doug748
Well-Known Member
I am fixing up a Nasa "Radar" using a VTronix emergency antenna. (I already have it so I might as well give it a try). The aerial uses tiny (c 4mm) co ax cable. Can I anticipate any problems with this set up?
Aerial for Nasa AIS
- Thread starter doug748
- Start date
captainslarty
N/A
no worries
lw395
Well-Known Member
It should be fine. The loss per metre of cable probably isn't great, but theres a lot less cable than in a masthead antenna.
I've mounted my ais Rx antenna about 12-15 ft up the backstay, on a bracket that puts the whip about 8in from the backstay and angled away from it about 30-40 degrees, and I get good coverage with the Nasa AIS radar.
I've mounted my ais Rx antenna about 12-15 ft up the backstay, on a bracket that puts the whip about 8in from the backstay and angled away from it about 30-40 degrees, and I get good coverage with the Nasa AIS radar.
doug748
Well-Known Member
Excellent, thanks for the response chaps. So much better than getting in touch with any manufacturer, where, for a variety of reasons, they feel they can't, or won't, give you a straight answer.
Endeavourquay
Well-Known Member
I am about to mount a Glomax ariel to the back rail, I wondered if I should try and get it up the back stay but I wasnt sure if I could simply strap it to the backstay or what?
fireball
Well-Known Member
The problem with putting it up the backstay is making sure it stays at the height you've selected, then making sure the bracket stays the right way round ... on a backstay that can twist ... also, if you come to take the mast down you have to take the antenna off ... or disconnect it ..
So - excellent if you can achieve this (twin backstays would be a doddle!), but the pushpit rail is a good start and where most ppl seem to mount theirs ... if you have a range problem you could always lift it a bit!
So - excellent if you can achieve this (twin backstays would be a doddle!), but the pushpit rail is a good start and where most ppl seem to mount theirs ... if you have a range problem you could always lift it a bit!
Salty John
Well-Known Member
Because the AIS signal is coming from a ship the transmitting antenna is very high. Because range is a function of the height of both rx and tx antennas the relatively small change in height you will achieve by moving the antenna up the backstay is negligible.
As an example, if the ships antenna is at 120' and your antenna is at 6' your theoretical range will be 13.8 miles. If you move your antenna up to 15' the range will only increase to 14.3 miles.
If you do put an antenna on the backstay, make sure it is vertical or range will deteriorate.
As an example, if the ships antenna is at 120' and your antenna is at 6' your theoretical range will be 13.8 miles. If you move your antenna up to 15' the range will only increase to 14.3 miles.
If you do put an antenna on the backstay, make sure it is vertical or range will deteriorate.
deep denial
Well-Known Member
have you thought of using a vhf splitter to separate the signal from your ordinary vhf aerial?
fireball
Well-Known Member
no no no no no!!
doug748
Well-Known Member
I have heard that folks have had problems with splitters.
This way I get to use the aerial and still have it ready for the VHF in an emergency.
This way I get to use the aerial and still have it ready for the VHF in an emergency.
Eygthene
Well-Known Member
Inconveniently, The NASA AIS "Radar" requires a BNC connector on the aerial lead, whilst most VHF sets use a UHF connector. I have ordered an adaptor, to allow either aerial to be substituted for the other.
pongoglo
Active Member
I too have found the problem with having a BNC adaptor on the NASA AIS2, and the larger connector onthe DSC radio. Would like to use my pushpit mounted Glomex as a back up..where can you aquire an adaptor? Incidentaly Im using the AIS engine with a Garmin 298C, and whilst Im find it an excellent aid (particularly in spotting the Redjet..) Im only getting detection ranges of about 3 miles? What ranges do others achieve?
Mark
Mark
AIDY
Well-Known Member
splitters are expensive and reduce the vhf range.
whipper_snapper
Well-Known Member
fireball
Well-Known Member
[ QUOTE ]
Im only getting detection ranges of about 3 miles? What ranges do others achieve?
[/ QUOTE ]
that is a terrible range - we're now getting 15-20nm on a pushpit antenna with a recently fixed Nasa AIS engine (mk1). 3Nm is useless - you can see the ship before the kit can!
Im only getting detection ranges of about 3 miles? What ranges do others achieve?
[/ QUOTE ]
that is a terrible range - we're now getting 15-20nm on a pushpit antenna with a recently fixed Nasa AIS engine (mk1). 3Nm is useless - you can see the ship before the kit can!
pongoglo
Active Member
Ok. Well thanks for that. Im using a NASA AIS 2 engine with a Garmin 298C plotter and a Glomex 1.5 antenna on the pushpit. Have only run one trial in Portsmouth harbour and out and around the 'forts'. Picked up the Bretagne, Redjet and IOW ferries, but expected to at least see all shipping coming out of Southampton water? Could it be the aerial connection? Had to cut off the UHF connector and replace with a BNC. Interestingly the AIS 2 picked up some ships with no aerial at all! The red light is constant. The green flicks intermitantly at varying intervals. Thanks in advance.
Mark
Mark
fireball
Well-Known Member
IIRC the red light means you've got power and the green is the data - in the solent around portsmouth/forts you should be picking up vessels in the deep water anchorage around the back of bembridge ... you won't pick up too much up Southampton water - we didn't on the pushpit - only the larger vessels with higher antenna.