2018-01-25, 09:18 PM
(2018-01-19, 03:06 PM)Rooney Wrote: The external antenna is supplied by the BNC connector. You could use any GNSS dome antenna, however the integrated GNSS patch antenna is quite good. Depending on your boat material, you could even use the HAT below deck without the need of an external antenna.
The standard connector type for marine GPS antennas is either BNC or TNC. SMA is mostly used for the smaller antennas with magnetic plate. The BNC connector might be used up to 4 GHz, so no need to worry that it can't cope with GNSS frequency.
The SO-239 connector (standard for AIS antenna) is very big. This would have a not negligible impact on board size and would cause mechanical stress on the HAT, if the antenna is attached. In this case SMA is the better choice. There are SMA to SO-239 and SMA to BNC pigtails available anyway, so this is no big deal.
I agree with your comments on the mechanical stress factor of the SO-239 connector on the board, but the same argument applies to BNC (albeit to a lesser extent). BNC does indeed work into the SHF frequency range but they have to very good quality connectors and assembled to a very high standard. SMA is easier to assemble, reliably, IMO.
The use of one SMA and one BNC mystifies me.
Why not go BNC for both if worried about keeping costs down?
I think I would rather go for SMA for both with good gold plated connectors and use pigtails for both.
If the device is built into a cabinet of some kind then pigtails to external connectors on the case will be required anyway. May as well go for the quality, reliability and small form factor of the SMA.