The Standard Horizon GX3500S Quantum marine VHF radio has a large front panel that is fitted with an alphanumeric keypad used for data entry and functional control. Three hefty rotary knobs control volume, squelch, and channel selection.
On the left side of the radio front panel the alphanumeric keypad shares space with the speaker box. We found this compromise had a significant effect on audio performance.

Standard Horizon GX3500S
Pushbuttons on the GX3500S microphone let you change radio channels and quick select 16 or 9.
Performance
Cutting down the size of the speaker grille to accommodate the keypad lowered the audio output on the GX3500 by 6 dBA when compared to its cousin the GX2360S even though both share the same speaker and audio amplifier. Audio quality remained excellent.
Transmitter performance was quite good, ranking among the best with very stable transmitter power output and a transmitter frequency stability rating of excellent. Receiver sensitivity was rated good while Standard claims a selectivity specification of greater than 70 dB.
The Standard Horizon GX3500S displays channel numbers in large block letters with customizable channel comments alongside. Time and position, frequency group, transmitter power, and transmit/receive icons are also shown. Backlighting has 7 levels of brightness and 7 levels of contrast. We rated the display screen excellent.
Operation
Most operations in the Quantum 3500 are controlled with a function key and one of the alphanumeric keys. Heres an example: Pressing F then 1 selects the screen backlighting dimmer, F then 2 the memory function, F then 3 starts and stops scanning, etc. Other keys select the remaining functions, some of which include Dual Watch, PA (Hailer), and Foghorn. Single dedicated push buttons remain for quick picking channel 16 or 9, selecting weather channels, and changing transmitter power.
Digital Selective Calling
The 3500S will send and receive distress, individual, all ships, group, and send and receive position data, it only lacks the ability to receive geographical and transmit and receive polling calls. Individual and group directories contain the MMSI numbers of other vessels you wish to call. Up to 30 numbers can be stored with names a maximum of 11 characters long. The alphanumeric keypad makes entering data in the individual or group directories easy.
Odds and Ends
The 30-watt hailer built into the GX3500S can be operated manually or in the automatic foghorn mode. The hailer/foghorn menu is selected with the PA/FOG key. Powerboat underway, powerboat underway not making way, sailing vessel underway, vessel under tow, vessel aground, and vessel at anchor are the selectable sound patterns. A horn and siren sound is also available. Foghorn tone can be adjusted from 250 to 850 Hz. We found the hailer/foghorn easy to use and able to produce more than adequate volume.
Compare Prices for VHF Radios.
Final Thoughts
The Quantum GX3500S is waterproof and carries a 3-year warranty. Excellent overall performance, an alphanumeric keypad, and a reasonable price make it a good buy.