[70521]
Well-Known Member
We best not discuss it
lets just say I have the same kit as RichardS found fitting it a lot easier than climbing a mast to fit another antenna.
Flipping stupid AIS aerial - what am I doing wrong?
- Thread starter Rivers & creeks
- Start date
lets just say I have the same kit as RichardS found fitting it a lot easier than climbing a mast to fit another antenna.
RichardS
N/A
I'm intrigued. Can the splitter really affect the signal directionality? If so, how?
Richard
Momac
Well-Known Member
I have a motorboat. A new antenna (was less cost than a splitter) from.............
http://www.saltyjohn.co.uk/product/metz-ais-antenna/
The antenna cable supplied to the length I needed with fittings from..............
http://www.kcb.co.uk/shop2/
My antenna is probably 3m off the water to the base of the antenna. Not sure what range I get but it is sufficient .
On a yacht with the VHF antenna already on the mast a splitter makes good sense.
http://www.saltyjohn.co.uk/product/metz-ais-antenna/
The antenna cable supplied to the length I needed with fittings from..............
http://www.kcb.co.uk/shop2/
My antenna is probably 3m off the water to the base of the antenna. Not sure what range I get but it is sufficient .
On a yacht with the VHF antenna already on the mast a splitter makes good sense.
PaulRainbow
Well-Known Member
If it isn't soldered, how is it fixed ? If it's just pushed through, it's unlikely to work properly.
Bru
Well-Known Member
True if it's a standard PL259! At the masthead, I use solderless PL259s though, unless the mast is down, 'cos getting a sodering iron to work 30 feet off the deck is a right PITA!
JumbleDuck
Well-Known Member
I have a gas-powered one.
Bru
Well-Known Member
So have I, a bloody big one! (And two small ones). In any sort of breeze getting enough heat into a PL259 to do a proper job of soldering the centre core to the pin whilst dangling in a harness 30 foot or more off the deck is, as I said, a right PITA. I'd kiss the bloke who invented the solderless PL259!
Habebty
Well-Known Member
Sorry to hijack CWs useful thread but I too have an AIS issue....
Vesper XB8000 (the wifi one) fed through a Vesper splitter using a new patch lead and the original masthead vhf coax. Vesper supply an app which shows system status and a relative vswr meter. The app says the system is fully operational with a goodish vswr reading, yet I never show on Marinetraffic, only briefly on Vessel finder, and only at short range - 1 mile or so on friends boats receivers. I only receive from up to 2 or 3 miles away. VHF radio works fine yet very poor output and receive on the AIS.
With my limited knowledge and reading this thread it would seem I need to replace my Hawk aerial with something tuned for both Radio VHF and AIS VHF??
So Bru, give me a call/pm next time you are near Ipswich and there could be some beer tokens in it for you
and make me feel better at spending lots of hard earned on a small plastic box.
Vesper XB8000 (the wifi one) fed through a Vesper splitter using a new patch lead and the original masthead vhf coax. Vesper supply an app which shows system status and a relative vswr meter. The app says the system is fully operational with a goodish vswr reading, yet I never show on Marinetraffic, only briefly on Vessel finder, and only at short range - 1 mile or so on friends boats receivers. I only receive from up to 2 or 3 miles away. VHF radio works fine yet very poor output and receive on the AIS.
With my limited knowledge and reading this thread it would seem I need to replace my Hawk aerial with something tuned for both Radio VHF and AIS VHF??
So Bru, give me a call/pm next time you are near Ipswich and there could be some beer tokens in it for you
and make me feel better at spending lots of hard earned on a small plastic box.
Daverw
Well-Known Member
I'm not sure how an app can measure vswr, from what you describe it does seem like the antenna is not tuned, has broken or bad connection.
RichardS
N/A
Sorry to hijack CWs useful thread but I too have an AIS issue....
Vesper XB8000 (the wifi one) fed through a Vesper splitter using a new patch lead and the original masthead vhf coax. Vesper supply an app which shows system status and a relative vswr meter. The app says the system is fully operational with a goodish vswr reading, yet I never show on Marinetraffic, only briefly on Vessel finder, and only at short range - 1 mile or so on friends boats receivers. I only receive from up to 2 or 3 miles away. VHF radio works fine yet very poor output and receive on the AIS.
With my limited knowledge and reading this thread it would seem I need to replace my Hawk aerial with something tuned for both Radio VHF and AIS VHF??
So Bru, give me a call/pm next time you are near Ipswich and there could be some beer tokens in it for you
I also have an XB8000 with the SP160 active splitter connected into a standard VHF masthead antenna. My VSWR shows the 1:1 light at the far left hand end of the scale. Is yours on the good scale or down as far as the red scale at 3:1? I wonder if you just have a poor connection somewhere? Have you checked the accessible cables and connectors with an ohm-meter?
Richard
Habebty
Well-Known Member
Down at the 1.2 end, i'm guessing as low a resistance as possible is desirable on the ohm meter, or am I checking for a short between the core and the braid?. Masthead coax is about 14 years old. I'll do the rounds again with the connections.
Bru
Well-Known Member
Many AIS transceivers have a built in VSWR meter, the app is simply relaying the info from the transceiver
My suspicions would be with the splitter but the antenna and cabling want checking thoroughly (but a good VSWR reading tends to suggest they're probably OK)
Not sure when I'll be up Ipswich next Pete, maybe in September but we haven't made any plans for our autumn cruise. I can drive up but the travel will eat up beer tokens :/
RichardS
N/A
I was thinking about checking for a slight short between the core and the braid but I guess that also checking the resistance of the core and braid at either end would also be good as it should be close to zero ohms as you say.
Richard
Bru
Well-Known Member
I'm sure you know this but unplug the antenna first! Unless the manufacturer states a resistance reading between the core and sheath with the antenna plugged in, measuring the resistance is futile (geddit, I like that one ... well I amuse myself anyway)
Daverw
Well-Known Member
You cannot check with a normal meter, the 50ohms is impedance not resistance. You need to check with antenna analyser, you are likely to have a reading if the antenna is connected, check for full open circuit meg ohms with coax disconnected at both ends but this does not always show an issue. I spend loads of my time help test antennas at our club as many are so poorly installed, being a radio ham I've got the gear.
Habebty
Well-Known Member
This is the tech spec for a Hawk antenna, so the frequency range is good enough, Does the DC grounded mean a 10k 0hms resistance between the core and the braid or the core and say, the mast? - Cheers
Frequency Range: 156 - 162 MHz
Gain: 3 dBi
V.S.W.R.: <1.5:1 @ resonance
Length: 0.9 m
Weight: 0.25 kg
Sections: 1
Max Power Input: 50
DC Grounded: Reads 10K ohms
Frequency Range: 156 - 162 MHz
Gain: 3 dBi
V.S.W.R.: <1.5:1 @ resonance
Length: 0.9 m
Weight: 0.25 kg
Sections: 1
Max Power Input: 50
DC Grounded: Reads 10K ohms
Daverw
Well-Known Member
You never have connection from core to ground, this would short out output transistors and blow them. They appear to show 10k balance resistor to ground most likely to assist the ground plane. Transmitter output is ac not dc voltage.
Note that antennas are just a simple tuned wire cut to a length to match the frequency on the centre core with the screen to the ground. The 50 ohm is the effect of the capacitance of the air / insulation gap between the core and the screen, you could actually just strip the screen back about 900mm lay it out 180 degrees to the centre core and you've just made a dipole antenna that would actually work nearly as well at the whip you've bought. The only antenna I've only ever bought was the GPs / AIS combined antenna, and that was actually free with the AIS anyway. Antennas really easy to make for pennies.
Note that antennas are just a simple tuned wire cut to a length to match the frequency on the centre core with the screen to the ground. The 50 ohm is the effect of the capacitance of the air / insulation gap between the core and the screen, you could actually just strip the screen back about 900mm lay it out 180 degrees to the centre core and you've just made a dipole antenna that would actually work nearly as well at the whip you've bought. The only antenna I've only ever bought was the GPs / AIS combined antenna, and that was actually free with the AIS anyway. Antennas really easy to make for pennies.
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RichardS
N/A
Definitely. We're talking about checking the integrity of the cables only.
We're not talking about checking the impedance, just the integrity of the cables. A normal multimeter is fine for this.
Richard
Bru
Well-Known Member
Erm, yes and then again no!
DC coupled antennas do have a connection from core to ground. It can meter as anything from a dead short to a resistance of 10k to 20k depending on the antenna
The coupling is DC only, and as you say the transmission is not DC
weustace
Well-Known Member
I have installed an AIS transceiver using a home made antenna on the pushpit consisting of the top two sections of an unused antenna support structure (aka telescopic gfrp fishing rod) with a wire half wave dipole (tuned to AIS centre Freq of 162MHz). It is admittedly a corrupt half wave dipole by virtue of having the coax running very close to the counterpoise...
This is centred about 1.5m above the waterline, and even though I didn't want to cut the 10m or so of lossy RG58, I still see ships well over 8nm away. I am visible on Marine Traffic out in Lyme Bay no problem, so think the transmitter is ok too. I didn't see much in a marina, so would suggest trying it at sea before you condemn it.
Edit: sorry, didn't read whole thread, cardinal sin so my apologies. Might suggest trying a dipole or similar in open water with known other craft (via an app of some sort) to rule out transceiver problems?
This is centred about 1.5m above the waterline, and even though I didn't want to cut the 10m or so of lossy RG58, I still see ships well over 8nm away. I am visible on Marine Traffic out in Lyme Bay no problem, so think the transmitter is ok too. I didn't see much in a marina, so would suggest trying it at sea before you condemn it.
Edit: sorry, didn't read whole thread, cardinal sin so my apologies. Might suggest trying a dipole or similar in open water with known other craft (via an app of some sort) to rule out transceiver problems?
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