In article . com,
wrote:

Hi,

AIS operates on 162MHz which is in the maritime VHF band, I think. Can
I split the VHF aerial line to feed both a DSC VHF set and a stand
alone AIS receiver??? - this receiver in particular
http://www.allgadgets.co.uk/ag/produ...pf%5Fid=AG3933

TVMIA


Actually, if one were to do a bit of RF Engineering, it is possible
to accomplish the above relatively simply. Motorola built a Modar
Triton Bridge to Bridge that had a transceiver and a Ch. 13 Monitor
Receiver all in one package, that split the Receive Antenna line
after the Tx/Rx Switch. These are still one of the best VHF Radio's
ever built and still fond on a whole passel of commercial vessels.

What one would have to do is reengineer the receive path, after the
Tx/Rx switch, and bring out a Rg-174/u line for the secondary receiver.
this would surfice for a Passive AIS Receiver System. for an Active
System one would have to do a bit more and discribing it is beyound what
I would consider easy, for this forum, but it isn't impossible.
The govt. boys would use Larry's idea of Ferrite Ring Circulators
cause they have all out TAX dollars to spend.
One of the best resouces on AIS is Mark Johnson of ShineMicro near Port
Ludlow, Washington. He was one of the design engineers for SEA, and now
is BIG into AIS. Last time I chatted with him, he had prototypes out on
SeaTrials, and expected to be in production this spring, with some
consumer versions.
Just another note, if antennas were as narrow as Doug suggests most
of the Marine Vhf's would have given up their magic smoke long ago.
A Passive AIS Receiver will work very nicely with ANY VHF antenna.
Any VHF Transmitter that can't sustain full power into an open antenna
port, isn't engineered correctly, and needs more heatsink area on the
final Amp transistors. Never had a SEA156 or 157 give up any Magic
Smoke when transmitting continously into an open antenna port. That
was one of the design criterias for any SEA Radio System. Sure beats
paying for all the Warrentee Repairs when the sailing public get it
wrong with their fancy new radios.

Bruce in alaska
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