User's Manual

Rev B

port (PORT 2), to accommodate special applications (e.g., GPS or DSP_500 interfaces). A 15-pin

(DE-15P) connector is also provided for antenna switching using Lotek’s ASP_8 controller.

See the figures above for locations of front and rear panel connectors.

Maintenance and storage

The SRX_400 should be protected from dust and moisture. If cleaning is required, the housing

and front panel can be cleaned using a soft cloth. You may need to use cleaning solution. If so,

wipe the housing with a soft, damp cloth using a mild solution of soap and water. Do not allow

any liquid inside the housing. When not in use, the unit should be stored in a dry place.

Lightning protection

Any system with SRX_400 and aerial antennas should be protected from a direct lightning

strike, as well as from voltage induced in antenna cables due to drainage of a surge to ground.

The latter can be achieved through the use of lightning arresters in the antenna lines right at the

SRX antenna input. Working frequency is one of the factors to consider when selecting lightning

arresters. For protection from a direct lightning strike it is recommended to erect a mast with a

lightning rod connected to a grounding pin with a flexible copper cable. The structure will

provide a ‘protective cone shade’ for the antenna. The antenna itself should be connected to the

grounding system.

Memory

Operating firmware is contained in permanent read only memory and cannot be overwritten

or erased. Variables used by the operating system are likewise indestructible, since they are

reinitialized on startup. All other memory, including user-specified parameters like frequency

tables and gain settings, and also the time and date, are saved in battery backed-up RAM. Back-

up power is supplied by the main batteries, as long as they have sufficient charge, and by an on

board lithium battery which will provide memory protection for approximately 6 months if the

main batteries are discharged or removed.

The basic SRX_400 receiver provides 64K bytes of data memory, of which roughly half is used

by the operating system. In models equipped with the ASP-8-512 memory expansion option,

512K bytes of additional (bank switched) memory are supplied for user application data.

SRX_400 ‘A’ models can accommodate 1M byte of extended memory (ASM_8_1M).

Start-up and the Command Environment

The SRX_400 is shipped with the batteries charged and time and date set. To operate the

receiver, attach the antenna to the front panel RF jack and turn the

OFF/VOL switch on

(clockwise). The receiver will display the software version information, followed by the date and

time, followed by the current frequency and gain. The receiver is now ready to accept

commands.

From the main command environment (display shows frequency on the left and gain on the

right) all key functions are accessible and the receiver is in its audio mode. By judicious use of

gain and audio volume controls, signal bearings may be obtained using a directional antenna

and isolating headphones. Some keypad commands return you to this environment after

adjusting some receiver parameter (frequency, gain, scan time, etc.). Others transfer control to a