didn't want to uncoil and measure it directly, so I terminated each end with PL259's and measured insertion loss to get a closer estimate. Before I could make that accurately, I had to be sure the connectors were installed properly. I did a return loss sweep from 100 to 500mhz with an N to SO239 adapter on each end and a lab-grade 50ohm load on the end. My RL measurements were nowhere near the "UHF 3" measurements listed by the author in your link. He doesn't describe his test setup much either. There's no doubt N connectors are superior, but not very much at 150 MHz. Pl259's are common and relatively cheap. They are fine for VHF applications.

Your calculated loss examples appear to be using the UHF 3 measurement (dark blue in the insertion loss table) which is actually a PL259 and a 2" SO239 barrel. The N connector listed is said to be two SMA/N adapters with a barrel between. When calculating connector loss, you should be using UHF 1 which is a PL259 and around 0.2dB insertion loss. It's hard to read because most of the connectors are right on top of each other there, but definitely below 0.25 and tracking slightly above the n connector through 300 MHz.

Finally, your calculations on your setup are right at 3dB loss to the antenna, which is typical in many cases and totally acceptable. Some of the points made in this thread would suggest otherwise. If you were to change to LMR400, it wouldn't be worth the trouble for the little gain at this point.
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Old 20-08-2013, 02:26   #55
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Re: Amazing Power of Good Antennas

Quote:
Originally Posted by El Rubio View Post
Times Microwave, rates almost all LMR series cable for outdoor use and standard LMR is rated 20 years for UV. If water gets into any cable, it will most likely be all over by the time it's noticed. Braided shield will wick moisture too. It's not always necessary to pull a mast to replace coax and is certainly easier with smaller diameter cable. I have never seen LMR 240 or 400 stretched and elongated. I don't think that's possible with just the 50 feet or so inside of a mast.


My comparison was not a knock on your installation, but the size of the cable. The fact that you used the term "fat" fit in with my point. I hope I didn't offend you, as it's obvious you put a lot of thought into your setup and made good choices.

Your reference on connectors is suspect. The reason I say this is primarily the SWR measurements where the connectors are listed with high vswr. I have made many, many measurements with properly calibrated test gear and have never, ever seen those kinds of results. One test I recall, I had a length of RG214, maybe 200'. I didn't want to uncoil and measure it directly, so I terminated each end with PL259's and measured insertion loss to get a closer estimate. Before I could make that accurately, I had to be sure the connectors were installed properly. I did a return loss sweep from 100 to 500mhz with an N to SO239 adapter on each end and a lab-grade 50ohm load on the end. My RL measurements were nowhere near the "UHF 3" measurements listed by the author in your link. He doesn't describe his test setup much either. There's no doubt N connectors are superior, but not very much at 150 MHz. Pl259's are common and relatively cheap. They are fine for VHF applications.

Your calculated loss examples appear to be using the UHF 3 measurement (dark blue in the insertion loss table) which is actually a PL259 and a 2" SO239 barrel. The N connector listed is said to be two SMA/N adapters with a barrel between. When calculating connector loss, you should be using UHF 1 which is a PL259 and around 0.2dB insertion loss. It's hard to read because most of the connectors are right on top of each other there, but definitely below 0.25 and tracking slightly above the n connector through 300 MHz.

Finally, your calculations on your setup are right at 3dB loss to the antenna, which is typical in many cases and totally acceptable. Some of the points made in this thread would suggest otherwise. If you were to change to LMR400, it wouldn't be worth the trouble for the little gain at this point.
How could anyone possibly be offended by your extremely interesting and thoughful posts? uzzled:

No, of course I am grateful for this very useful knowledge dump. You are obviously much more knowledgeable and experienced than I am, so I am getting more out of this than you are.

What I take away from the whole discussion so far is that:

1. Wise men (and tests) disagree about whether UHF connectors are (a) horrible at VHF frequencies; or (b) merely somewhat worse, than modern connectors. Your arguments, and Bill Trayfor's, add considerable weight to variant (b).

2. Therefore, it's probably not worth ripping out a well-installed setup using UHF connectors.

3. If you learned to solder PL259's on Guglielmo Marconi's knee, you're probably going to keep doing so even if there are better variants -- natural human conservatism.

4. Since I got to know PL259's and Type "N" connectors simultaneously, I don't have any special attachment to PL259's. So since no one has ever disputed that Type "N" connectors are at least somewhat better in every way than UHF connectors (or dramatically better, depending on who you believe), I will continue to use them wherever possible. Especially since I now own a genuine Amphenol Type "N" connector crimp tool

5. Wise men disagree about whether foam core coax is acceptable or not for marine use. I will keep absorbing information with an open mind.
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Old 20-08-2013, 02:37   #56
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Re: Amazing Power of Good Antennas

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Originally Posted by goboatingnow View Post
Dockhead, Ive never seen tinned RG213/U , where did you get it.

Dave
Widely available, see for example:

Ancor Coax Cable Rg-213 (Tinned) Binnacle.com

Coaxial Cable Rg213 Tinned 100' Spool

In the UK, I use Salty John:

Salty John: Metz Manta- 6 Marine VHF Antenna Accessories and other fine boat products.

I believe Nevada Radio also sell it. DAB Radios, Internet Radios, Amateur Radio, Scanners and CB - Nevada Radio

The most common tinned RG213 is made by Ancor.
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Old 20-08-2013, 05:04   #57
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Re: Amazing Power of Good Antennas

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the antenna really does make a big difference. It is a dipole made of silver-plated elements. Being a dipole, it doesn't need any ground plane at all. .
What's the specific model number?

I looked up 'galaxy' but they have all sorts of different models under that brand name.
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Old 20-08-2013, 05:45   #58
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Re: Amazing Power of Good Antennas

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What's the specific model number?

I looked up 'galaxy' but they have all sorts of different models under that brand name.
Mine is a Galaxy XP, specifically, the Galaxy 5400-XP:

Shakespeare Galaxy XP High Performance Antennas
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Old 20-08-2013, 06:04   #59
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Re: Amazing Power of Good Antennas

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Originally Posted by Dockhead View Post
In my humble opinion -- very humble, since I'm relatively new at this -- this is bad advice.

First of all, the cable. LMR240 has foam dielectric and like LMR400 is not really recommended for outdoor, much less marine duty. If water gets into it, then it's all over. ..........
Quote:
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...........

5. Wise men disagree about whether foam core coax is acceptable or not for marine use. I will keep absorbing information with an open mind.
FWIW, we use a fair bit of a waterproof variant of LMR400 onboard off-shore oil/gas platforms and FPSOs.

As with all things, correctly installed, the foam core isn't an issue.
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Old 20-08-2013, 06:12   #60
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Re: Amazing Power of Good Antennas

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Originally Posted by MarkJ View Post
With some AIS thats connected to a PC you get a program called ProAIS2 that has a built in VSWR meter. The closer to 1:1 the reading the better. Mine on my top of the mast antenna gives 1:1. Thats a bit crazy as thats 'perfect'. My aft rail gives 1:1.5.
When I first installed it on my mast top using a splitter and old coax I was getting 1:2.6
Probably not so crazy because your antenna probably isn't perfect because your VSWR measuring technique isn't perfect ().

A long run of coax between your VSWR meter and the antenna will mask the real VSWR of your antenna. To be truly accurate, you will need to insert the VSWR meter right at the antenna itself. A run of coax up the mast will certainly affect the readings. In fact, if you make the coax long enough, you can leave the antenna disconnected and still get a reasonable VSWR.
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