What would I get longer range from a 49in 3db antenna or a 35in 6db marine antenna?

The Aquatronics MS1550G is a marine stereo, not an antenna. If you are looking to mount an antenna to your boat, you will need to find a suitable location for the antenna mount and then run the coaxial cable to the location where you plan to install your marine radio.
Typically, the coaxial cable will run from the antenna to a hole or grommet in the boat's hull or deck and then be connected to the back of the marine radio. The specific location and process for running the cable will depend on the type of antenna and the layout of your boat.
If you are unsure of the best way to install your antenna, it is recommended that you consult with a professional marine electronics installer or refer to the installation manual for your specific antenna and radio

Attach a larger. longer antenna if possible.

On the Remote Control
Press
1 TONE
ToneControl•OFF-
2 Use selection button to select "ON".
ON : Allow tone adjustment (bass, treble).
OFF : Playback without tone adjustment.
NOTE
The tone cannot be adjusted in the direct
mode.
3 Press
to select an item to be set, and use
TONE
to select a setting value.
Bass : Adjust low frequency range (bass).
• -6dB - +6dB (0dB)
Treble : Adjust high frequency range (treble).
• -6dB - +6dB (0dB)
"Bass" or "Treble" can be set when "Tone Control" is set to
"ON

Yup. The marine antenna is just covered to protect it from salt spray.

Move closer. That's not always an option though. Here are some tips to improve the range of wireless routers:

1) Locate the router higher in the building rather than lower (1st or second floor is better than a basement location).

2) Place the router in a location that will offer the least resistance to the signals - it is easier to pass wifi signals through gypsum board than it is for concrete / brick or walls with aluminum siding on them.

3) Change the antenna(s) on the router to a type that offers more gain. Typical router omni directional antennas offer 3dB to 5dB or gain - there are others that offer 7 dB or more of omnidirectional gain for reasonable prices. The antenna gain works for both transmit from and receive to the router.

4) if the device you wirsh to connect to the router is in one place, consider a directional Yagi antenna. These antennas concentrate the entire wifi signal in a direction that is 30 degrees wide and can allow the signal to be seen 5, 6 or even more times further in one direction - instead of being spread out over 360 degrees. These antennas cost a little more, but can solve the problem quickly.

5) Replace the manufacturer's stock firmware of selected routers with a 3rd party type such as DD-WRT or Tomato. Either of these will work with your Linksys WRT54G router. One of the benefits is the ability to boost output power of the wifi radio in the new settings the firmware offers. Read about both and decide if either is something you're comfortable doing.

6) Add additional wifi routers configured as a bridge or an access point to extend the wifi signal into an underserved area. DD-WRT supports bridging as shown here.

I hope this helps & good luck!

If the crossover is made to accept speaker level input from amp then.....Amp/head spkr output + to crossover + input. Amp/head spkr output - to crossover - input. Crossover midbass + out to midbass spkr + input. Crossover midbass - out to midbass spkr - input. Crossover vari-tweeter + out to tweeter spkr + input. Crossover vari-tweeter -3 or -0 or -6 out to tweeter spkr - input. You have to choose for your preference. 0db makes the tweeter respond normally. -3db mean 3db lower in volume...and -6 means 6db lower in volume. Choose based on your liking.

I would assume you're talking about the radar? it's a RSB0093-074 it's just for the 1623. There are no other options. If you're referring to gps antennas then any antenna that outputs nmea can be used.

The antenna which came with the radio is the appropriate antenna for the unit. It is engineered to be the proper duct length for the frequency band the radio is on. If you change to a longer antenna, you may get worse reception, as the antenna will not longer match.

To improve range, consider this rule of thumb: Height and placement of antenna determines range. Hold the radio with the antenna perpendicular to the ground (straight up) for best range. Tilting the radio to the side can reduce your range by up to 2/3s. Face the direction you are talking.

If these tips do not increase your range, you may need the assistance of a repeater. Check with your local dealer for available options in your area.

Rule of thumb: Height and placement of the antenna determines the range. If your FCC license allows, raise the antenna.

As for types of antennas, there are a variety depending on the situation. (Too many to list.) Common would be Unity Gain (aka quarterwave), 3db gain and 5 db gain. Each has their own advantages according to placement and terrian. Talke to your local radio professional or call one of the experienced online companies to get some advice according to your particular situation.

Lastly, be certain your antenna is tuned to the frequency you are using. This alone can add range to your radio.

Marine two way radios operate on 156 MGZ. You have to use an antenna desinated for that purpose. Type marine vhf antenna on google search and it will pop-up lots of web sites.good luck