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Old 18-07-2013, 01:28   #16
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Re: Amazing Power of Good Antennas

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Originally Posted by fairbank56 View Post
Skywave propagation via VHF is possible via sporadic-E (aka, skip) but not routine and/or reliable.
Or meteor scatter, moonbounce, etc. I'm not going to beat up on someone because in a general non-technical discussion they call ducting "skip", but yes they are different phenomena, at least as skip is usually defined.

As for the antenna not being a factor, certainly antennae do go bad due to corrosion, etc. Perhaps the old antenna had a bad internal connection? Who can say??? Anyway, the new installation sounds very good.
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Old 18-07-2013, 03:04   #17
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"Of course it can't be the antenna, because my cheap GP is functionally equivalent to your expensive dipole"

"Of course it is ducting and thus an anomaly; the distances you make don't count”

Recognize the "what I have is best so your better results are a fluke" mentality again?

Since when are atmospheric conditions anomaly? We frakking use calculators on HF to get to use them. Without them we wouldn't make it 100nm out on HF and we'd all be still on MF using power to get what, 400nm may be!

Of course there is a huge difference using a high quality dipole vs a ground plane antenna. For starters, the dipole is not connected to ships ground, slashing noise figures which greatly improves SNR. Or does improving receive performance not count either?

Also, with two masts, I am able to compare antennas. The Galaxy is able to do those 100nm communications while at the same time, the GP antennas with their coils and functional equality, can not. Not my 2nd antenna and also not my neighbours who have their antennas even higher than my primary (ketch is lower antenna). So yes it is ducting of course but it is the antenna quality that permits to take advantage of it when conditions are so-so. Transmit might work for the others but is useless when they can't hear the other side.

Let's also not forget the radio. Surely an Icom 600 has a better receiver than a $25 Cobra. Which brings us to the cable where halving the loss or better makes all the difference again.

People need to realize that there is no magic bullet. You need to get it all correct using all top quality components for each and every part of the installation to get these excellent results. And when you get those results, it is not a fluke but often directly because of the extra money put into it. It does not matter for 5nm links, but it does for 50nm links which will be routine for the OP and not fluke as it will be for the boats with their rg8X, steel whip with coil and Cobra radio.

On AIS I am with Mark... I always run it from my cheap steel whip on my mizzen mast and I always see all targets at 50nm and many targets between 50 and 100nm. I ALWAYS see a couple targets at 100nm range. When your AIS has a 5nm range limit then there is something wrong. 5nm is also not good enough and reduces safety. IMHO of course.
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Old 18-07-2013, 03:50   #18
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Re: Amazing Power of Good Antennas

Nick keep your knickers un-twisted will you,

my initial comment in no way diminishes what an excellent installation Dockhead has done, ( I have a similar setup, using my favourite which is Banten ( collinear Dipole) antennas, and Standard Horizon radios, and yes I too, outperform my neighbours easily.

However the huge range increases DockHead is seeing must be benefitting from some ducting and conditions at the moment do suggest that there is ducting potential around coast of southern Uk and atlantic france, which I beleive is where he is.

Dave
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Old 18-07-2013, 05:28   #19
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Re: Amazing Power of Good Antennas

Thanks Nick, good post.

None of us are going to be using the information at 100nms for CPA but, as Nick says, the better the range we occasionaly pick up and regularly pick up contacts means our kit is working well.



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Old 18-07-2013, 07:05   #20
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Re: Amazing Power of Good Antennas

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Originally Posted by s/v Jedi View Post
On AIS I am with Mark... I always run it from my cheap steel whip on my mizzen mast and I always see all targets at 50nm and many targets between 50 and 100nm. I ALWAYS see a couple targets at 100nm range.
Really? Always??? You're not talking about base stations with tall towers, are you? I've got a good AIS installation, and I've seen some spectacular distances, but there are plenty of times when I've seen ships drop off the screen at 20 miles. In my experience reception beyond radio line of sight is a function of propagation conditions, and while a good antenna/ cable / receiver are necessary, these are hardly sufficient -- the propagation needs to be there as well.
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Old 18-07-2013, 08:38   #21
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Re: Amazing Power of Good Antennas

Quote:
Originally Posted by fairbank56
Skywave propagation via VHF is possible via sporadic-E
Quote:
Originally Posted by Paul Elliott View Post
Or meteor scatter, moonbounce, etc. I'm not going to beat up on someone because in a general non-technical discussion they call ducting "skip", but yes they are different phenomena, at least as skip is usually defined.
Iv'e always considered this a technical forum. Moonbounce is not a form of skywave propagation.

Eric
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Old 18-07-2013, 12:28   #22
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Quote:
Originally Posted by Paul Elliott View Post

Really? Always??? You're not talking about base stations with tall towers, are you? I've got a good AIS installation, and I've seen some spectacular distances, but there are plenty of times when I've seen ships drop off the screen at 20 miles. In my experience reception beyond radio line of sight is a function of propagation conditions, and while a good antenna/ cable / receiver are necessary, these are hardly sufficient -- the propagation needs to be there as well.
Yes, some drop off at 20 miles but with the gear continuously on, there is always 1 or 2 at the 100nm range. I'm sure most of their updates are missed, but some come through, even with all the local traffic of hundreds of targets at the Panama Canal.

They are always big ships with high antennas but still far beyond radio horizon.
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Old 14-08-2013, 10:58   #23
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Re: Amazing Power of Good Antennas

My experience is like Nick's -- I always see at least some AIS targets from more than 50 miles. I am seeing the whole stream of Channel traffic from behind the Isle of Wight and up the Hamble from my mooring. And that's from an antenna which is only 10 meters above the water. Maybe the signal is more or less depending on ducting and so forth, but I've never not seen the Channel traffic.

From that same antenna -- it's a Diamond amateur radio antenna, about 2 meters tall, and with its own radials (so not relying on any part of the boat for a ground plane), I am getting very strong communication with the Portsmouth 2 meter repeater despite the fact that I am only using 5 watts (my handheld, connected to the antenna through an adapter). That's the very edge of coverage, with much better signal than people using 50 watts from their cars from shorter distance.

I really had no idea that the antenna was so important. I knew it was important, but not like that.

I'm sure ducting played a role in my phenomenal contacts during July, but even now, without the super high pressure, I hear a constant stream of chatter from France 70 miles away, and not just the French coast guard with their big antennas. I have had to start using the attenuator (DX/LO button) to get rid of the French signals, and for most purposes now I am turning my transmitter down to 1 watt.

Thanks again to Nick for the tip about using a dipole antenna. I am guessing that this makes an enormous difference, as your mast truck is just not working as an efficient ground plane.

The radio is much more pleasant to use with a good antenna system. Received signals are much clearer, besides being much stronger.
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Old 14-08-2013, 19:50   #24
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Thank DockHead posts like yours might help to convince others because not many believe it... keep insisting 10nm is good and I'm mad which is half true but they got the wrong half heheh

Besides the antenna, the cable also plays it's part in the overall performance. It was only a short while ago that I saw somebody post that rg8x is fine because it "only" has 2dB extra attenuation or so. I don't think people understand the logarithmic scale where a 3dB loss means half the signal is gone.

Insertion loss of connectors, crimp and solder connections are important too. It's not easy to get right but when it is, it's a thing of beauty VHF transmitter- and antenna design is what got me to study electronics.
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Old 14-08-2013, 20:07   #25
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Re: Amazing Power of Good Antennas

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
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Old 14-08-2013, 21:17   #26
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Re: Amazing Power of Good Antennas

Good antennas make things so good. Good cable is good too to get as much power to the antenna instead of lost through it because of cheep stuff. I've seen radios that didn't look too great but worked nicely with a good antenna. At the same time, you can have state of the art gear but not communicate effectively because of a bad antenna.

I got into ham radio 18 yrs ago in high school and the interest of antennas and communications got me a good career with the military working with radios. I joke with people saying I have a full time hobby.
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Old 15-08-2013, 06:09   #27
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Re: Amazing Power of Good Antennas

I've been wanting to upgrade our VHF antenna, which is currently on our cabintop and not very effective. Trouble is, our mast is in a tabernacle and we frequently fold it down for trailering or to pass under bridges. I could mount a Galaxy at the masthead and run RG213 down inside the hollow mast . . . but I would need a weatherproof quick-disconnect at the base. Does such a thing exist?
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Old 15-08-2013, 06:34   #28
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Re: Amazing Power of Good Antennas

try bulgin Designers & manufacturers of Waterproof Connectors, mains connectors, fuseholders, vandal resistant switches & more., they do IP68 BNC.

and
Waterproof RF Connectors, Custom Connectors: Intelliconnect USA
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Old 15-08-2013, 07:16   #29
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Re: Amazing Power of Good Antennas

Quote:
Originally Posted by Dockhead View Post
Thanks again to Nick for the tip about using a dipole antenna. I am guessing that this makes an enormous difference, as your mast truck is just not working as an efficient ground plane.
I am betting that the majority of your improved performance came from the new higher quality cable and connectors you installed and not the antenna.

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Old 15-08-2013, 07:30   #30
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Re: Amazing Power of Good Antennas

The efficacy of any antenna is measured on it's ability to radiate efficiently.

Any antenna can be made to radiate efficiently.

Therefore, any antenna can be "good"
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